Numerical study of spectral shaping in high energy Ho:YLF amplifiers

Abstract

We present a new chromatic numerical approach to simulate the amplification of laser pulses in multipass laser amplifiers. This enables studies on spectral effects such as gain narrowing and spectral shaping with optical elements expressed by a transmission transfer function. We observe good agreement between our simulations and measurements with a Ho:YLF regenerative amplifier (RA). To demonstrate the capabilities of our simulation model, we numerically integrate an intra-cavity etalon in this laser and find optimum etalon parameters that enhance the peak power of the output pulses up to 65%.

Study on laser characteristics of Ho:YLF regenerative amplifiers: Operation regimes, gain dynamics, and highly stable operation points

“…Equivalently, the standard deviation of the output pulse fluence in percent of the mean output fluence is used as a measure for the output noise. The simulation framework was already presented in detail in [16], where the model was spectrally generalized and used to study spectral shaping effects in Ho:YLF RAs. Here, we used the monochromatic version as it is computationally less expensive.…”

“…Typically, this means that CW pumping cannot be considered with this set of equations. In this work, the equations were modified to include the inversion decay losses by considering the inversion decay law [24], allowing for the simulation of CW pumped laser gain media with an excited state life time of ≳7 ms [16].…”

“…The complete simulation model was comprehensively presented in [16], but in contrast to [16] where the equations were further modified to the spectral regime, for this work here, the classical monochromatic FN equations were used. In the following, the general simulation approach and the used equations are summarized.…”

Millijoule-level, kilohertz-rate, CPA-free linear amplifier for 2 μm ultrashort laser pulses

“…The inverted fraction is iterated along the propagation axis of the gain medium with a fixed pump and laser mode diameter. A similar approach has been presented by Kroetz et al [15], where the inverted fraction is updated after each pump and amplification cycle, however, without slicing the gain medium along the propagation direction. Here we use an approach similar to the one described in Ref.…”

“…Here we use an approach similar to the one described in Ref. [15], but with sequential calculation of the pulse evolution by longitudinal splitting of the gain medium in vertical slices and, at the same time, adapting the beam size for every crystal slice. In this way, we are able to determine the pulse peak intensity for each corresponding crystal slice.…”