JP7617632B2 - Laser Sensor - Google Patents

Description

The present invention relates to a laser device and a manufacturing method thereof.

Solid-state lasers are usually constructed by placing a laser medium inside a resonator made of two precisely parallel mirrors using a mechanical mechanism, and combining a semiconductor light source or laser light source as an excitation source (see Patent Document 1, etc.). This resulted in a large device and required an even larger power supply.

JP 2016-15476 A

Conventional solid-state lasers have not yet been miniaturized to the extent that they can be used in small electronic devices. If solid-state lasers could be miniaturized, they could be installed in wearable devices and smartphones, enabling their use in devices where solid-state lasers could not be used before.

The present invention aims to provide a laser device that can be made smaller than conventional devices.

A laser device according to a first aspect of the present invention includes:
a resonator having a plate-like laser medium body including a laser medium and a reflective film formed on the front and back surfaces of the plate-like laser medium body;
a semiconductor laser element arranged so that light emitted from an emission surface is incident on the laser medium of the resonator;
a cooling member for cooling heat generated in the resonator and the semiconductor laser element;
The present invention is characterized in that it is integrally provided with the above.

The semiconductor laser element may be arranged so that the light emitted from the emission surface is incident on the end face of the laser medium of the resonator. In this case, the emission surface of the semiconductor laser element and the end face of the laser medium may be in contact with each other, or may be bonded together. The emission surface of the semiconductor laser element and the end face of the laser medium may be arranged adjacent to each other with an optical element or atmosphere therebetween. The semiconductor laser element may be arranged so that the light emitted from the emission surface is incident on the laser medium via a reflecting surface formed on the front or back surface of the pair of laser media.

By adopting such a configuration, it is possible to miniaturize the laser device.

The laser medium may also have multiple regions made of the first medium and multiple regions made of the second medium. The medium may also be three or more types. With this configuration, a small laser device can be realized that can output multiple wavelengths of laser light corresponding to each medium.

In this embodiment, the laser medium may include a wavelength-tunable laser medium, and the resonator may further include a wavelength selection element between the laser medium and the reflecting film. With this configuration, a wavelength-tunable laser device can be realized.

In this embodiment, the laser medium may have a transparent region made of a transparent material, and the reflective film formed on the surface of the laser medium opposite the emission side may be a wavelength-selective reflective film that reflects light of a wavelength (frequency) oscillated by the resonator and transmits at least a portion of the other wavelengths. Furthermore, the laser device may include a photodetector disposed in contact with the wavelength-selective reflective film for detecting light that has transmitted through the wavelength-selective reflective film.

A laser device with this configuration can simultaneously irradiate laser light and measure the incident light. This makes it ideal for use in measurements such as Raman measurements, which detect light of a different wavelength from the irradiated laser light.

A second aspect of the present invention is a method for manufacturing a laser device, comprising:
A first step of disposing a semiconductor laser element and the laser medium in a plate-like laser medium such that an emission surface of the semiconductor laser element is in contact with the plate-like laser medium or is adjacent to the plate-like laser medium via an optical element or atmosphere;
a second step of forming a reflective film on a first surface of the laser medium and a second surface opposite to the first surface;
a third step of providing a cooling member for cooling heat generated in the laser medium and the semiconductor laser element on at least one of the reflecting surfaces and the semiconductor laser element after the first step and the second step;
The present invention is characterized by comprising:

In this embodiment,
The method further includes a step of preparing the laser medium, the step including:
A step of alternately stacking laser media and transparent materials to generate a first stack;
cutting the first laminate into a plurality of portions along a plane parallel to a lamination direction;
rearranging the cut portions to generate a second stack;
cutting the second laminate along a plane parallel to a lamination direction to obtain a plurality of the laser media;
may include:

The present invention makes it possible to provide a compact laser device.

1 is a diagram showing a laser device according to a first embodiment; FIG. 13 is a diagram showing a laser device according to a second embodiment. 6A to 6C are diagrams illustrating a method for manufacturing a laser crystal according to a second embodiment. 6A to 6C are diagrams illustrating a method for manufacturing a laser crystal according to a second embodiment. FIG. 13 is a diagram showing a laser device according to a third embodiment. FIG. 13 is a diagram showing a laser sensor according to a fourth embodiment. FIG. 1 is a diagram showing the configuration of a Raman measurement apparatus according to a first embodiment. FIG. 4 is a diagram showing the measurement results obtained by the Raman measurement apparatus according to the first embodiment.

