10  J operation of a conductive-cooled Yb:YAG active-mirror amplifier and prospects for 100  Hz operation

Abstract

We report, to the best of our knowledge, the highest power conductive-cooled active-mirror amplifier (CcAMA) using Yb:YAG with a pulse energy of 10 J. By using four liquid-nitrogen circulating cooled laser heads, we achieved a repetition rate, pulse energy, and average power of 33.3 Hz, 9.3 J, and 310 W, respectively. The problem of wavefront distortion, which is difficult to solve with a large-aperture active-mirror laser, is suppressed by using reinforcing materials with the same thermal expansion coefficient. We have confirmed that the wavefront distortion is small ( 0.15 λ P-V per head) at 100 Hz operation, which paves the way for 100 Hz operation with the CcAMA concept.

High‐Power Laser Systems

“…[111,149,150] Based on the cryogenically cooled Yb:YAG active mirrors and pulsed diode laser pumping, Wang et al reported a laser pulse output of 1 kHz, 4.5 ps, 1.1 J, which is the highest average power Joule-level ps laser reported at that time. [64] Based on four liquid nitrogen circulating cooled laser heads, [49] Ogino et al achieved a laser output of 9.3 J, 10 ns, at 33.3 Hz.…”

“…The master amplifier consisted of four large‐aperture Yb:YAG ceramics (a diameter of 60 mm and thickness of 7 mm), liquid nitrogen cooled at 78 K, and PDL pumped. [ 49 ] They aimed to scale the energy to 100 J with 10 GW peak power by combining more than 10 large‐aperture laser heads. However, there is still no public report of more than 10 GW peak power by the active mirror.…”

“…[ 47 ] On the other hand, taking advantage of the excellent energy storage volume, the traditional slab laser (zigzag & active‐mirror slab in Figure 1d) can reach ≈1 GW peak power with ≈10 ns pulse width ≈10 J energy. [ 48,49 ] The integrated thin‐film multislab with a more substantial heat dissipation capability allows larger‐sized crystals, which increase the energy of the 10 ns pulse to ≈100 J level with peak power over 10 GW. [ 50,51 ]…”

“…[47] On the other hand, taking advantage of the excellent energy storage volume, the traditional slab laser (zigzag & active-mirror slab in Figure 1d) can reach ≈1 GW peak power with ≈10 ns pulse width ≈10 J energy. [48,49] The integrated thin-film multislab with a more substantial heat dissipation capability allows larger-sized crystals, which increase the energy of the 10 ns pulse to ≈100 J level with peak power over 10 GW. [50,51] With sub-mm thickness, the disk has a greater energy storage capacity than optical fiber and a higher heat dissipation area ratio than the slab, allowing it to produce CPA-free average power of kW level, picosecond (ps) pulsed output energy of mJ level, and peak power exceeding GW.…”

Strong Double Space-Time Wave Packets from Optical Parametric Amplification

“…Consequently, an e cient ampli er is required, but which must keep the ST correlation unchanged. Because of low gain (e.g., ~3× per 7mm in a conductive-cooled Yb:YAG [29]), the population inversion ampli er containing energy-level laser media requires a long-length propagation and/or a multiple-pass con guration for high energy ampli cation, which is not suitable here. OPA based on the three-wave coupling in nonlinear crystals can realize high gain within a thin crystal (e.g., 20× per 0.5mm in a 40 fs typeI-BBO OPA [30] and 10 6 × per 15mm in a 3 ps typeI-BBO OPA [31]), which might be an ideal ampli er for ST wave packets.…”