JP4822115B2 - Optical path switching method and optical path switching apparatus - Google Patents

Description

  The present invention relates to an optical path switching device and an optical path switching method used in the fields of optical communication and optical information processing.

  In order to cope with the explosive increase in network traffic accompanying the spread of the Internet and intranets within a company / home, there is a need for an optical path switching device (optical switch) that does not pass through an electrical signal, that is, an optical-optical direct switch. As an apparatus / method for switching an optical path, that is, an optical fiber, an optical waveguide, or a path of light propagating in space, for example, a space division type that switches an optical path in or between optical waveguides, and a plurality of multiplexed Wavelength-division multiplexing type that switches light of wavelength by dividing it into optical paths according to wavelength, time-division multiplexing type that switches the optical path of light that is time-division multiplexed every certain time, mirror or shutter for the optical path of light propagating in space There are known methods such as a free space type that spatially divides and synthesizes. Each of these methods can be multiplexed or used in combination.

  The space division type optical switch uses a directional coupler, makes a copy of an optical signal with an optical branching device, turns on and off the light with a gate element, and guides the waveguide at the intersection of the intersection or Y branch. Proposals have been made to transmit or reflect light propagating through a waveguide by changing the refractive index, but it is still in the research and development stage. It is said that a thermooptic effect by heating an electric heater is used to change the refractive index of the waveguide of a Mach-Zehnder interferometer type optical waveguide switch, but the response speed is about 1 millisecond. Not only is it slow, it has the disadvantage that an electrical signal must be used to operate the optical switch.

  The free space type optical switch includes a micro electro mechanical system (abbreviated as MEMS), an exciton absorption / reflection switch (abbreviated as Exciton Absorption Reflection Switch; EARS switch), and a multistage. Beam shifter type optical switches, hologram type optical switches, liquid crystal switches, and the like have been studied. These have problems such as the presence of mechanically movable parts and polarization dependence, and it cannot be said that they are still in practical use.

  On the other hand, an all-optical thermal lens forming optical element or light that directly modulates the intensity or frequency of light with light using the change in transmittance or refractive index caused by irradiating the thermal lens forming optical element with light. Research on control methods is actively conducted. The present inventors have used an organic nanoparticle photothermal lens forming element (see Non-Patent Document 1) in which an organic dye aggregate is dispersed in a polymer matrix with the aim of developing a new information processing technique using an all-optical type optical element. I have studied light control systems. Currently, the control light (660 nm and 980 nm) is used to modulate the signal light (780 nm and 1550 nm). The control light and the signal light are coaxially and confocally incident and formed transiently by absorption of the control light. An element with the principle of operation that signal light is refracted by a thermal lens is developed, and a high-speed response of about 20 nanoseconds is achieved. Forming the thermal lens by irradiating control light to a thermal lens forming optical element made of a photoresponsive composition and reversibly changing the transmittance and / or refractive index of signal light in a wavelength band different from the control light An optical control method for performing intensity modulation and / or light flux density modulation of the signal light transmitted through an optical element, wherein the control light and the signal light are converged and irradiated to the thermal lens forming optical element, and Adjusting the optical paths of the control light and the signal light so that regions having the highest photon density in the vicinity (beam waist) of the respective focal points of the control light and the signal light overlap each other in the thermal lens forming optical element. A light control method is disclosed (see Patent Document 1 to Patent Document 7). The thermal lens forming optical element made of a photoresponsive composition is irradiated with control light and signal light having different wavelengths, and the wavelength of the control light is selected from a wavelength band absorbed by the photoresponsive composition, A signal light that reversibly forms a thermal lens based on a density change distribution caused by a temperature rise generated in a region where the photoresponsive composition absorbs the control light and a peripheral region thereof, and transmits the thermal lens. A light control method for performing intensity modulation and / or light beam density modulation is disclosed (see Patent Document 8). For example, a dye / resin film or a dye solution film is used as the thermal lens forming optical element, and the response time of the signal light with respect to the control light irradiation at the control light power of 2 to 25 mW is described as less than 2 microseconds. (See Patent Document 8). These methods are excellent in controlling light with light and can respond at high speed. However, there is a problem in that the shape of the light beam formed at the time of control light irradiation becomes a donut shape, so that the coupling efficiency to the optical fiber is small. .

  Here, the thermal lens effect means that molecules that absorb light in the central part of light absorption convert light into heat, and this heat is propagated to the surroundings, resulting in a temperature distribution. The refractive index of the light changes such that the refractive index changes spherically from the light absorption center to the outside, resulting in a distribution in which the refractive index at the light absorption center is low and the refractive index increases toward the outside, which functions like a concave lens. Indicates. The thermal lens effect has been used for a long time in the field of spectroscopic analysis, and now it is possible to perform ultrasensitive spectroscopic analysis that detects light absorption by a single molecule (Non-Patent Document 2 and Non-Patent Document). 3).

  As a method of deflecting an optical path using a thermal lens effect or a refractive index change due to heat, a method of deflecting light by applying heat to a medium with a heating resistor to generate a refractive index distribution in the medium is disclosed ( (See Patent Document 9). However, the above-described method inherently has a problem of “spreading of heat” because heat is generated by the heating resistor and the medium is heated by heat conduction. That is, due to the spread of heat, a fine thermal gradient cannot be given within a wide area, and it is difficult to obtain a desired refractive index distribution. Further, even if the photolithography technique used in the semiconductor integrated circuit is adopted for the fine processing of the heating resistor, there is a certain limit in practice, and the element must be enlarged. As the element becomes larger, the optical system becomes more complicated and larger. In addition, since the medium is heated by heat generation by generating heat with a heat generating resistor, the response is slow and the problem that the frequency of refractive index change cannot be increased is an essential problem.