The following describes the embodiments of the present invention with reference to the drawings, but the present invention is not limited to these. The components of each embodiment described below can be combined as appropriate.

<Embodiment 1>
The present embodiment is directed to a small solid-state laser device 1 that can also be used for wearable applications. Figures 1A and 1B are a side view and a plan view of the laser device 1 according to the present embodiment.

As shown in the figure, the laser device 1 according to this embodiment is composed of a semiconductor laser element (LD element) 10, a resonator 20, and a heat sink 40. The resonator 20 is composed of a laser medium 21 and reflective films 31, 32 formed on the upper and lower surfaces thereof.

The LD element 10 has a structure in which an N-type semiconductor layer, a light emitting layer (P-N junction active layer), and a P-type semiconductor layer are laminated. The material of the active layer can be selected from any material such as AlGaAs, InGaAsP, AlGaInP, and GaN depending on the application. The emission surface of the LD element 10 is bonded to the end surface of the laser medium 21. In this disclosure, the end surface of the laser medium 21 means the surface of the laser medium 21 on which the reflective films 31 and 32 are not formed. The end surface of the laser medium 21 can also be said to be the surface of the laser medium 21 that is perpendicular to the reflective films 31 and 32. The emission surface of the LD element 10 may be bonded to the reflective film 31 or 32 of the laser medium 21.

The laser medium (gain medium) 21 is a host (crystal or glass) doped with an active species that acts as a laser. Examples of crystals include YAG, sapphire, ruby, and alexandrite. Examples of active species that act as a laser include trivalent ions (Cr3 ⁺ , Nd3 ⁺ , Ti3 ^+, etc.).

Reflective films 31, 32 are formed on the emission surface (transmission surface) and rear end surface (reflection surface) of the laser medium 21, and the laser medium 21 and the reflective films 31, 32 function as a resonator 20 that oscillates light of a specific wavelength among the incident light from the LD element 10. That is, the light emitted from the laser medium 21 excited by the laser light from the LD element 10 travels back and forth between the reflective films 31, 32, and the light of the specific wavelength is oscillated and emitted from the emission surface.

The heat sink 40 is a cooling member that dissipates heat generated in the LD element 10 and the resonator 20, thereby cooling the LD element 10 and the resonator 20.

A method for manufacturing the laser device 1 according to this embodiment will be described. First, a plate-shaped laser medium 21 and LD element 10 are prepared, and the emission surface of the LD element 10 is bonded to the end surface of the laser medium 21. Then, reflective films 31 and 32 are formed on both sides of the laser medium 21, for example, by a dielectric film formation technique, to obtain the resonator 20. Then, the entire LD element 10 and resonator 20 are bonded to a heat sink 40 to obtain the laser device 1.

In this way, the laser device 1 can be miniaturized by constructing the laser device 1 as an integrated unit of the LD element 10, the resonator 20, and the heat sink 40. By bonding the LD element 10 to the laser medium 21, a small laser device 1 can be obtained. In addition, miniaturization can be achieved by simultaneously cooling the LD element 10 and the resonator 20 with one heat sink 40. The LD element 10 is about 10 to 100 μm x 100 μm in size, and the laser medium 21 is about 1 mm x 1 mm x several hundred μm in size, so the overall size of the laser device 1 is about 1 mm square. When miniaturization is achieved in this way, it can be installed in a portable information terminal or a wristwatch (including a wristwatch-type portable information terminal).

In this embodiment, the emission surface of the LD element 10 and the end face of the laser medium 21 are bonded to each other, but other configurations may be used as long as the light emitted from the emission surface of the LD element 10 is incident on the end face of the laser medium 21. For example, the emission surface of the LD element 10 and the end face of the laser medium 21 may be arranged so as to simply contact each other without being bonded. The emission surface of the LD element 10 and the end face of the laser medium 21 may be arranged adjacent to each other with an optical element or atmosphere therebetween. When manufacturing such a laser device 1, instead of bonding the emission surface of the LD element 10 to the end face of the laser medium 21, the LD element 10 and the laser medium 21 may be arranged so that the emission surface of the LD element 10 and the end face of the laser medium 21 are in contact with each other or adjacent to each other with an optical element or atmosphere therebetween. Examples of the optical element include a substrate such as sapphire or quartz, a lens, a nonlinear optical crystal, and a saturable absorber. The atmosphere may be air or a vacuum.

