Method and apparatus for adjusting an angular mirror in a laser resonator

Abstract

The present disclosure provides a method and device for adjusting an angle mirror in a laser resonator cavity, the method comprising: setting an OC coupling output mirror, so that the OC coupling output mirror, a laser gain medium and a front cavity mirror of the laser form a sub-resonator cavity to generate a reference laser; setting a first aperture diaphragm between the OC coupling output mirror and the angle mirror, adjusting the angle mirror so that the angle mirror is aligned with the center of the aperture diaphragm; placing the angle mirror according to an estimated reflection angle, setting a second aperture diaphragm in the reflection direction of the angle mirror to keep the pitch angle of the angle mirror unchanged, adjusting the angle mirror so that the reference laser reflected by the angle mirror passes through the center of the second aperture diaphragm; adjusting the height of the angle mirror so that the reference laser is aligned with the center of the angle mirror again; measuring the power of the reference laser reflected by the angle mirror, and adjusting the yaw angle of the angle mirror until the power is maximum.

Description

Technical Field

[0001] This disclosure relates to the field of laser technology, and in particular to a method and apparatus for adjusting an angle reflector in a laser resonant cavity. Background Technology

[0002] Lasers are one of the most outstanding technological achievements created by mankind in the last century. Since their development, solid-state lasers have attracted much attention. Due to their high peak power, large output energy, and compact and durable design, they are widely used in industry, agriculture, precision measurement and detection, communication and information processing, medicine, and the military, and have brought about revolutionary breakthroughs in many fields. The resonant cavity, an indispensable component of a laser, is an optical device composed of two or more optical mirrors that provides positive optical feedback. With the continuous development of solid-state lasers, the composition of resonant cavities has become increasingly complex, with angle mirrors frequently appearing within them. When the angle mirrors are accurately placed at the incident angle of the coating, the loss within the resonant cavity is minimized, and the cavity is more easily stabilized. However, accurately placing the angle mirrors at a specific angle within the resonant cavity has always been a challenging problem, especially when multiple angle mirrors are present in the same cavity, making the adjustment process even more difficult.

[0003] The current method for adjusting angle mirrors in laser resonant cavities typically uses helium-neon lasers as collimating light and then adjusts the mirror's position by estimating its approximate rotation angle. This method suffers from significant adjustment errors. For more complex cavity types such as Z-cavities, X-cavities, and toroidal cavities, the optical path is often folded multiple times to achieve a more compact structure and smaller overall size. These resonant cavities generally use a large number of angle mirrors. In these cavities, the helium-neon laser not only travels a long distance but also passes through numerous optical components, including laser gain media, frequency-changing crystals, various lenses, and Q-switches. This significantly weakens the helium-neon laser's intensity and increases its spot size, making it extremely difficult to adjust the angle mirrors using the same method. Furthermore, estimating the placement angle of the angle mirror is inherently random and lacks a specific standard, often resulting in a significant waste of time and effort in practice. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method and apparatus for adjusting the angle reflector in a laser resonant cavity to solve the above technical problems.

[0005] The first aspect of this disclosure provides a method for adjusting an angle mirror in a laser resonator. The method includes: setting an OC (Optical Coupling) output mirror between a laser gain medium and an angle mirror inside the laser resonator, such that the OC output mirror, the laser gain medium, and a front cavity mirror constitute a sub-resonator to generate a reference laser; setting a first aperture stop between the OC output mirror and the angle mirror; and adjusting the pitch angle and height of the angle mirror so that after the reference laser passes through the center of the first aperture stop and reaches the angle mirror, the light reflected back by the angle mirror also passes through the first aperture stop. The reference laser is positioned at the center of the first aperture stop and aligned with the center of the angled reflector. The angled reflector is placed at the estimated reflection angle, while maintaining its pitch angle. A second aperture stop, at the same height as the first aperture stop, is set in the reflection direction of the angled reflector. The angled reflector is adjusted so that the reference laser reflected by it passes through the center of the second aperture stop. The height of the angled reflector is adjusted so that the reference laser is again aligned with the center of the angled reflector. The power of the reference laser reflected by the angled reflector is measured, and the yaw angle of the angled reflector is adjusted until the power is at its maximum, at which point the adjustment is stopped.

[0006] According to an embodiment of this disclosure, the method further includes: setting a third aperture stop behind the angle reflector, wherein the first aperture stop and the third aperture stop are at the same height; and adjusting the angle of the OC coupling output mirror and the front cavity mirror before adjusting the angle reflector, so that the reference laser passes through the center of the first aperture stop and the third aperture stop, and the reference laser is horizontal.

[0007] According to an embodiment of this disclosure, when the angle reflector is a concave angle reflector, adjusting the angle reflector so that the reference laser passes through the center of the first aperture stop and reaches the angle reflector, and the light reflected back by the angle reflector also passes through the center of the first aperture stop, further includes: attaching a target paper to the angle reflector, adjusting the height of the angle reflector, and removing the target paper after the reference laser is aligned with the center of the target paper, thus completing the alignment of the reference laser with the center of the angle reflector.

[0008] According to an embodiment of this disclosure, the method further includes: adjusting the second aperture stop to be at the same height as the first aperture stop.

[0009] According to an embodiment of this disclosure, adjusting the height of the angle reflector so that the reference laser is aligned with the center of the angle reflector again includes: attaching a target paper to the angle reflector, adjusting the height of the angle reflector, and removing the target paper after the reference laser is aligned with the center of the target paper, thus completing the alignment of the reference laser with the center of the angle reflector.

[0010] According to an embodiment of this disclosure, the method further includes: removing the first aperture stop and the second aperture stop after the angle reflector has been adjusted.

[0011] The second aspect of this disclosure provides an adjustment device for an angle mirror in a laser resonator, applied to the adjustment method described in any one of the first aspects, comprising: an OC coupling output mirror disposed between a laser gain medium and an angle mirror inside the laser resonator, coaxial with the laser gain medium and the mirror inside the laser resonator, for forming a sub-resonator with the laser gain medium and a front cavity mirror to generate a reference laser; a first aperture stop disposed between the OC coupling output mirror and the angle mirror, for assisting in adjusting the angle mirror so that the reference laser is aligned with the angle mirror; a second aperture stop disposed in the reflection direction of the angle mirror, for assisting in calibrating the reflection angle of the angle mirror during the adjustment process; and a power meter disposed after the angle mirror for measuring the power of the reference laser after reflection by the angle mirror.

