JP7141972B2 - Semiconductor laser light source - Google Patents

Description

The present invention relates to a semiconductor laser light source, and more particularly to a semiconductor laser light source comprising a semiconductor laser and an optical fiber into which laser light emitted from the semiconductor laser is incident.

Conventionally, as disclosed in Patent Documents 1 and 2, for example, there has been known a semiconductor laser light source comprising a semiconductor laser and an optical fiber separated from the semiconductor laser so as to be coupled with the laser light emitted from the semiconductor laser. It is Among semiconductor laser light sources of this type, those that emit laser light with wavelengths in the visible region are widely used in fields such as biomicroscopes, medical inspection equipment, particle measurement, and semiconductor inspection equipment.

In various fields such as those mentioned above, analog information is often used to acquire image information. Therefore, for semiconductor laser light sources used in these fields, it is desired to suppress the generation of low-level noise, which is not particularly problematic in the case of digital modulation in the optical communication band.

In a semiconductor laser light source comprising a semiconductor laser and an optical fiber spaced apart from it, the return light described in Patent Documents 1 and 2 is well known as one of noise sources that generate noise. . The return light is light that is reflected by the light incident end face of the optical fiber and returns to the semiconductor laser.

FIG. 5 explains this return light in detail. As shown here, a laser beam L emitted from a semiconductor laser 10 is collimated by a collimating lens 11 , then condensed by a condensing lens 12 as a condensing optical system, and enters an optical fiber 13 . The optical fiber 13 consists of a core 13a and a clad 13b having a lower refractive index than the core 13a and arranged around the core 13a. The laser light L is condensed by the condensing lens 12 so as to converge on the light incident end face 13c of the optical fiber 13, and enters the inside of the optical fiber 13, that is, the core 13a. The laser light L incident on the core 13a propagates through the core 13a while repeating total reflection at the interface with the clad 13b, and is sent to a predetermined utilization position. When the laser light L is incident on the optical fiber 13 as described above, the laser light L can be reflected by the light incident end face 13c of the optical fiber 13 and return to the semiconductor laser 10 as return light L1.

As described in Patent Document 1, in order to increase the optical coupling efficiency between the laser light L and the optical fiber 13, the condenser lens 12 is arranged with its optical axis deviated from the beam center of the laser light L. Such a configuration is also shown in FIG. Conventionally, in order to prevent the return light L1 from entering the semiconductor laser 10, the light incident end surface 13c of the optical fiber 13 is cut obliquely with respect to the optical axis of the condensing lens 12 in front of it. known, and FIG. 5 also shows this structure.

By obliquely cutting the light incident end surface 13 c in this manner, the optical path of the return light L 1 can be made to go away from the semiconductor laser 10 . In many cases, a prism pair is arranged between the collimator lens 11 and the condenser lens 12 for making the beam cross-sectional shape of the laser light L circular, but its illustration is omitted in FIG. there is

As a configuration for preventing the return light L1 from entering the semiconductor laser 10, in addition to obliquely cutting the light incident end face 13c of the optical fiber 13 as described above, as shown in FIG. It is also known to dispose a mask (spatial filter) 20 for blocking the return light L1 between the semiconductor laser 10 and the semiconductor laser 10 . Even if the light incident end surface 13c is obliquely cut as described above, a part of the beam skirt is covered with the opening of the condenser lens 12, so that part of the return light L1 travels toward the semiconductor laser 10, but the space By arranging the filter 20, it is possible to block the returning light L1 that travels in this way. Patent Literature 2 also shows an example of such a configuration. In this FIG. 4, elements equivalent to those in FIG. 5 described above are denoted by the same numbers, and descriptions thereof will be omitted unless particularly necessary (the same applies hereinafter).

Japanese Patent Publication No. 7-119857 Japanese Patent No. 5074253

However, according to the research of the present inventor, as described above, in a semiconductor laser light source in which the condenser lens is arranged with its optical axis deviated from the beam center of the laser beam, the light incident end surface of the optical fiber is obliquely cut or returned. It has been found that even if a mask for blocking light is provided, noise due to return light may still occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. In a semiconductor laser light source in which the optical axis of a condensing lens is arranged away from the center of the beam of laser light, the generation of noise due to return light can be more reliably prevented. intended to