<Embodiment 2>
This embodiment is a laser device 2 that outputs multi-wavelength laser light. Figures 2A and 2B are a side view and a plan view of the laser device 2 according to this embodiment. As shown in the figures, a laser medium body 21 of this embodiment is configured to include a first laser medium 22, a second laser medium 23, and a transparent material 24. The first laser medium 22 and the second laser medium 23 each have a gain at a different wavelength. Note that the heat sink 40 is omitted in Figure 2.

The laser device 2 in this embodiment is capable of outputting laser light of a first wavelength from a region consisting of a first laser medium 22 and outputting laser light of a second wavelength from a region consisting of a second laser medium 23.

The manufacturing method of the laser crystal according to this embodiment will be described with reference to Figs. 3 and 4. As shown in Fig. 3A, a transparent material 24 is sandwiched between the first laser medium 22 and the second laser medium 23, and a plurality of the first laser medium 22 and the second laser medium 23 are alternately stacked and fused to obtain a laminate 26. As shown in Fig. 3B, the laminate 26 is cut into a plurality of flat parts at a cross section 25 parallel to the stacking direction. As shown in Fig. 3C, the cut parts are rearranged and stacked and fused again to obtain a laminate 28. As shown in Fig. 4A, the laminate 28 is cut into a plurality of flat parts at a cross section 27 parallel to the stacking direction. As a result, a laser crystal body 21 having a plurality of local regions of the first laser medium 22, the second laser medium 23, and the transparent material 24 as shown in Fig. 4B is obtained.

Note that, although an example using two types of laser media is shown here, three or more types of laser media may be used. Also, although transparent material 24 is used here, transparent material 24 does not have to be used. The arrangement of each region shown in Figure 2B etc. is merely an example, and the arrangement method may be arbitrary.

<Embodiment 3>
This embodiment is a laser device 3 capable of varying the wavelength of the laser light to be output. Fig. 5 is a side view of the laser device 3 according to this embodiment. The basic configuration is the same as that of the first embodiment, but is different in that a wavelength selection element 29 is provided between the emission surface of the laser medium 21 and the reflective film 31. The wavelength selection element 29 can be, for example, a liquid crystal wavelength tunable filter. The wavelength of the output laser light can be controlled by adjusting the voltage applied to the liquid crystal wavelength tunable filter. The laser medium used is a wavelength tunable solid-state laser medium or a solid-state laser medium that oscillates in a wide wavelength range.

According to this embodiment, a small laser device can be realized that can change the wavelength of the output laser light.

<Embodiment 4>
This embodiment is a laser sensor that outputs and detects laser light. Here, a laser sensor for measuring CARS light (coherent anti-Stokes Maran scattered light) will be described.

A known method for non-invasively measuring blood glucose levels (blood glucose concentration) involves irradiating two wavelengths of laser light into the human body and measuring the CARS light generated by the molecular vibrations of glucose in the blood.

There is a demand for wearable biosensors that can monitor blood glucose levels all day for health management, but currently there are no biosensors small enough to be worn all day.

Figure 6 is a side view showing the configuration of the laser sensor (biosensor) 4 according to this embodiment. The laser sensor 4 according to this embodiment is composed of an LD element 10, a laser medium 21, reflective films 31, 32 formed on the upper and lower surfaces of the laser medium 21, a heat sink 40, and a light detection element 50. Note that the heat sink 40 is omitted from Figure 6.

As in the second embodiment, the laser medium 21 is composed of a first laser medium 22, a second laser medium 23, and a transparent material 24. The oscillation wavelengths of the first laser medium 22 and the second laser medium 23 are equal to the excitation wavelength of the CARS light.

In this embodiment, the reflective film 32 provided on the rear end face is a wavelength-selective reflective film formed by a two-wavelength coating, which reflects light of the wavelength (excitation wavelength) of the laser light output by the laser sensor 4 and transmits CARS light generated from the subject. The light emitted from the first laser medium 22 and the second laser medium 23 excited by the laser light from the LD element 10 travels back and forth between the reflective films 31 and 32, and the light of two wavelengths for exciting the CARS light is laser-oscillated and emitted from the emission surface.

The light detection element 50 is provided in contact with the wavelength-selective reflective film 32 and detects the CARS light that has passed through the wavelength-selective reflective film 32. A photodiode or a phototransistor can be used as the light detection element 50.

