CN109449750B

CN109449750B - Laser light path stabilizing device

Info

Publication number: CN109449750B
Application number: CN201811533796.1A
Authority: CN
Inventors: 周淼淼
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-12-14
Filing date: 2018-12-14
Publication date: 2021-03-02
Anticipated expiration: 2038-12-14
Also published as: CN109449750A

Abstract

The invention relates to the technical field of laser, in particular to a laser light path stabilizing device which comprises a grating, three reflectors and four connecting rods, wherein the four connecting rods are movably connected through rotating shafts to form a deformable rhombohedron; the light paths reflected by the grating and the three reflectors are kept parallel to the central axis of a connecting rod connected with a rotating shaft where the grating and the three reflectors are located; the deformable rhomboid is formed by movably connecting the four connecting rods through the rotating shaft, and the reflector is arranged on the rotating shaft, so that light can be corrected through deformation of the rhomboid.

Description

Laser light path stabilizing device

Technical Field

The invention relates to the technical field of laser, in particular to a laser light path stabilizing device.

Background

Semiconductor lasers, generally, lasers using semiconductor materials as working media, have low manufacturing cost, high light emitting efficiency, wide spectral range and very wide application. Most commonly, the common articles are daily necessities such as laser pens and the like. However, the resonant cavity of the semiconductor laser is simple in design and has poor effects on mode selection and frequency stabilization, which results in a wider output wavelength band width ratio of the semiconductor laser and is insufficient when the wavelength is required to be precise.

In order to improve the frequency stabilization and mode selection characteristics of a semiconductor laser, a common method is to add an external cavity, that is, on the basis of a resonator of the semiconductor laser, a resonator is added, and two cavities select modes together, so that the number of gain modes is reduced, and the precision is improved.

Fig. 1 is a schematic diagram of a self-aligned external cavity frequency stabilized semiconductor laser. In fig. 1, a is the normal output light of the semiconductor laser, b is the positive order diffraction of the grating, and c is the zero order diffraction (reflection) of the grating. A general semiconductor laser has output light similar to a point light source or a line light source and has a certain spread angle. After being focused by the lens, parallel light output is formed, and as shown in a, the structure is the common parts such as a laser pen and the like. In the design of external cavity frequency stabilization, a wavelength selection component is generally added, most commonly a grating, and the angle selectivity of diffracted light can be utilized to limit a laser mode to a mode. As shown in b, the first order diffracted light with a specific wavelength has a direction opposite to a and a slightly weaker energy, returns to the semiconductor laser part, participates in resonance amplification, wins out the mode with the wavelength, and finally leads to the mode of the whole laser, and only the mode is left. In practical use, because the direction of b can return to the semiconductor laser within a certain angle, the wavelength selectivity of the semiconductor laser also has certain precision, and the precision depends on the grating constant of the grating and the size of the angle range of b light allowed by the diaphragm. c is the zero-order diffracted output light, the energy is weakest in a, b, c, which has a relation to a, similar to the incident light reflected light, the direction is related to the grating angle and the direction of a. If the grating theta is rotated, c will change direction 2 theta.

The technical scheme of fig. 1 is feasible for a semiconductor laser that does not need to adjust the wavelength, because the first-order diffracted light of the blazed grating is relatively strong, a stable and efficient resonant cavity can be formed, the grating can provide high-resolution wavelength selection, and finally single-mode laser output is formed. But this structure results in a rotation of the output light direction when wavelength adjustment is required. Although this rotation is not much, it still results in an overall adjustment of the subsequent optical path.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provided is a laser light path stabilizing device capable of outputting laser light whose direction is stabilized and wavelength is adjustable.

In order to solve the technical problems, the invention adopts the technical scheme that:

the grating and the three reflectors are respectively connected to the four rotating shafts of the rhombohedron, and the reflecting surfaces of the grating and the three reflectors are superposed with the axial lead of the rotating shafts of the rhombohedron;

the light paths reflected by the grating and the three reflectors are kept parallel to the central axis of the connecting rod connected with the rotating shaft where the grating and the three reflectors are located.