The semiconductor laser light source according to the present invention is
a semiconductor laser;
a condensing optical system for converging the laser light emitted from the semiconductor laser, the condensing optical system being arranged in a state in which the optical axis is separated from the beam center of the laser light;
an optical fiber for propagating the laser light that has passed through the condensing optical system, the optical fiber having a light incident end face into which the laser light is incident that is obliquely cut with respect to the optical axis of the condensing optical system;
In a semiconductor laser light source consisting of
A spatial filter is provided for blocking the reflected light of the laser light reflected at the light incident end surface of the optical fiber,
A transmission loss member is provided between the semiconductor laser and the optical fiber to limit the transmittance of the laser light traveling toward the optical fiber to 95% or less.
It is characterized by In addition, the above-mentioned "beam center" means the wavefront normal line of the laser beam.

The transmittance of the transmission loss member is more preferably 87% or less, more preferably 80% or less.

In the semiconductor laser light source of the present invention, it is desirable that the light incident end surface is a non-coated surface.

Moreover, it is desirable that the optical fiber is provided with an end cap at the end on the light incident side.

The semiconductor laser is preferably formed from a GaN substrate and emits laser light with a wavelength of 375 to 520 nm. However, the semiconductor laser is not limited to this, and may be formed from a GaAs substrate and emit laser light with a wavelength of 630 to 880 nm.

According to the inventor's research, even if the light incident end face of the optical fiber is obliquely cut or a mask is provided to block the return light, noise due to the return light is still generated for the following reasons. I understand. In other words, a semiconductor laser light source, which consists of a semiconductor laser and an optical fiber into which the laser light emitted from the semiconductor laser is incident, is used by emitting the laser light from the light emitting end face (far end) opposite to the light incident end face of the optical fiber. Although the laser light is supplied to the position, the laser light is also reflected at this light emitting end face, and the reflected light can return to the semiconductor laser side. In general, an optical system such as a condensing lens and a mirror for condensing the laser beam is arranged beyond the light emitting end face. can be traced in reverse to enter the semiconductor laser side as returned light.

In view of this new knowledge, the semiconductor laser light source of the present invention is provided with a transmission loss member between the semiconductor laser and the optical fiber for limiting the transmittance of the laser light traveling toward the optical fiber to 95% or less. be. Therefore, according to the semiconductor laser light source of the present invention, it is possible to attenuate the return light that follows the optical path of the laser light from the semiconductor laser to the optical fiber by the transmission loss member, thereby reducing the occurrence of optical noise in the semiconductor laser. Become.

The lower the transmittance of the transmission loss member, the more remarkable the effect of reducing the occurrence of optical noise. When the semiconductor laser is relatively strong against return light, or when the amount of return light from the far end of the optical fiber or the optical system beyond it is relatively small, the transmittance of the transmission loss member is 90% or less, or 87%. % or less, the optical noise can be reduced to the extent that there is no practical problem. As an example of the case where the amount of light returned from the optical system is relatively small, AR (anti-reflection) coating is applied to glass such as lenses constituting the optical system, and the reflectance there is 0.0. In some cases, it can be suppressed to about 5%.

On the other hand, when the semiconductor laser is relatively weak against return light, or when the amount of return light from the far end of the optical fiber or the optical system beyond it is relatively large, the transmittance of the transmission loss member is 80% or less. Specifically, if it is set to 70%, 60%, 50%, etc., the optical noise can be reduced to about 0.5% rms (root mean square), which is practically acceptable. As an example of the case where the semiconductor laser is relatively weak against the return light, even if the reflectance at the far end of the optical fiber is about 4%, the optical noise will be higher than 0.5% rms if no measures are taken. is reached. Further, as an example of the case where the amount of light returned from the optical system is relatively large, there is a case where the optical system includes a mirror whose reflectance is approximately 100%. It should be noted that the state of occurrence of optical noise in the case where the transmittance of the transmission loss member is the numerical value given above will be specifically described later according to the embodiment.

Further, according to the semiconductor laser light source of the present invention, since the spatial filter is provided for blocking the reflected light of the laser light reflected at the light incident end face of the optical fiber, this reflected light becomes return light and enters the semiconductor laser. can also be prevented. As a result, it is possible to reduce the occurrence of optical noise caused by this return light.

