阅读说明：本技术 一种高稳定法布里-珀罗腔装置及其应用的激光输出系统 (High-stability Fabry-Perot cavity device and laser output system applying same ) 是由 周月婷 郭松杰 周晓彬 田建飞 赵刚 马维光 于 2020-05-14 设计创作，主要内容包括：本发明公开了一种高稳定法布里-珀罗腔装置,包括有法布里-珀罗腔体、真空室、壳体,法布里-珀罗腔体内设置有平面反射镜、凹面反射镜,真空室罩设于法布里-珀罗腔体外,在真空室两端设有密封法兰窗片,真空室通过抽气支管连接分子泵,分子泵法对法布里-珀罗腔体、真空室与密封法兰窗片构成抽的空间进行抽真空,壳体套设于真空室外,在壳体外表面设置有半导体制冷片,半导体制冷片连接有水冷机。本发明采用膨胀系数在10<Sup>-6</Sup>k<Sup>-1</Sup>微晶玻璃制成法布里-珀罗腔,对其进行温度控制,并使其处于真空环境中,降低激光频率噪声,提高激光频率稳定性,同时使用PDH技术,压窄激光线宽,获得高稳定性、复现性、窄线宽宽等优点的632.8nm频率参考及激光。(The invention discloses a high-stability Fabry-Perot cavity device, which comprises a Fabry-Perot cavity, a vacuum chamber and a shell, wherein a plane reflector and a concave reflector are arranged in the Fabry-Perot cavity, the vacuum chamber is covered outside the Fabry-Perot cavity, sealing flange window sheets are arranged at two ends of the vacuum chamber, the vacuum chamber is connected with a molecular pump through an air exhaust branch pipe, the molecular pump is used for vacuumizing a pumped space formed by the Fabry-Perot cavity, the vacuum chamber and the sealing flange window sheets, the shell is sleeved outside the vacuum chamber, a semiconductor refrigerating sheet is arranged on the outer surface of the shell, and a semiconductor system is arranged on the outer surface ofThe cold plate is connected with a water cooler. The invention adopts the expansion coefficient of 10 ‑6 k ‑1 The microcrystalline glass is made into a Fabry-Perot cavity, the temperature of the Fabry-Perot cavity is controlled, the Fabry-Perot cavity is positioned in a vacuum environment, the laser frequency noise is reduced, the laser frequency stability is improved, meanwhile, the laser line width is narrowed by using a PDH technology, and 632.8nm frequency reference and laser with the advantages of high stability, reproducibility, narrow line width, wide line width and the like are obtained.)

1. A high stable Fabry-Perot cavity device is characterized in that: the vacuum Fabry-Perot vacuum pump comprises a Fabry-Perot cavity (1), a vacuum chamber (2) and a shell (3), wherein an optical channel (4) penetrating through the Fabry-Perot cavity (1) is arranged in the Fabry-Perot cavity (1), two ends of the optical channel (4) along the central axis thereof are respectively provided with a plane reflector (5) and a concave reflector (6) which have the same size, the vacuum chamber (2) is covered outside the Fabry-Perot cavity (1), two ends of the vacuum chamber (2) are provided with sealing flange window sheets (13) in an opening manner, an air exhaust branch pipe (7) is arranged on the vacuum chamber (2), the air exhaust branch pipe (7) is connected with a molecular pump (8), and the molecular pump (8) is used for vacuumizing the space formed by the Fabry-Perot cavity (1), the vacuum chamber (2) and the sealing flange window sheets (13), real empty room (2) surface is provided with thermistor (9), thermistor (9) electricity is connected with temperature controller (10), casing (3) laminating cover is located real empty room (2) surface, casing (3) with real empty room (2) laminating department is equipped with heat conduction silicone grease layer casing (3) surface is provided with semiconductor refrigeration piece (11), semiconductor refrigeration piece (11) both ends are connected with water-cooling machine (14) through water-cooling head (12), temperature controller (10) are connected to semiconductor refrigeration piece (11) electricity.

2. A highly stable fabry-perot cavity device according to claim 1, wherein: the Fabry-Perot cavity (1) is a hollow cylinder with the length of 100mm and the diameter of 50mm and has the expansion coefficient of 10^-6K^-1The glass ceramics.

3. A highly stable fabry-perot cavity device according to claim 2, wherein: plane reflecting mirror (5), concave surface reflecting mirror (6) are made by fused silica, diameter 25mm, thickness 6.35.mm, the concave surface curvature radius of concave surface reflecting mirror (6) is 1000mm, plane reflecting mirror (5), concave surface reflecting mirror (6) relative surface side are equipped with high reflectance coating, and the opposite side is equipped with the antireflection coating, high reflectance coating is 99.9885% at 0 of 632nm department of reflectivity, and the deviation is between plus-minus 0.0035%, 0 of transmittance at 632nm department of antireflection coating is about 0.01%, and the fineness is 27000, and the linewidth is 55 KHz.