  The thermal lens forming optical element made of a photoresponsive composition and at least an intensity distribution adjusting means for irradiating the thermal lens forming optical element with a wedge-shaped light intensity distribution. A deflecting element using a thermal lens forming optical element is disclosed, wherein a refractive index distribution is formed in a lens forming optical element, and signal light having a wavelength different from that of the control light is deflected by the refractive index distribution. (See Patent Document 10). This method is excellent in that the light is controlled by light, but the loss of control light is large due to the intensity distribution adjusting means for irradiating the thermal lens forming optical element with a wedge-shaped light intensity distribution. In addition, it is difficult to freely form a wedge-shaped light intensity distribution, and there is a problem that the optical path switching direction cannot be freely set.

  In addition, there has been proposed a method for deflecting laser light by changing the refractive index of the material irradiated with laser light by irradiating the laser light to heat the material (see Patent Document 11 and Patent Document 12). In both methods, the beam diameter is large, and the deflection of the laser beam is very small unless a large power is input. The method of Patent Document 11 is a method in which the irradiation light itself is deflected by heating the irradiation light. When this method is used for light deflection, the irradiation light is absorbed in order to change the refractive index by heating, so that the light transmitted through the substance is greatly reduced in principle.

  The method of Patent Document 12 is an optical switch that takes no electrical or mechanical means, changes the refractive index of the switch material by irradiation of a control beam, and changes the optical path of the signal beam. However, even in this case, neither the control beam nor the signal beam is collected using a lens, and the laser beam that causes the refractive index change requires a large power. In addition, the device becomes large. In addition, since it is not possible to take a means for the refractive change region to expand as the beam progresses as in the present proposal, the deflection angle cannot be increased too much.

  In both Patent Document 11 and Patent Document 12, as described in this proposal, a means for separating and condensing non-deflected light and deflected light, and an optical fiber as a light detecting means, and using the optical fiber for the non-deflected light and deflected light to the optical fiber. No means or the like for performing high-accuracy separation between unpolarized light and deflected light by utilizing the difference in incident angle is not described.

Takashi Hiraga, Norio Tanaka, Kikuko Hayami, Tetsuro Moriya, Creation of dye aggregates / aggregates, structural evaluation, photophysical properties, "Electronics Research Institute Vocabulary", Ministry of International Trade and Industry 59, No. 2, pp. 29-49 (1994) Takao Fujiwara, Keiichiro Fuwa, Takayoshi Kobayashi, Laser-induced thermal lens effect and its application to colorimetric method, "Chemical", Kagaku Dojin, Vol. 36, No. 6, pp. 432-438 (1981) Takehiko Kitamori, Goro Sawada, Photothermal Conversion Spectroscopy, “Bunseki”, published by the Japan Society for Analytical Chemistry, March 1994, pp. 178-187 JP-A-8-286220 JP-A-8-320535 JP-A-8-320536 Japanese Patent Laid-Open No. 9-329816 Japanese Patent Laid-Open No. 10-90733 JP-A-10-90734 Japanese Patent Laid-Open No. 10-148852 Japanese Patent Laid-Open No. 10-148853 Japanese Patent Laid-Open No. 60-14221 JP-A-11-194373 US Pat. No. 4,776,677 US Pat. No. 4,585,301

    The present invention enables light deflection with a small control light power without using complicated and expensive electric circuits and mechanical moving parts, so that failure is extremely low, durability is high, and polarization dependence is extremely low. The optical path can be switched while the optical intensity of the signal light is less attenuated and the energy distribution in the cross section of the signal light is diffractive optically easy to converge (for example, Gaussian distribution). It is an object of the present invention to provide a compact optical path switching device and an optical path switching method that can be performed at the same time and are capable of one input and multiple outputs with a high extinction ratio.

  The present invention has the following features.

(1) Control light and signal light are incident on a light absorption layer in a thermal lens forming optical element including at least a light absorption layer, and the presence or absence of irradiation of the control light is selected according to desired information, and the control The light and the signal light are irradiated so as to converge in the light absorption layer, and the control light and the signal light are irradiated such that the positions of the convergence points of the control light and the signal light are different in the direction perpendicular to the optical axis, The wavelength of the control light is different from the wavelength of the signal light, the wavelength of the control light is selected from a wavelength band that is absorbed by the light absorption layer, and the wavelength of the signal light is from a wavelength band that is not absorbed by the light absorption layer. The control light and the signal light are diffused after converging on the incident surface of the light absorption layer or inside thereof in the traveling direction of the light, thereby diffusing the control light in the light absorption layer and The temperature that occurs in the surrounding area The resulting thermal lens is reversibly formed on the increase, and the refractive index changes, changing the traveling direction of the signal light, the signal light irradiation of the control light did not change the selection Sarezu traveling direction, wherein and irradiation of the control light is changed the traveling direction is selected signal light, an optical path switching method for converging or focused on the light detecting means by the same optical means.

  (2) The optical path switching method according to (1), wherein the control light and the signal light are converged or condensed in the light absorption layer in a light traveling direction.

  (3) The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed while being irradiated with the control light have an apparent convergence point in the light absorption layer. The optical path switching method according to (1) or (2) above, which is separated.

  (4) The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed while being irradiated with the control light are converged or condensed by the same lens, respectively, The optical path switching method according to any one of (1) to (3), wherein light is received.

  (5) A plurality of signals corresponding to the number of optical path switching is obtained by irradiating the light absorption layer with a plurality of control lights according to the number of optical path switching, changing the traveling direction of the signal light according to the combination of the plurality of control lights. The optical path switching method according to any one of (1) to (4), wherein the light and the signal light whose signal direction is not changed are converged or condensed on the light detection means.

  (6) The apparent convergence point distance of the signal light incident on the optical fiber, the signal direction of which has not changed, and the one or more signal lights whose optical paths are switched in the light absorption layer is the distance between the light receiving optical fibers The optical path switching method according to any one of (3) to (5), which is a distance obtained by dividing by a lens magnification.