1 is a schematic configuration diagram showing a semiconductor laser light source according to a first embodiment of the present invention; FIG. Graph showing return light attenuation effect in the semiconductor laser light source of FIG. FIG. 2 is a schematic configuration diagram showing a semiconductor laser light source according to a second embodiment of the present invention; Schematic configuration diagram showing an example of a conventional semiconductor laser light source Schematic configuration diagram showing another example of a conventional semiconductor laser light source

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the configuration of a semiconductor laser light source according to a first embodiment of the invention. As shown, this semiconductor laser light source comprises a semiconductor laser 10, a collimating lens 11, a condensing lens 12 and an optical fiber 13 similar to those in the semiconductor laser light source shown in FIG. Also, in FIG. 1, in order to more realistically represent the state of application of the semiconductor laser light source, a condensing lens 14 for condensing the laser light L emitted from the light emitting end face 13d of the optical fiber 13 and a condensing lens 14 further disposed thereon. 1 schematically shows a mirror 15 which

In the configuration of FIG. 1 as well, the condenser lens 12 is arranged with its optical axis deviated from the beam center of the laser beam L in order to increase the optical coupling efficiency between the laser beam L and the optical fiber 13 . A spatial filter 20 made of a light shielding mask is arranged between the condenser lens 12 and the collimator lens 11 . The spatial filter 20 in this embodiment has a different shape from that shown in FIG. An aperture (opening) 20a is provided in this portion. Also in the semiconductor laser light source of this embodiment, the beam cross-sectional shape of the laser light L that has passed through the collimating lens 11 is made into a perfect circle by a prism pair (not shown). The spatial filter 20 is arranged at a position closer to the optical fiber 13 than the prism pair.

Detailed specifications of each part in this semiconductor laser light source will be described below. The optical output of the semiconductor laser 10 is 50 mW, the wavelength of the laser light L is 488 nm in the visible region, and the beam diameter ( ¹ /e2 diameter, hereinafter the same) of the laser light L after being collimated and circularized is 0.0. 6 mm. On the other hand, the diameter of the aperture 20a is 0.5 mm, and the spatial filter 20 is arranged so that the center of the aperture 20a coincides with the beam center of the laser light L. As shown in FIG. In such a configuration, the transmittance of the laser light L through the aperture 20a is 70%. That is, the portion of the spatial filter 20 provided with the aperture 20a functions as a transmission loss member that impairs the transmission of the laser light L. As shown in FIG.

On the other hand, the optical fiber 13 is a polarization preserving (polarization plane preserving) fiber with a core 13a having a diameter of 4 μm. A light incident end face 13c of the optical fiber 13 is obliquely cut and polished so as to form an angle of 8° with respect to a plane perpendicular to the core axis. The light incident end surface 13c is a non-coated surface that is not AR (antireflection) coated.

The operation of the semiconductor laser light source having the above configuration will be described below. A laser beam L emitted from a semiconductor laser 10 is collimated by a collimating lens 11, then condensed by a condensing lens 12 and entered into an optical fiber 13, that is, a core 13a. The laser light L incident on the core 13a propagates through the core 13a, is emitted from the light emitting end surface 13d, and is sent to a predetermined utilization position. In this example, the laser beam L emitted from the light emitting end surface 13d is condensed by the condensing lens 14, and then sent to the laser beam utilizing section including the mirror 15 and the like.

In the above configuration, when the laser light L enters the optical fiber 13 , the laser light L is reflected by the light incident end surface 13 c of the optical fiber 13 . Since the light incident end surface 13c is obliquely cut as described above, the reflected laser light does not follow the optical path of the laser light L incident on the light incident end surface 13c in reverse, but is incident on the condenser lens 12. After that, it can become the return light L1 that travels toward the semiconductor laser 10 . Since the return light L1 reflected from the light incident end face 13c returns 1.6 mm away from the laser light L1 at the position of the spatial filter 20, most of this return light L1 is blocked by the spatial filter 20 made of a light shielding mask. and is prevented from returning to the semiconductor laser 10 . Specifically, with respect to the optical output of the semiconductor laser 10, the return light L1 incident thereon was attenuated to -89 dB. As a result, the optical noise caused by the return light L1 can be reduced to 0.2% rms or less compared to 1% rms (root mean square) when the spatial filter 20 is not provided.

