JP2024155050A - Optical resonator and external cavity laser devices - Google Patents

Abstract

To provide an optical resonator and an external resonator type laser device capable of easily adjusting an angle of a reflector while maintaining airtightness of detection target gas.SOLUTION: The optical resonator comprises: a first reflector 230 receiving a laser beam emitted from a laser element 11; a second reflector 260 provided opposite the first reflector 230 and feeding back the reflected beam to the laser element 11; a cylindrical body 21 on both ends of which the first reflector 230 and the second reflector 260 are arranged; a gas introduction port 220 for introducing gas to the cylindrical body 21 and a gas discharge port 250 for discharging the gas from the cylindrical body 21; a first movable member 23 to which the first reflector 230 is attached; a second movable member 26 to which the second reflector 260 is attached; and alignment mechanisms 241-243, 271-273 adjusting the inclination of the first and second movable members 23, 26. The cylindrical body 21 is hermetically held by the first and second movable members 23, 26 via a pair of elastic members 28, 29.SELECTED DRAWING: Figure 2

Description

The present invention relates to an optical resonator and an external cavity type laser device, and in particular to an optical resonator and an external cavity type laser device for detecting a specific gas.

Conventionally, laser devices using optical resonators are known. For example, Patent Document 1 discloses an external resonator type laser device that has a first resonator in which the laser light output from the laser element is repeatedly reflected between the end face of the laser element and a first reflector, and a second resonator in which the laser light that has passed through the first reflector is repeatedly reflected between the first reflector and a second reflector, and that analyzes the analytical sample by introducing an analytical sample into the second resonator, applying the resonated laser light to the analytical sample, and detecting the optical interaction that occurs.

Patent No. 3878257

In recent years, there has been a demand for small gas detection devices capable of detecting even trace amounts of gas components, for applications such as quality control of hydrogen gas at hydrogen stations. In such gas detection devices, by using an external resonator, the laser light can be reflected back and forth in the space between two reflectors into which the gas to be detected is introduced, and the effective optical path length can be made longer than the actual optical path length, making it possible to detect trace amounts of gas despite the small size. However, such gas detection devices require delicate adjustments when installed, and if used for a long period of time, the angles of the reflectors at both ends that make up the external resonator may shift, resulting in inappropriate resonance of the laser light and the inability to properly detect the gas to be detected.

The present invention aims to provide an optical resonator and an external resonator type laser device that can easily adjust the position, including the angle, of the reflector while maintaining the airtightness of the gas to be detected.

The optical resonator of the present invention comprises a first reflector onto which laser light emitted from a laser element is incident, a second reflector disposed opposite the first reflector and feeding back reflected light to the laser element, a cylindrical body having the first reflector and the second reflector disposed at both ends, a gas inlet for introducing gas into the cylindrical body and a gas outlet for discharging gas within the cylindrical body, a first movable member to which the first reflector is attached, a second movable member to which the second reflector is attached, and an alignment mechanism for adjusting the inclination of the first and second movable members, and the cylindrical body is airtightly clamped by the first and second movable members via a pair of elastic members.
In the above optical resonator, the alignment mechanism can be configured to have a first tilt adjustment mechanism that adjusts the tilt of the first movable member and a second tilt adjustment mechanism that adjusts the tilt of the second movable member, a first end member having the first tilt adjustment mechanism on the end side of the first movable member, and a second end member having the second tilt adjustment mechanism on the end side of the second movable member.
In the above optical resonator, the first tilt adjustment mechanism can be configured to include a plurality of first pressing members that adjust the tilt of the first reflector by pressing the first movable member in a direction along the optical axis of the laser light, and the second tilt adjustment mechanism can be configured to include a plurality of second pressing members that adjust the tilt of the second reflector by pressing the second movable member in a direction along the optical axis of the laser light.
In the above optical resonator, a first protective member having a harderness than the first pressing members is arranged on a surface of the first movable member that is pressed by the plurality of first pressing members, and a second protective member having a harderness than the second pressing members is arranged on a surface of the second movable member that is pressed by the plurality of second pressing members.
In the above optical resonator, the first tilt adjustment mechanism can be configured to include a plurality of first adjustment members that adjust the insertion positions of the plurality of first pressing members, and a first locking mechanism that fixes the insertion positions of the plurality of first adjustment members, and the second tilt adjustment mechanism can be configured to include a plurality of second adjustment members that adjust the insertion positions of the plurality of second pressing members, and a second locking mechanism that fixes the insertion positions of the plurality of second adjustment members.
In the above optical resonator, the alignment mechanism can be configured to have a first position adjustment mechanism that adjusts the position of the first movable member in a direction perpendicular to the optical axis, and a second position adjustment mechanism that adjusts the position of the second movable member in a direction perpendicular to the optical axis, the first position adjustment mechanism comprising a third pressing member that adjusts the position of the first reflector in the direction perpendicular to the optical axis by pressing the first movable member in the direction perpendicular to the optical axis, and the second position adjustment mechanism comprising a fourth pressing member that adjusts the position of the second reflector in the direction perpendicular to the optical axis by pressing the second movable member in the direction perpendicular to the optical axis.
The external resonator type laser device according to a first aspect of the present invention is an external resonator type laser device having the above-mentioned optical resonator, a laser element that emits laser light that is incident on the optical resonator, and a detection device that detects light of a specific wavelength generated by the action of gas introduced into the optical resonator and the laser light, and has an optical system between the optical resonator and the detection device that focuses the light of the specific wavelength that has passed through the cylindrical body and makes it incident on the detection device.
An external cavity type laser device according to a second aspect of the present invention comprises the above-mentioned optical resonator, a laser element having an anti-reflection layer formed on one end face and a total reflection layer formed on the other end face, and a wavelength-selective filter provided between the laser element and the optical resonator.