  (7) A signal light source that emits signal light having one or more wavelengths, a control light source that emits control light having a wavelength different from the signal light, the signal light is transmitted, and the control light is selectively used A thermal lens forming optical element including a light absorption layer that absorbs light, and a condensing means for condensing the control light and the signal light on the light absorption layer with different convergence points in a direction perpendicular to the optical axis. And the thermal lens forming optical element diffuses the control light and the signal light after converging at or near the incident surface of the light absorption layer in the light traveling direction. The thermal lens formed reversibly due to the temperature rise occurring in the region where the control light is absorbed in the layer and the surrounding region, the refractive index is changed, the traveling direction of the signal light is changed, Control light is not irradiated and the direction of travel does not change A signal light Tsu, wherein the control light irradiated signal light traveling direction has been changed is the optical path switching device having an optical detection means is converged or focused by the same optical means.

  (8) The optical condensing unit according to (7), wherein the condensing unit converges or condenses in the light absorption layer in a light traveling direction.

  (9) The thermal lens formed in the light absorption layer of the thermal lens forming optical element has the traveling direction changed by irradiating the control light and the control light without being irradiated with the control light and the control light. The optical path switching method according to (7) or (8), wherein an apparent convergence point of the signal light in the light absorption layer is separated from each other.

  (10) The optical path switching device according to any one of (7) to (9), wherein the detection unit is an optical fiber.

  (11) The apparent convergence point distance of the signal light incident on the optical fiber whose signal direction has not changed and the one or more signal lights whose optical paths are switched in the light absorption layer is the distance between the light receiving optical fibers. The optical path switching device according to (9) or (10), which is a distance obtained by dividing by a lens magnification.

  (12) The control light source emits a plurality of control lights of two or more according to the number of optical path switching, and the condensing means sets a convergence point of the plurality of control lights in a direction perpendicular to the optical axis. The optical path switching device according to any one of (7) to (11), wherein the optical path switching device is converged or condensed on the light absorption layer.

  According to the present invention, the light power density can be locally increased by condensing the control light and irradiating the light absorption layer, and the local temperature of the light absorption layer can be increased with low power. The refractive index of the part and the vicinity can be changed. Further, by collecting the signal light and making it incident on the light absorption layer near the irradiation position of the control light, the change in the refractive index due to the control light can be used efficiently, and the optical path can be switched using the deflection of the signal light. .

  Furthermore, since the deflected signal light is output from the thermal lens forming optical element in the same shape as the beam cross section before condensing, it is highly practical when the deflected signal light is subsequently condensed and used. .

  Furthermore, a plurality of control lights can be incident on the same light absorption layer, and one input can be switched to a plurality of different optical paths.

  In addition, since a plurality of control lights, signal lights, and a plurality of optical path switching signal lights can be incident and detected by adjacent optical fibers, a small and inexpensive apparatus can be provided.

  In the present invention, the control light and the signal light can be condensed and the light condensing points can be brought close to each other, so that the optical path can be switched at high speed.

  In addition, since a low-power semiconductor laser can be used, a small and inexpensive device can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration example of an optical path switching apparatus according to the first embodiment of the present invention. The optical path switching device according to the first embodiment of the present invention includes a signal light incident terminal 1 that is a signal light source and a first collimating lens that makes the signal light substantially parallel light, as schematically illustrated in FIG. 2, a control light incident terminal 3 that is a control light source, a second collimating lens 4 that makes the control light substantially parallel, a light mixer 5 that combines the signal light and the control light, and the signal light and the control light. Are condensed on the light absorption layer of the thermal lens forming optical element 7, the thermal lens forming optical element 7, and the light transmitted through the thermal lens forming optical element 7 into substantially parallel light. A third collimating lens 8, a wavelength selective transmission filter 9, and a second condenser lens 10 for condensing the non-deflected light on the first detector 11 and the deflected light on the second detector 12. Have.

  Although not shown, signal light was incident on the signal light incident terminal 1 by an optical fiber. In this embodiment, the signal light wavelength is 1550 nm. The signal light may have any wavelength as long as it transmits the light absorption layer of the thermal lens forming optical element 7. In this embodiment, the signal light is incident through an optical fiber, but a laser that emits signal light may be directly installed at the signal light incident terminal 1.

  The material of the light absorption layer, the wavelength band of the signal light, and the wavelength band of the control light in the thermal lens forming optical element used in the light deflection method and the light deflection apparatus of the present invention are combinations of these according to the purpose of use. Appropriate combinations can be selected and used. As a specific setting procedure, for example, first, the wavelength or wavelength band of signal light is determined according to the purpose of use, and a combination of the material of the light absorption layer film and the wavelength of control light that is optimal for controlling this is selected. It only has to be selected. Alternatively, after determining the combination of the wavelengths of the signal light and the control light according to the purpose of use, a material for the light absorption layer film suitable for this combination may be selected. For example, when an image or a character is to be directly displayed using signal light, visible light having a wavelength of 400 to 800 nm is used as signal light, infrared light having a wavelength of 980 nm is used as control light, and the light absorbing layer material is the above-described material. A material that transmits visible light having a wavelength and absorbs infrared light having the wavelength is used. In addition, for example, when light having a wavelength corresponding to the longest wavelength λ1 of the absorption maximum in the light absorption spectrum of the material of the light absorption layer to be used is used as control light, light having a wavelength longer than λ1 is preferably used as signal light. Can do. Specifically, when perylene is used as the material of the light absorption layer, the control light can be 405 nm, for example, and the signal light can be 540 nm, 660 nm, 780 nm, 830 nm, 980 nm, 1310 nm, or 1550 nm. When a copper phthalocyanine derivative is used as the material of the light absorption layer, the control light can be set to 650 nm, for example, and the signal light can be set to 690 nm, 780 nm, 830 nm, 980 nm, 1310 nm, or 1550 nm, for example.

