TY - JOUR
AU - Dementjev, Aleksandr S.
AB - We present results of beam quality investigation in Nd:YAG crystal fiber amplifier seeded by ns, sub-ns and ps laserpulses counter-propagating to continuous pump of < 110 W power at 808 nm wavelength. The maximum amplifiedpower of 44 W and energy of 3.2 mJ has been achieved with ns seed. We observed gain rise to < 75 with ps seed of1.6 mW average power when tuned emission spectra to ~ 1064.3 nm. Beam propagation coefficient M2 approach 1.2 atthe maximum pump power with high quality seed pulse emitted by 6 ps fiber laser. Amplification of sub-ns seed pulsesfrom microchip laser led to an M2 increase from ~1.2 to ~< 1.5. New analytical solution for temperature distribution inend-pumped thin long single crystal fiber with temperature dependent thermal conductivity coefficient is found forpolynomial transverse pump distribution. The analytical relation between thermal coefficients of refractive index at zerostresses and zero strains is found for YAG type cubic crystals. Using plane strain approximation the analytical expressionfor thermal radial and tangential changes of refractive index is found, and the relation between different expressions forso-called photoelastic constants Cr, is established. The methods of numerical calculation of rays and Gaussian beampropagation in a graded-index medium of active element are developed. The error in widely used formula for M2 ofGaussian beam with quartic phase aberration is corrected. It is shown that beam quality degradation can be explained byactive thermal lens in power amplifier when changes of transverse beam shape or beam width during amplification aretaken into account.
TI - Beam quality investigation in Nd:YAG crystal fiber amplifier pumped at >110w
JF - Proceedings of SPIE
DO - 10.1117/12.2079294
DA - 2015-02-20
UR - https://www.deepdyve.com/lp/spie/beam-quality-investigation-in-nd-yag-crystal-fiber-amplifier-pumped-at-D0O0tLt5jz
SP - 934207
EP - 934207-16
VL - 9342
IS - 
DP - DeepDyve
ER -