The positive-branch confocal unstable resonator with inhomogeneous gain medium was studied for the normal used high energy COIL system. The fast changing process of the resonator’s eigenmodes was coupled with the slow changing process of the thermal deformation of cavity mirrors. Influences of the thermal deformation of cavity mirrors to the output beam quality and transmission loss of high frequency components of high energy laser were computed. The simulations are done using program compiled by GLAD software. Effects of thermal distortion, misaligned of cavity mirrors and inhomogeneous distribution of gain medium were considered to simulate the real physical circumstances of laser cavity. The wavefront distribution and beam quality (including RMS of wavefront, power in the bucket, Strehl ratio, diffraction limit β, position of the beam spot center, spot size and intensity distribution in far-field ) of the distorted output beam were studied. The conclusions of the simulation agree with the experimental results and the simulation results computed by ANSYS and FLUENT programs. This work would supply references of wavefront correction range to the adaptive optics system of interior alleyway.
The positive-branch confocal unstable resonator with inhomogeneous gain medium was studied for the normal used high energy DF laser system. The fast changing process of the resonator’s eigenmodes was coupled with the slow changing process of the thermal deformation of cavity mirrors. Influences of the thermal deformation of cavity mirrors to the outcoupled beam quality and transmission loss of high frequency components of high energy laser were computed. The simulations are done through programs compiled by MATLAB and GLAD software and the method of combination of finite elements and Fox-li iteration algorithm was used. Effects of thermal distortion, misaligned of cavity mirrors and inhomogeneous distribution of gain medium were introduced to simulate the real physical circumstances of laser cavity. The wavefront distribution and beam quality (including RMS of wavefront, power in the bucket, Strehl ratio, diffraction limit β, position of the beam spot center, spot size and intensity distribution in far-field ) of the distorted outcoupled beam were studied. The conclusions of the simulation agree with the experimental results. This work would supply references of wavefront correction range to the adaptive optics system of interior alleyway.
A totally self-designed experimental system based on dynamic light scattering is developed. The method of photon correlation spectroscopy is used to simulate the autocorrelation of measured scattering photons and scattering field. The dynamic autocorrelation software is self-compiled to replace the popular hardware digital correlator for much more correlation channels and much lower costs. Several inverse algorithms such as 1st-order Cumulants, 2nd-order Cumulants, NNLS, CONTIN and Double Exponents are used to compute the particle sizes and decay linewidths of both monodisperse systems and polydisperse systems. The programs based on these inverse algorithms are all self-compiled except the CONTIN. Influences of systematical parameters such as sample time, the last delay time, elapsed time, suspension's concentration and the baseline of scattering photons autocorrelation on the scattering photon counts, the autocorrelations of scattering photons and scattering field and the distribution of particle sizes are all investigated detailedly and are explained theoretically. The appropriate choices of systematical parameters are pointed out to make the experimental system more perfect. The limitations of the inverse algorithms are described and explained for the self-designed system. The methods of corrected 1st-order Cumulants and corrected Double Exponents are developed to compute particle sizes correctly at wide time scale. The particle sizes measured by the optimized experimental system are very accurate.
The measuring system based on photon correlation spectroscopy is improved through several means. The distribution
of nanometer particle's sizes measured by new systems is more stable and accurate. All of the experiments are done in an
ultra-clean chamber. The temperature is controlled and changes from about 13 degrees centigrade to 22 degrees
centigrade. Fibers with different core diameters are used to transmit scattering light. The "Y" type fibers with different
core diameters are used to transmit both the incident laser and the scattering light. The microscope objectives with
different numerical apertures are used to collect and couple the scattering light into fiber. The software of real time
correlation is tried to be used in the measuring system and it is compared with the static correlation. The Labview is used
to integrate the software of correlation and inverse algorithms of nanometer particle sizes. Influences of incident laser
with different power and mode are analyzed.
A series of dynamic light scattering (DLS) experimental systems basing on photon correlation spectroscopy (PCS) are
brought forth for measuring the size of nanometer particles and the corresponding measuring results are shown. The
results obtained through these experimental systems are all compared with the results obtained by instrument of
Brookhaven. Mono-disperse and double disperse nanometer particle solutions systems are both studied. The light source
is the diode laser with the single transverse mode and its wavelength is 532 nm. It is the avalanche photon diode (APD)
instead of the traditional photomultiplier tube (PMT) is selected as the detector for its high quantum efficiency. The
scattering light transmits in a closed channel. The experimental systems are designed in two different kinds. The first
kind of experimental system is a system without fiber. The second kind of experimental system introduces one fiber for
transmission of scattering light. In these two kinds of experimental system, the influences of the polarization state of the
incident laser are investigated. The photon counting board is a product of self designed and the dynamic software
correlation system is introduced instead of the traditional hardware digital correlator for lower costs. The size of the
nanometer particles is computed by the famous CONTIN and NNLS programs.
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