  Although not shown, control light was incident on the control light incident terminal 3 by an optical fiber. In this embodiment, the control light wavelength is 980 nm. As for the control light, any wavelength can be used as long as it is absorbed by the light absorption layer of the thermal lens forming optical element 7. In the present embodiment, the control light is incident through an optical fiber, but a laser that emits control light may be directly installed at the control light incident terminal 3.

  As the first collimating lens 2 and the second collimating lens 4, aspherical lenses having a focal length of 8 mm were used. Needless to say, the focal length need not be 8 mm, and a shorter focal length may be used in order to obtain a smaller optical path switching device. Further, although it is not necessary to use an aspheric lens, an aspheric lens is used to reduce the size and weight.

  The optical mixer 5 is a dichroic mirror that transmits signal light and reflects control light. Of course, it goes without saying that a dichroic mirror in which the signal light is reflected and the control light is transmitted can be used by switching the positions of the signal light incident terminal and the control light incident terminal.

  As the condenser lens 6, an aspherical lens having a focal length of 8 mm was used. Needless to say, the focal length need not be 8 mm, and a shorter focal length may be used in order to obtain a smaller optical path switching device. Further, although it is not necessary to use an aspheric lens, an aspheric lens is used to reduce the size and weight.

  In this embodiment, the signal light 1550 nm is incident on the signal light incident terminal with a single-mode quartz optical fiber having a core diameter of 9.5 μm, and the control light 980 nm is incident on the control light incident terminal with a single-mode quartz optical fiber having a core diameter of 9.5 μm. The first collimating lens 2 and the second collimating lens 4 having a focal length of 8 mm make the signal light and the control light substantially parallel light, the thickness of the light absorption layer is 500 μm, and the dye concentration of the light absorption layer is 0.1 to 0. The condensing lens 6 having a focal length of 8 mm is applied to the thermal lens forming optical element 7 having a transmittance of 95 to 80% at a wavelength of 1550 nm and a transmittance of 24 to 0.1% at 980 nm. It converged (condensed) and entered.

The signal light and the control light are converged by the condenser lens 6 on the incident surface of the light absorption layer or in the vicinity thereof in the light traveling direction. When the signal light and the control light are converged (condensed) at the same position in the vicinity of the incident surface of the light absorption layer, the signal light spreads in a donut shape. This situation is shown in FIG . When there is no control light, the signal light which was a round beam as shown in the photograph 1a in FIG. 10 (a) is irradiated with the control light at the same place at the same time, as shown in the photograph 1b in FIG. 10 (b). become. It is considered that the light-absorbing layer incident surface has a clear and large donut shape. Therefore, in this embodiment, the light absorption layer is referred to as an incident surface where the donut shape is clear and large. Of course, in this embodiment, the signal light and the control light are separated from each other by about 25 to 50 μm at the position of the convergence (condensation) point. To form a donut shape, and then the convergence (condensing) points of the signal light and the control light are separated. In addition, when the distance between the convergence points of the signal light and the control light is less than 25 μm, the round beam as shown in FIG. When the signal light of the crescent moon beam is subsequently condensed and incident on the optical fiber, the incident efficiency is reduced, which may impair practicality.

  The thermal lens forming optical element 7 has a configuration as shown in FIG. 4, but in this embodiment, only the light absorption layer is shown for easy explanation. In FIG. 4, the light absorption layer 25 of the thermal lens forming optical element 26 is used by sealing a dye in a solvent in a glass container 27. As the dye soluble in the solvent, a known dye having absorption in the wavelength region of the control light to be used and having no absorption in the wavelength region of the signal light to be used can be used. The glass container 27 through which the laser beam 28 is transmitted has a glass thickness of about 500 μm, and the light absorption layer 25 has a thickness of 200 to 1000 μm. Specific examples of the dye include, for example, xanthene dyes such as rhodamine B, rhodamine 6G, eosin and phloxine B, acridine dyes such as acridine orange and acridine red, azo dyes such as ethyl red and methyl red, porphyrin dyes, Phthalocyanine dyes, cyanine dyes such as 3,3′-diethylthiacarbocyanine iodide, 3,3′-diethyloxadicarbocyanine iodide, triarylmethane dyes such as ethyl violet and Victoria Blue R, naphthoquinone A dye, an anthraquinone dye, a naphthalene tetracarboxylic acid diimide dye, a perylene tetracarboxylic acid diimide dye, or the like can be suitably used. Moreover, these pigment | dyes can be used individually or in mixture of 2 or more types. As the solvent, a solvent that dissolves at least the dye to be used can be used. However, the temperature (boiling point) of boiling without being thermally decomposed when the temperature rises during the formation of the thermal lens is 100 ° C. or higher, preferably 200. Those having a temperature of at least ° C, more preferably at least 300 ° C can be suitably used. Specifically, inorganic solvents such as sulfuric acid, halogenated aromatic hydrocarbons such as o-dichlorobenzene, aromatic substituted aliphatics such as 1-phenyl-1-xylylethane or 1-phenyl-1-ethylphenylethane Organic solvents such as hydrocarbons and nitrobenzene derivatives such as nitrobenzene can be suitably used.

  When the control light is absorbed by the light absorption layer of the thermal lens forming optical element 7, the temperature of the light absorption layer rises and the refractive index changes. As the temperature increases, the refractive index generally changes in a decreasing direction. The intensity distribution of laser light emitted from a normal laser light source and laser light emitted from a normal laser light source and transmitted through an optical fiber is a Gaussian distribution. Further, the light obtained by condensing the laser light with a lens or the like has a Gaussian distribution. Therefore, in the refractive index distribution in the light absorption layer irradiated with the control light, the refractive index is the lowest on the optical axis of the control light, and the refractive index is less reduced around the control light. Further, since there is heat conduction, the refractive index changes even in a portion where light is not irradiated.

