Method and device for stabilizing double-longitudinal mold laser frequency based on thermoelectric cryostat

Abstract

The invention is concerned with stabilized frequency method and equipment of double longitudinal modes laser based on thermoelectric cooler. The stabilized frequency method is piezoelectric ceramics, and so on. Detect the circumstance temperature T0 of laser to confirm heat balance temperature Tset, start electrical source of laser to test current temperature Treal of laser tube at real time. Adjust countercurrent I according to different value between current temperature Treal and heat balance temperature Tset and heat up laser tube to keep temperature arrive to Tset. Detect optical power Pm and Pm+1of m order and m+1order on the mutual vertical polarization direction to laser and count the different valueDeltP of the two powers. When the temperature of laser tube is near to heat balance temperature Tset, afford forward or counter current to thermoelectric cooler according to the forward or counter to the different valueDeltP, keep the symmetry of two longitudinal mode laser frequency and make the different valueDeltP close to zero, by controlling the temperature of laser tube, the length of resonant cavity and laser longitudinal mode frequency. The two longitudinal mode frequencies are steady, and this product is fit for stabilized frequency.

Description

technical field [0001] The invention belongs to the technical field of laser applications, in particular to a method and device for stabilizing the frequency of a dual longitudinal mode laser based on a thermoelectric cooler. Background technique [0002] One of the characteristics of laser is good monochromaticity, and the laser linewidth limit caused by spontaneous emission noise is very small, but due to the influence of various unstable factors, the optical frequency drift of the free-running laser is far greater than the linewidth limit. In the application fields of precision interferometry, optical frequency standard, optical communication and precision spectrum research, laser as a length standard requires good stability of optical frequency (wavelength). [0003] According to different actuators, laser frequency stabilization methods can be mainly divided into piezoelectric ceramic frequency stabilization methods, electric cooked wire frequency stabilization methods,...

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Problems solved by technology

The piezoelectric ceramic frequency stabilization method uses piezoelectric crystals to control the cavity length, and its frequency uncertainty can be as high as 10 in the application of the large ultra-precision diamond lathe laser heterodyne interferometry system in the Lawrence Laboratory of the United States. -9 , but the process structure is complicated, the price is expensive, the creep of the piezoelectric material is large and the service life is short

The electric heating wire frequency stabilization method controls the current of the electric heating wire wound outside or inside the laser tube, adjusts the temperature of the laser tube and the length of the resonant cavity to stabilize the output optical frequency of the laser. The US Hewlett-Packard Company uses this method to obtain 10 -8 Frequency stability, but this method not only requires the system to have good heat dissipation conditions, but also prevents temperature instability caused by too fast heat exchange, so its thermal structure design is difficult, and due to the capacitive hysteresis of thermal tuning, this method It cannot be used in a frequency stabilization system where the feedback signal is locked to an extreme value (such as the Zeeman effect frequency difference peak)

The discharge current frequency stabilization method is similar to the heating wire frequency stabilization method. By adjusting the discharge current of the laser tube, changing the temperature of the laser tube and the length of the resonant cavity to stabilize the output optical frequency of the laser, but changing the discharge current will affect the feedback of light intensity and optical frequency difference. The size of the signal and the position of the center frequency point of the gain curve, so its frequency stability is generally not higher than 10 -7

The air-cooled frequency stabilization method can actively reduce the temperature of the laser tube, and the heat dissipation conditions are good, but the temperature rise can only be caused by the laser tube itself, the symmetry design of the thermal control curve is difficult, and the air flow is easy to cause vibration, which affects the frequency stabilization Effect

[0004] In addition, it is one of the important conditions for the laser to achieve thermal equilibrium during the frequency stabilization process. The above frequency stabilization methods all preheat the heating wire with a constant voltage, especially in the heating wire frequency stabilization method, it is generally set The target temperature of the laser tube preheating is a fixed value and is greater than the thermal equilibrium temperature of the natural operation of the laser tube. Therefore, the preheating effect and the preheating time are quite different under different external environments, and it is difficult to achieve stable frequency even if the preheating time is longer than 1 hour. requirements, which affect the application of these methods in the industrial field

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