[0012] According to an embodiment of this disclosure, the adjustment device further includes: a third aperture stop, disposed behind the angle reflector and at the same height as the first aperture stop, used to cooperate with the first aperture stop to calibrate the reference laser in the horizontal direction before adjusting the angle reflector.

[0013] According to an embodiment of this disclosure, the adjustment device further includes: a three-axis adjustment frame connected to the angle reflector, used to adjust the height, front-back and left-right displacement of the angle reflector.

[0014] The above-described at least one technical solution adopted in the embodiments of this disclosure can achieve the following beneficial effects:

[0015] This disclosure provides a method and apparatus for adjusting an angle mirror in a laser resonant cavity. By inserting an OC coupling output mirror behind the laser gain medium, the mirror, laser gain medium, and OC coupling output mirror form a new sub-resonant cavity. Under the action of an end-face pump source, this sub-resonant cavity self-oscillates to generate a reference laser. Using this reference laser, an aperture stop, a target paper, and a power meter, the angle mirror within the resonant cavity can be adjusted quickly and accurately. Compared to existing methods that use helium-neon light to roughly estimate the reflection angle and adjust the angle mirror, this patent is faster, simpler, and more accurate. This method is particularly suitable for concave mirrors coated with a high-reflection film at the incident angle. This adjustment method does not require other sophisticated equipment and is not limited by the application environment. The adjustment apparatus provided in this disclosure includes only an OC coupling output mirror, an aperture stop, and a power meter. It uses very few components, has a very simple structure, is easy to implement, and is inexpensive, making it suitable for adjusting angle mirrors in most experimental scenarios. Attached Figure Description

[0016] To gain a more complete understanding of this disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, wherein:

[0017] Figure 1 A flowchart illustrating the method for adjusting an angle mirror in a laser resonator provided in an embodiment of this disclosure is shown schematically.

[0018] Figure 2 This schematic diagram illustrates an adjustment device for an angle mirror in a V-shaped folded cavity laser made of emerald crystal provided in an embodiment of the present disclosure.

[0019] Figure 3 This schematic diagram illustrates an adjustment device for an adjustable angle reflector in an emerald sapphire according to an embodiment of the present disclosure;

[0020] Figure 4 This schematic diagram illustrates an adjustment device for an angle mirror in a Z-shaped folded cavity laser made of emerald crystal provided in an embodiment of the present disclosure.

[0021] Figure 5 The illustration shows a schematic diagram of an adjustment device for an angle mirror in a long cavity self-Q-switched alexandrite laser provided in an embodiment of the present disclosure. Detailed Implementation

[0022] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0024] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0025] The accompanying drawings show some block diagrams and / or flowcharts. It should be understood that some blocks or combinations thereof in the block diagrams and / or flowcharts can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when executed by the processor, these instructions can create means for implementing the functions / operations described in these block diagrams and / or flowcharts.

[0026] This disclosure provides a method and apparatus for adjusting an angle reflector in a laser resonant cavity. The adjustment apparatus includes an OC coupling output mirror, a first aperture stop, a second aperture stop, a third aperture stop, and a power meter. The system includes: an OC coupling output mirror, located between the laser gain medium and the angle mirror inside the laser resonant cavity, coaxial with the laser gain medium and the front cavity mirror, forming a sub-resonant cavity to generate a reference laser; a first aperture stop, located between the OC coupling output mirror and the angle mirror, assisting in adjusting the angle mirror to align the reference laser with it; a second aperture stop, located in the reflection direction of the angle mirror, assisting in calibrating the reflection angle of the angle mirror during adjustment; a third aperture stop, located behind the angle mirror at the same height as the first aperture stop, used in conjunction with the first aperture stop to calibrate the reference laser in a horizontal direction before adjusting the angle mirror; and a power meter, located after the second aperture stop, used to measure the power of the reference laser after reflection by the angle mirror.

[0027] Figure 1 The flowchart illustrates a method for adjusting an angle mirror in a laser resonator provided in an embodiment of the present disclosure.

[0028] like Figure 1 As shown, an embodiment of this disclosure provides a method for adjusting an angle reflector in a laser resonant cavity, comprising steps S110 to S150.

[0029] S110, an OC coupling output mirror is set between the laser gain medium and the angle reflector inside the laser resonant cavity, so that the OC coupling output mirror, the laser gain medium and the front cavity mirror form a sub-resonant cavity to generate a reference laser.

[0030] In this embodiment, after the sub-resonator generates oscillating laser light, the front and rear cavity mirrors need to be continuously fine-tuned until the oscillating laser light is horizontal. Two equal-height first and third aperture stops are placed behind the OC coupling output mirror, with a certain distance between them. The third aperture stop can be positioned behind the angle reflector. By continuously fine-tuning the front cavity mirror and the OC coupling output mirror, the oscillating laser light is allowed to pass through the center of both aperture stops simultaneously. At this point, the oscillating laser light is adjusted to be horizontal and can be used as a reference laser.

[0031] S120: A first aperture stop is set between the OC coupling output mirror and the angle mirror. The pitch angle and height of the angle mirror are adjusted so that the reference laser passes through the center of the first aperture stop and reaches the angle mirror. The light reflected back by the angle mirror also passes through the center of the first aperture stop and is aligned with the center of the angle mirror.

[0032] In this embodiment, the first aperture stop is placed between the OC coupling output mirror and the angle mirror. At this time, the position of the angle mirror is approximately facing the reference laser. The reference laser needs to pass through the center of the aperture stop and be perpendicularly incident on the surface of the angle mirror. That is, the pitch direction of the angle mirror is adjusted so that the reference laser reflected by the angle mirror still passes through the center of the aperture stop.

