Phase miss match compensation heater of high power internal cavity freguency multiplier laser and its method

Abstract

This invention discloses a phase mismatch compensation heater and a method for a high power inner cavity multiple frequency laser including a KTP multiple crystal set in a closed metallic box inserted with a temperature sensor and a heating tube, the bottom is set with a semiconductor refrigerator and the box is set with a solid relay of a control box. The method includes: designing a KTP crystal boundary temperature value, increasing power of the heating pipe at low temperature to reduce voltage of the refrigerator to let the temperature approach to the designed value so as to keep the boundary temperature of the KTP multiple crystal at a stable state during the process dynamic balance.

Description

technical field [0001] The invention relates to a high-power intracavity frequency-doubling laser phase mismatch compensation heater and a method thereof, which belong to the technology of green lasers. Background technique [0002] Laser diode pumped high repetition frequency (1-50kHz), high average power (>20W), inner cavity frequency doubling green solid-state laser, due to its high efficiency, good beam quality, small size, long life, low operating cost, etc. It has important applications in industrial processing, laser medical treatment, seabed detection, isotope separation and scientific research. [0003] Acousto-optic Q-switching Nd:YAG intracavity frequency doubling technology based on KTP nonlinear optical crystal is one of the important ways to achieve high-power green light output. However, under the infrared laser radiation with an average output power of several hundred watts, the infrared light and green light power will be linearly absorbed inside the cry...

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Problems solved by technology

However, under the infrared laser radiation with an average output power of several hundred watts, the infrared light and green light power will be linearly absorbed inside the crystal, and nonlinear absorption such as two-photon absorption and other third-order nonlinear effects may occur. KTP crystal absorbs The laser power will generate a temperature gradient distribution inside, which will limit the conversion efficiency in the following two aspects. On the one hand, due to the uneven temperature distribution, the distribution of the refractive index of the KTP crystal will be uneven, thus destroying the best phase matching of the crystal. The environment causes the frequency doubling efficiency of the crystal to decrease; on the other hand, the internal temperature of the crystal is not uniform, which leads to the uneven distribution of the refractive index, which leads to the generation of thermal stress, and the corresponding thermal lens response, which will change the frequency of the laser during the cavity frequency doubling. Resonant cavity parameters, resulting in instability of laser power and decrease in frequency doubling efficiency

[0004] At present, the phase compensation technology of frequency-doubling crystals in high-power green lasers has methods of cooling at low temperature (4-10°C) and changing the angle of the frequency-doubling crystal (that is, changing the angle at which infrared light is incident on the crystal), but due to the low temperature cooling environment Reduces the damage threshold of KTP crystals, which easily leads to the appearance of 'gray traces' of KTP crystals (the so-called gray traces refer to the damage phenomenon in KTP crystals due to lattice defects at low temperatures)

In addition, although changing the angle of the frequency doubling crystal can compensate the phase mismatch to a certain extent, but because the incident direction of the infrared light is changed, the loss of the infrared light is increased, and the output power of the green light is reduced. The refraction of the green light will lead to the phenomenon of multiple spots in the output of green light

However, the technology of phase mismatch compensation heater and method used in high-power intracavity all-solid-state green lasers can overcome the above shortcomings. At present, there are no relevant patents and literatures using this technical solution.

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