# Advances in High-Power, Ultrashort Pulse DPSSL Technologies at HiLASE
## 1 Introduction
### Perla A and Perla B Platforms  
Both the Perla A and Perla B platforms are CPA systems, which aim to high energy pulses. The Perla B was redesigned [32] in order to provide a burst of pulses and better fit experimental requirements. Intra-burst repetition rate was set to 10 kHz, and a burst repetition rate of 100 Hz with optional switching back to original configuration operating continuously at a repetition rate of 1 kHz was described in detail in References [24; 27]. In the burst mode, each 1-ms long pulse burst \begin{table}
\begin{tabular}{c c c c c} \hline
**Year** & **Perla A** & **Perla B** & **Perla C** & **Perla D** \\ \hline
**2015** & Not available & 45 mJ; 1 kHz; 45 W; & 1 mJ; 1 kHz; 90 W; 1.9 ps & Not available \\ \hline
**2017** & 100 mJ; 10 Hz & 45 mJ; 1 kHz; 45 W; & 9 mJ; 50 kHz; 450 W; or & \\  & proof-of-principle & \textless{1 ps, M}^{2} \textless{1.3}\), & 4.5 mJ; 100 kHz; 450 W; & Under design \\  & experiments, under design & Also new: & 1.3 ps, M\({}^{2}\) \textless{1.5}-2; & \\  & design & 50 W; 10 kHz burst & RMS stability \textless{1.3}\% & \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of progress in typical average output power, pulse energy, pulse repetition rate, pulse length (full width at half maximum (FWHM)), and beam quality of Perla thin-disk laser platforms achieved since 2015 [27]. \begin{table}
\begin{tabular}{c c c c c} \hline
**Year** & **Second Harmonic** & **Fourth Harmonic** & **Fifth Harmonic** & **Mid-IR OPG + OPA** \\
**515 nm** & **257.5 nm** & **205 nm** & **1.5–3 μm** \\ \hline
**2015** & 11 W; 100 kHz; 40\% & 2 W; 100 kHz; 18\% & \\  & conversion & conversion & Not available & Under design \\  & efficiency & efficiency & & 1.7–2.6 μm tunability (both \\
**2017** & 40 W; 100 kHz; 56\% & 6 W; 100 kHz; 18\% & 0.8 W; 100 kHz; & signal + idiller waves); \\  & conversion & conversion & 20\% conversion & 8.5 W signal (\textless{2} μm); \\  & efficiency & efficiency & efficiency & 5 W idler (\textgreater{}2 μm); \\  & & & 77 kHz \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison of progress in typical average output power, pulse repetition rate, and conversion efficiency of frequency up- and down-conversion stages pumped by the picosecond Perla C thin-disk laser platform since 2015 [27]. Mid-IR OPG: optical parametric generation producing mid-infrared pulses; Mid-IR OPA: optical parametric amplification amplifying mid-infrared pulses. Figure 2: Typical performance of the actual status of the Perla C amplifier with a ring cavity: (**a**) Output power and optical-to-optical efficiency in pulsed operation (50 and 100 kHz) compared with continuous wave (CW) performance of the ring cavity; (**b**) nearly diffraction-limited beam profile (Gaussian, normalized, red – peak power, blue – low power, violet - background) at average power of 320 W and 50 kHz repetition rate as used for experiments (M\({}^{2}\)\textless{1.8}\). consists of ten 1-2-ps long pulses. The pulses are generated from an Yb-doped fiber oscillator (nJ pulse energy), stretched to 1.5 ns by a chirped-fiber Bragg grating stretcher, and preamplified in a system of fiber preamplifiers to approximately 10 \(\upmu\)J. A 100-\(\upmu\) pulse burst is after the preamplification seeded to a thin disk-based regenerative amplifier and amplified to 10 mJ per pulse, i.e., 100 mJ per burst. The amplifier is quasi-continuous wave (QCW) pumped (1 ms pulse length) by fiber-coupled laser diodes at zero-phonon line wavelength (968.8 nm), and is switched on and off by a pair of 10 \(\times\) 10 \(\times\) 22 mm\({}^{3}\) BBO crystals. The output beam is nearly diffraction-limited, and the M\({}^{2}\) parameter measured for continuous pulsing at 1 kHz was better than 1.3. Finally, the amplified pulses will be boosted up to 600 mJ per burst in a 10-pass thin disk-based multipass amplifier. The amplifier is pumped at 940 nm by a fiber-coupled laser diode module (2 kW). Both the amplification stages employ a diamond-bonded Yb:YAG thin-disk with a thickness of 220 \(\upmu\)m, 7 at.