  FIG. 5 is a diagram illustrating a situation where the signal light is deflected. In order to simplify the explanation, in FIG. 5, the refraction of light due to the difference in refractive index between the light absorption layer and the medium around the light absorption layer is ignored. In FIG. 5, in the light absorption layer 25 of the thermal lens forming optical element, the light intensity distribution 29 of the control light in the vicinity of the convergence (condensing) point, and the light intensity distribution of the control light at a position away from the convergence (condensing) point. 30, a control light convergence (condensation) point 31, a signal light convergence (condensation) point 33, and an apparent signal light convergence (condensation) point 32 are illustrated. FIG. 5A shows the case where the control light and the signal light are converged (collected) on the incident surface of the light absorption layer 25. FIG. When converged (condensed) at the advanced position, FIG. 5C shows the converged (condensed) position where the control light and the signal light have advanced further into the light absorbing layer by several tens of μm from the incident surface of the light absorbing layer. ) Schematically shows the optical path of the laser beam.

  When the control light is not irradiated, the signal light goes straight. When the control light is irradiated, the signal light is deflected. The signal light transmitted through the light absorption layer 25 is converged (condensed) on the apparent signal light of the light absorption layer 25 shown in FIG. 5 to the first detector 11 and the second detector 12 shown in FIG. ) It converges (condenses) as signal light is emitted from the point 32. In the case of FIG. 5b, the convergence (condensation) point 33 of the signal light almost coincides with the apparent convergence (condensation) point 32 of the signal light, but the case of FIGS. 5a and 5c is shifted. The direction of deviation is opposite in the case of FIG. 5a and FIG. 5c.

  In FIG. 5, the control light and the signal light are shown at the same position in the light traveling direction, but need not be the same.

  The signal light that passed through the light absorption layer was converted into parallel light by the third collimating lens 8. The third collimating lens 8 was an aspheric lens having a focal length of 8 mm. Needless to say, the focal length need not be 8 mm, and a shorter focal length may be used in order to obtain a smaller optical path switching device. Further, although it is not necessary to use an aspheric lens, an aspheric lens is used to reduce the size and weight.

  The wavelength selective transmission filter 9 is a dielectric filter that blocks control light that slightly passes through the thermal lens forming optical element 7 and transmits signal light. If the control light is absorbed to the extent that there is no practical problem with the thermal lens forming optical element 7, it is not necessary to use the wavelength selective transmission filter 9.

  The signal light transmitted through the wavelength selective transmission filter 9 was converged (condensed) and incident on the first detector 11 and the second detector by the second condenser lens 10. The second condenser lens 10 was an aspheric lens having a focal length of 8 mm. Needless to say, the focal length need not be 8 mm, and a shorter focal length may be used in order to obtain a smaller optical path switching device. Further, although it is not necessary to use an aspheric lens, an aspheric lens is used to reduce the size and weight. Further, in this embodiment, the signal light is converged (condensed) by the third collimating lens 8 and the second condensing lens 10, but may be converged (condensed) by one lens. .

  The first detector 11 and the second detector 12 shown in FIG. 1 are provided with the two-core optical fiber ferrule shown in FIG. The optical fiber 35 attached to the two-core optical fiber ferrule is a 9.5 μm single mode quartz optical fiber. The signal light was converged (condensed) on the optical fiber, transmitted through the optical fiber, and then detected. Of course, it goes without saying that a photodetector may be installed directly.

The signal light receiving optical fiber 35 of the two-core optical fiber ferrule shown in FIG. 7A was used by etching a clat layer of a single-mode quartz optical fiber having a core diameter of 9.5 μm to a desired thickness with hydrofluoric acid. The part to be etched was only a few mm of the tip of the optical fiber. The thickness “ω” of the optical fiber after the etching was set to 25 μm in this example. “Ω” has the following relationship with the distance “χ” perpendicular to the optical axis between the convergence point 33 of the signal light converged (condensed) on the light absorption layer and the apparent convergence point 32 of the signal light.
(Formula 1)
ω = m × χ
Here, m is an imaging magnification formed by the third collimating lens 8 and the second condenser lens 10 shown in FIG. In the present embodiment, m = 1, but m may be set so that the incident efficiency to the optical fiber is maximized.

The above “χ” can be changed by changing the following conditions.
1. 1. Position of light absorption layer of thermal lens forming optical element with respect to convergence (condensation) point of first condenser lens 6 for signal light and control light. 2. Control light power Control light position (distance perpendicular to the optical axis of signal light and control light at the condensing point of the first condenser lens 6)
4). 4. Thickness of light absorption layer of thermal lens forming optical element Control light wavelength and signal light wavelength.
6). Dye concentration in the light absorption layer

  FIG. 6 shows the position of incidence (light absorption layer position) of the convergence (condensation) point of the signal light and control light to the light absorption layer 25 of the thermal lens forming optical element 7 shown in FIG. 4, and the position of the detector. An example of measurement data of the separation distance between non-deflected light and deflected light is shown. In the case of FIG. 6, the separation distance is close to 0 when the incident position (that is, the light absorption layer position) of the convergence (condensation) point of the signal light and the control light to the light absorption layer 25 is 40 to 60 μm. This is the case in the state of FIG. 5b. When the incident position on the light absorption layer 25 is deviated from this, the separation distance increases. When the incident position on the light absorption layer 25 (light absorption layer position) was 200 μm or more, there was no significant change in the separation distance. In FIG. 6, the positive and negative signs of the separation distance are such that the incident point of the signal light to the light absorption layer 25 is the origin (that is, 0 point) and the deflection direction is positive. The separation distance becomes positive in the state of FIG. 5c, and becomes negative in the state between FIGS. 5a and 5b.