The amount of attenuation of the return light L1 by the spatial filter 20 changes according to the distance between the laser light L and the return light L1. Therefore, the distance between the center of the beam of the laser light L and the center of the return light L1 was varied in five ways, and the above-described attenuation amount was examined in each case. The results are shown in FIG. Specifically, when the distances are 1 mm, 1.2 mm, 1.4 mm, 1.6 mm (values in this embodiment), and 1.8 mm, the attenuation amounts are -35 dB, -50 dB, and -68 dB, respectively. , -89 dB, and -122 dB. The above 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, and 1.8 mm correspond to the oblique cut angles of the light incident end surface 13c of the optical fiber 13 of 5°, 6°, 7°, 8°, and 9°, respectively. The distance is changed by changing .

In the semiconductor laser light source of FIG. 1, not only the return light L1 from the light incident end surface 13c described above, but also the light reflected by the light emitting end surface (far end) 13d of the optical fiber 13 and the condensed light beyond it. Light reflected by an optical system such as the lens 14 and the mirror 15 can also enter the semiconductor laser 10 as return light. If the light emitting end face 13d is uncoated, the amount of reflected light, for example, about 4% of the laser light L incident thereon is generated. These reflected lights are hereinafter collectively referred to as return light L2. This return light L2 can return to the semiconductor laser 10 by following the same optical path as the laser light L emitted from the semiconductor laser 10, and become a noise source that causes the semiconductor laser 10 to generate optical noise.

The portion of the spatial filter 20 where the aperture 20a is provided, that is, the portion that functions as a transmission loss member for the laser light L attenuates the return light L2 that can become a noise source as described above. Specifically, in this example, since the transmittance of the laser beam L at the portion provided with the aperture 20a is 70%, the transmittance of this portion in the round trip is 49%.

Thereby, the optical noise of the semiconductor laser 10 caused by the return light L2 is suppressed. Specifically, in this embodiment, the optical noise caused by the return light L2 could be reduced to 0.2% rms or less compared to 1% rms or more when no transmission loss is given by the aperture 20a. The value of 0.2% rms is equal to the noise of the semiconductor laser 10 alone. That is, the semiconductor laser light source of FIG. 1 can reduce optical noise due to return light without degrading the noise performance inherent in the semiconductor laser 10 . Further, if the spatial filter 20 having the aperture 20a is removed, the return light L1 from the light incident end surface 13c causes large optical noise of several percent.

As described above, in this embodiment, the optical noise caused by the return light L1 from the light incident end face 13c of the optical fiber 13 and the return light L2 from the light exit end face 13d of the optical fiber 13 and the optical system therebelow. It is possible to reduce both optical noise. Further, in this embodiment, since the light incident end surface 13c is a non-coated surface that is not AR-coated, variations in optical noise due to variations in reflectance of the AR-coating can be suppressed. In addition, cost reduction can be achieved by eliminating the need for AR coating.

In the present embodiment, the diameter of the core 13a of the polarization preserving optical fiber 13 is 4 μm, but the same effects as described above can be obtained when the polarization preserving optical fiber 13 having the diameter of the core 13a of 3.5 μm is used. rice field.

Here, reduction of optical noise will be described with respect to five design examples having basically the same configuration as the configuration shown in FIG. 1 but with different specifications. In any of these five design examples, the optical noise is 1.0% rms or more when the spatial filter 20 having the aperture 20a is not used. In any of these five design examples, the oblique cut angle of the light incident end face 13c of the optical fiber 13 with respect to the plane perpendicular to the core axis is a common 8°.
<Design example 1>
The optical output of the semiconductor laser 10: 50 mW, the wavelength of the laser light L: 488 nm, the beam diameter of the laser light L: 0.6 mm, the diameter of the aperture 20a: 0.5 mm, and the transmittance at the aperture 20a: 70%. The optical noise in this case was 0.1% rms or less.
<Design example 2>
The optical output of the semiconductor laser 10: 100 mW, the wavelength of the laser light L: 405 nm, the beam diameter of the laser light L: 0.6 mm, the diameter of the aperture 20a: 0.8 mm, and the transmittance at the aperture 20a: 95%. The optical noise in this case was 0.2% rms or less.
<Design example 3>
The optical output of the semiconductor laser 10: 100 mW, the wavelength of the laser light L: 640 nm, the beam diameter of the laser light L: 0.6 mm, the diameter of the aperture 20a: 0.8 mm, and the transmittance at the aperture 20a: 95%. The optical noise in this case was 0.2% rms or less.
<Design example 4>
The optical output of the semiconductor laser 10: 100 mW, the wavelength of the laser light L: 445 nm, the beam diameter of the laser light L: 0.6 mm, the diameter of the aperture 20a: 0.8 mm, and the transmittance at the aperture 20a: 95%. The optical noise in this case was 0.2% rms or less.
<Design example 5>
The optical output of the semiconductor laser 10: 80 mW, the wavelength of the laser light L: 488 nm, the beam diameter of the laser light L: 0.6 mm, the diameter of the aperture 20a: 0.6 mm, and the transmittance at the aperture 20a: 87%. The optical noise in this case was 0.2% rms or less.