4. A highly stable fabry-perot cavity device according to claim 3, wherein: the sealing flange window sheet (13) is made of quartz glass, and 632.8nm laser antireflection films are plated on two surfaces of the window sheet.

5. A highly stable Fabry-Perot cavity device according to claim 4, wherein: the outer both ends of casing (3) are equipped with frame (28) of fixed casing (3) upper and lower two parts, frame (28) are square.

6. A highly stable Fabry-Perot cavity device according to claim 5, wherein: the semiconductor refrigerating pieces (11) are arranged at the upper end and the lower end of the shell (3) respectively, the rated voltage is 12V, the rated current is 2A, and the rated power of a temperature controller (10) electrically connected with the semiconductor refrigerating pieces (11) is 250W.

7. A laser output system using the highly stable fabry-perot cavity device as claimed in any of claims 1 to 6, wherein: comprises a PDH frequency locking device and an optical path device, wherein the PDH frequency locking device comprises a modulation and demodulation unit (15), a servo control unit (16), a high-voltage amplifier unit (17) and an oscilloscope (18), the light path device comprises a laser (19) for outputting 632.8nm laser, a fiber beam splitter (20), an optical isolator (21), a half wave plate (22), a convex lens (23), a polarization beam splitter prism (24), a quarter wave plate (25) and a high-stability Fabry-Perot cavity device at the tail end, wherein the fiber beam splitter (20), the optical isolator (21), the half wave plate (22), the convex lens (23), the polarization beam splitter prism (24) and the quarter wave plate (25) are, the polarization beam splitter prism (24) and the quarter wave plate (25) form a circulator to extract a reflected light signal of a cavity front mirror, and a first photoelectric detector (26) and a second photoelectric detector (27) are respectively arranged at two ends of the high-stability Fabry-Perot cavity device.

8. The laser output system of a highly stable fabry-perot cavity device as claimed in claim 7, wherein: the laser (19) is an external cavity grating feedback semiconductor laser for outputting 632.8nm laser, the wavelength tuning range is about 6nm, the output laser line width is about 1MHz in a free running state, the mode-hopping-free tuning range is larger than 5GHz, and the output power is 30 mW.

Technical Field

The invention relates to the technical field of laser, in particular to a high-stability Fabry-Perot cavity device and a laser output system applying the same.

Background

Since the first ruby laser was made by the american physicist melman the year, the laser has had a history of years of development and to date the variety of lasers has been varied. Compared with a common light source, the laser has good monochromaticity and narrow line width. The free-running laser still cannot meet the research fields with higher requirements on line width and frequency stability, such as laser ranging, optical frequency standards, gravitational wave detection, precision measurement and the like. Therefore, there is a need for further development of narrow line width, high frequency stable laser sources.

People adopt some passive measures to reduce the laser frequency noise, such as temperature control and isolation of mechanical vibration on the laser, so that the laser runs more stably, and the laser frequency stability is effectively improved. The laser linewidth can be effectively narrowed by using an active frequency stabilization technique. The specific methods are two, one is to use the central frequency of the atomic transition spectral line as a frequency reference, such as saturated absorption frequency stabilization, and the other is to use an external frequency standard as a frequency reference, such as the resonance frequency of an F-P cavity as a frequency reference, and then combine the Pound-Drever-HallPDH technology to perform frequency stabilization. Any frequency stabilization method requires frequency reference, and the basic requirements of the frequency reference are high stability, reproducibility, narrow spectral line width and the like, so that the frequency stabilization effect is directly influenced by selecting the proper frequency reference.

The existing laser with the output center wavelength of 632.8nm has the output laser linewidth larger than 1MHz in a free running state, and can not meet the research fields with higher requirements on linewidth and frequency stability, such as laser ranging, optical frequency standard, gravitational wave detection, precision measurement and the like. Therefore, passive measures and active frequency stabilization techniques are required to effectively narrow the laser linewidth.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the high-stability Fabry-Perot cavity device and the laser output system using the same are provided, and 632.8nm frequency reference and laser with the advantages of high stability, reproducibility, narrow spectral line width and the like are obtained.