The invention has the beneficial effects that: the light paths reflected by the grating and the three reflectors are kept parallel to the central shaft of the connecting rod connected with the rotating shaft of the grating, the light can be corrected while the rotation angle of the grating is adjusted through deformation of the rhombohedron, so that when the grating rotates, the direction of an output light beam is stable, the wavelength bandwidth of the output light is narrow, the output light characteristic is kept unchanged, and the stable and continuous output of the variable wavelength of the auto-collimation external cavity frequency stabilization semiconductor laser is realized.

Drawings

FIG. 1 is a schematic diagram of a prior art self-collimating external cavity frequency stabilized semiconductor laser;

fig. 2 is a schematic structural diagram of a laser light path stabilizing device according to an embodiment of the present invention;

description of reference numerals: 1. a base; 2. a grating; 3. a mirror; 4. a movable rod; 5. fixing the rod; 6. a motor; 7. a focusing lens; 8. a polarizer; 9. a laser mount; 10. a rotating shaft; 11. an orientation block; 12. an orientation bar; 13. a laser.

Detailed Description

In order to explain technical contents, achieved objects, and effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.

The most key concept of the invention is as follows: the deformable rhombohedron is formed by movably connecting the four connecting rods through the rotating shaft, and the reflector is arranged on the rotating shaft, so that light can be corrected through deformation of the rhombohedron.

Referring to fig. 1 and 2, a laser light path stabilizing device includes a grating 2, three reflectors 3 and four connecting rods, the four connecting rods are movably connected by a rotating shaft 10 to form a deformable rhomboid, the grating 2 and the three reflectors 3 are respectively connected to the four rotating shafts 10 of the rhomboid, and the reflecting surfaces of the grating 2 and the three reflectors 3 are coincident with the axial line of the rotating shaft 10 of the rhomboid;

the light paths reflected by the grating 2 and the three reflectors 3 are kept parallel to the central axis of the connecting rod connected with the rotating shaft 10 where the grating is located.

From the above description, the beneficial effects of the present invention are: the four connecting rods are movably connected through the rotating shaft 10 to form a deformable rhombohedra and the reflecting mirror 3 is arranged on the rotating shaft 10, the light path reflected by the grating 2 and the three reflecting mirrors 3 is kept parallel to the central shaft of the connecting rod connected with the rotating shaft 10 where the grating is located, the light path can be deformed through the rhombohedra, the light is corrected while the rotating angle of the grating 2 is adjusted, when the grating rotates, the output light beam direction is stable, the output light wavelength bandwidth is narrow, the output light characteristic is unchanged, and the stable and continuous output of the variable wavelength of the auto-collimation external cavity frequency stabilization semiconductor laser is realized.

Further, laser light path stabilising arrangement still includes base 1, the connecting rod is a dead lever 5 and three movable rod 4, dead lever 5 is fixed on base 1, the speculum 3 that forms the emergent light is emergent speculum 3, dead lever 5 for be provided with the pivot 10 of being connected with grating 2 and be provided with the connecting rod of the pivot 10 of being connected with emergent speculum 3.

As is apparent from the above description, the stability of the grating 2 and the exit mirror 3 can be maintained by the arrangement of the fixing bar 5.

Further, the laser light path stabilizing device further comprises a motor 6, and the motor 6 is movably connected with one of the movable rods 4 and is used for driving the movable rod to move.

From the above description, one of the three movable rods 4 is driven by the motor 6 to move, so as to realize more accurate angle adjustment of the laser light path stabilizing device, thereby controlling the output wavelength.

Further, the light emitting direction of the exit mirror 3 is parallel to the central axis of the fixing rod 5.

Further, a focusing lens 7 is arranged on the side edge of the grating 2.

Further, a polarizer 8 is disposed between the grating 2 and the focusing lens 7.

As is apparent from the above description, the number of modes of the laser light can be reduced by the polarizer 8.

Further, a laser installation seat 9 is arranged on the base 1, the focusing lens 7 is connected to the laser installation seat 9, and the polarizer 8, the focusing lens 7 and the grating 2 are located on the same straight line.

Further, an orientation block 11 is further arranged between the rotating shaft 10 and the grating 2 or the reflector 3, the orientation block 11 is connected with the rotating shaft 10, an orientation rod 12 and an orientation groove are fixed on the orientation block 11, and the orientation rod 12 and the orientation groove of the orientation block 11 which are opposite to each other are matched with each other.