Next, a semiconductor laser light source according to a second embodiment of the present invention will be described with reference to FIG. In this FIG. 3, elements equivalent to those in FIG. 1 described previously are denoted by the same numbers, and description thereof will be omitted unless particularly necessary. The semiconductor laser light source of this embodiment basically differs from the semiconductor laser light source shown in FIG. 1 in that an end cap 16 is fused to the light incident side of the optical fiber 13 . The end cap 16 is an optical fiber having no core structure, and in this example, the light incident end face 16a of the end cap 16 is used as the light incident end face of the optical fiber.

As the semiconductor laser 10 in this semiconductor laser light source, one that is formed from a GaN substrate and emits a laser beam L having a wavelength in the visible region is used. Since the wavelength of this laser light L is short, if there is no end cap 16, the core 13a of the optical fiber 13 may be damaged near the light incident end surface 13c or organic matter may adhere to the light incident end surface 13c when the light power density increases. This causes a decrease in transmittance. Especially when the wavelength of the laser light L is 405 nm, this problem becomes conspicuous. For example, when the optical output exceeds 30 mW and the energization time reaches about 100 hours, the laser output starts to decrease due to the above problem.

Since the end cap 16 has a window structure without a core, the laser light L is incident on the light incident end surface 16a with a relatively large beam diameter. As a result, the light power density of the laser light L at the light incident end surface 16a is lowered, and the above-described damage and adhesion of organic substances are reduced. Therefore, if an optical fiber with an end cap is used, the decrease in laser output can be prevented, and the life quality of the semiconductor laser light source, which is 10000 hours or longer, which is the life of the semiconductor laser 10 itself, can be ensured. Recently, semiconductor lasers with an oscillation wavelength of 405 nm have been developed for higher output, and lasers with outputs of 100 mW, 200 mW, 300 mW, etc. are commercially available. Therefore, when using such a high-output semiconductor laser 10, an optical fiber with an end cap is extremely effective.

In this embodiment, as an example, when the beam diameter of the laser light L is 0.6 mm, the diameter of the aperture 20a is 0.8 mm, and the distance between the beam center of the laser light L and the center of the return light L1 is 1.6 mm, , and a spatial filter 20 having a transmittance of about 80% and about 90% at the apertures 20a. Moreover, the above effects could be similarly obtained in any case where the end cap length (the length of the longest portion of the end cap 16) was 0.3 mm, 0.5 mm, or 0.9 mm.

When the optical fiber 13 with the end cap 16 fused is used, the laser light L is usually focused so that the beam waist position is not on the light incident end face 16a of the end cap 16 but on the light incident end face 13c of the optical fiber 13. . In this case, since the amount of the return light L1 reflected by the light incident end surface 16a is relatively low, the spatial filter 20 can more reliably block the return light.

As the spatial filter 20, specifically, it is possible to use a metal plate having a hole formed by cutting to form the aperture 20a. In addition to this, it is also possible to use a glass substrate formed with a metal thin film as a mask portion and having an aperture 20a formed thereon by etching.

Also, the cut angle of the light incident end surface of the optical fiber may be 4°, 6°, or the like, instead of 8°. If the optical fiber 13 is a polarization preserving fiber, linearly polarized light can be obtained by matching the polarization directions of the semiconductor laser 10 and the optical fiber 13 . At this time, the optical fiber 13 is rotated about its axis to align the polarization directions of the semiconductor laser 10 and the optical fiber 13 . In an optical fiber with an end cap, when the optical fiber is rotated as described above, axial misalignment occurs and the fiber coupling efficiency decreases during polarization adjustment, making it difficult to achieve both fiber coupling efficiency adjustment and polarization adjustment. If the cut angle of the light incident end face of the optical fiber is as small as 4° or 6° , the above-mentioned axial misalignment is reduced, and the effect is obtained that the number of man-hours for adjustment can be reduced.

