Method for improving frequency doubling efficiency of CO2 laser
A laser and frequency doubling technology, which is applied in the field of nonlinear optics, can solve the problems of uneven transmittance of the fundamental frequency light of the wafer, the interface loss is difficult to further reduce, and the thickness deviation of the wafer is large, so as to reduce the breakage rate of the wafer and reduce the single-layer thickness of the wafer. The effect of less thickness variation, improved machining quality and precision
Active Publication Date: 2021-06-08
BEIJING UNIV OF TECH
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[0005] The content of the present invention is to solve the problem of large thickness deviation between wafers due to the thin thickness and easy deformation of the current quasi-phase matching wafer processing process, the uneven transmittance of the wafer to the fundamental frequency light after thermal bonding, and the interface loss is difficult to further improve. lowering the problem, a raised CO 2 A New Method of Laser Frequency Doubling Efficiency
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[0021] Such as figure 1 As shown, the present invention uses a third-order quasi-phase-matched crystal to prepare a multilayer frequency doubling device, and the preparation process can be divided into the following steps. The first step is to determine the crystal orientation of the gallium arsenide wafer, [0-11] is the light transmission direction, [0-1-1] is the polarization direction of the fundamental frequency light, and [100] is the crystal polarization direction. Cut into thin slices with a thickness of 2mm; the second step is double-sided thinning and polishing to the specified thickness, and pre-bonding is performed under vacuum conditions; the third step is high-temperature thermal bonding.
[0022] The absorption coefficient of gallium arsenide crystal is 0.005cm -1 , the second-order nonlinear coefficient is 83pm / V, which is an order of magnitude smaller than the commonly used quasi-phase-matched crystal gallium phosphide and two orders of magnitude smaller than ...
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The invention discloses a method for improving the frequency doubling efficiency of a CO2 laser, which adopts a mode of increasing the thickness of a single-layer wafer, the thickness is increased to more than 300 microns, the thickness error between wafers can be controlled to be 0.5 lambda = 0.3 microns, the planeness peak valley value is 0.056 lambda, and the root mean square value is 0.009 lambda. And the polished crystals are stacked by reversing 180 degrees according to the polarization direction of the adjacent wafers, and the wafers are firmly combined together through a high-temperature pressurizing thermal bonding process in a vacuum environment. The method has substantive features and remarkable progress, and compared with a CO2 laser frequency doubling mode adopted at present, the method has the following advantages that the wafer machining quality and precision are improved, the thickness error is small, and the roughness and planeness are reduced; the number of bonding layers can reach more than 50, and the average single-layer interface loss after thermal bonding is low; the clear aperture is large and can reach 20 mm; and the output power and the conversion efficiency of frequency doubling of the CO2 laser are effectively improved.
Description
technical field [0001] The invention relates to a frequency doubling device prepared by quasi-phase matching gallium arsenide crystal, which is used for CO 2 The frequency doubling of the laser produces mid-infrared laser, which belongs to the field of nonlinear optics. Background technique [0002] CO 2 Laser frequency-doubled light is in the 3-5μm band, which has the characteristics of low absorption and small scattering in the atmosphere. The atmospheric transmittance of this band is above 70%, which can realize long-distance transmission in the atmosphere. It is used in infrared detection, remote sensing, spectroscopy and other fields. is of great significance. Simultaneous output of high-power, high-efficiency frequency-doubled light is of great significance to the application of mid-infrared lasers. Compared with birefringent matching crystals, which mostly have low thermal conductivity and low laser damage threshold, quasi-phase matching crystals can achieve higher...
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Login to View More IPC IPC(8): C30B33/06C30B29/42H01S3/109B24B1/00
CPCC30B33/06C30B29/42H01S3/109B24B1/00
Inventor 李强边慧征王晨旭雷訇惠勇凌朱占达
Owner BEIJING UNIV OF TECH