The high-stability Fabry-Perot cavity device comprises a Fabry-Perot cavity, a vacuum chamber and a shell, wherein an optical channel penetrating through the Fabry-Perot cavity is arranged in the Fabry-Perot cavity, two ends of the optical channel along the central axis are respectively provided with a plane reflector and a concave reflector which have the same size, the vacuum chamber is covered outside the Fabry-Perot cavity, two ends of the vacuum chamber are provided with sealed flange window sheets, the vacuum chamber is provided with an air exhaust branch pipe, the air exhaust branch pipe is connected with a molecular pump, the molecular pump is used for vacuumizing a space formed by the Fabry-Perot cavity, the vacuum chamber and the sealed flange window sheets, the outer surface of the vacuum chamber is provided with a thermistor, and the thermistor is electrically connected with a temperature controller, the casing laminating cover is located real empty room surface, the casing with real empty room laminating department is equipped with heat conduction silicone grease layer the casing surface is provided with the semiconductor refrigeration piece, semiconductor refrigeration piece both ends are connected with the water-cooled generator through the water-cooling head, temperature controller is connected to the semiconductor refrigeration piece electricity.

As a further improvement of the scheme, the Fabry-Perot cavity is a hollow cylinder with the length of 100mm and the diameter of 50mm and is formed by an expansion coefficient of 10^-6k^-1The glass ceramics.

As a further improvement of the above scheme, the planar reflector and the concave reflector are made of fused quartz, the diameter of the planar reflector and the concave reflector is 25mm, the thickness of the planar reflector and the concave reflector is 6.35.mm, the radius of curvature of the concave surface of the concave reflector is 1000mm, the opposite sides of the planar reflector and the concave reflector are provided with high reflection films, the other sides of the planar reflector and the concave reflector are provided with antireflection films, the 0-degree reflectivity of the high reflection films at 632nm is 99.9885%, the deviation is between plus and minus 0.0035%, the 0-degree transmissivity of the antireflection films at 632nm is about 0.01%, the fineness is 27000, and the line width is 55 KHz.

As a further improvement of the scheme, the sealing flange window is made of quartz glass, and 632.8nm laser antireflection films are plated on two surfaces of the window.

As a further improvement of the scheme, the two ends outside the shell are provided with frames for fixing the upper part and the lower part of the shell, and the frames are square.

As a further improvement of the scheme, the semiconductor refrigerating pieces are provided with two pieces which are respectively arranged at the upper end and the lower end of the shell, the rated voltage is 12V, the rated current is 2A, and the rated power of a temperature controller electrically connected with the semiconductor refrigerating pieces is 250W

The laser output system applying the highly stable Fabry-Perot cavity device provided for realizing the purpose of the invention comprises a PDH frequency locking device and an optical path device, the PDH frequency locking device comprises a modulation and demodulation unit, a servo control unit, a high-voltage amplifier unit and an oscilloscope, the light path device comprises a laser for outputting 632.8nm laser, a fiber beam splitter, an optical isolator, a half wave plate, a convex lens, a polarization beam splitter prism, a quarter wave plate and a high-stability Fabry-Perot cavity device at the tail end, which are arranged on a laser emergent light path in sequence, the polarization beam splitter prism and the quarter wave plate form a circulator to extract a reflected light signal of a cavity front mirror, the focal length of the convex lens is 500mm, and a first photoelectric detector and a second photoelectric detector are respectively arranged at two ends of the high-stability Fabry-Perot cavity device.

As a further improvement of the scheme, the laser is an external cavity grating feedback semiconductor laser for outputting 632.8nm laser, the wavelength tuning range is about 6nm, the output laser line width is about 1MHz in a free running state, the mode-hopping-free tuning range is larger than 5GHz, and the output power is 30 mW.

The invention has the beneficial effects that:

compared with the prior art, the high-stability laser system with the Fabry-Perot cavity device, provided by the invention, has the advantages that the Fabry-Perot cavity is isolated through the vacuum chamber when the laser system is used, so that the Fabry-Perot cavity is prevented from influencing the frequency locking effect due to tiny changes of cavity length caused by external air flow, environmental temperature changes and vibration caused by sound and machinery, on the basis, the environmental gas close to vacuum is rare, the heat transfer efficiency is greatly reduced, but the Fabry-Perot cavity is extremely sensitive to temperature, and in order to further avoid the influence of the environmental temperature on the Fabry-Perot cavity, an aluminum metal material shell and a refrigerating sheet arranged on the surface of the metal material shell are arranged to control the temperature of the whole vacuum chamber. So as to obtain 632.8nm frequency reference and laser with the advantages of high stability, reproducibility, narrower spectral line width and the like.

