Comprehensive Analysis And Control Research On Aberration Of Large Aperture And High Output Power Disk Laser

Since the advent of the laser in 1960,in nearly 60 years of development,the application of the laser in in the field of military,industrial,medical and scientific research has always been a hot spot that the world's major countries pursues,and the trend is more and more clearly in recent years.As far as the laser itself is concerned,the output power and beam quality is the first condition of its application prospect.Diode pumped disk laser with round disk gain medium can achieve high power,high efficiency and high beam quality at the same time.The disk laser is designed to operate efficiently in a pulsed state and can be used as a q-switched laser or laser amplifier.The disk laser can also achieve high average power and high efficiency in the generation and amplification of ultrashort pulses.so this article aiming at the large diameter disk medium's beam quality control to carry out the following research work:`(1)On the basis of analyzing the thermogenic aberration of thin disk media,the phase distortion caused by optical path changes through the disk due to the thermal expansion and thermal induced refractive index change(thermal lens effect)are discussed,the local strong point model in the unstable resonator is established,the wavefront distortion analysis method of the boundary between pump and non-pump areas is constructed,the edge effect of thin disk media was analyzed.All of these have laid a foundation for analyzing the aberration characteristics of large diameter disk media.(2)In this paper,the evolution of aberration in a positive-branch confocal unstable resonator is analyzed,and the method of aberration evolution is discussed,the aberration transmission evolution results of 4-disk media in a positive-branch confocal unstable resonator is simulated numerically,In addition,the aberration correction is also calculated,and the field distribution of the unsteady resonator output beam is calculated by the fast Fourier transform(3)For the complex aberration disturbance in the unsteady resonator,a variety of measures are used to calibrate the static aberration in advance.Based on the numerical simulation and experimental study;this paper analyzed the influence of the cooler on the wavefront distortion of thin disk media from the effects of the material mechanics and structure characteristics of the cooler;on the basis of analyzing the mechanism of the disk coating film distortion,the correction method of film coating on the front and back of the thin disk was analyzed,and experimental study was carried out;based on the study of the intrinsic characteristics of the aberration zernike polynomials,a self-correcting method for the aberration in the laser resonator of the thin disk laser is proposed,the system static aberration can be reduced without any other auxiliary correction element inserted in the resonator.All these measures lay a good foundation for dynamic aberration correction in laser star-up stage.(4)An optical axis detection method based on near field spot sampling is proposed,It avoids the phenomenon that the optical axis deviation is affected by the aberration in the resonator,which leads to the deviation of the true value of the optical axis deviation detection results,It is theoretically proved that the optical axis deviation based on near field spot sampling is independent of aberration,experimental results show that the detection equivalence under the condition of small aberration;the optical axis detection technology based on the near field spot sampling and combined with the in-resonator back and forth detection technology to effectively correct the optical axis tilt,so as to achieve stable power output.(5)A method for correction of in-resonator aberration combined active and passive is proposed based on back and forth detection is proposed,an experimental study was carried out on the bonding of seven large diameter disk medium with unsteady resonator,After correction,the laser output of 5.4k W at 200 Hz repetition frequency is realized,and the beam quality is improved greatly by ?=6.8,compared with the beam quality before correction of?=32.Under the condition of 500 Hz repetition frequency,the laser output with single pulse energy greater than 20J(average pulse energy is 22.3J)and beam quality ? is between 5.5 and 7.5.