[0033] When the angled mirror is concave, it's necessary to align the reference light to the center of the mirror using a target paper. Before attaching the target paper, the reference light before and after reflection is made to have the same height. This is done by placing the angled mirror perpendicular to the reference light, making the mirror approximately directly facing the reference laser. Then, a first aperture stop is placed in front of the angled mirror, and the reference laser must pass through the center of this first aperture stop. The pitch of the angled mirror is adjusted until the reflected reference light also passes through the center of the first aperture stop; at this point, the height of the reference light before and after reflection is consistent. Next, the target paper is attached to the mirror surface. This time, only the height of the angled mirror is adjusted to align the reference laser with the center of the target paper. The target paper is then removed, completing the alignment of the reference laser with the center of the angled mirror.

[0034] When the angle mirror is a planar angle mirror, there is no need to attach target paper. You only need to make the angle mirror face the sub-resonator and continuously adjust the height and pitch of the angle mirror until the reference laser reflected by the angle mirror passes exactly through the center of the first aperture stop between the OC coupling output and the angle mirror.

[0035] In this embodiment, the angle reflector is placed on a three-axis adjustment frame, which can move horizontally along the optical path, horizontally perpendicular to the optical path, and vertically perpendicular to the optical path, and its forward and backward, left and right displacement and height can be adjusted.

[0036] S130, place the angle mirror according to the estimated reflection angle, and keep the pitch angle of the angle mirror unchanged. Set the second aperture stop in the reflection direction of the angle mirror. Adjust the angle mirror so that the reference laser reflected by the angle mirror passes through the center of the second aperture stop.

[0037] In this embodiment, the second aperture stop is at the same height as the first aperture stop.

[0038] The most common reflection angles for angle mirrors are 45°, 30°, and 22°. In this embodiment, the angle mirror used is a high-reflection coated mirror with an incident angle of 22° and 45°, and a wavelength of 700–800 nm. When placing the angle mirror based on a rough estimate of the reflection angle, in order to ensure that the pitch of the angle mirror remains unchanged before and after placement, a second aperture stop at the same height as the first aperture stop needs to be set in the direction directly opposite the mirror surface. The angle mirror is then finely adjusted so that the reference laser passes through the center of this second aperture stop.

[0039] S140, adjust the height of the angle reflector so that the reference laser is aligned with the center of the angle reflector.

[0040] In this embodiment, the placement of the angle reflector is adjusted in the direction perpendicular to the reference optical path so that the reference laser is aligned with the center of the target paper on the angle reflector again, and then the target paper on the angle reflector is removed.

[0041] Specifically, the operations of S120 and S130 have ensured that the height of the reference laser is consistent before and after reflection by the angle reflector. At this point, it is only necessary to adjust the position of the angle reflector on the vertical optical path to re-align the reference laser with the center of the angle reflector. Once the reference laser is aligned with the center of the target paper, the target paper is removed, thus completing the alignment of the reference laser with the center of the angle reflector.

[0042] S150: Measure the power of the reference laser reflected by the angle reflector, adjust the yaw angle of the angle reflector until the power is at its maximum, and then stop adjusting.

[0043] In this embodiment, a power meter is placed in the direction of reflection by the angle reflector, and the yaw of the angle reflector is finely adjusted until the measured power is at its maximum. Since the pitch of the angle reflector has already been adjusted due to the operations in steps S120 and S130, only the yaw of the angle reflector needs to be finely adjusted now.

[0044] According to steps S110 to S150, the angle reflectors included in the laser are adjusted sequentially. After the angle reflectors are adjusted, the first aperture stop, the second aperture stop, the third aperture stop, and the power meter are removed.

[0045] The following specific examples illustrate the method for accurately and quickly adjusting the angle of the resonant cavity mirror.

[0046] Figure 2 The schematic diagram illustrates an adjustment device for an angle mirror in a V-shaped folded cavity laser made of emerald crystal provided in an embodiment of the present disclosure.

[0047] like Figure 2 As shown, the V-shaped folded cavity laser with emerald crystal provided in this embodiment includes: a pump source 1, a collimator 2, a half-wave plate 3, a PBS polarizing beam splitter 4, a half-wave plate 5, a lens 6, a mirror 7, an emerald crystal 8, an angle mirror 9, a polarizer 10, a quarter-wave plate 11, a Q switch 12, and an output mirror 13; the entire resonant cavity structure is V-shaped, wherein the intersection of the first arm and the second arm is the angle mirror 9. The first arm sequentially houses the pump source 1, collimator 2, half-wave plate 3, PBS polarizing beam splitter 4, half-wave plate 5, lens 6, mirror 7, emerald crystal 8, and angle mirror 9; the second arm sequentially houses the polarizer 10, quarter-wave plate 11, Q switch 12, and output mirror 13.

[0048] The working principle of this resonant cavity is as follows: After being collimated by collimator 2, the pump source 1 passes through a linearly polarized light generator composed of half-wave plate 3, PBS polarizing beam splitter prism 4, and half-wave plate 5, generating maximum horizontal linearly polarized light. Since the polarization direction of the maximum horizontal linearly polarized light is parallel to the b-axis of the emerald crystal 8, the emerald crystal 8 can obtain the maximum absorption efficiency. Oscillating laser light is then formed in the resonant cavity composed of front cavity mirror 7 and output mirror 13. The oscillating laser light then passes through a Q-switching system composed of polarizer 10, quarter-wave plate 11, and Q switch 12 to achieve pulsed oscillating laser output. In the entire optical path, OC coupling output mirror 14, first aperture stop 15, third aperture stop 16, second aperture stop 17, and power meter 18 are all components used to adjust the angle mirror in the resonant cavity and need to be removed during the final operation of the optical path. The entire resonant cavity is approximately 160mm long, the distance from mirror 7 to angle mirror 9 is approximately 60mm, and the distance from angle mirror 9 to output mirror 13 is approximately 100mm. Reflector 7 and angle mirror 9 are plane mirrors, both coated with antireflective films for the 638nm pump light band. Mirror 7 has a high-reflectivity film for the 0° incident 700–800nm ​​laser band on the cavity-facing side, while angle mirror 9 has a high-reflectivity film for the 45° incident 700–800nm ​​laser band on the cavity-facing side. Output mirror 13 is also a plane mirror coated with a dielectric film for the 700–800nm ​​wavelength band, with a reflectivity of 99%. Half-wave plate 3 and half-wave plate 5 are coated with 638nm pump source high-transmittance films on both sides. Lens 6 is a plano-convex lens, with a flat side facing the resonant cavity, and both sides coated with a 0° incident 638nm high-transmittance dielectric film, with a focal length of 50mm.

