A helium-neon dual wavelength laser

Abstract

The application belongs to laser technology and discloses a helium-neon double-wavelength laser, which comprises a straight cavity resonant cavity body, a plane mirror, a spherical mirror, an anode and a cathode. The straight cavity resonant cavity body is a cuboid glass. Gas storage holes are opened at both ends of the cuboid glass along the length direction. A main discharge gain hole is further opened in the cuboid glass for connecting the two gas storage holes. The anode and the cathode are arranged on the surface of the cuboid glass. Two discharge gain holes are opened in the cuboid glass perpendicularly to the main discharge gain hole for connecting the anode and the cathode with the main discharge gain hole. The plane mirror and the spherical mirror are connected to the end faces of the cuboid glass along the length direction through optical cement. The plane mirror is arranged close to the anode, and the spherical mirror is arranged close to the cathode. A diaphragm hole is arranged in the main discharge gain hole between the anode and the gas storage hole close to the plane mirror.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser, and particularly relates to a helium-neon double-wavelength laser. BACKGROUND

[0002] He-Ne laser has good output beam quality and high frequency stability, and is widely used in the field of measurement. Multi-frequency laser can realize high-precision large-size measurement, and it is very difficult to realize visible light He-Ne double-wavelength output.

[0003] By means of 633nm laser oscillation, Raman scattering between 633nm and metastable state of Ne atom can be realized through reasonable design of gain characteristics and metastable state of Ne atom, and 633nm and 650nm lasers can be simultaneously and stably oscillated by realizing amplification of 650nm gain.

[0004] Under the pumping action of He-Ne discharge, the gain coefficient of general working substance to 633nm laser is inversely proportional to the diameter d of the capillary tube. Ne atoms excited and radiated to the lower energy level are transferred to the metastable 1S energy level by means of spontaneous radiation, and then return to the ground state through the way of collision with the tube wall.

[0005] Theoretical research shows that the root of 650nm generation is related to the metastable state of Ne atom. The 650nm line is an electron Raman line, which is pumped by 633nm. The 650nm photon is generated by interaction of 633nm photon and metastable Ne atom. This interaction causes the metastable atom to be promoted to a high energy level, so that the photon is scattered to a lower energy 650nm. In this way, the phenomenon of losing 633nm photons reduces the oscillation energy of 633nm laser.

[0006] One 633nm photon interacts with one metastable Ne atom, and scatters 650nm scattered light. The scattering efficiency is not only proportional to the number of 633nm photons, but also proportional to the number of metastable Ne atoms.

[0007] If the tube diameter d is increased, the opportunity of collision between atoms and the tube wall is reduced, and the atoms remaining in the 1S state can absorb spontaneous radiation photons to return to the lower energy level of laser, thereby reducing the inversion population. SUMMARY

[0008] The application aims to provide a He-Ne double-wavelength laser, which can realize simultaneous and high-stable output of 633nm and 650nm in He-Ne laser.

[0009] A helium-neon double-wavelength laser comprises a straight cavity resonant cavity, a plane mirror, a spherical mirror, an anode, and a cathode.

[0010] The straight cavity resonant cavity is a cuboid glass; the cuboid glass has gas storage holes opened at both ends along the length direction inside, and a main discharge gain hole is also opened inside the cuboid glass for connecting the two gas storage holes;

[0011] An anode and a cathode are arranged on the surface of the cuboid glass respectively, and two discharge gain holes perpendicular to the main discharge gain hole are opened inside the cuboid glass for connecting the anode and the cathode to the main discharge gain hole respectively from the discharge gain holes;

[0012] The cuboid glass is connected with a plane mirror and a spherical mirror through optical cement at both ends along the length direction respectively; and the plane mirror is arranged close to the anode, and the spherical mirror is arranged close to the cathode;

[0013] A diaphragm hole is arranged in the main discharge gain hole between the anode and the gas storage hole close to the plane mirror.

[0014] Further, the total length of the straight cavity resonant cavity is not more than 230 mm.

[0015] Further, the diameter of the discharge gain hole is between 3.5 mm and 5 mm.

[0016] Further, the diameter of the diaphragm hole is 1.95 mm, and the length is 3 mm.

[0017] Further, the distance between the cathode and the anode is between 150 mm and 170 mm.

[0018] Further, the transmittance of the plane mirror is 0.02%, and the curvature radius of the spherical mirror is 3 m to 6 m.

[0019] Further, the plane mirror is a circular pie-shaped glass, and first annular grooves of the same size are opened at both ends, and the distance between the bottoms of the two first annular grooves is 0.6 mm to 2 mm.

[0020] The central plane is an optical reflection plane, and the outer ring surface is a connecting plane connected with the straight cavity resonant cavity.