The present invention provides an optical resonator and an external resonator type laser device that can easily adjust the angle of the reflector while maintaining the airtightness of the gas to be detected.

1 is a configuration diagram showing an external cavity laser device according to a first embodiment. 1 is a side cross-sectional view of an optical resonator according to a first embodiment. FIG. 2 is an enlarged cross-sectional side view of the optical resonator according to the first embodiment. FIG. 2A is a front view of the optical resonator according to the first embodiment, and FIG. 2B is a rear view of the optical resonator according to the first embodiment. 3 is a front cross-sectional view taken along line VV in FIG. 2. 4 is a graph showing the results of detecting an air component in the external cavity laser device according to the first embodiment. 5 is a graph showing the results of detecting oxygen gas mixed into hydrogen gas and ammonia gas mixed into argon gas in the external cavity laser device according to the first embodiment. FIG. 11 is a configuration diagram showing an external cavity laser device according to a second embodiment. FIG. 11 is a plan cross-sectional view of an external cavity laser device according to a third embodiment. FIG. 11 is a side cross-sectional view of an external cavity laser device according to a third embodiment. FIG. 13 is a plan cross-sectional view of an optical resonator according to a third embodiment. FIG. 13A is a front view of the optical resonator according to the third embodiment, and FIG. 13B is a rear view of the optical resonator according to the third embodiment.

Below, we will explain the embodiments of the optical resonator and external cavity type laser device according to the present invention with reference to the drawings.

First Embodiment
1 is a configuration diagram showing an external resonator type laser device 1 according to the first embodiment. As shown in FIG. 1, the external resonator type laser device 1 according to the present embodiment mainly comprises a semiconductor laser element 11, an optical resonator 20, and a plurality of detection devices 30. The external resonator type laser device 1 emits laser light from the semiconductor laser element 11, introduces the emitted laser light into the optical resonator 20, and then irradiates the resonated laser light onto a gas introduced into a measurement target space S in the optical resonator 20 while resonating the laser light in the optical resonator 20. The detection device 30 detects light of a specific wavelength (Raman scattered light in this embodiment) generated by collision of the laser light with the gas.

In addition, in the external cavity laser device 1 according to the present embodiment, gases including, for example, SO ₂ , CO ₂ , O ₂ , CO, N ₂ , H ₂ S, CH ₄ , NH ₃ , and H ₂ can be introduced and irradiated with laser light. In addition, the present invention can be applied not only to irradiating the introduced gas with laser light, but also to a gas detection device that detects a specific gas by detecting light of a specific wavelength generated by irradiating the introduced gas with laser light, a gas measurement device that measures the concentration of a gas based on the intensity of the detected light of a specific wavelength, a gas identification device that identifies the type of gas present in the measurement target space, and a monitoring device that monitors whether the gas to be detected exists in the measurement target space. Each component of the external cavity laser device 1 according to the first embodiment will be described below.

The semiconductor laser element 11 emits laser light in the blue-violet wavelength range (for example, around 416 nm) toward the optical resonator 20. For example, commercially available GaN-based semiconductor lasers or GaInN-based semiconductor lasers can be used as the semiconductor laser element 11 in the blue-violet wavelength range. In addition, the semiconductor laser element 11 according to this embodiment has a reflective coating applied to the end face 111 located on the opposite side to the laser light emission side (optical resonator 20 side) to reflect the laser light, while the end face 112 located on the laser light emission side (optical resonator 20 side) has a coating applied to prevent reflection of the laser light. The laser light output from the semiconductor laser element 11 is collimated or converged by the collimating lens 12, and then introduced into the optical resonator 20 via the bandpass filter 13. The bandpass filter 13 has the function of transmitting laser light in the desired blue-violet wavelength range and blocking laser light of other wavelengths.

Figure 2 is a side cross-sectional view of the optical resonator 20 according to the first embodiment, and Figure 3 is a partially enlarged view of the side cross-section of the optical resonator 20. Note that Figures 2 and 3 are side cross-sectional views taken along line II-II in Figure 1. Also, Figure 4(A) is a front view of the optical resonator 20 according to the first embodiment, and Figure 4(B) is a rear view of the optical resonator 20 according to the first embodiment. Furthermore, Figure 5 is a front cross-sectional view taken along line V-V in Figure 2.

As shown in FIG. 2, the optical resonator 20 according to this embodiment is broadly composed of seven parts. Specifically, the optical resonator 20 has a cylindrical body 21, a first annular member 22, a first movable member 23, a first end member 24, a second annular member 25, a second movable member 26, and a second end member 27. In this embodiment, the optical resonator 20 also has four O-rings 28, 29, 210, and 211.