  By setting the separation distance equal to the thickness “ω” of the light receiving optical fiber, it becomes possible to efficiently detect non-deflected light and deflected light.

  In FIG. 6, a line 38 (solid line connecting diamond points) has a control light power of 15.4 mW, a line 39 (solid line connecting square points) has a control light power of 18 mW, and a line 40 (solid line connecting triangle points) is In this case, the control light power is 20.5 mW. This measurement is performed by moving a detector having a slit opening at the position of the first detector 11 shown in FIG. In FIG. 6, the thickness of the light absorption layer is 1000 μm, the control light position (distance perpendicular to the optical axis of the signal light and the control light at the condensing point of the first condenser lens 6) is 25 μm, and the dye concentration Was 0.1%, and the transmittance of the light absorption layer was 95% at a wavelength of 1550 nm and the transmittance at 980 nm was 0.1%.

  In the present embodiment, a thermal lens forming optical element having a light absorption layer thickness of about 1000 μm is used, the control light power is about 16 mW, the light absorption layer position is 500 μm, the control light position (at the condensing point of the first condenser lens 6). The distance in the direction perpendicular to the optical axes of the signal light and the control light is 25 μm. In order to adjust the incident efficiency to the light receiving optical fiber, the position of the first detector for detecting the non-deflected light was first adjusted, and then the control light power was adjusted to improve the incident efficiency to the second detector. .

  The reason why the light absorption layer position is 500 μm is that the incident angle to the optical fiber is different between the unpolarized light and the deflected light when the position is less than this, and the incident efficiency to both optical fibers cannot be increased.

  FIG. 8 shows the incident position (light absorbing layer position) of the convergence (condensing) point of the signal light and control light to the light absorbing layer 25 of the thermal lens forming optical element 7 and the deflection angle data of the deflected light. . In the present embodiment, the third collimator lens 8 and the second condenser lens 10 have the same focal length of 8 mm, so that the deflection angle of the optical axis of the deflected light incident on the optical fiber and the non-deflected light This is the angle between the optical axis. For this reason, when the incident position (light absorption layer position) of the convergence (condensation) point of the signal light and the control light to the light absorption layer 25 of the thermal lens forming optical element 7 is 500 μm or less, Incidence efficiency could not be increased. The reason for this is as follows.

The numerical aperture (hereinafter referred to as NA) of a 9.5 μm single mode quartz optical fiber is generally 0.1. The maximum incident angle θc that can propagate through an optical fiber with NA = 0.1 is given by the following equation and is about 5.7 degrees.
(Formula 1)
θc = Sin ⁻¹ (0.1) ≈5.7 degrees Further, since the signal light is incident on the single-mode quartz optical fiber having a core diameter of 9.5 μm, the NA is 0.1, and the signal light itself The convergence (condensing) angle is about 5.7 degrees. For this reason, when the non-deflected light is adjusted to the maximum incident light amount, a part of the deflected light exceeds the maximum incident angle θc of the deflected optical fiber, and the light amount decreases. The amount of the non-deflected light is reduced by exceeding the maximum incident angle θc of the non-deflected optical fiber.

  In FIG. 8, the control light power is about 12.9 mW, the control light position (distance perpendicular to the optical axis of the signal light and the control light at the condensing point of the first condenser lens 6) is 35 μm, and the light The thickness of the absorption layer was 1000 μm, the dye concentration was 0.1%, and the transmittance of the light absorption layer was 95% at a wavelength of 1550 nm and the transmittance at 980 nm was 0.1%.

  An example of measurement data is shown in FIG. In FIG. 9, since there was no reliability of the value of 0.1 μW or less of the measuring instrument used for the measurement, the values of 0.1 μW or less were all set to 0.1 μW or less including the case of 0 μW, and the extinction ratio was In the calculation, all the cases of 0.1 μW or less are calculated as 0.1 μW. Both unpolarized light and deflected light had an extinction ratio of about 40 dB.

(Comparative Example 1)
In the first embodiment, the condensing lens 6 is not used, and the collimated signal light and control light are irradiated to the thermal lens forming optical element 7 without converging, and the third collimating lens 8 is not used. Except for this point, the same experiment as in the first embodiment was performed. However, when the control light power was about 18 mW, no deflection of the signal light was observed even when the control light was irradiated. Therefore, when the control light source is changed to Ti: cypher laser and further irradiated with high power control light (980 nm), the solvent of the dye solution in the thermal lens forming optical element is detected before the deflection of the signal light is detected. Started boiling and it was confirmed that it was difficult to deflect the signal light. Furthermore, the power of the control light was lowered to just before the start of boiling, and the arrangement of the signal light and control light and the distance between the beams until entering the thermal lens forming optical element were finely adjusted, but the optical path deflection of the signal light was observed. Was not. Furthermore, although the arrangement of the signal light and the control light and the distance between the beams in the light absorption layer in the thermal lens forming optical element were finely adjusted, no optical path deflection of the signal light was observed. That is, when the control light is converged and diffused in the light absorbing layer in the thermal lens forming optical element so that light absorption does not occur, and it is irradiated as a collimated parallel beam, it is sufficient to deflect the optical path of the signal light. It was found that no size thermal lens was formed.

(Second Embodiment)
FIG. 2 is a schematic configuration example of an optical path switching apparatus according to the second embodiment of the present invention. In the second embodiment of the present invention, the same optical members as those in the first embodiment are given the same numbers.

  FIG. 2 shows an optical path switching device having a second signal light incident terminal 15, a second control light incident terminal 16, and a first imaging lens 17 having a focal length of 8 mm. The other components are the same as in FIG. Further, the wavelength of the signal light used was 1550 nm, and the wavelength of the control light was 980 nm. However, it goes without saying that the wavelength of the signal light and the wavelength of the control light may be other wavelengths as in the first embodiment. It is the same as in the first embodiment that the deflection amount (deflection angle) changes when the power of the control light is changed.

