Research On Single Frequency And Frequency-Stabilitied Laser Based On Gain Grating

Q-switched single-frequency stabilized laser,compared with other types of lasers,there are very prominent advantages,such as:long coherence length,narrow line width,stable frequency,pulse peak power.These salient features make the Q-switched single-frequency stabilized laser have very important application prospects in remote sensing and telemetry,laser radar,scientific research and military application.It is an important research and development direction of laser technology in the world.In the conventional laser to achieve single-frequency stabilized frequency Q-Switched output,the cavity will be added to Q-switched,the choose mode and frequency components,which increases the system complexity and instability.In recent years,coherent beam interference in the media to form a gain grating,and produce phase conjugate output,under the conditions of in the absence of Q-switched and the choose mode component to get single-frequency pulse output.Because the gain grating has the adaptive characteristic,the formation of the gain grating is guided by the injection of the external single frequency seed light,and the conjugate output of the seeded light can be obtained.The realization of the steady frequency is the focus of this paper.In this paper,the main method of realizing single-frequency frequency-stabilized output laser is analyzed,and the idea of using single-frequency stabilized pulse output with gain grating is proposed.The present situation of reciprocal and nonreciprocal gain grating lasers is discussed.After comparison,it is considered that the impulse pumped nonreciprocal structure is the way to realize the single frequency frequency-stabilized and pulse output.Based on the four-wave mixing physical mechanism of optical conjugation and degeneracy,the transmission gratings and reflection gratings in the medium are analyzed,and the two-dimensional characteristics of degenerate four-wave mixing in saturated gain media are analyzed.The interaction of four-wave mixing in steady state,transient state and general time state is analyzed respectively.The spatial filtering effect and frequency stabilization principle of gain grating are analyzed.The structure design of the non-reciprocal single-frequency pulsed laser is discussed.The choice of the laser structure,the gain medium and the pump source is discussed,and the relationship between the output,the pump and the medium gain is analyzed.Select Nd:YVO₄ as a gain medium to ensure the gain of the loop.Use the bounce structure,improve the compactness of the system while ensuring that the angle of the self-crossed light is small enough to improve the diffraction efficiency and output efficiency of the grating.Built self-starting non-reciprocal gain grating laser,to achieve a self-starting Q-pulse output.By optimizing the output mirror transmittance,the ability of nonreciprocal elements to distinguish polarized light,the intersection angle of the crossed light,and the matching of the gain grating region to the pumping region.Improve the matching degree of the whole system,improve the single-frequency output of the energy,get single pulse energy 0.9m J,line width of 0.98pm single-frequency output.On the basis of self-starting single-frequency pulse output,the external seed is injected into the loop along the direction of the signal light to guide the gain grating to make the gain grating record all the information of the seed.The conjugate output of the center wavelength in the spectral range of the seed light is obtained,which proves the idea of realizing the output of the steady frequency by the gain grating.