1 and 2, the laser light emitted from the semiconductor laser element 11 passes through the through holes 240, 231 provided in the first end member 24 and the first movable member 23, and reaches the first reflector 230. Most of the laser light that reaches the first reflector 230 is reflected by the first reflector 230, and travels back and forth between the first reflector 230 and the end face 111 of the semiconductor laser element 11, resonating. Therefore, as shown in FIG. 1, in this embodiment, the space between the first reflector 230 and the end face 111 of the semiconductor laser element 11 functions as a first resonator. In addition, a part of the laser light that has reached the first reflector 230 from the semiconductor laser element 11 passes through the first reflector 230, travels through the internal space S inside the cylinder 21, and after reaching the second reflector 260, most of the laser light is reflected by the second reflector 260 and resonates by traveling back and forth between the first reflector 230 and the second reflector 260. Therefore, as shown in FIG. 1, in this embodiment, the space between the first reflector 230 and the second reflector 260 functions as a second resonator. In particular, in this embodiment, by strengthening the laser light in the first and second resonators, the intensity of the laser light in the second resonator can be strengthened to an intensity of 2000 times or more (for example, exceeding 100 W) compared to the intensity of the laser light emitted from the semiconductor laser element 11. A portion of the laser light that reaches the second reflector 260 passes through the second reflector 260 and through the through holes 261 and 270 provided in the second movable member 26 and the second end member 27, and is then absorbed by the beam diffuser 40. Each of the components that make up the optical resonator 20 will be described below.

The cylinder 21 is a cylindrical member disposed between the first reflector 230 and the second reflector 260, and the hollow interior constitutes a gas cell. In the internal space S of the cylinder 21, the laser light is repeatedly reflected by the first reflector 230 and the second reflector 260, and the laser light resonates. As shown in FIG. 2, the internal space S of the cylinder 21 is connected to the gas inlet 220 of the first annular member 22, and the detection target gas introduced from the gas inlet 220 can flow. In particular, in the cylinder 21, the laser light reciprocates in the longitudinal direction of the cylinder 21, and the detection target gas flows, so that the laser light and the detection target gas have more opportunities to collide, making it easier to detect Raman scattered light generated by the collision of the laser light with the detection target gas. In addition, the cylinder 21 is mainly made of glass, and the Raman scattered light generated by the collision of the laser light with the detection target gas can be detected by the detection device 30 disposed on the side of the cylinder 21. The cylindrical body 21 can also be configured to have a low-pass filter on the inner or outer side. The cylindrical body 21 is tightly sandwiched between the first annular member 22 and the second annular member 25 via the elastic O-rings 210 and 211, preventing the detection target gas from leaking out from between the cylindrical body 21 and the first annular member 22 and the second annular member 25, ensuring airtightness.

The first annular member 22 is a metal member formed in an annular shape so that the first movable member 23 can be accommodated therein. As shown in FIG. 3, the first annular member 22 has a first annular portion 221 whose inner diameter is larger than the outer diameter of the cylindrical body 21, and a second annular portion 222 whose inner diameter is smaller than the first annular portion 221 and smaller than the outer diameter of the cylindrical body 21. Furthermore, the first annular member 22 has a gas inlet 220, and it is possible to introduce a gas containing the detection target gas from the gas inlet 220 into the cylindrical body 21. Similarly to the first annular member 22, the second annular member 25 is a metal member formed in an annular shape so that the second movable member 26 can be accommodated therein. As shown in FIG. 3, the second annular member 25 also has a first annular portion 251 whose inner diameter is larger than the outer diameter of the cylindrical body 21, and a second annular portion 252 whose inner diameter is smaller than the first annular portion 251 and smaller than the outer diameter of the cylindrical body 21. Furthermore, the second annular member 25 has a gas exhaust port 250, and gas in the cylindrical body 21 can be exhausted from the gas exhaust port 250. In this embodiment, both the gas inlet 220 and the gas exhaust port 250 are connected to the cylindrical body 21, and the gas introduced from the gas inlet 220 of the first annular member 22 flows through the cylindrical body 21 and is exhausted from the gas exhaust port 250 of the second annular member 25.

The first movable member 23 has a main body portion 232 and a flange portion 233, and the first movable member 23 can be fitted to the first annular member 22 by inserting the first movable member 23 into the ring of the first annular member 22 from the main body portion 232 side. Specifically, as shown in FIG. 3, the inner diameter of the first annular portion 221 of the first annular member 22 is configured to be larger than the outer diameter of the flange portion 233 of the first movable member 23, and the inner diameter of the second annular portion 222 of the first annular member 22 is configured to be larger than the outer diameter of the main body portion 232 of the first movable member 23. Therefore, the first movable member 23 is held in the first annular member 22 with a certain gap between the flange portion 233 and the first annular portion 221 and between the main body portion 232 and the second annular portion 222. Particularly, in this embodiment, the outer diameter of the flange portion 233 of the first movable member 23 is larger than the outer diameter of the main body portion 232, and a step surface 234 is formed between the flange portion 233 and the main body portion 232, and the outer diameter of the first annular portion 221 of the first annular member 22 is larger than the outer diameter of the second annular portion 222, and a step surface 223 is also formed between the outer diameters of the first annular portion 221 and the second annular portion 222. The step surface 234 of the first movable member 23 and the step surface 223 of the first annular member 22 face each other, and an O-ring 28, which is an elastic member, is disposed between the facing step surface 234 and step surface 223. In this embodiment, the first movable member 23 presses the O-ring 28 by an alignment adjustment mechanism described later, so that the O-ring 28 is sandwiched in a compressed state between the step surface 234 of the first movable member 23 and the step surface 223 of the first annular member 22, thereby ensuring the airtightness of the internal space S of the optical resonator 20. Similarly, the second movable member 26 also has a main body portion 262 and a flange portion 263, and can be fitted to the second annular member 25 by inserting the second movable member 26 into the ring of the second annular member 25 from the main body portion 262 side. The second movable member 26 is also held in the second annular member 25 with a certain gap between the flange portion 263 and the first annular portion 251 of the second annular member 25 and between the main body portion 262 and the second annular portion 252 of the second annular member 25. Furthermore, an O-ring 29 is disposed between the step surface 264 of the second movable member 26 and the step surface 253 of the second annular member 25, and the O-ring 29, which is an elastic member, is clamped in a compressed state between the step surface 264 and the step surface 253, thereby ensuring the airtightness of the optical resonator 20.