[0021] Further, the spherical mirror is a circular pie-shaped glass, and second annular grooves of the same size are opened at both ends, and the distance between the bottoms of the two second annular grooves is 0.6 mm to 2 mm.

[0022] The central plane is a concave spherical surface as an optical reflection plane, and the outer ring surface is a connecting plane connected with the straight cavity resonant cavity.

[0023] Further, the plane mirror and / or the spherical mirror are further connected with a displacement adjusting assembly outside;

[0024] The displacement adjusting assembly is a circular pie-shaped metal, and third annular grooves of the same size are opened at both ends, and the distance between the bottoms of the two third annular grooves is 0.6 mm to 2 mm.

[0025] The displacement adjusting assembly is centrally provided with a threaded through hole, and a hollow frequency stabilizing pin is screwed in the threaded through hole;

[0026] The laser is output through the hollow frequency stabilizing pin at one end of the plane mirror;

[0027] Each of the two third annular grooves is provided with a piezoelectric ceramic, and the hollow frequency stabilizing pin is driven to move axially through the two piezoelectric ceramics, so that the central optical reflection plane of the plane mirror and / or the spherical mirror moves axially to change the working longitudinal mode of the output laser.

[0028] Further, the surface shape of the straight cavity resonant cavity body along the length direction of the two end faces is less than 0.5, and the local surface shape is less than 0.1; the two end faces are perpendicular to the axial direction of the main discharge gain hole, and the perpendicularity is less than 20 arc seconds, and the parallelism of the two end faces is less than 5 arc seconds.

[0029] The beneficial effects of the present application are as follows:

[0030] The present application provides a laser for simultaneously stabilizing output dual-wavelength lasers in the same laser straight cavity resonant cavity, which ensures that the output light beam has strong coherence, small laser divergence angle and excellent laser quality; and can effectively eliminate common-mode errors in the measurement output in dual-frequency interference measurement.

[0031] After the laser of the present application is operated in the frequency stabilization mode, the output dual-wavelength lasers have the same high-precision wavelength stability and frequency stability; in large-size laser length measurement, the large wavelength difference between the dual-wavelength lasers is beneficial to improve the measurement precision and measurement range.

[0032] The present application adopts optical mechanical manufacturing technology, which is convenient for precision control of laser parameters and ensures the consistency of laser products.

[0033] The present application adopts the comprehensive technology of optical cementing of the mirror and the cavity and indium sealing of the electrode and the cavity, reduces the pollution of the laser gain medium, effectively improves the working gas purity and stability of the laser, prolongs the working life of the laser, and improves the working reliability of the laser. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present application, the specific drawings of the embodiments will be described below.

[0035] Figure 1 It is a schematic diagram of energy level transition of a helium-neon laser;

[0036] Figure 2 It is a structure schematic diagram of a He-Ne dual-wavelength laser and a control device provided by the embodiment of the present application;

[0037] Figure 3A helium-neon laser sectional view provided by the embodiment of the present application;

[0038] Figure 4 A spherical mirror schematic diagram provided by the embodiment of the present application;

[0039] Figure 5 A plane mirror schematic diagram provided by the embodiment of the present application;

[0040] Figure 6 A displacement adjustment assembly schematic diagram provided by the embodiment of the present application;

[0041] Figure 7 A light intensity synchronous scanning mode curve schematic diagram provided by the embodiment of the present application;

[0042] In the figure, 1 is a straight cavity resonant cavity, 2 is an anode, 3 is a cathode, 4 is a plane mirror, 5 is a spherical mirror, 6 is a displacement adjustment assembly, 7 is a frequency stabilization pin, 8 is a photodetector, 9 is a preamplifier, 10 is a control electronic device, 11 is an optical diaphragm, 12 is a main discharge gain hole, 13 is a gas storage hole. DETAILED DESCRIPTION

[0043] This part is the embodiment of the present application, which is used to explain and illustrate the technical solution of the present application.

[0044] The present application provides a He-Ne dual-wavelength laser, which can realize the simultaneous high-stable output of 633nm and 650nm in the He-Ne laser.

[0045] 1. The He-Ne straight cavity laser is composed of a straight cavity resonant cavity 1 and a plane mirror 4, a spherical mirror 5, an anode 2 and a cathode 3.

[0046] 2. The straight cavity resonant cavity 1 is integrally manufactured by using ultra-low expansion microcrystalline glass or other low expansion materials, the cavity length is less than 230mm, the discharge gain tube diameter is greater than 3.5mm and less than 5mm; a circular diaphragm is designed and manufactured in the light transmission hole, the diaphragm size is 1.95mm and the length is 3mm. The straight cavity cavity is perpendicular to the discharge and light transmission hole at both ends, the perpendicularity is less than 20 angular seconds, and the parallelism of the two ends is less than 5 angular seconds. The two end face shapes reach the aperture N less than 0.5 and ΔN less than 0.1.

