Picosecond gain and saturation measurements in a KrF laser amplifier depumped by amplified spontaneous emission

Abstract

The input/output characteristic of a large aperture (270-mm diam) electron-beam-pumped KrF laser amplifier is obtained for pulses of 6- and 40-ps duration. The off-resonance absorption coefficient is estimated by measurement of loss at 268 nm. The gain-to-loss ratio is found to decrease from 8 to 6 as the specific pump rate is increased from 0.3 to 0.65 MW cm−3. Gain depumping due to amplified spontaneous emission (ASE) is treated by a simple 1D code and found to give good agreement with experiment. A 3D code incorporating wall reflections gives even better agreement. The spatial distribution of gain and ASE is recorded using visible and ultraviolet imaging.

Spectral effects of gain saturation in the β-phase of poly(9,9-dioctylfluorene)

“…Rather interesting in our experiment, the excitation density dependence of the ASE intensity at both 478 and 470 nm is well reproduced ͑see Fig. 4,18,19 However we observe that the ASE depletion of the emitting state cannot lead to the observed different excitation density dependence of the two ASE bands, as this process affects the population of the higher level of the stimulated emission transition, which is the same for the two ASE bands. From the best fit values of the parameters we estimated 478 Ϸ 2 470 .…”

Theoretical study of amplified spontaneous emission using a model based on a geometrically dependent gain coefficient

“…These values for the gain coefficients are slightly lower than the other reported measured gain values close to this length. For example it is 0.043 cm −1 for l AMP = 80 cm [17], 0.023 cm −1 for l AMP = 82 cm [35], and ∼0.042-0.054 cm −1 for 100 cm long apparatus [36], as it is also tabulated in table 2 of [27] for the analysis of excimer laser systems. In a saturated system, for a very large z, we have the saturated gain g sat → 0, which means that actually the net gain, g net , in the saturated condition is equal to zero, if we assume that the system is experiencing saturated absorption similar to that which the gain coefficient has.…”