In the first movable member 23, the first reflector 230 is attached to the main body 232. Specifically, the main body 232 of the first movable member 23 has a recess 235, and the first reflector 230 is fitted into the recess 235. In this embodiment, a pair of O-rings are installed along the outer periphery of the first reflector 230 on both sides of the first reflector 230 so as to sandwich the first reflector 230 from both sides in the recess 235. In the first movable member 23, a through hole 231 communicating with the recess 235 is formed, and the pair of O-rings are arranged without gaps while sandwiching the first reflector 230, so that the O-ring and the first reflector 230 maintain airtightness in the optical resonator 20. Similarly, in the second movable member 26, the second reflector 260 is fitted into the recess 265 of the main body 262. In addition, in the second movable member 26, a pair of O-rings are installed along the outer periphery of the second reflector 260 on both sides of the second reflector 260 in the recess 265 so as to sandwich the second reflector 260 from both sides, thereby fixing the second reflector 260 and maintaining the airtightness of the optical resonator 20.

In this embodiment, the first reflector 230 and the second reflector 260 are reflective mirrors, but are not limited to mirrors and may be optically polished members such as optical filters and glass substrates. However, the first reflector 230 is a member having a lower reflectance than the second reflector 260. For example, in this embodiment, a reflective mirror having a reflectance of 99.99% may be used as the first reflector 230, and a reflective mirror having a reflectance of 99.999% may be used as the second reflector 260. Note that the first reflector 230 and the second reflector 260 have a property of transmitting some laser light without reflecting it, since their reflectance is not 100%. In this embodiment, the reflectance of the first reflector 230 is smaller than that of the second reflector 260, so that the proportion of laser light that transmits through the first reflector 230 is high, and as a result, it is possible to enhance the laser light in the second resonator shown in FIG. 1.

The first end member 24 is detachable from the first annular member 22, and can hold the first movable member 23 together with the first annular member 22, as shown in FIG. 2. The first end member 24 has a through hole 240 for passing the laser light emitted from the semiconductor laser element 11, as well as tilt adjustment screws (pressing members) 241-243, as shown in FIGS. 3 and 4. The tilt adjustment screws 241-243 penetrate the main body of the first end member 24 and can abut against the pressing surface 236 of the first movable member 23. The insertion position (insertion depth) of the tilt adjustment screws 241-243 is adjustable, and the more the tilt adjustment screws 241-243 are inserted toward the pressing surface 236, the higher the pressure with which the tilt adjustment screws 241-243 press the pressing surface 236, and the greater the deformation of the O-ring 28. As a result, for example, when only the tilt adjustment screw 241 located at the top in FIG. 4 is inserted deeply into the pressing surface 236, the first movable member 23 crushes the O-ring 28 at the position where it abuts against the tip of the tilt adjustment screw 241, making it possible to tilt the first reflector 230 downward. In this embodiment, as shown in FIGS. 4 and 5, tilt adjustment screws 242, 243 are also provided on the lower left and lower right sides of the first movable member 23, respectively, so that the tilt of the first reflector 230 can be adjusted up, down, left, and right by the three tilt adjustment screws 241-243. In this way, in this embodiment, the tilt adjustment screws 241-243 function as an alignment adjustment mechanism for adjusting the tilt of the first reflector 230.

5, the first annular member 22 is also provided with position adjustment screws 224, 225 and a biasing member 226 as an alignment mechanism. The position adjustment screws 224, 225 can adjust the position of the first reflector 230 held by the first movable member 23 by pressing the side surface 237 of the first movable member 23. The biasing member 226 is an elastic member such as a coil spring or a leaf spring, and is disposed between the first annular member 22 and the first movable member 23. In this embodiment, the biasing member 226 is disposed at a position opposite the position adjustment screws 224, 225 via the first movable member 23, and therefore biases the first movable member 23 in the direction in which the position adjustment screws 224, 225 are disposed. This makes it possible to adjust the position of the first movable member 23 in the vertical direction (Z-axis direction) and the horizontal direction (X-axis direction) according to the insertion position (insertion depth) of the position adjustment screws 224, 225. Furthermore, in this embodiment, the robustness of the optical resonator 20 can be improved by configuring the first annular member 22 and the second annular member 25 to be connected by a metal rod or the like.