The following detailed description of embodiments of the invention is provided in conjunction with the appended drawings, in which:

FIG. 1 is a schematic diagram of a Fabry-Perot cavity device according to the present invention;

FIG. 2 is a schematic diagram of a vacuum chamber structure of the Fabry-Perot cavity device according to the present invention;

FIG. 3 is a schematic diagram of a Fabry-Perot cavity apparatus according to the present invention;

FIG. 4 is a flow chart of a laser output system employing a highly stable Fabry-Perot cavity device according to the present invention;

FIG. 5 is a statistical chart of frequency locking performance evaluation of the laser output system of the present invention;

fig. 6 is a graph of the frequency drift of the invention for successive hours after frequency lock.

Detailed Description

As shown in fig. 1 to 6, the high stability fabry-perot cavity device provided by the present invention is characterized in that: the Fabry-Perot vacuum pump comprises a Fabry-Perot cavity 1, a vacuum chamber 2 and a shell 3, wherein a light channel 4 penetrating through the Fabry-Perot cavity 1 is arranged in the Fabry-Perot cavity 1, two ends of the light channel 4 along the central axis thereof are respectively provided with a plane reflector 5 and a concave reflector 6 which have the same size, the vacuum chamber 2 is covered outside the Fabry-Perot cavity 1, two ends of the vacuum chamber 2 are provided with sealing flange window sheets 13, the vacuum chamber 2 is provided with an air exhaust branch pipe 7, the air exhaust branch pipe 7 is connected with a molecular pump 8, the molecular pump 8 is used for vacuumizing a space formed by the Fabry-Perot cavity 1, the vacuum chamber 2 and the sealing flange window sheets 13, the outer surface of the vacuum chamber 2 is provided with a thermistor 9, and the thermistor 9 is electrically connected with a temperature controller 10, the utility model discloses a temperature controller, including casing 3, the laminating cover of casing is located 2 surfaces in real empty room, casing 3 with 2 laminating departments in real empty room are equipped with heat conduction silicone grease layer 3 surfaces of casing are provided with semiconductor refrigeration piece 11, 11 both ends of semiconductor refrigeration piece are connected with water-cooled generator 14 through water-cooling head 12, temperature controller 10 is connected to 11 electricity of semiconductor refrigeration piece.

A laser output system applying a high-stability Fabry-Perot cavity device comprises a PDH frequency locking device and a light path device, wherein the PDH frequency locking device comprises a modulation and demodulation unit 15, a servo control unit 16, a high-voltage amplifier unit 17 and an oscilloscope 18, the light path device comprises a laser 19 for outputting 632.8nm laser, an optical fiber beam splitter 20, an optical isolator 21, a half wave plate 22, a convex lens 23, a polarization beam splitter prism 24, a quarter wave plate 25 and a high-stability Fabry-Perot cavity device at the tail end, the polarization beam splitter prism 24 and the quarter wave plate 25 form a ring-shaped device for extracting a reflected light signal of a cavity front mirror, and a first photoelectric detector 26 and a second photoelectric detector 27 are respectively arranged at two ends of the high-stability Fabry-Perot cavity device.

When the system is used, the wavelength tuning range is about 6nm, the line width of the output laser is about 1MHz in a free running state, the mode-hopping-free tuning range is larger than 5GHz, the external cavity grating feedback semiconductor laser 19 with the output power of 30mW outputs 632.8nm laser, the laser is divided into two beams through the optical fiber beam splitter 20, one beam is directly output for use, the other beam passes through the optical isolator 21 for reducing the reflected light of the high-stability Fabry-Perot cavity device to feed back the laser 19, the laser efficiently passes through the polarization beam splitter prism 24 through the half wave plate 22, and meanwhile, the convex lens 23 with the focal length of 500mm, which is arranged between the half wave plate 22 and the polarization beam splitter prism 24, completes the laser to the high-Determining the mode matching of the Fabry-Perot cavity device, extracting a reflected light signal of a cavity front mirror by a circulator consisting of a polarization beam splitter prism 24 and a quarter wave plate 25, then enabling laser to enter the high-stability Fabry-Perot cavity device, enabling the laser to penetrate through a sealing flange window sheet 13 which is arranged on a vacuum chamber 2 and is made of quartz glass, plated with 632.8nm laser antireflection films on two sides, enter a Fabry-Perot cavity 1, sequentially penetrate through a plane reflector 5 which is 25mm in diameter and 6.35mm in thickness and is respectively plated with a high reflection film and an antireflection film on two sides of the cavity and a light channel 4 arranged in the Fabry-Perot cavity 1, and then penetrate out from a concave reflector 6 arranged at the tail end of the light channel 4. The vacuum chamber 2 is made of stainless steel material and is sleeved outside the Fabry-Perot cavity 1, the Fabry-Perot cavity 1 is a hollow cylinder with the length of 100mm and the diameter of 50mm, and the expansion coefficient is 10^-6k^-1The microcrystalline glass is made of the microcrystalline glass, the light channel 4 is a cylindrical space penetrating through the Fabry-Perot cavity 1, a planar reflector 5 and a concave reflector 6 which are the same in size are respectively arranged at two ends of the central axis of the light channel, a high-reflection film and an antireflection film are respectively plated on two sides of the mirror body, the high-reflection films are arranged on the opposite sides of the two reflectors, the curvature radius of the concave surface of the concave reflector 6 is 1000mm, the 0-degree reflectivity of the high-reflection film at 632nm is 99.9885%, the deviation is between plus and minus 0.0035%, the 0-degree transmissivity of the antireflection film at 632nm is about 0.01%, the fineness is 27000, and the line width is 55 KHz.

