Research On Injection Locked A Single-frequency Self-Q-swithched Solid-state Laser Oscillator Based On Gain Gratings And Its Linewidth Measyrement

Single-frequency narrow-width diode-pumped solid-state lasers have been widely used in fields such as optical communications,high resolution spectroscopy,and pulse coherent Doppler lidar because of their good monochromaticity and coherence.Especially in the field of laser radar,lasers,which are key components of pulsed coherent Doppler lidar transmission systems,are required to achieve single-frequency narrow linewidth output.Based on this requirement,currently used methods for single-longitudinal-mode Q-switched lasers require the addition of mode selection and Q-switching devices,which will result in system instability.Recent studies have shown that in a laser resonator,two coherent light beams interact in a gain medium to form an interference field,generating a spatial hole burning phenomenon,and a holographic gain grating can be formed,which has an adaptive characteristic,gain saturation characteristics,high diffraction efficiency and spectrum selection characteristics.In this paper,the external grating is used to inject the single linewidth narrow-width seed source into the self-starting resonant cavity of the gain grating,and the output light is locked at the seed source frequency after the injection to obtain a single-frequency Q-narrow linewidth output.The main research contents of paper are as follows:1.This paper investigates and analyzes the current methods of single-frequency frequency stabilized output at home and abroad,summarizes the current research status and existing problems of non-reciprocal and reciprocal gain grating lasers.And the idea of using self-adaptation of gain gratings is proposed.For achieving the idea of a single-frequency frequency stabilized output,we use externally injected single-frequency narrow linewidth lasers to achieve output frequency and linewidth injection locking.2.We introduce and analyze the principle and physical mechanism of injection-locked non-reciprocal gain grating single-frequency Q-switched lasers.Starting from the rate equation of laser gain coefficients,it solves the single transmission grating equation under steady-state and transient conditions,respectively.The degenerate four-wave coupling equation is quantitatively described.The self-pumped phase conjugation,dual-phase conjugate,and self-starting adaptive laser resonators are introduced.The principle of frequency stabilization using gain gratings is analyzed.3.An injection-locked non-reciprocal gain grating single-frequency Q-switched laser was designed and constructed experimentally.The gain medium and the pumpsource were discussed,and the self-starting Q-switched output was achieved using a grazing incidence structure.By optimizing the self-intersection angle and the pump width,a single-frequency Q-switched output with a pulse width of 7ns and a single pulse energy of 0.99 mJ is realized.On this basis,the gain grating is formed on the seed light by externally injecting a single-frequency narrow-linewidth seed source,and the relationship between the output pulse width and the output energy under different injected optical powers is compared.The injection power is increased and the output light is obtained.The width of the pulse has been broadened.By controlling and raising the temperature of the crystal and increasing the optical power of the seed,the center wavelength of the output spectrum after the injection is shifted toward the long wavelength and locked at the center wavelength of the injected spectrum,and injection locking is achieved.4.This paper introduced different line width measurement methods and analyzed their respective advantages and disadvantages.A FRM-based fiber Delayed Self-heterodyne Interferometer linewidth measurement system is experimentally designed,and the continuous seed light width is measured.The relationship between the frequency stability of the self-starting output laser and the stability of the output light frequency after injection locking is analyzed.It is concluded that the frequency of the injected output light is more stable than that of the self-starting output light,and the possibility of using the gain grating to achieve frequency stabilization is proved.