In this embodiment, in order to protect the pressing surface 236 or side surface 237 of the first movable member 23 that is pressed by the tilt adjustment screws 241-243 or the position adjustment screws 224, 225, a protective member having a higher hardness than the tilt adjustment screws 241-243 and the position adjustment screws 224, 225 can be arranged on the pressing surface 236 and/or side surface 237. As such a protective member, for example, a contact pad made of sapphire can be used.

Next, the detection device 30 will be described. As shown in FIG. 1, in the first embodiment, four detection devices 30 are arranged on the side of the optical resonator 20 (cylinder 21). The detection device 30 is a device that detects light of a specific wavelength generated when a laser light collides with a gas in the internal space S inside the cylinder 21. An example of such a device is a detection device using a photomultiplier tube. In addition, in this embodiment, the detection device 30 is configured to detect Raman scattered light generated when a laser light collides with a gas. Here, even if the wavelength of the laser light is the same, the wavelength of the Raman scattered light changes depending on the type of gas that collides with the laser light. Therefore, in this embodiment, four detection devices 30 are used to detect Raman scattered light of different wavelengths, thereby simultaneously detecting four types of gas. Specifically, in this embodiment, bandpass filters 31a to 31d that transmit only light of different specific wavelengths are provided in front of the detection devices 30. For example, if the bandpass filter 31a has the property of transmitting Raman scattered light generated when the laser light collides with _SO2 gas, the bandpass filter 31b has the property of transmitting Raman scattered light generated when the laser light collides with CO gas, the bandpass filter 31c has the property of transmitting Raman scattered light generated when the laser light collides with _H2S gas, and the bandpass filter 31d has the property of transmitting Raman scattered light generated when the laser light collides with _CH4 gas, the external cavity laser device 1 can simultaneously detect light originating from _SO2 , CO, _CH4 , and _H2S at once using the multiple detection devices 30.

Furthermore, the higher the concentration of the gas introduced into the optical resonator 20, the higher the intensity of the Raman scattered light generated in the optical resonator 20. Therefore, the detection device 30 can not only detect the presence or absence of _SO2 , CO, _CH4 , and _H2S , but also detect the concentrations of _SO2 , CO, _CH4 , and _H2S based on the intensity of the Raman scattered light originating from _SO2 , CO, _CH4 , and _H2S .

Next, an example of the external resonator type laser device 1 according to this embodiment will be described. In this example, a reflecting mirror with a reflectance of 99.97% was used as the first reflector 230, and a reflecting mirror with a reflectance of 99.999% was used as the second reflector 260. In this example, the semiconductor laser element 11 was adjusted so that the wavelength of the laser light was 416 nm and the intensity was in the range of 5 to 50 mW, and the optical intensity of the laser light amplified inside the optical resonator 2 was adjusted to be in the range of 5 to 100 W. Then, using the external resonator type laser device 1 adjusted in this way, detection of oxygen, nitrogen, carbon dioxide, and water vapor in air, detection of oxygen (10 ppm) in hydrogen gas, and detection of ammonia (1 ppm) in argon gas were performed.

Figure 6 is a graph showing the results of detecting oxygen, nitrogen, carbon dioxide, and water vapor in the air. Specifically, Figure 6(A) is a graph showing the results of detecting oxygen and nitrogen, Figure 6(B) is a graph showing the results of detecting carbon dioxide, and Figure 6(C) is a graph showing the results of detecting water vapor. As shown in Figures 6(A) to (C), it was confirmed that oxygen, nitrogen, carbon dioxide, and water vapor in the air can be detected by using the external cavity laser device 1 according to this embodiment.

Figure 7 (A) is a graph showing the detection results of oxygen gas when 10 ppm of oxygen gas is mixed into hydrogen gas. It was found that oxygen gas can be detected even when the oxygen gas is 10 ppm. Note that the graph shown in Figure 7 (A) also includes the detection results for hydrogen gas only.

Furthermore, FIG. 7(B) is a graph showing the detection results of ammonia gas when 1 ppm of ammonia gas is mixed into argon gas. The graph shown in FIG. 7(B) also superimposes the detection results for argon gas alone. In this way, by comparing the detection results when ammonia gas is included with the detection results when ammonia gas is not included, it is possible to detect the presence of ammonia gas even when the amount of ammonia gas is as small as 1 ppm.

As described above, the optical resonator 20 according to the first embodiment has, as an alignment mechanism, the tilt adjustment screws 241-243 and the position adjustment screws 224, 225 that press the first movable member 23 to which the first reflector 230 is attached, and it is possible to adjust the tilt and position of the first movable member 23 (or the first reflector 230) by adjusting the insertion position (insertion depth) of these screws. Similarly, the optical resonator 20 according to the first embodiment has, as an alignment mechanism, the tilt adjustment screws 271-273 and the position adjustment screws 254, 255 that press the second movable member 26 to which the second reflector 260 is attached, and it is possible to adjust the tilt and position of the second movable member 26 (or the second reflector 260) by adjusting the insertion position (insertion depth) of these screws. Furthermore, in this embodiment, the tilt adjustment screws 241-243, 271-273 and the position adjustment screws 224, 225, 254, 255 can be operated from the outside by a user or a maintenance person, and the position including the tilt of the first and second reflectors 230, 260 can be easily adjusted without disassembling the optical resonator 20. In addition, in this embodiment, by using the semiconductor laser element 11, the device as a whole can be made small and the device can be carried around, but it is more susceptible to vibrations caused by carrying it around and external shocks, and the tilt and position of the reflectors 230, 260 in the optical resonator 20 are easily changed. However, by allowing the user or a maintenance person to easily adjust the tilt and position of the reflectors 230, 260, it is possible to provide a device that is more suitable for carrying it around.