From the above description, it can be known that, through the arrangement of the orientation block 11, a stable scheduling adjustment can be formed, the fixed orientation rod 12 is responsible for twisting the angle of the current mirror base, and the orientation rod 12 in the orientation groove provides a transverse force for the opposite mirror base, changes the direction, and cooperates with each other, so that the transverse force applied to the rotating shaft 10 or between the orientation block 11 and the rotating shaft 10 is relatively uniform, and the sliding wear is reduced.

Further, the reflecting mirror 3 is a metal film reflecting mirror 3.

As is apparent from the above description, the mirror 3 can be used at a relatively specific reflection angle by using the metal film, and can be applied to a case where the reflection angle and the reflection wavelength are not fixed.

Example one

A laser light path stabilizing device is used for manufacturing an external cavity frequency stabilization semiconductor laser light path with the central wavelength of 405nm and the output power of about 100 mW;

the grating and the three reflectors are respectively connected to four rotating shafts of the rhombohedron, and the reflecting surfaces of the grating and the three reflectors are superposed with the axial lead of the rotating shafts of the rhombohedron; the dead lever is fixed on the base, the reflector that forms the emergent light is the emergent reflector, the dead lever be provided with the pivot of being connected with the grating and be provided with the connecting rod of the pivot of being connected with the emergent reflector. The emergent light direction of the emergent reflector is parallel to the central axis of the fixing rod.

The laser light path stabilizing device further comprises a motor, and the motor is movably connected with one of the movable rods and is used for driving the movable rod to move.

And a focusing lens is arranged on the side edge of the grating. And a polarizer is also arranged between the grating and the focusing lens. The laser device comprises a base, a polarizer, a focusing lens and a grating, wherein the base is provided with a laser device mounting seat, the focusing lens is connected to the laser device mounting seat, and the polarizer, the focusing lens and the grating are positioned on the same straight line.

The grating or reflector is characterized in that an orientation block is further arranged between the rotating shaft and the grating or reflector, the orientation block is connected with the rotating shaft, an orientation rod is fixed on the orientation block, an orientation groove is formed in the orientation block, and the orientation rod and the orientation groove of the orientation block which are opposite to each other are matched with each other.

The reflector is a metal film reflector.

The semiconductor laser diode selects ML320G2-11 of Thorlabs company, the central wavelength is 405nm, and the stable output energy is 120 mW. The equivalent resistance was about 42 Ω and the power was 0.6W when calculated from the operating current of 120mA at 405nm and the operating voltage of 5V. At the highest power, the wavelength is 410nm, the current is 160mA, the voltage is 6V, the equivalent resistance is about 37.5 omega, and the power is 0.96W. Therefore, this semiconductor diode laser requires a power supply with a voltage of at least 6V and a current of at least 160 mA.

The focusing lens matched with the laser diode uses a 0.5 inch f =15.0mm lens with SM05 threads installed, model LA1540-A-ML, material N-BK7, antireflection film 350-.

400nm blazed gratings of Thorlabs company are selected as the gratings. The blazed grating is a reflective grating, and the intensity of the positive-order diffraction light can reach 70% of the incident light intensity; the remaining light intensity is mainly concentrated on the 0 th order diffracted light. The grating selected is a 1200 line/mm grating, the first order diffracted light has a wavelength variation ratio of 0.81nm/mrad with direction, i.e., about 0.0573 ° for every 1mrad angle, and the diffracted light has a wavelength variation of 0.81 nm. Then, converting, every time the angle changes by 1 degree, the wavelength of the diffracted light changes by 14.14 nm; for every 1nm wavelength change, the angle changes by 0.0707 °, 1.23mrad, that is, for a moving arm with the same direction of light, the ratio of the distance moved by the end to the length of the arm, for a 1nm wavelength change, is about 1/810.

The rotation angle of the movable arm is 2 times of the rotation angle of the grating, and the rotation angle of the first-order diffraction light is 2 times of the rotation angle of the grating; when the movable arm is rotated, the grating rotates along with the rotation, so that the first-order diffraction light also rotates, if the wavelength is not changed, the rotation angle of the first-order diffraction light is 2 times of the rotation angle of the grating, and the direction of the first-order diffraction light is the same as that of the movable arm, so that a similar following effect is formed.