[0049] The crystal in the resonant cavity is Alexandrite (Cr). 3+ The crystal (BeAl2O4) has antireflection coatings with wavelengths of 700-800nm ​​on both ends. To suppress the thermal lensing effect of the laser crystal and improve the stability of output power and beam quality, the emerald crystal is wrapped with indium foil and placed in a self-designed and processed copper block fixture, which is connected to a circulating water cooling system with the water temperature controlled at 20℃.

[0050] In the Q-switching system, the polarizer 10 must be incident at the Brewster angle, the quarter-wave plate 11 is coated with a high-transmittance dielectric film with a wavelength of 700-800nm ​​on both sides, and the Q switch 12 adopts a BBO, RTP, LGS electro-optic or acousto-optic Q switch that can achieve high repetition rate turn-off. The two light-transmitting end faces of the Q switch 12 crystal are coated with a 700-800nm ​​wavelength anti-reflection film.

[0051] In this embodiment, the angle reflector 9 divides the entire optical path into two parts, which are not on the same optical axis. This causes the light rays in the optical path to be refracted once in the resonant cavity, making the structure of the resonant cavity more compact and thus shortening its length. In this case, the angle reflector 9 is a flat 45° angle reflector. When the laser is incident at a 45° angle, the reflection efficiency is the highest. The following example will be used to explain in detail the adjustment method of the above-mentioned flat 45° angle reflector.

[0052] The inserted OC coupling output mirror 14 has a reflectivity of 97% with a dielectric film coated on both sides for high transmittance at 638nm wavelength and a dielectric film coated on the side facing the laser crystal for high reflectivity at 700-800nm ​​wavelength. When the angle mirror is adjusted, the position inserted into the resonant cavity is located between the emerald crystal 8 and the angle mirror 9, and the mirror 7, the emerald crystal 8, and the OC coupling output mirror 14 are located on the same optical axis.

[0053] When adjusting the angle reflector 9, the first aperture stop 15 and the third aperture stop 16 need to be placed between the OC coupling output mirror 14 and the angle reflector 9, and behind the angle reflector 9. Using the reflector 7 as the front cavity mirror, together with the emerald crystal 8 and the OC coupling output mirror 14, a sub-resonant cavity for generating reference light is formed. After generating the oscillating laser, the reflector 7 and the OC coupling output mirror 14 need to be continuously adjusted so that the oscillating laser simultaneously passes through the center of the first aperture stop 15 and the third aperture stop 16 (these two stops are at the same height). This oscillating laser is used as the reference laser to adjust the angle reflector.

[0054] Then, the reflecting surface of the angle mirror 9 is placed directly opposite the sub-resonant cavity, and the pitch of the angle mirror 9 is continuously adjusted so that after the reference laser is incident at 0° onto the plane of the angle mirror 9, the light reflected back by the angle mirror also passes through the center of the first aperture stop 15, so as to ensure that the height of the reference laser is consistent before and after passing through the angle mirror.

[0055] Finally, place the angle mirror 9 at the estimated angle and rotate its YAW position to position it at the estimated 45° (using a protractor or triangular cardboard). After placing the angle mirror, ensure that its pitch remains constant before and after rotation. At this point, place a second aperture stop 17 (at the same height as the first two stops) behind the angle mirror 9, near the Q-switching system. When the reference light passes through the centers of these two stops simultaneously, the height of the reference light remains unchanged after reflection by the angle mirror 9, meaning the pitch of the angle mirror remains constant before and after rotation. Then, place a power meter 18 behind the angle mirror 9, near the Q-switching system, to measure the power of the reference light reflected by the angle mirror 9. Since the angle mirror 9 is placed at an estimated angle, the placement angle at this point has a large error compared to 45°. While ensuring the reference light is aligned with the center of the angle mirror 9, the YAW of the angle mirror 9 is finely adjusted to maximize the power measured by the power meter 18. At this point, the placement of the angle mirror 9 is optimal. Then, the power meter 18 is removed from the optical path, completing the adjustment of the angle mirror. Using this reference laser, the position of the last output mirror 13 is adjusted until the reference light can return along its original path. At this point, the aperture stop added to the entire optical path is removed.

[0056] Figure 3 The schematic diagram illustrates an adjustment device for an adjustable angle reflector in an emerald sapphire according to an embodiment of the present disclosure.

[0057] like Figure 3 As shown in the embodiments of this disclosure, the tunable alexandrite laser with angle mirror adjustment device includes: pump source 1, collimator 2, half-wave plate 3, PBS polarizing beam splitter 4, half-wave plate 5, lens 6, mirror 7, alexandrite crystal 8, angle mirror 9, wavelength tuning element 10, quarter-wave plate 11, Q switch 12, and output mirror 13; the entire resonant cavity shape is still V-shaped, wherein the nodes of the first and second arms are angle mirrors 9.

[0058] The working principle of this resonant cavity is as follows: the pump light emitted from pump source 1 is collimated by collimator 2 and then passes through a linearly polarized light generator composed of half-wave plate 3, PBS polarizing beam splitter prism 4, and half-wave plate 5 to generate maximum horizontal linearly polarized light, which is used to pump the alexandrite crystal 8 to generate oscillating laser. The oscillating laser passes through wavelength tuning elements and Q-switching system to finally achieve a pulsed laser with tunable output wavelength. The OC coupling output mirror 14, first aperture stop 15, third aperture stop 16, second aperture stop 17, and power meter 18 in the optical path are components used for adjusting the angle mirror in the resonant cavity and need to be removed during the final operation of the optical path. The entire resonant cavity is approximately 300 mm long, the distance from mirror 7 to angle mirror 9 is approximately 140 mm, and the distance from angle mirror 9 to output mirror 13 is approximately 160 mm. Both half-wave plate 3 and half-wave plate 5 in the optical path are coated with a 638 nm light-reflecting antireflection medium film with 0° incident light. Lens 6 is a plano-convex lens, with a flat side facing the resonant cavity. Both sides are coated with a 0° incident 638nm fully transparent dielectric film, and the focal length is 50mm. The laser crystal in the resonant cavity is emerald green crystal, and the coating and cooling methods are the same as in Case 1.