[0047] Generally, the 633 nm comprehensive spectral line is broadened by about 1600 MHz at normal temperature, and the laser with frequency stabilization is basically at the central frequency position during operation. Considering the gain loss ratio and the mode competition of the gas laser, the comprehensive broadening of the light bandwidth is about 1300 MHz. Therefore, the longitudinal mode interval should be greater than 650 MHz. According to the calculation formula of the longitudinal mode interval of the straight cavity laser, the maximum cavity length is 230 mm. If the cavity length is further reduced, the gain length will be reduced, and the output power of the laser will be reduced.

[0048] The gain of the 633 nm laser of the He-Ne laser is proportional to the gain length and inversely proportional to the diameter of the gain hole, that is, inversely proportional to the particle number density of the Ne atoms in the 1S state. The gain of the enhanced Raman laser at 650 nm is proportional to the particle number density of the Ne atoms in the 1S state and the number density of the 633 nm photons in the resonant cavity. The gain hole size determined by theory and experiment is greater than 3.5 mm and less than 5 mm.

[0049] The design of the diaphragm comprehensively considers the characteristics of the oscillating Gaussian beams of the 633 nm and 650 nm lasers in the resonant cavity. On the one hand, it ensures that the loss of the zero-order mode required for output is minimized, and the high-order mode is increased in loss by diffraction of the diaphragm, and does not produce oscillation. On the other hand, considering the diameter of the oscillating Gaussian beam of the resonant cavity passing through the diaphragm and the relationship between the high-order mode and the zero-order mode volume, and considering the diaphragm position and the processing error factors, the designed and verified diaphragm size is 1.95 mm in diameter and 3 mm in length.

[0050] 3. The straight cavity laser adopts a plane-spherical mirror resonant cavity, the plane mirror is an output mirror, and the spherical mirror has a curvature radius of 3 m to 6 m. The displacement plane mirror assembly is composed of a plane mirror 4, a displacement adjusting assembly 6, and a frequency stabilization pin 7, wherein the transmittance of the plane mirror is 0.02%. The displacement adjusting assembly 6 can adjust a range of more than 12 microns under the control of a control electronic device 10. The displacement adjusting assembly 6 can generate a position displacement of more than 12 microns under the control of a control electronic device 10. The photoelectric detector 8 adopts a general function silicon photoelectric detector. The structures of the spherical mirror, the plane mirror, and the displacement adjusting assembly are shown in Figure 4 、 Figure 5 、 Figure 6

[0051] The beam characteristics of the oscillating Gaussian beam of the plane-spherical mirror laser resonant cavity and the stability of the output beam depend on the curvature radius of the spherical mirror. Considering the resonant cavity processing precision, the oscillating beam optimization, and the diaphragm parameters, the designed and verified curvature radius of the spherical mirror is 3 m to 6 m. ​

[0052] The gain-loss design of the resonant cavity is the key to ensure the output optical power. In order to balance the relationship between the gain optical field and the output optical intensity in the resonant cavity, and to consider the factors of gain and loss, the transmittance of the plane mirror is designed and verified to be 0.02%, and the spherical mirror is designed to be a high-reflectivity mirror with a small residual transmittance, which is sufficient to meet the requirements of frequency stabilization and mode discrimination detection.

[0053] 4. The output plane mirror 4 and the spherical mirror 5 are connected and sealed with optical cement between the resonant cavity 1. The electrode anode 2 and the cathode 3 are connected with the resonant cavity of the laser by indium sealing.

[0054] 5. The control electronic device 10 mainly includes a discharge excitation system and a frequency stabilization and mode discrimination system.

[0055] The discharge excitation system has the functions of ignition and discharge current control. The ignition voltage is not less than 1500V, and the control precision of the discharge current control system is that the current stability is less than 0.1%, and the current adjustment range is 0.5mA to 1.2mA.

[0056] The He-Ne gas laser is excited by discharge. The research on the gas glow discharge and gain characteristics shows that the output laser is related to the discharge current, and there is an optimal discharge current value. Under the given design and determined parameters, the optimal discharge current of the laser is about 0.8mA. The designed and verified current adjustment range is to adjust the total output optical power and take into account the parameter differences of individual lasers.

[0057] The frequency stabilization and mode discrimination system has the functions of mode scanning, mode discrimination and frequency stabilization. The mode scanning curve is as shown in Figure 7 , and the system can realize the functions of applying a gradient voltage of 10V / s from 0V to 280V and from 280V to 0V, detecting the peak optical intensity, discriminating the modes of 633nm and 650nm, determining the frequency stabilization mode and automatically stabilizing the frequency.

