High-power Nd: Yag Lasers And Fiber-coupled System Theory And Experiment

This thesis mainly aims to high power continuous fundamental frequency Nd:YAG laser with LD array side-pumped laser rod, symmetrical parallel plane resonator, and laser optical fiber coupling system.Simulate the pump energy deposition of the LD arrays side-pumped laser rod. For TEMoo mode matching, pump configuration should use large waist pump beam and small absorption laser rod.Analyzed thermo-optic effect of the Nd:YAG laser rod, according to uniform heat load in the laser rod and heat conduction equation via side cooling. The optical distortions in laser rod which is caused by temperature and thermal photo elastic depended index change was equivalent with a thermal lens, focal length was calculated and measured for further study. Approximated the thermal lens to the lens like medium, the stability of the plane parallel resonant with a thermal lens was analyzed by round-trip ray transfer matrix. The laser output power curves were consistent with the resonator stability analysis.An experiment compare with a concaved laser rod and a grooved laser rod were studied. The concaved laser rod is disadvantage for compensating the thermal lens in the entire dynamic range; the grooved laser rod is advantage for reducing the temperature inside the laser rod since large cooling surface and high thermal conductivity. A maximum laser output Pιmax=915W was measured while the total slope efficiency isη= 0.171.According to mixed-mode Gaussian distribution (GLD), AE Siegman's second order definition of the laser beam width in the beam axis coordinate system, the beam parameters (beam waist, beam width, divergence angle and M2) calculation equations were derived in the laboratory coordinate system, and a test method based on grey level histogram is illustrated. A He-Ne laser's diffraction limit factor were measured Mx2=3.87 and My2=4.42 by using histogram, respectively.By ABCD law of the Gaussian like beam (GLB) and ZEMAX optimization, a fiber coupling design was given which is combined reversed Galilean telescope with single focus lens, in detail the lens of the telescope is spherical geometry and the focus lens is aspheric (Quadrics) geometry. Fiber coupling design is aberrations (mainly spherical aberration) free and high efficiency.