[0059] Angle mirror 9 is a plano-concave mirror, with one concave side facing the emerald crystal. It is coated with a dielectric film that reflects 700-800nm ​​light incident at 22° and transmits 638nm light. It not only plays the role of total reflection oscillating laser and filtering out residual pump light, but also plays the role of folding the optical path.

[0060] Both sides of the reflector 7 are coated with antireflective coatings for the 638nm pump light band, with the side facing into the cavity also coated with a high-reflectivity coating for the 700-800nm ​​laser band at 0° incident angle. The output mirror 13 is a plane mirror coated with a dielectric film for the 700-800nm ​​wavelength band with a reflectivity of 99%. The wavelength tuning element consists of three birefringent filters of a certain thickness ratio. These birefringent filters are placed at Brewster's angle in the optical path, which not only tunes the wavelength of the oscillating laser but also polarizes it. This saves a polarizer in the subsequent Q-switching system. Other components in the Q-switching system, such as the quarter-wave plate 11 and the Q switch 12, are the same as those used in Case 1.

[0061] In this embodiment, the angle reflector 9 is a plano-concave 22° angle reflector. When the oscillating laser is incident at 22°, the reflection efficiency of the angle reflector is the highest. The following example will be used to explain in detail the adjustment method of the above-mentioned 22° plano-concave angle reflector.

[0062] The OC coupling output mirror 14 is coated with a 638nm wavelength high-transmittance film on both sides, and the side facing the emerald crystal 8 is coated with a dielectric film with a high reflectivity of 95% to 97% for wavelengths of 700 to 800nm.

[0063] When adjusting the angle mirror, the OC coupling output mirror must first be placed between the emerald crystal 8 and the angle mirror 9. The mirror 7, emerald crystal 8, and OC coupling output mirror 14 are aligned on the same optical axis. Together, they form a sub-resonant cavity within the large resonant cavity, used to generate the calibration reference laser. This calibration laser must be horizontal. To ensure this, a first aperture stop 15 and a third aperture stop 16 are placed between the OC coupling output mirror 14 and the angle mirror 9, and behind the angle mirror 9. The front and rear cavity mirrors of the sub-resonant cavity are continuously fine-tuned until the oscillating laser simultaneously passes through the center of both aperture stops. At this point, the oscillating laser remains horizontal.

[0064] Next, adjust the reference laser to align with the center of the 22° concave-planar reflector. During this adjustment, the 22° concave-planar reflector needs to be fixed on a three-axis adjustment frame. By adjusting the pitch and yaw of the reflector, ensure the reference laser is perpendicularly incident on the plane of the reflector, meaning that after reflection by the reflector 9, the reference laser still passes through the center of the first aperture stop 15. Then, attach a pre-cut target paper to the plane of the reflector. While keeping the pitch and yaw constant, adjust the height of the reflector so that the reference laser is precisely perpendicularly incident on the center of the target paper. At this point, the adjustment of the reference laser to align with the center of the 22° concave-planar reflector is complete.

[0065] Finally, rotate the YAW of the angle mirror 9 and place it at the estimated angle. A protractor and triangular cardboard can be used to estimate the placement angle. Throughout the process, it is necessary to ensure that the pitch direction of the angle mirror 9 is consistent before and after placement. At this point, a second aperture stop 17, with the same height as the first aperture stop 15 and the third aperture stop 16, needs to be placed behind the angle mirror 9, near the Q-switching system. When the reference light passes simultaneously through the centers of the first aperture stop 15 and the second aperture stop 17, the height of the reference light after reflection by the angle mirror 9 remains unchanged; that is, the pitch of the angle mirror remains unchanged before and after rotation. Then, a power meter 18 is placed between the 22° angle mirror 9 and the wavelength tuning element 10 to measure the power of the reference laser after reflection by the angle mirror. Before measuring the power, since the angle mirror is placed at an estimated angle, this estimated angle deviates significantly from 22°. To maximize the power measured by the power meter 18, the angle mirror's YAW can be finely adjusted while keeping the angle mirror's PITCH constant and the reference laser aligned with the center of angle mirror 9. At this point, the angle mirror 9 is at its optimal placement angle, and the adjustment is complete. The power meter 18 then needs to be removed from the optical path. This continues until the position of the last output mirror 13 is adjusted, ensuring the reference light returns along the entire optical path. Then, the OC-coupled output mirror 14 and all aperture stops used during the adjustment process are removed from the optical path.

[0066] Figure 4 The schematic diagram illustrates an adjustment device for an angle mirror in a Z-shaped folded cavity laser made of emerald crystal provided in an embodiment of the present disclosure.

[0067] See Figure 4 This diagram illustrates the angle mirror adjustment device in a Z-shaped folded cavity laser using an emerald crystal. The optical path includes: a pump source 1, a collimator 2, a half-wave plate 3, a PBS polarizing beam splitter 4, a half-wave plate 5, a lens 6, a mirror 7, an emerald crystal 8, an angle mirror 9, an output mirror 10, and a mirror 11. Mirrors 7 and 11 are positioned at opposite ends of the large resonant cavity optical path. Mirrors 7, emerald crystal 8, and 11 together constitute the oscillating resonant cavity of the entire optical path. In this embodiment, to make the resonant cavity structure more compact and shorten its length, the angle mirror 9 and output mirror 10 fold the entire optical path twice. The OC-coupled output mirror 13, the first aperture stop 14, the third aperture stop 15, the power meter 16, the second aperture stop 17, the power meter 18, and the aperture stop 19 are all components used for angle mirror adjustment within the resonant cavity and need to be removed during the final operation of the optical path.