[0058] 6. The frequency stabilization and mode discrimination system has the functions of sweep mode and discrimination mode and frequency stabilization. When the laser discharge is ignited normally and enters the steady flow glow discharge condition, the system is started to realize the linear loading from 0V to 280V voltage on the PZT piezoelectric element of the displaceable spherical mirror assembly, the gradient of the voltage application is 10V / s, at the same time, the output laser intensity is detected, in the control system, the relationship between the applied voltage and the light intensity is obtained, the work is maintained at 280V for 10 seconds, then the voltage applied on the PZT is reduced with the gradient of-10V / s, at the same time, another set of voltage and light intensity relationship is obtained. The voltage value corresponding to the peak light intensity in the two sets of relationships is solved, and the sequential peak voltage values are compared, when the difference between them is less than 20V, the minimum voltage in the peak light intensity of the rising applied voltage is obtained, which will be the initial voltage reference value of the mode setting of the frequency stabilization work. Given the initial value, the frequency stabilization system enters the automatic closed loop control state. In this state, the laser output will meet the simultaneous output conditions of 633nm and 650nm.

Claims

1. A helium-neon dual-wavelength laser, characterized by: The laser comprises a straight cavity resonant cavity (1), a plane mirror (4), a spherical mirror (5), an anode (2), and a cathode (3). The straight cavity resonant cavity is a cuboid glass; the cuboid glass is internally provided with gas storage holes (13) at both ends along the length direction, and is further provided with a main discharge gain hole (12) for connecting the two gas storage holes (13); the total length of the straight cavity resonant cavity (1) is less than 230 mm; the diameter of the discharge gain hole is between 3.5 mm and 5 mm. The cuboid glass is provided with the anode (2) and the cathode (3) on the surface respectively, and is internally provided with two discharge gain holes which are perpendicular to the main discharge gain hole (12) and which respectively connect the anode (2) and the cathode (3) with the main discharge gain hole (12). The cuboid glass is connected with the plane mirror (4) and the spherical mirror (5) through optical cement at both ends along the length direction; the plane mirror is installed close to the anode (2), and the spherical mirror (5) is installed close to the cathode (3). The main discharge gain hole between the anode (2) and the gas storage hole close to the plane mirror is provided with a diaphragm hole (11); the diaphragm hole (11) has a diameter of 1.95 mm and a length of 3 mm. The plane mirror (4) and / or the spherical mirror (5) are further connected with a displacement adjusting assembly (6) outside. The displacement adjusting assembly (6) is a circular cake-shaped metal, and both ends are provided with third annular grooves of the same size, and the distance between the bottoms of the two third annular grooves is 0.6 mm to 2 mm. The displacement adjusting assembly (6) is centrally provided with a threaded through hole, and a hollow frequency stabilizing pin (7) is screwed in the threaded through hole. The laser is output through the hollow frequency stabilizing pin (7) at one end of the plane mirror. One piezoelectric ceramic is arranged in each of the two third annular grooves, and the hollow frequency stabilizing pin is driven to move axially through the two piezoelectric ceramics, so as to drive the central optical reflection plane of the plane mirror and / or the spherical mirror to move axially, so as to change the working longitudinal mode of the output laser. The face shape of the straight cavity resonant cavity (1) at both ends along the length direction is less than 0.5, and the local aperture is less than 0.1; the two ends are perpendicular to the main discharge gain hole, and the perpendicularity is less than 20 arc seconds, and the parallelism of the two ends is less than 5 arc seconds.

2. The laser of claim 1, wherein: The distance between the cathode (3) and the anode (4) is between 150 mm and 170 mm.

3. The laser of claim 2, wherein: The transmittance of the plane mirror (4) is 0.02%, and the curvature radius of the spherical mirror (5) is 3 m to 6 m.

4. The laser of claim 3, wherein: The plane mirror (4) is a circular cake-shaped glass, both ends are provided with first annular grooves of the same size, and the distance between the bottoms of the two first annular grooves is 0.6 mm to 2 mm. The central plane is used as an optical reflection plane, and the outer ring surface is used as a connecting plane connected with the straight cavity resonant cavity (1).

5. The laser of claim 4, wherein: The spherical mirror (5) is a circular cake-shaped glass, both ends are provided with second annular grooves of the same size, and the distance between the bottoms of the two second annular grooves is 0.6 mm to 2 mm. The central plane is processed into a concave spherical surface as an optical reflection plane, and the outer ring surface is used as a connecting plane connected with the straight cavity resonant cavity (1).

Images