When the laser sensor 4 according to this embodiment is used as a biosensor, it is used as follows. First, the emission surface is brought into contact with a human body (subject), and the two wavelengths of excitation laser light irradiated from the emission surface are made incident on the human body. CARS light (scattered light) generated by irradiation with the excitation laser light passes through the transparent material 24 and the wavelength-selective reflective film 32 of the laser medium 21, and is detected by the light detection element 50.

In this way, by using two laser media in the laser medium 21, laser light of two wavelengths can be incident on the human body. In addition, by including a transparent material in the laser medium 21, CARS light generated by molecular vibration of glucose in the blood can be detected by the photodetector 50 without using a lens (optical system) or the like.

Because the laser sensor 4 is small (approximately 1 mm per side), it can be mounted on a wearable device such as a wristwatch, enabling 24-hour measurement. Thus, according to this embodiment, it is possible to realize a wearable device that uses a laser to measure blood glucose levels non-invasively and instantly. In addition, by adjusting the wavelength and calculation method, it is also possible to measure other biological information such as lipids and oxygen saturation.

Example 1
An embodiment of a Raman measurement device for measuring a Raman spectrum will be described with reference to the drawings.

7 is a diagram showing the configuration of a Raman measurement device 100 according to this embodiment. The Raman measurement device 100 is configured by mounting a semiconductor laser element (LD element) 101, a resonator 102, a nonlinear optical crystal 105, a separation mirror 106, and a detector 107 on a substrate 108 that also serves as a heat sink. The resonator 102 has a structure in which a laser crystal 103 is sandwiched between two mirror films 104. In this embodiment, the laser crystal 103 is YAG. A laser beam with a wavelength of 808 nm is emitted from the LD element 101, and this laser beam is input to the resonator 102 via the mirror film 104. The resonator 102 oscillates and emits a laser beam with a wavelength of 1064 nm. In this embodiment, the nonlinear optical crystal 105 is a KTP (KTiPO ₄ ) crystal, and generates a second harmonic (wavelength 532 nm). The separation mirror 106 transmits only the second harmonic wave having a wavelength of 532 nm.

Laser light 110 output from the biosensor is irradiated onto sample S (living organism) via optical fiber 109 with a diameter of 100 μm. Raman scattered light 111 generated in sample S is input to detector 107 via optical fiber 109. Detector 107 is equipped with a wavelength selection filter, a spectrometer, and a CCD detector, and detects Raman shift signals in a predetermined wavenumber range.

Figure 8 shows the results of measuring the Raman shift of an ethanol solution using the Raman measurement device 100 of this embodiment. As shown in the figure, by acquiring a laser emitted from a micro-area with a radius of about 100 μm and a signal obtained from a similar micro-area with a radius of about 100 μm, a Raman spectrum characteristic of the ethanol solution can be obtained by the Raman measurement device 100 of this embodiment. The present invention aims to stack these micro-areas.

1, 2, 3: Laser output device 4: Laser sensor (biosensor)
10: Semiconductor laser element (LD element) 20: Resonator 21: Laser medium 22: First medium 23: Second medium 24: Transparent material 31, 32: Reflection film 40: Heat sink 50: Photodetector element

Claims (4)

a resonator having a plate-like laser medium body including a laser medium and a reflective film formed on the front and back surfaces of the plate-like laser medium body;
a semiconductor laser element arranged so that light emitted from an emission surface is incident on an end surface of the laser medium of the resonator ;
As a whole ,
the laser medium has a plurality of regions made of a first medium, a plurality of regions made of a second medium, and a plurality of transparent regions made of a transparent material;
the first medium and the second medium have gains at different wavelengths that excite CARS light in a human body on which the excitation laser light from the laser medium is incident,
a reflective film formed on a surface of the laser medium opposite to the emission side thereof is a wavelength-selective reflective film that reflects the excitation light oscillated by the resonator and transmits the CARS light,
a photodetector disposed in contact with the wavelength-selective reflective film for detecting the CARS light transmitted through the transparent region and the wavelength-selective reflective film;
Laser sensor . the emission surface of the semiconductor laser element is in contact with an end face of the laser medium or is adjacent to the end face via an optical element or atmosphere;
The laser sensor according to claim 1 . The CARS light is generated by molecular vibration of glucose in the blood of the human body.
3. The laser sensor according to claim 1 or 2. Further comprising a cooling member for cooling heat generated in the resonator and the semiconductor laser element.
The laser sensor according to claim 1 .

Images