[0068] In the entire optical path, both half-wave plate 3 and half-wave plate 5 are coated with a 638nm optically transparent dielectric film with 0° incident light. Lens 6 is a plano-convex lens, with a flat side facing the resonant cavity, and both sides are coated with a 638nm optically transparent dielectric film with 0° incident light. The laser crystal in the resonant cavity is an emerald crystal, with 700-800nm ​​optically transparent films coated at both ends, and the temperature is controlled at 20℃. Both reflector 7 and output mirror 10 are plane mirrors, and both sides are coated with a 638nm wavelength antireflection dielectric film. Reflector 7 is coated with a 700-800nm ​​wavelength total reflection dielectric film with 0° incident light on the cavity side, and output mirror 10 is coated with a 700-800nm ​​wavelength high reflection dielectric film with 22° incident light on the cavity side, with a reflectivity of 99%. Angle reflector 9 and reflector 11 are both plano-concave reflectors. Angle reflector 9 has its concave side facing the emerald crystal and is coated with a dielectric film that fully reflects 700-800nm ​​light with 22° incident light and fully transmits 638nm light, enabling it to fully reflect oscillating laser light and filter out residual pump light. Reflector 11 has its concave side facing the resonant cavity and is coated with a 700-800nm ​​wavelength total reflection dielectric film with 0° incident light.

[0069] In this embodiment, both the angle mirror 9 and the output mirror 10 are angle mirrors, which divide the entire optical path into three parts. The arms of each pair are not on the same optical axis, causing the light to fold twice within the resonant cavity. The following example will be used to explain in detail the adjustment method of the aforementioned angle mirror 9 and output mirror 10.

[0070] When adjusting these angle mirrors, an OC coupling output mirror 13 first needs to be inserted between the emerald crystal 8 and the angle mirror 9. This OC coupling output mirror 13 uses a double-sided coating process, with both ends coated with a 638nm wavelength antireflection film. The side facing the resonant cavity is coated with a dielectric film that is highly reflective to wavelengths of 700–800nm, achieving a reflectivity of 95%–97%. At this point, the mirror 7, the emerald crystal 8, and the OC coupling output mirror 14 are located on the same optical axis, forming a sub-resonant cavity for generating reference light. This sub-resonant cavity is located inside the large resonant cavity and shares the front cavity mirror and laser gain medium with it. The distance between the OC coupling output mirror 13 and the emerald crystal 8 in the sub-resonant cavity needs to be as close as possible to ensure very low loss throughout the sub-resonant cavity, making it easy to generate reference laser light. After the sub-resonator generates oscillating laser, it is necessary to continuously adjust the front and rear cavity mirrors until the oscillating laser is in a horizontal state. Specifically, the first aperture stop 14 and the third aperture stop 15 are placed between the OC coupling output mirror 14 and the angle reflector 9 and behind the angle reflector 9. These two aperture stops are at the same height. By continuously adjusting the reflector 7 and the OC coupling output mirror 13, the oscillating laser is made to pass through the center of these two aperture stops at the same time. At this time, the reference light is in a horizontal state.

[0071] Secondly, the angle reflector 9 is a plano-concave 22° reflector. During adjustment, the reference laser must first be aligned with the center of the plano-concave 22° angle reflector. Specifically, the reflective surface of the angle reflector 9 is placed facing the resonant cavity. By adjusting the pitch of the reflector 9, the reference laser is perpendicularly incident onto its plane, meaning the reference light, after reflection by the reflector 9, still passes through the center of the first aperture stop 14. Then, the pre-cut target paper is pasted onto the plane of the angle reflector. While keeping the pitch of the reflector 9 unchanged, only the vertical height of the angle reflector 9 perpendicular to the reference light is adjusted, making the center of the reference laser and the target paper coaxial. At this point, the reference laser is aligned with the center of the plano-concave 22° angle reflector.

[0072] Then, keeping the pitch of the angle reflector constant, place the angle reflector at the estimated angle. When estimating the angle, you can use auxiliary tools such as a protractor or triangular cardboard. To keep the pitch of the angle reflector constant during placement, a second aperture stop 17 needs to be placed between reflector 9 and reflector 10. This stop is at the same height as the first aperture stop 14. After the angle reflector is placed at the estimated angle, the reference light passing through the center of the first aperture stop 14, after being reflected by reflector 9, still passes through the center of the second aperture stop 17. At this point, the reference light before and after reflectingor 9 is at the same height, meaning the pitch of the angle reflector remains constant before and after placement.

[0073] Finally, since there is still a significant deviation between the reflection angle and 22°, a power meter 16 needs to be placed behind the reflector 9, close to the output mirror 10. While ensuring the reference light is aligned with the center of the reflector 9, the YAW of the angle reflector 9 is finely adjusted. The optimal adjustment state of the plano-concave 22° reflector is achieved when the power measured by the power meter 17 reaches its maximum. After the angle reflector 9 is adjusted, the power meter 17 can be removed.

[0074] The output mirror 10 is a flat 22° reflector. Its reflection efficiency is highest when incident light with a wavelength of 700–800 nm is incident at a 22° angle. When adjusting the output mirror 10, a fourth aperture stop 19, with the same height as the second aperture stop 17, needs to be placed between the output mirror 10 and the reflector 11. This ensures that the reference laser before and after reflection from the output mirror 10 passes through the centers of both the second and fourth aperture stops 17, maintaining a constant height before and after reflection. After rotating the output mirror 10 by the estimated angle, its pitch may change slightly. To ensure consistent height of the reference laser before and after reflection from the output mirror 10, the pitch of the output mirror 10 needs to be fine-tuned so that the reference laser passes through the centers of both the second and fourth aperture stops 17 simultaneously. At this point, the pitch of the output mirror 10 remains unchanged. Then, a power meter 18 is placed between the output mirror 10 and the reflector 11 to measure the power reflected by the output mirror 10. While keeping the pitch of output mirror 10 unchanged, fine-tune the yaw of output mirror 10 until the power measured by power meter 18 is at its maximum. At this point, the adjustment of output mirror 10 is complete, and power meter 18 is removed.

[0075] After the last reflector 11 is placed, the reference laser in the entire optical path can return along the same path after being reflected by the reflector 11. At this point, the OC coupling output mirror 13, all aperture stops and power meters in the entire optical path can be removed.

[0076] Figure 5 The illustration shows a schematic diagram of an adjustment device for an angle mirror in a long cavity self-Q-switched alexandrite laser provided in an embodiment of the present disclosure.

