Research On Measurement And Compression Technology Of Phase Noise Of Solid-state Lasers

The solid-state laser has the characteristics of simple structure and stable power,and its excellent single longitudinal mode and low noise characteristics are widely used in the fields of coherent optical communication,coherent detection,and optically controlled phased radar.Nowadays,homodyne coherent optical communication technology is developing rapidly,and this technology has higher and higher performance requirements for light sources.However,the accuracy and accuracy of traditional linewidth measurement technology is not enough to completely characterize the performance of narrow linewidth low-noise lasers,so it is necessary to study the laser linewidth based on phase noise measurement.The research content of this article mainly includes the following parts:First,using the semi-classical theory of lasers,based on the output spectrum line type of the solid laser,the meaning of the line width of the solid laser is demonstrated in detail.The internal relationship between the phase noise of solid-state lasers and its intrinsic linewidth is explored,and starting from the basic principles of solid-state lasers,the conditions and methods for realizing laser single longitudinal mode output are studied,and the phase and frequency noise power spectrum of the laser are deduced.Density function.The demodulation principle of the laser phase noise measurement system based on Mach-Zehnder interferometer is demonstrated in detail,and the formula for demodulating the phase noise of the laser under test from the measurement system is deduced.Second,based on the theoretical analysis of solid-state lasers,two narrow-line-width solid-state lasers have been built under laboratory conditions.One is a linear short-cavity solid-state laser,which uses a short cavity length to achieve single longitudinal mode output;the other is the former's Technically,the selectivity of the volume Bragg grating is used to replace the output mirror of the resonator to achieve narrow linewidth laser output.After that,the performance of the two lasers was tested through experiments.Third,for low-noise and narrow-linewidth solid-state lasers,a solid-state laser phase noise measurement system based on an unbalanced Mach-Zehnder interferometer is designed and built.Through this measurement system and combined with standard instruments such as spectrum analyzers and oscilloscopes,the phase noise and frequency noise characteristics of linear short-cavity solid-state lasers,narrow linewidth solid-state lasers based on volume Bragg gratings,and commercial semiconductor lasers have been measured,and the characteristics of phase noise and frequency noise have been measured with manufacturers.The data is compared to verify the accuracy and effectiveness of the measurement system.Fourth,the active and passive suppression schemes of solid-state laser phase noise are analyzed in detail.Among them,the passive noise suppression scheme is mainly to fix the measurement system on a stable optical platform to enhance the anti-interference of the entire system against external vibration,combined with temperature control,to improve the frequency stability of the laser output light,thereby reducing the phase noise of the solid-state laser.The feasibility of active suppression of solid-state laser based on PDH frequency stabilization technology is analyzed,and a specific experimental plan is given.