  The second signal light incident terminal 15 and the second control light incident terminal 16 are provided with the two-core optical fiber ferrule shown in FIG.

The signal light emitting fiber 37 and the control light emitting fiber 36 of the two-core optical fiber ferrule in FIG. 7B were used by etching a 9.5 μm single-mode quartz optical fiber clat layer to a desired thickness with hydrofluoric acid. The part to be etched was only a few mm of the tip of the optical fiber. The thickness “ω” of the optical fiber after etching is the following relationship with the distance “χ” perpendicular to the optical axis of the convergence (condensation) of the signal light and control light converged (condensed) on the light absorption layer: I made it.
(Formula 2)
ω = χ / n
Here, n is the imaging magnification of the fourth condenser lens 17. In this example, n was 1. If n is decreased, the thickness of the optical fiber after etching can be increased. If n is increased, the thickness of the optical fiber after etching must be decreased.

  In the present embodiment, n is 1 and ω is 25 μm. As is clear from the first embodiment, when ω is increased, the deflection angle is reduced, so that ω is preferably 25 to 50 μm. When the thickness was 25 μm or less, the transmittance of laser light was deteriorated. In particular, the transmission of 980 nm laser light was poor, and the transmittance with a 1 m fiber was 20% to 80%.

  The optical fiber for control light and the optical fiber for signal light were used after being fixed to the hole of the ferrule with a thickness of 2ω + several μm with an adhesive and then polishing the tip.

  In this embodiment, a single mode optical fiber having a core diameter of 9.5 μm is used. However, when changing the wavelength of the laser light, it is necessary to use an optical fiber having a core diameter suitable for it. For example, when the control light is 660 nm, it is better to set the core diameter to 4.5 μm.

  The light deflection amount (deflection angle) in the present embodiment is substantially the same as in the first embodiment.

(Third embodiment)
FIG. 3 is a schematic configuration example of an optical path switching apparatus according to the third embodiment of the present invention. In the third embodiment of the present invention, the same optical members as those in the first embodiment and the second embodiment are given the same numbers. The third embodiment is an example in which the number of control lights is increased by one from the second embodiment and the optical path to be switched is set to 3. In FIG. 3, a third signal light incident terminal 19, a third control light incident terminal 20, a fourth control light incident terminal 21, a third detector 22, a fourth detector 23, and a fifth detector. Except 24, it is the same as FIG. 1 and FIG. Further, the wavelength of the signal light used was 1550 nm, and the wavelength of the control light was 980 nm. However, it goes without saying that the wavelength of the signal light and the wavelength of the control light may be other wavelengths as in the first embodiment and the second embodiment. It is the same as the first embodiment and the second embodiment that the deflection amount (deflection angle) changes when the power of the control light is changed.

  In the third signal light incident terminal 19, the third control light incident terminal 20, and the fourth control light incident terminal 21, the three-core optical fiber ferrule shown in FIG.

The signal light emitting fiber 37 and the control light emitting fiber 36 of the three-core optical fiber ferrule in FIG. 7 (d) were used by etching a 9.5 μm single-mode quartz optical fiber clat layer to a desired thickness with hydrofluoric acid. The part to be etched was only a few mm of the tip of the optical fiber. The thickness “ω” of the optical fiber after etching is the following relationship with the distance “χ” perpendicular to the optical axis of the convergence (condensation) of the signal light and control light converged (condensed) on the light absorption layer: I made it.
(Formula 3)
ω = χ / n
Here, n is the imaging magnification of the first condenser lens 17. In the present embodiment, n is 1. If n is decreased, the thickness of the optical fiber after etching can be increased. If n is increased, the thickness of the optical fiber after etching must be decreased.

  For the third detector 22, the fourth detector 23, and the fifth detector 24, the three-core optical fiber ferrule shown in FIG. The optical fiber 35 attached to the three-core optical fiber ferrule is a single mode quartz optical fiber having a core diameter of 9.5 μm. The signal light was converged (condensed) on the optical fiber, transmitted through the optical fiber, and then detected. Of course, it goes without saying that a photodetector may be installed directly.

The signal light receiving optical fiber of the three-core optical fiber ferrule shown in FIG. 7 (c) has a clat layer of a single-mode quartz optical fiber having a core diameter of 9.5 μm, like the two-core signal light receiving optical fiber of FIG. It was used after etching to a desired thickness with hydrofluoric acid. The part to be etched was only a few mm of the tip of the optical fiber. The thickness “ω” of the optical fiber after the etching was set to 25 μm in this example. “Ω” is a distance “χ” perpendicular to the optical axis between the convergence point 33 of the signal light converged (condensed) on the light absorption layer and the apparent convergence point 32 of the signal light shown in FIG. There is a relationship.
(Formula 4)
ω = m * χ
Here, m is the magnification of the second imaging lens 18. In the present embodiment, m = 1. In the present embodiment, m = 1, but m may be set so that the incident efficiency to the optical fiber is maximized.

  The three-core optical fiber shown in FIG. 7D is an example in which the optical path is switched one-dimensionally, but the third control light incident terminal 20 and the fourth control light incident terminal 21 are set at a right angle or an angle of 120 degrees. You may go in two dimensions.

  FIG. 7 (f) shows the signal light and the control light when the six control light emitting fibers 36 are installed around the signal light emitting fiber 37 and the optical path is switched in this direction including the case where the control light is not irradiated. This is an example of a seven-core optical fiber ferrule that makes the light incident. It is used by being installed at the position of the signal light incident terminal and the control light incident terminal shown in FIG. In this case, the optical path switching is detected using, for example, a seven-core optical fiber ferrule having seven signal light receiving optical fibers as shown in FIG. In FIG. 7 (e), seven optical fibers having the same thickness are finely arranged. Six signal light receiving optical fibers 35 are arranged around the central signal light receiving optical fiber 35. The manufacturing method of the 7-core optical fiber ferrule is the same as the manufacturing method of the 2-core and 3-core optical fiber ferrule.