[0077] like Figure 5As shown, the optical path of the angle mirror adjustment device in the long-cavity self-Q-switched alexandrite laser includes: pump source 1, collimator 2, half-wave plate 3, PBS polarizing beam splitter 4, half-wave plate 5, lens 6, mirror 7, alexandrite crystal 8, mirror 9, output mirror 10, mirror 11, and mirror 12. The entire resonant cavity structure is W-shaped. Mirrors 9, 10, and 11 fold the entire resonant cavity three times, dividing it into four parts. The cavity length is approximately 1330 mm. Mirrors 7 and 12 are planar mirrors, while mirrors 9 and 11 are plano-concave mirrors with a curvature of 300 mm. Their inner surfaces are coated with a high-reflectivity film in the 700–800 nm laser band. The reflector 7 has anti-reflection coatings on both sides for the 638nm pump light band; the output mirror 10 is also a plane mirror coated with a dielectric film that provides high reflectivity for wavelengths of 700-800nm, with a reflectivity of 99%. Furthermore, a TEC temperature control device is used to maintain the temperature of the emerald crystal at 20℃. The pump source 1 is a 638nm LD pump, and the collimator 2 is a Thorlabs C40SMA-B fiber collimator with a focal length of 40mm and an anti-reflection coating range of 650-1050nm. Both half-wave plates 3 and 5 are coated with 638nm high-transmittance films, and the center wavelength transmitted by the PBS polarizing beam splitter 4 is also 638nm. The OC coupling output mirror 13, the first aperture stop 14, the third aperture stop 15, the power meter 16, the second aperture stop 17, the power meter 18, the fourth aperture stop 19, the power meter 20, and the fifth aperture stop 21 in the entire optical path are all components used for adjusting the angle reflector in the resonant cavity, and they all need to be removed during the final operation of the optical path.

[0078] In this embodiment, the angle reflectors include a reflector 9, an output mirror 10, and a reflector 11. These angle reflectors fold the entire optical path three times, with the optical path not aligned with a single axis before and after each fold. The adjustment method of the aforementioned angle reflectors will be explained in detail below using this example.

[0079] Before adjusting these angle mirrors, an OC coupling output mirror 13 needs to be inserted between the emerald crystal 8 and the mirror 9, making the mirror 7, emerald crystal 8, and OC coupling output mirror 13 coaxial. At this point, the mirror 7, emerald crystal 8, and OC coupling output mirror 13 together form a sub-resonant cavity for generating the reference laser. When the oscillating laser is horizontal, it can be used as the reference light for adjusting the angle mirrors. To ensure the oscillating laser is horizontal, two equally heightened first aperture stops 14 and third aperture stops 15 are placed behind the OC coupling output mirror. The front and rear cavity mirrors are continuously fine-tuned until the oscillating laser simultaneously passes through the center of both aperture stops. At this point, the oscillating laser remains horizontal, and the output laser at this time is used as the reference laser.

[0080] Secondly, reflector 9 is a 22° reflector. When the incident light is incident at 22°, the loss of reflected light is minimized. During adjustment, the reference laser needs to be aligned with the center of the angle reflector 9. Specifically, reflector 9 is placed directly opposite the sub-resonant cavity. By adjusting the pitch and yaw of the angle reflector 9, the reference laser is made to pass through the center of the first aperture stop 14 and then be perpendicularly incident into the plane of the angle reflector. That is, after being reflected by the angle reflector 9, the reference laser still passes through the center of the first aperture stop 14. Then, a pre-cut target paper is attached to the inside of the angle reflector. While keeping the pitch and yaw of the angle reflector 9 unchanged, the height of the angle reflector is adjusted so that the reference laser is exactly perpendicularly incident on the center of the target paper. At this point, the adjustment of aligning the reference laser with the center of the 22° angle reflector is complete.

[0081] Next, the angle mirror 9 is placed at the estimated angle. During this placement process, the angle mirror YAW needs to be continuously rotated. To ensure that the pitch direction of the angle mirror remains unchanged before and after rotation, a second aperture stop 17 is placed between the output mirror 10 and the mirror 9. The second aperture stop 17 and the first aperture stop 14 have been height-equipped to further ensure that the height of the reference laser remains consistent before and after reflection by the angle mirror 9. When the light rays before and after reflection by the reference light pass through the center of the first aperture stop 14 and the second aperture stop 17 simultaneously, the pitch of the angle mirror remains unchanged before and after rotation.

[0082] When placing the angle reflector at the estimated angle, the mirror surface may shift slightly. In this case, the point where the reference laser is incident on the reflector 9 will deviate from the center of the mirror surface. It is necessary to adjust the displacement of the reflector 9 to realign the reference laser with the center of the reflector 9.

[0083] Finally, a power meter 16 is placed between the reflector 9 and the output mirror 10 to measure the power of the reference light reflected by the reflector 9. Since the angle reflector is placed according to the estimated angle, its placement angle still has a certain difference from the optimal value. To ensure that the reference light is aligned with the center of the angle reflector 9, the YAW of the reflector 9 is finely adjusted until the power measured by the power meter 16 is at its maximum. At this point, the adjustment of the reflector 9 is complete, and the power meter 16 can be removed.

[0084] The output mirror 10 is a flat 22° reflector, and its reflection efficiency is highest when the incident light is incident at 22°. When adjusting the output mirror 10, a fourth aperture stop 19, with the same height as the first aperture stop 14, needs to be inserted between the output mirror 10 and the reflector 11. This fourth aperture stop 19 is used to calibrate the height of the reference laser light before and after the output mirror 10, ensuring that their heights are consistent. That is, after the reference laser light passing through the center of the second aperture stop 17 is incident on the output mirror 10, the reflected reference laser light simultaneously passes through the center of the fourth aperture stop 19. Then, keeping the pitch of the output mirror 10 unchanged, the output mirror 10 is rotated to the estimated angle. Because the estimated placement angle has a large error, a power meter 18 needs to be placed between the output mirror 10 and the reflector 11 to measure the power of the reference light reflected by the output mirror 10. By fine-tuning the YAW of the output mirror 10 until the power measured by the power meter 18 is at its maximum, the adjustment of the output mirror 10 is complete. Afterwards, the power meter 18 needs to be removed.