Second Embodiment
Next, a second embodiment of the present invention will be described. FIG. 8 is a configuration diagram showing an external resonator type laser device 1a according to the second embodiment. The external resonator type laser device 1a according to the second embodiment includes a single detection device 30, and the detection device 30 is arranged in a position that is aligned with the semiconductor laser element 11 and the optical resonator 20. More specifically, the semiconductor laser element 11, the optical resonator 20, and the detection device 30 are all arranged on the optical axis of the laser light emitted from the semiconductor laser element 11. In addition, in the second embodiment, the Raman scattered light generated by the collision of the laser light with the gas to be detected in the optical resonator 20 is emitted to the outside from the second end member 27 of the optical resonator 20, and then enters the detection device 30 and is detected by the detection device 30.

In addition, in the second embodiment, in order to efficiently detect the Raman scattered light in the detection device 30, it is preferable to form an optical coating for highly reflecting the Raman scattered light or a reflective film of a metal such as aluminum on the inner surface of the cylinder 21, for example by a method such as deposition. This prevents the Raman scattered light from being transmitted to the outside from the side of the cylinder 21 (in a direction intersecting the optical axis of the laser light), and allows the Raman scattered light to be efficiently incident on the detection device 30 located on the optical axis of the laser light.

The detection device 30 according to the second embodiment also has a switching mechanism for the bandpass filter 31, allowing the bandpass filter 31 to be freely switched. Therefore, by switching the bandpass filter 31 according to the type of gas to be detected, it is possible to detect the desired gas.

As described above, the external resonator type laser device 1a according to the second embodiment also has an alignment mechanism in the optical resonator 20 that can adjust the tilt and position of the first reflector 230 and the second reflector 260, making it possible to easily adjust the positions including the tilt of the first reflector 230 and the second reflector 260. In addition, the external resonator type laser device 1a according to the second embodiment has a configuration with a single detection device 30, and the semiconductor laser element 11, the optical resonator 20, and the detection device 30 are arranged in a straight line, making it possible to make the entire device more compact. It has been confirmed that the external resonator type laser device 1a according to the second embodiment detects the target gas with a sensitivity equal to or higher than that of the external resonator type laser device 1 according to the first embodiment by detecting Raman scattered light along the optical axis L of the laser light.

Third Embodiment
Next, a third embodiment of the present invention will be described. Fig. 9 is a plan sectional view of an external cavity laser device 1b according to the third embodiment, and Fig. 10 is a side sectional view of the external cavity laser device 1b according to the third embodiment. Fig. 9 is a sectional view taken along line IX-IX shown in Fig. 10, and Fig. 10 is a sectional view taken along line X-X shown in Fig. 9.

As shown in FIG. 9, the external cavity laser device 1b according to the third embodiment has a semiconductor laser element 11, an optical resonator 50, a beam diffuser 40, a detection device 30, and a filter switching device 33.

Figure 11 is a plan cross-sectional view of the optical resonator 50 according to the third embodiment, which, like Figure 9, is a cross-sectional view of the optical resonator 50 taken along line IX-IX in Figure 10. Also, Figure 12(A) is a front view of the optical resonator 50 according to the third embodiment, and Figure 12(B) is a rear view of the optical resonator 50 according to the third embodiment. As shown in Figure 11, the optical resonator 50 according to the third embodiment has a light-guiding member 51, a first movable member 52, a first end member 53, a second movable member 54, and a second end member 55.

As shown in FIG. 12, the first end member 53 has a through hole 530 through which the laser light emitted from the semiconductor laser element 11 passes, and three tilt adjustment screws 531-533 that function as an alignment mechanism for adjusting the position, including the tilt, of the first movable member 52. The tips of the tilt adjustment screws 531-533 come into contact with the first surface 521 of the first movable member 52, and the first surface 521 can be pressed by inserting the tilt adjustment screws 531-533 to a deep position. Note that in the third embodiment as well, the tilt of the first movable member 52 (the tilt of the first reflector 520) can be adjusted up, down, left, and right by adjusting the insertion positions of the three tilt adjustment screws 531-533.

A first reflector 520 is attached to the first movable member 52. The first movable member 52 abuts against the tilt adjustment screws 531-533 on the first surface 521 on the first end member 53 side, and abuts against the O-ring 56 on the second surface 522 opposite the first surface 521. Specifically, a groove for engaging the O-ring 56 is formed on the second surface 522 in accordance with the shape of the O-ring 56, and the O-ring 56 is fitted into this groove. The first reflector 520 is housed in the first recess 513 of the light-guiding member 51, but there is a gap between the first reflector 520 and the first recess 513 such that the first reflector 520 does not come into contact with the first recess 513 even if the tilt or position of the first reflector 520 is changed. Therefore, when the first surface 521 is pressed by the tilt adjustment screws 531 to 533, the second surface 522 presses the O-ring 56 around the pressed position, and the O-ring 56 is deformed, thereby making it possible to change the tilt of the first reflector 520. In this embodiment, a plate-shaped protective member 523 is attached to the portion of the first surface 521 that abuts against the tilt adjustment screws 531 to 533. The protective member 523 is a member for preventing the first surface 521 from being deformed by the pressure of the tilt adjustment screws 531 to 533, and may be, for example, a contact pad made of sapphire. In the optical resonator 50 according to the third embodiment, no position adjustment screw is provided for adjusting the position of the first reflector 520, but a configuration in which a position adjustment screw is provided to adjust the position of the first reflector 520 may be used.