If the wavelength needs to be changed, for example, 1nm is increased, light with an angle of 1.23mrad with the original direction needs to be selected and rotated to the incident light direction, and the light needs to be rotated by 1.23mrad, and because the rotation angle of the light is the same as the rotation angle of the rotating arm, the rotation of the rotating arm by 1.23mrad can be realized. Therefore, the moving arm only needs to move in a mode of changing the wavelength of 1nm and the moving proportion of the tail end 1/810 every time, the first-order diffraction light of the grating can always keep the same angle, and therefore the adjustment and control of the output wavelength are achieved.

PF10-03-F01 ultraviolet enhanced aluminized film reflecting mirrors are selected as the reflecting mirrors, an adjusting frame is installed, a KS1 model 1-inch round precision adjusting frame of Thorlabs is selected, and the adjusting frame can be used for installing an optical device with the diameter of 1 inch and adjusting the deflection angle of the optical device. The three adjusting knobs are arranged, the rotation is carried out simultaneously, the front position and the rear position of the optical device can be slightly changed, and the three adjusting knobs are suitable for occasions which need to precisely adjust the positions and are not suitable for mounting a displacement platform.

The polarizer is a Taylor prism with a clear aperture of 10mm, and is of a GL10-A model of Thorlabs.

The motor adopts a 50mm linear direct current motor driver of Thorlabs company, and the precision of the motor can reach 1 um.

The motor is for controlling rhombus part removal, the length of link is 150mm, and the removal control point is the center of the activity pole that both ends are connected with the activity pole respectively, and equivalent arm length is 150 x 1.5=225mm, and the wavelength changes 1nm, corresponds to and removes 225/810=5/18=0.278 mm. Since the wavelength range of the semiconductor laser diode is about 400-410nm, the shift range is 10 × 0.278=2.78 mm.

When the motor is completely straightened, the motor is at a 50mm position, and the included angle between the corresponding movable arm and the corresponding fixed arm is 27 degrees. And the blazed angle of the blazed grating is 13 degrees 53 ', the corresponding included angle is 27 degrees 46', and the blazed wavelength is 400 nm. According to the calculation, when the wavelength is 400nm, the corresponding length of the motor is 46.989 mm; the length is 44.209mm when the wavelength is 410 nm. In the interval of 400-410nm, the variation of the wavelength along with the length of the motor can be approximately considered as linear variation.

The standard of perfect grating installation is that zero-order light and the rotating arm are in the same direction, positive first-order diffracted light and incident light are at the same height, the angle can deviate, but the heights must be consistent. Optimally, the strongest spot of the positive first order diffracted light is totally reflected back to the laser diode.

The first reflector is installed and adjusted, the direction of emergent light is adjusted to be parallel to the sliding arm, then whether a light spot is in the right and left middle of the collimating plate or not is observed, if deviation exists, the front and back of the reflector are adjusted, the light direction is calibrated again, and whether the light reaches the center or not is observed. If the light does not arrive, the user can observe whether the light is close to or far away, and according to the change, the front and back positions of the reflector are adjusted again until the light is at the center of the collimation plate and is parallel to the sliding arm. The remaining mirror mounting standards are similar.

The final mirror direction needs to be collimated by external components, and then the front and back positions of the mirrors are adjusted. If no proper external auxiliary component can be found, the wavelength is directly changed after the laser is adjusted, whether the light spot is shifted or not is observed, and then the front and back positions are adjusted according to the shifting direction. The direction of the reflector determines the light emitting direction, and the direction is not strictly required to be the same as the fixed arm and can be freely selected. As long as the front and back positions are the centers of the rotating shafts, the light emitting direction can not be changed theoretically.

And adjusting the position of the motor to enable the positive first-order diffraction light of the grating to enter the laser diode and check the wavelength of the output light. If the wavelength of the output light has obvious bandwidth narrowing, the external cavity frequency stabilization is successful, otherwise, the grating direction needs to be adjusted, more diffracted light enters the laser diode, and the feedback intensity of the frequency stabilization is increased.