[0085] Reflector 11 is a plano-concave 22° reflector. Its adjustment method is the same as that for reflector 9. A fifth aperture stop 21 needs to be placed between reflectors 11 and 12 to calibrate the height of the reference light before and after passing through reflector 11. After aligning the reference laser with the center of reflector 11, keep the pitch constant and rotate reflector 11 to position it at the estimated angle. Then adjust the displacement of reflector 11 to align the reference light with the center of reflector 11 again. Since the estimated angle deviates from the optimal position, a power meter 20 needs to be placed between reflectors 11 and 12 to measure the power of the reference light reflected by reflector 11. Fine-tune the YAW of reflector 11 until the power measured by power meter 20 reaches its maximum. At this point, the adjustment of reflector 11 is complete, and power meter 20 needs to be removed.

[0086] After the last reflector 12 is placed, the light in the entire optical path can return along the same path after passing through the reflector 12. At this point, the OC coupling output mirror 13 and all aperture stops in the entire optical path can be removed.

[0087] The method and apparatus for adjusting the angle mirror in a laser resonator provided in this disclosure involve inserting an OC coupling output mirror behind the laser gain medium, forming a new sub-resonator with the front cavity mirror, laser gain medium, and OC coupling output mirror. This sub-resonator oscillates under the action of an end-face pump source, generating a reference laser. Using this reference laser, an aperture stop, a target paper, and a power meter, the angle mirror within the resonator can be adjusted quickly and accurately. Compared to existing methods that use helium-neon light to roughly estimate the reflection angle and adjust the angle mirror, this patent is faster, simpler, and more accurate. This adjustment method is particularly suitable for concave mirrors coated with a high-reflection film at the incident angle, as it does not require other sophisticated equipment and is not limited by the application environment. Furthermore, the adjustment apparatus only includes an OC coupling output mirror, an aperture stop, a target paper, and a power meter; it uses very few components, has a very simple structure, is easy to implement, and is inexpensive, making it suitable for adjusting angle mirrors in most experimental scenarios.

[0088] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0089] Although this disclosure has been shown and described with reference to specific exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made to this disclosure without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Therefore, the scope of this disclosure should not be limited to the above embodiments, but should be defined not only by the appended claims, but also by their equivalents.

Claims

1. A method for adjusting an angle reflector in a laser resonant cavity, characterized in that, The method includes: An OC coupling output mirror is placed between the laser gain medium and the angle reflector inside the laser resonant cavity, so that the OC coupling output mirror, the laser gain medium and the front cavity mirror in the laser form a sub-resonant cavity to generate a reference laser. A first aperture stop is set between the OC coupling output mirror and the angle reflector. The angle reflector is adjusted so that after the reference laser passes through the center of the first aperture stop and reaches the angle reflector, the light reflected back by the angle reflector also passes through the center of the first aperture stop and is aligned with the center of the angle reflector. The angle reflector is placed according to the estimated reflection angle. In order to keep the pitch angle of the angle reflector constant, a second aperture stop is set in the reflection direction of the angle reflector. The angle reflector is adjusted so that the reference laser reflected by the angle reflector passes through the center of the second aperture stop. Adjust the height of the angle reflector so that the reference laser is aligned with the center of the angle reflector again; Measure the power of the reference laser reflected by the angle reflector, adjust the yaw angle of the angle reflector until the power is at its maximum, and then stop adjusting.

2. The adjustment method according to claim 1, characterized in that, The method further includes: A third aperture stop is provided behind the angle reflector, and the first aperture stop and the third aperture stop are at the same height; Before adjusting the angle reflector, adjust the angles of the OC coupling output mirror and the front cavity mirror so that the reference laser passes through the center of the first aperture stop and the third aperture stop simultaneously, making the reference laser horizontal.

3. The adjustment method according to claim 1, characterized in that, When the angle reflector is a concave angle reflector, adjusting the angle reflector so that the reference laser light, after passing through the center of the first aperture stop and reaching the angle reflector, also passes through the center of the first aperture stop, further includes: A target paper is attached to the angle reflector, and the height of the angle reflector is adjusted. Once the reference laser is aligned with the center of the target paper, the target paper is removed, thus completing the alignment of the reference laser with the center of the angle reflector.

4. The adjustment method according to claim 1, characterized in that, The method further includes: Adjust the second aperture stop to be at the same height as the first aperture stop.

5. The adjustment method according to claim 1, characterized in that, Adjusting the height of the angle reflector so that the reference laser is once again aligned with the center of the angle reflector includes: A target paper is attached to the angle reflector, and the height of the angle reflector is adjusted. Once the reference laser is aligned with the center of the target paper, the target paper is removed, thus completing the alignment of the reference laser with the center of the angle reflector.

6. The adjustment method according to claim 1, characterized in that, The method further includes: After the angle reflector is adjusted, remove the first aperture stop, the second aperture stop, and the power meter.

7. An adjustment device for an angle reflector in a laser resonant cavity, applied to the adjustment method described in any one of claims 1 to 6, characterized in that, include: An OC-coupled output mirror is disposed between the laser gain medium and the angle mirror inside the laser resonant cavity. It is coaxial with the laser gain medium and the front cavity mirror inside the laser resonant cavity and is used to form a sub-resonant cavity with the laser gain medium and the front cavity mirror to generate a reference laser. A first aperture stop is disposed between the OC coupling output mirror and the angle reflector to assist in adjusting the angle reflector so that the reference laser is aligned with the angle reflector. The second aperture stop is located in the reflection direction of the angle mirror and is used to assist in calibrating the reflection angle of the angle mirror during the adjustment process of the angle mirror. A power meter, located after the angle reflector, is used to measure the power of the reference laser after it is reflected by the angle reflector.

8. The adjusting device according to claim 7, characterized in that, The regulating device further includes: The third aperture stop is located behind the angle mirror and at the same height as the first aperture stop. It is used to coordinate with the first aperture stop to calibrate the reference laser in the horizontal direction before adjusting the angle mirror.

9. The adjusting device according to claim 7, characterized in that, The regulating device further includes: A three-axis adjustment bracket is connected to the angle reflector and is used to adjust the height, forward / backward and left / right displacement of the angle reflector.

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