The second movable member 54 and the second end member 55 have the same configuration as the first movable member 52 and the first end member 53, and as shown in FIG. 12, the second end member 55 is provided with tilt adjustment screws 551-553 as an alignment mechanism for changing the tilt of the second movable member 54.

9 and 10, the third embodiment has a piezo controller 58 and actuators 59 ₁ and 59 2 as an alignment adjustment mechanism for adjusting the insertion positions (insertion depth) of the tilt adjustment screws 531 to 533 and ₅₅₁ to 553. For example, a user can operate the piezo controller 58 to determine the insertion positions (insertion depth) of the tilt adjustment screws 531 to 533 and 551 to 553, so that the piezo controller 58 controls the driving of the actuators 59 ₁ and 59 ₂ , causing the actuators 59 ₁ and 59 ₂ to adjust the insertion positions of the tilt adjustment screws 531 to 533 and 551 to 553. The actuators 59 ₁ and 59 ₂ also function as a lock mechanism for fixing the insertion positions (insertion depth) of the tilt adjustment screws 531 to 533 and 551 to 553.

The light-guiding member 51 according to the third embodiment is a hollow member, and an internal space S is formed inside. The light-guiding member 51 also has a gas inlet 511, a gas outlet 512, recesses 513 and 514, small diameter through holes 515 and 516, a cylindrical mirror 517, a cylindrical lens 518, and an optical filter 519. As with the cylinder 21 according to the first embodiment, the gas to be detected is introduced into the internal space S from the gas inlet 511, and after passing through the internal space S, is discharged from the gas outlet 512. In this embodiment, the light-guiding member 51 has recesses 513 and 514 and small diameter through holes 515 and 516 on the optical axis L of the laser light, and the laser light emitted from the semiconductor laser element 11 passes through the recess 513 and the small diameter through hole 515, and a part of the laser light passes through the first reflector 520 to be irradiated into the internal space S. In addition, in the internal space S, the laser light collides with the gas introduced into the internal space S while being repeatedly reflected by the first reflector 520 and the second reflector 540, and Raman scattered light corresponding to the gas is generated. In this embodiment, a cylindrical mirror 517 is provided on the side of the internal space S (the side perpendicular to the reflection direction of the laser light) on which the detection device 30 is not present, and the light radiated toward the cylindrical mirror 517 side out of the Raman scattered light generated by the collision between the laser light and the gas is reflected by the cylindrical mirror 517 toward the cylindrical lens 518 side. On the other hand, a cylindrical lens 518 is provided on the side of the internal space S (the side perpendicular to the reflection direction of the laser light) where the detection device 30 is located, and the Raman scattered light emitted toward the cylindrical lens 518 is converted into a linear (one-dimensional) shape while passing through the cylindrical lens 518, then passes through an optical filter 519, is collected by a focus lens 32, and is detected by the detection device 30. In the third embodiment, the filter switching device 33 has bandpass filters 31a and 31b that transmit Raman scattered light of different wavelengths, and can switch between the bandpass filters 31a and 31b depending on the Raman scattered light of a predetermined wavelength detected by the detection device 30.

As described above, in the external resonator type laser device 1b according to the third embodiment, the light-guiding member 51 corresponds to the cylinder 21, the first annular member 22, and the second annular member 25 of the external resonator type laser device 1 according to the first embodiment, and the first movable member 52 is accommodated between the light-guiding member 51 and the first end member 53, and the second movable member 54 is accommodated between the light-guiding member 51 and the second end member 55, so that the inclination of the first movable member 52 and the second movable member 54 can be adjusted by the alignment mechanism (tilt adjustment screws 531-533, 551-553). Furthermore, in the external resonator type laser device 1b, the number of parts is reduced and it can be made smaller than the external resonator type laser device 1 according to the first embodiment.

The above describes preferred embodiments of the present invention, but the technical scope of the present invention is not limited to the above description of the embodiments. Various modifications and improvements can be made to the above embodiments, and such modifications or improvements are also included in the technical scope of the present invention.

For example, in the second embodiment, a single detection device 30 is arranged in a position aligned with the semiconductor laser element 11 and the optical resonator 20 (on the optical axis of the laser light), but this is not limited to this configuration. For example, in addition to the position aligned with the semiconductor laser element 11 and the optical resonator 20 (on the optical axis of the laser light), multiple detection devices 30 can be arranged on the side of the cylinder 21 (in a direction perpendicular to the optical axis of the laser light) as in the first embodiment, and Raman scattered light can be detected at the position aligned with the semiconductor laser element 11 and the optical resonator 20 and on the side of the cylinder 21. For example, by combining the arrangement configuration of the detection device 30 according to the first embodiment and the detection configuration of the detection device 30 according to the second embodiment, Raman scattered light can be detected by five detection devices 30, making it possible to detect five types of gases simultaneously.

