Abstract
We have optimized the input pulse width and injection time to achieve the highest possible output pulse energy in a double-pass laser amplifier using two Nd:YAG rods. For this purpose, we have extended the Frantz–Nodvik equation by simultaneously including both spontaneous emission and pump energy variation. The effective pump energy of the flash lamp was 8.84 J for each gain medium. The energy of 1 J could be amplified to an output energy of 12.17 J with the maximum achieved extraction efficiency of 63.18% when an input pulse having a pulse width of 168 $\unicode[STIX]{x03BC}$s is sent 10 $\unicode[STIX]{x03BC}$s after the absorbed pump energy becomes the maximum value.
Highlights
Among the various laser parameters, laser pulse width is a crucial factor to be selected carefully, depending on the application[1, 2]
We have extended the F–N equation to consider dynamically spontaneous emission and pump energy ignored during conventional simulations of the pulse amplification
Shorter pulses injected when the stored energy of the gain medium becomes maximum can produce higher possible output pulse energy through abrupt depletion of the upper-state ions while reducing the energy wasted by spontaneous emission and temporal overlap
Summary
Among the various laser parameters, laser pulse width is a crucial factor to be selected carefully, depending on the application[1, 2]. In the case of inputting an input pulse with a duration of 1 μs into a Nd:YVO4 amplifier[12], the fluorescence lifetime of the laser-active ions (90 μs) is significantly longer than the duration of the amplification. The pulse amplification ends before the excited ions spontaneously return to their ground state. In this case, the derivation conditions of the equation are satisfied. The existing F–N equation can only be applied if the input pulse width is significantly shorter than the fluorescence lifetime of the laser-active ions. We have extended the F–N equation to consider dynamically spontaneous emission and pump energy ignored during conventional simulations of the pulse amplification. We have verified that the optimal input pulse width and injection time can be realized within the given conditions to obtain the maximum output pulse energy
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