As described above, it is particularly preferable to apply the end cap 16 when the semiconductor laser 10 is formed from a GaN substrate and emits laser light with a wavelength of 375 to 520 nm. However, the semiconductor laser is not limited to that kind of semiconductor laser, and as in the design example 3 described above, it is possible to apply a laser formed from a GaAs substrate and emitting a laser beam with a wavelength of 630 to 880 nm.

Next, another example of the transmission loss member will be described. In the following description, the numbering shown in FIG. 1 is applied to each element to be taken up.
<Lens holder shape>
Various lenses may be arranged on the optical path of the laser light L traveling from the semiconductor laser 10 toward the optical fiber 13 . The inner diameter of the lens holder that holds such a lens from the periphery can be made smaller than the beam diameter of the laser light L to give the laser light L a transmission loss.

<Thin film transmittance of lens>
A thin film that reduces the transmittance of the laser beam L can be formed on each lens arranged as described above, and the lens can be used as a transmission loss member. For example, the transmittance may be set to 80%, 70%, or the like.

<Design of coupling lens>
When a coupling lens (for example, the condenser lens 12 in FIG. 1) is provided to couple the laser beam L with the optical fiber 13, the focal length of the coupling lens is deviated from the optimum design value to reduce the coupling efficiency, and the lens can have the function of a transmission loss member. For example, when the focal length of the optimum design value is 4 mm, the coupling efficiency can be lowered by setting the focal length to 5 mm, 3 mm, or the like.

<Adjustment of beam position with respect to optical fiber>
For example, by shifting the imaging position of the laser light L onto the core 13a by the condenser lens 12 in FIG. , can give the laser light L a transmission loss.

<Adjustment of imaging position with respect to optical fiber>
When a coupling lens (for example, the condenser lens 12 in FIG. 1) for coupling the laser beam L with the optical fiber 13 is provided, the focal position of the coupling lens is shifted back and forth so that the light incident end surface 13c is positioned at an off-focus position. , adjust the position of the optical fiber 13 . As a result, the coupling efficiency between the laser light L and the optical fiber 13 can be reduced, and the laser light L can be given transmission loss.

<Attenuator>
By arranging an attenuator with a transmittance lower than 95% in the optical path of the laser light L, transmission loss can be given. More specifically, for example, members having a transmittance of 90%, 80%, 70%, 60%, and 50% formed by forming a metal thin film or a dielectric multilayer film on a glass plate are prepared as attenuators and selected according to the application. do. If priority is given to output, an attenuator with a transmittance of 90% is selected, and if priority is given to noise reduction, an attenuator with a transmittance of 50% is selected to assemble the semiconductor laser light source.

REFERENCE SIGNS LIST 10 semiconductor laser 11 collimating lens 12, 14 condensing lens 13 optical fiber 13c light incident end face of optical fiber 13d light emitting end face of optical fiber 15 mirror 16 end cap 20 spatial filter 20a aperture

Claims (5)

a semiconductor laser;
a condensing optical system for converging the laser light emitted from the semiconductor laser, the condensing optical system being arranged in a state in which the optical axis is separated from the beam center of the laser light;
an optical fiber for propagating the laser light that has passed through the condensing optical system, the optical fiber having a light incident end surface on which the laser light is incident that is obliquely cut with respect to the optical axis of the condensing optical system;
In a semiconductor laser light source consisting of
a spatial filter for blocking the reflected light of the laser light reflected at the light incident end surface of the optical fiber is provided between the condensing optical system and the semiconductor laser ;
A transmission loss member is provided between the semiconductor laser and the optical fiber for limiting the transmittance of the laser beam traveling toward the optical fiber to 95% or less ,
The direction of the oblique cut of the light incident end face is the direction in which the laser beam incident radially outward from the light collecting optical system is reflected radially outward on the reflection side with the fiber axis interposed therebetween,
An end cap is fused to the end of the optical fiber on the light incident side ,
A semiconductor laser light source characterized by: 2. The semiconductor laser light source according to claim 1, wherein said light incident end surface is a non-coated surface. 3. The semiconductor laser light source according to claim 1, wherein said end cap has a length of 0.3 mm to 0.9 mm . 4. The semiconductor laser light source according to claim 1, wherein said semiconductor laser is formed from a GaN substrate and emits laser light with a wavelength of 375-520 nm. 4. The semiconductor laser light source according to claim 1, wherein said semiconductor laser is formed from a GaAs substrate and emits laser light with a wavelength of 630-880 nm.

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