  The optical path switching data obtained in this embodiment is almost the same as that in the first embodiment and the second embodiment.

  The deflection direction optical path switching method and the optical path switching apparatus of the present invention can be effectively used in the field of optical communication and the field of optical upper processing.

It is a conceptual diagram of the optical path switching apparatus of the 1st Embodiment of this invention. It is a conceptual diagram of the optical path switching apparatus of the 2nd Embodiment of this invention. It is a conceptual diagram of the optical path switching apparatus of the 3rd Embodiment of this invention. It is a figure which shows an example of a structure of a thermal lens formation optical element. It is a figure explaining deflection of signal light. It is a figure explaining deflection of signal light. It is a figure explaining deflection of signal light. It is a graph which shows the relationship between the separation distance of non-deflected light and deflected light. It is a conceptual diagram of an optical fiber ferrule. It is a graph which shows the relationship between a light absorption layer position and a deflection angle. It is a figure which shows optical path switching measurement data. It is a figure which shows the cross section of the output signal beam | light.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Signal light input terminal, 2 1st collimating lens, 3 Control light input terminal, 4 2nd collimating lens, 5 Optical mixer, 6 1st condensing lens, 7 Thermal lens formation optical element, 8 3rd Collimating lens, 9 wavelength selective transmission filter, 10 second condenser lens, 11 first detector, 12 second detector.

Claims (12)

The control light and the signal light are incident on the light absorption layer in the thermal lens forming optical element including at least the light absorption layer,
Select the presence or absence of the control light according to the desired information,
The control light and the signal light are irradiated so as to converge at the light absorption layer, and the control light and the signal light are irradiated such that the positions of the convergence points of the control light and the signal light are different in the direction perpendicular to the optical axis. And
The wavelength of the control light is different from the wavelength of the signal light, the wavelength of the control light is selected from a wavelength band that is absorbed by the light absorption layer, and the wavelength of the signal light is from a wavelength band that is not absorbed by the light absorption layer. Chosen,
The control light and the signal light are diffused after converging on the incident surface of the light absorption layer or inside thereof in the traveling direction of the light, thereby diffusing the control light in the light absorption layer and its peripheral region Due to the thermal lens that is formed reversibly due to the temperature rise that occurs, the refractive index changes, changing the traveling direction of the signal light,
A signal light irradiation of the control light did not change the selection Sarezu traveling direction, converging said control light irradiation is selected direction of travel altered signal light, the light detection means by the same optical means or An optical path switching method characterized by condensing light.   The optical path switching method according to claim 1, wherein the control light and the signal light are converged or condensed in the light absorption layer in a traveling direction of light.   The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed after being irradiated with the control light are separated from each other in the apparent convergence point in the light absorption layer. 3. The optical path switching method according to claim 1, wherein the optical path is switched.   The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed after being irradiated with the control light are converged or condensed by the same lens and received by the optical fiber. The optical path switching method according to any one of claims 1 to 3, wherein:   A plurality of control lights are applied to the light absorption layer according to the number of optical path switches, the traveling direction of the signal light is changed by a combination of the plurality of control lights, and a plurality of signal lights and signals according to the number of optical path switches 5. The optical path switching method according to claim 1, wherein the signal light whose direction has not been changed is converged or condensed on the light detection means.   The apparent convergence point distance of the signal light incident on the optical fiber, the signal direction of which does not change, and one or more signal lights whose optical paths are switched in the light absorption layer is the distance between the light receiving optical fibers and the lens magnification. 6. The optical path switching method according to claim 3, wherein the distance is a distance divided by. A signal light source that emits signal light of one or more wavelengths;
A control light source that emits control light having a wavelength different from that of the signal light;
A thermal lens forming optical element including a light absorbing layer that transmits the signal light and selectively absorbs the control light;
Condensing means for condensing the control light and the signal light on the light absorption layer with the convergence points different from each other in the direction perpendicular to the optical axis,
The thermal lens forming optical element is configured such that the control light and the signal light are diffused after converging at or near the incident surface of the light absorption layer in the light traveling direction, so that the control light in the light absorption layer is diffused. By the thermal lens that is reversibly formed due to the temperature rise that occurs in the region where the light is absorbed and its peripheral region, the refractive index is changed, and the traveling direction of the signal light is changed,
Furthermore, light detection in which the signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed while being irradiated with the control light is converged or condensed by the same optical system means An optical path switching device comprising means.   The optical path switching device according to claim 7, wherein the condensing unit converges or condenses within the light absorption layer in a traveling direction of light.   The thermal lens formed in the light absorption layer of the thermal lens forming optical element includes signal light that is not irradiated with the control light and whose traveling direction is not changed, and signal light that is irradiated with the control light and whose traveling direction is changed. The optical path switching device according to claim 7 or 8, wherein apparent convergence points in the light absorption layer are separated from each other.   The optical path switching device according to any one of claims 7 to 9, wherein the detection means is an optical fiber.   The apparent convergence point distance of the signal light incident on the optical fiber, the signal direction of which does not change, and one or more signal lights whose optical paths are switched in the light absorption layer is the distance between the light receiving optical fibers and the lens magnification. The optical path switching device according to claim 9 or 10, wherein the distance is a distance divided by. The control light source emits two or more control lights according to the number of optical path switching,
12. The light collecting layer according to claim 7, wherein the condensing unit converges or condenses the light on the light absorption layer by changing a convergence point of the plurality of control lights in a direction perpendicular to an optical axis. The optical path switching device according to claim 1.