After the frequency stabilization is successful, the position of the motor is changed, the wavelength and the corresponding energy are measured for multiple times, and the corresponding effective frequency stabilization range, namely the effective output wavelength range of the laser, is found. After the wavelength data is obtained, a wavelength calibration curve can be drawn according to the data, and then the motor position corresponding to each wavelength is obtained according to the curve.

If the automatic control is needed, the linear difference value is directly carried out on the calibration data to obtain a wavelength-position relation function, and then the position is adjusted according to the required wavelength.

In summary, the laser light path stabilizing device provided by the present invention forms a deformable rhomboid through the movable connection of the four connecting rods via the rotating shaft, and the reflecting mirrors are arranged on the rotating shaft, the light paths reflected by the grating and the three reflecting mirrors are kept parallel to the central axis of the connecting rod connected to the rotating shaft, and the light can be corrected while adjusting the rotation angle of the grating through the deformation of the rhomboid, so that the stable output light beam direction, the narrow output light wavelength bandwidth, and the unchanged output light characteristic are realized when the grating rotates, and the stable and continuous output of the variable wavelength of the auto-collimation external cavity frequency-stabilized semiconductor laser is realized.

Through the setting of dead lever, can keep the stability of grating and exit mirror.

One of the three movable rods is driven by the motor to move, so that the laser light path stabilizing device is accurately adjusted in angle, and the output wavelength is controlled.

The number of modes of the laser light can be reduced by the polarizer.

Through the setting of orientation piece, can form stable dispatch adjustment, fixed orientation lever is responsible for twisting the angle of present mirror seat, and orientation lever in the orientation groove then provides the transverse force for the mirror seat of counterpointing, and the redirecting mutually supports, just can let pivot department or the transverse force that receives between orientation piece and the pivot relatively more even, alleviates sliding wear.

The use of the metal film mirror enables the mirror to be used at a relatively special reflection angle, and is applicable to a case where the reflection angle and the reflection wavelength are not fixed.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to the related technical fields, are included in the scope of the present invention.

Claims

1. A laser light path stabilizing device is characterized by comprising a grating, three reflectors and four connecting rods, wherein the four connecting rods are movably connected through rotating shafts to form a deformable rhombohedral body, the grating and the three reflectors are respectively connected to the four rotating shafts of the rhombohedral body, and the reflecting surfaces of the grating and the three reflectors are superposed with the axial lead of the rotating shafts of the rhombohedral body;

the light paths reflected by the grating and the three reflectors are kept parallel to the central axis of a connecting rod connected with a rotating shaft where the grating and the three reflectors are located;

the laser light path stabilizing device further comprises a base, four connecting rods are a fixing rod and three movable rods, the fixing rod is fixed on the base, the reflector forming emergent light is an emergent reflector, and the fixing rod is provided with a rotating shaft connected with the grating and a connecting rod provided with a rotating shaft connected with the emergent reflector.

2. The apparatus of claim 1, further comprising a motor, wherein the motor is movably connected to one of the movable rods and is configured to move the movable rod.

3. The laser light path stabilizing apparatus according to claim 1, wherein the exit direction of the exit mirror is parallel to the central axis of the fixing rod.

4. The laser light path stabilizing device according to claim 1, wherein the side of the grating is further provided with a focusing lens.

5. The laser light path stabilizing device according to claim 4, wherein a polarizer is further disposed between the grating and the focusing lens.

6. The laser light path stabilizing device according to claim 5, wherein a laser mounting seat is arranged on the base, the focusing lens is connected to the laser mounting seat, and the polarizer, the focusing lens and the grating are located on the same straight line.

7. The laser light path stabilizing device according to any one of claims 1 to 6, wherein an orientation block is further disposed between the rotating shaft and the grating or the reflecting mirror, the orientation block is connected to the rotating shaft, an orientation rod and an orientation groove are fixed on the orientation block, and the orientation rod and the orientation groove of the orientation block which are opposite to each other are matched with each other.

8. The laser light path stabilizing device according to any one of claims 1 to 6, wherein the reflecting mirror is a metal film reflecting mirror.