Meanwhile, the molecular pump 8 is started, and the space formed by the Fabry-Perot cavity 1, the vacuum chamber 2 and the sealing flange window piece 13 is vacuumized through the air exhaust branch pipe 7 arranged on the vacuum chamber 2, so that an environment as vacuum as possible is manufactured, and the frequency locking effect is prevented from being influenced by the fact that the Fabry-Perot cavity 1 slightly changes in length due to external air flow, environmental temperature change, sound and vibration caused by machinery.

Meanwhile, the temperature of the vacuum chamber 2 is monitored in real time by a thermistor 9 arranged on the outer surface of the vacuum chamber 2, the feedback is made to a temperature controller 10 with the rated power of 250W, the square shell 3 is arranged on the outer surface of the vacuum chamber 2 in a laminating manner, a heat-conducting silicone layer is arranged on the laminating surface of the vacuum chamber 2 and the shell 3, the transmission efficiency between the shell and the shell is improved, the shell 3 consists of an upper detachable part and a lower detachable part which are symmetrical, the upper detachable part and the lower detachable part are fixed through a square frame 28 during use and pass through the upper end and the lower end of the shell 3, two square semiconductor refrigerating sheets 11 are arranged, and a water cooling machine 14 connected with the semiconductor refrigerating sheets 11 through a water cooling head 12 plays a role in controlling. The rated voltage of the semiconductor refrigerating sheet 11 is 12V, the rated current is 2A, and the refrigerating capacity of the water cooling machine 14 is 150W.

The reflected light of the fabry-perot cavity front mirror is detected by the first photodetector 26, the transmitted light is detected by the second photodetector 27, and the frequency locking state is monitored in real time using the oscilloscope 18. A modulation and demodulation unit 15 in the PDH frequency locking device outputs a sine wave of 18MHz to be input to a current alternating current port of an external cavity grating feedback semiconductor laser 19 to adjust laser frequency, a first photoelectric detector sends a signal output by a first photoelectric detector 26 back to the modulation and demodulation unit 15, a frequency locking error signal with the optimal signal-to-noise ratio is obtained by adjusting a proper phase, the error signal is sent to a servo control unit 16, an integral part passes through a high-voltage amplifier unit 17 and then is sent to a PZT input port of the laser 19, a low-pass part is sent to a DC-C input port, and wide-bandwidth frequency feedback control is completed.

After that, the line width of the output laser is tested through experiments, when the laser 19 is not locked, the light intensity signal measured by the first photodetector 26 is demodulated through the modulation and demodulation unit 15, a PDH error signal is obtained, the peak amplitude of the obtained error signal is 0.34V, the corresponding optical frequency is approximately equal to the cavity film line width 55kHz, the response of the PDH error signal amplitude to the frequency at the zero voltage offset is 55kHz/0.34V, namely 160kHz/V, after the laser is locked, the error signal is obtained again, the amplitude of the error signal at the moment is subjected to gaussian fitting, the 160kHz/V is substituted to calculate the half width of a gaussian function to be 7.3kHz, the obtained laser line width is approximately 12.4kHz, which is far less than the output laser line width 1MHz of the laser 19 in the free running state, as shown in fig. 5, the frequency locking performance evaluation statistical chart of the laser output system, the frequency distributions of the error signal in the scanning state and the error signal after locking are counted. After frequency locking, frequency drift monitoring was performed for successive hours, as shown in fig. 6. Thus proving that the system has remarkable effect of narrowing the output linewidth of the laser.

The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments may be combined with each other into a new embodiment. The above embodiments are only for illustrating the technical solutions of the present invention and are not limited thereto, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the technical solutions of the present invention.