Reference Signs List 1, 1a, 1b...External cavity type laser device 11...Semiconductor laser element 111, 112...End surface 12...Collimating lens 13...Bandpass filter 20...Optical resonator 21...Cylinder 22...First annular member 220...Gas inlet 221...First annular portion 222...Second annular portion 223...Step surface 224, 225...Position adjustment screw 226...Pressing member 23...First movable member 230...First reflector 231...Through hole 232...Main body 233...Flange portion 234...Step surface 235...Recess 236...Pressing surface 237...Side surface 24...First end member 240...Through hole 241-243...Tilt adjustment screw 25...Second annular member 250...Gas exhaust port Description of the reference numerals 251...first annular portion 252...second annular portion 253...step surface 254, 255...position adjustment screws 26...second movable member 260...second reflector 261...through hole 262...main body portion 263...flange portion 264...step surface 265...recess 266...pressing surface 267...side surface 27...second end member 270...through hole 271-273...tilt adjustment screws 28-211...O-ring 30...detection device 31, 31a-31d...bandpass filter 32...focus lens 33...filter switching device 40...beam diffuser 50...optical resonator 51...light guiding member 511...gas inlet 512...gas outlet 513, 514...recess 515, 516...thin through hole 517: Cylindrical mirror 518: Cylindrical lens 519: Optical filter 52: First movable member 520: First reflector 521: First surface 522: Second surface 523: Protective member 53: First end member 530: Through hole 531-533: Adjusting screw 54: Second movable member 540: Second reflector 541: First surface 542: Second surface 543: Protective member 55: Second end member 550: Through hole 551-553: Adjusting screw 56, 57: O-ring 58: Piezo controller 59 ₁ , 59 ₂ : Actuator

Claims (8)

a first reflector onto which the laser light emitted from the laser element is incident;
a second reflector provided opposite to the first reflector and feeding back reflected light to the laser element;
a cylinder having the first reflector and the second reflector disposed at both ends;
a gas inlet for introducing gas into the cylindrical body and a gas outlet for discharging gas from within the cylindrical body;
a first movable member to which the first reflector is attached;
a second movable member to which the second reflector is attached; and
an alignment mechanism that adjusts the inclination of the first and second movable members;
The optical resonator comprises a pair of elastic members, and the cylindrical body is hermetically sandwiched between the first and second movable members. the alignment mechanism includes a first tilt adjustment mechanism that adjusts a tilt of the first movable member and a second tilt adjustment mechanism that adjusts a tilt of the second movable member;
a first end member having the first tilt adjustment mechanism at an end side of the first movable member;
2. The optical resonator according to claim 1, further comprising a second end member having said second tilt adjustment mechanism, said second end member being disposed on an end side of said second movable member. The optical resonator according to claim 2, wherein the first tilt adjustment mechanism includes a plurality of first pressing members that adjust the tilt of the first reflector by pressing the first movable member in a direction along the optical axis of the laser light, and the second tilt adjustment mechanism includes a plurality of second pressing members that adjust the tilt of the second reflector by pressing the second movable member in a direction along the optical axis of the laser light. a first protective member having a hardness higher than that of the first pressing members is disposed on a surface of the first movable member that is pressed by the plurality of first pressing members;
4. The optical resonator according to claim 3, further comprising a second protective member having a harder hardness than the second pressing members, the second protective member being disposed on a surface of the second movable member that is pressed by the second pressing members. the first inclination adjustment mechanism includes a plurality of first adjustment members that adjust insertion positions of the plurality of first pressing members, and a first lock mechanism that fixes the insertion positions of the plurality of first adjustment members,
4. The optical resonator according to claim 3, wherein the second tilt adjustment mechanism comprises a plurality of second adjustment members that adjust the insertion positions of the plurality of second pressing members, and a second locking mechanism that fixes the insertion positions of the plurality of second adjustment members. the alignment mechanism includes a first position adjustment mechanism that adjusts a position of the first movable member in a direction perpendicular to an optical axis, and a second position adjustment mechanism that adjusts a position of the second movable member in a direction perpendicular to the optical axis,
the first position adjustment mechanism includes a third pressing member that presses the first movable member in a direction perpendicular to the optical axis to adjust a position of the first reflector in the direction perpendicular to the optical axis,
3. The optical resonator according to claim 2, wherein the second position adjustment mechanism includes a fourth pressing member that presses the second movable member in a direction perpendicular to the optical axis to adjust the position of the second reflector in the direction perpendicular to the optical axis. An optical resonator according to any one of claims 1 to 6,
a laser element that emits laser light that is incident on the optical resonator;
An external cavity type laser device having a detection device that detects light of a specific wavelength generated by the action of a gas introduced into the optical cavity and a laser light,
an external cavity type laser device having an optical system between the optical resonator and the detection device, which focuses the light of the specific wavelength that has passed through the cylindrical body and makes it incident on the detection device; An optical resonator according to any one of claims 1 to 6,
a laser element having a non-reflective layer formed on one end face and a total reflection layer formed on the other end face;
a wavelength selection filter provided between the laser element and the optical resonator;
An external cavity laser device comprising: