Calculation of the gain coefficient in cryogenically cooled Yb : YAG disks at high heat generation rates

Abstract

We have calculated the stored energy and gain coefficient in disk gain elements cooled to cryogenic temperatures. The problem has been solved with allowance for intense heat generation, amplified spontaneous emission and parasitic lasing, without averaging over any spatial coordinate. The numerical simulation results agree well with experimental data, in particular at high heat generation rates. Experimental data and theoretical analysis indicate that composite disk gain elements containing an undoped region can store considerably more energy due to suppression of amplified spontaneous emission and parasitic lasing.

Configuration of vortex-antivortex lattices at output mirror of wide-area microchip laser

“…where E n ( r) is electric field envelope at output mirror, f is nonlinear gain transfer function, L r is cavity length, L a << L r is a thickness of amplifying medium relevant to experimental situation [12], R is reflectivity of output mirror, D( r) = R exp[−| r| 2 /D 2 0 ] is diaphragm function corresponding to transversely inhomogeneous linear losses, key parameter for comparison with experiments [3] was D 0 ∼ 50 − 2000µm , G n ( r) = σN n ( r)L a is transversely inhomogeneous linear gain, σ is simulated emission cross-section, N n ( r) is density of resonant ions per unit volume, δω is detuning from gain line center, T 2 and T 1 are transverse and longitudinal relaxation times correspondingly, δE( r) is random noise due to spontaneous emission term emulated as multimode random process [13], δN ( r) is fluctuating part of optical pump also defined as spatially smooth multimode random process, N f = D 2 0 /(λL r ) is Fresnel number, λ is lasing wavelength. The convergence rate to equilibrium solutions (stationary eigenmodes) for dicrete time step δt = 2L r n/c proved to be 20 -100 iterates [14].…”

“…where E n ( r) is electric field envelope at output mirror, f is nonlinear gain transfer function, L r is cavity length, L a << L r is a thickness of amplifying medium relevant to experimental situation [12], R is reflectivity of output mirror,…”

Amplified spontaneous emission intensity at the side surface of thin disk lasers

“…The application of an anti-reflection layer to decrease the ASE phenomenon was also examined 5 , 6 . The composite multilayer disk structures have also been recommended to decrease the effect of the ASE phenomenon 7 , 8 . ASE signal emission in a cryogenically cooled disk of an Yb:YAG laser was also examined 9 and the threshold gain coefficient was estimated at which the ASE signal emerged.…”

“…5,6 The composite multilayer disk structures have also been recommended to decrease the effect of the ASE phenomenon. 7,8 ASE signal emission in a cryogenically cooled disk of an Yb:YAG laser was also examined 9 and the threshold gain coefficient was estimated at which the ASE signal emerged. Chvykov et al 10 showed that in a thin disk, the main portion of the ASE power is emitted from the disk's side surface, which they called transverse ASE (TASE) and they presented a model to calculate TASE signal numerically.…”

Ways of improvement of high energy capacity disk lasers

“…One of known methods for suppressing ASE is the using of disk active elements with undoped cup. In the present paper we use the numerical model described in [4] to analyze the influence of the AE geometry on the efficiency of suppressing ASE. The calculations are performed for a disk shaped and composite active elements 15 mm in diameter made of Yb:YAG/YAG with 10% doping ( fig.…”