High sustained average power cw and ultrafast Yb:YAG near-diffraction-limited cryogenic solid-state laser

Abstract

We report what we believe to be record performance for a high average power Yb:YAG cryogenic laser system with sustained output power. In a CW oscillator-single-pass amplifier configuration, 963 W of output power was measured. In a second configuration, a two amplifier Yb:YAG cryogenic system was driven with a fiber laser picosecond ultrafast oscillator at a 50 MHz repetition rate, double-passed through the first amplifier and single-passed through the second, resulting in 758 W of average power output. Pulses exiting the system have a FWHM pulsewidth of 12.4 ps, an energy/pulse of 15.2 μJ, and a peak power of 1.23 MW. Both systems are force convection-cooled with liquid nitrogen and have been demonstrated to run reliably over long time periods.

The Application of Cryogenic Laser Physics to the Development of High Average Power Ultra-Short Pulse Lasers

“…CW cryogenic Yb:YAG lasers with CW output power ě400 W have been reported by a number of groups, including 455 W [3], 400 W [129], 550 W [130], 500 W [135], and 494 W [138]. The largest CW power for a Yb:YAG cryogenic laser reported to date, 963 W, was for a Yb:YAG cryogenic oscillator driven double-passed Yb:YAG preamplifier followed by a Yb:YAG power amplifier demonstrated by our group [132]. We include Yb:CaF 2 here due to a recent high power demonstration with a quantum-defect of only 1.11% [134].…”

“…We begin by first looking at the evolution of Yb:YAG, Yb:YLF, and Yb:CaF 2 CW cryogenic lasers; Yb:YAG and Yb:YLF materials have been used for the highest power CW demonstrations to date. Figure 44 shows the CW output power obtained from Yb:YAG cryogenically-cooled lasers operating near 80 K. The corresponding data and references are shown in Table 7 [1,3,4,30,108,109,[126][127][128][129][130][131][132][133][134][135][136][137][138][139]. The first CW Yb:YAG demonstration was by Lacovara [1], who reported 40 W output power.…”

Concepts, performance review, and prospects of table-top, few-cycle optical parametric chirped-pulse amplification

“…The level scheme becomes an almost four-level minimizing reabsorption, the stimulated cross-section improves by ∼5, while the thermal conductivity increases 2.5 to 4 times depending on the dopant level. 81 However, the emission linewidth and thus, the amplification bandwidths of these systems reduce to typically <1 nm, corresponding to a transform-limited pulse duration of ∼5 ps. A few cryogenically cooled systems have been presented, such as a system generating 287 W average power with 5.5 ps duration pulses corresponding to 3.7 μJ pulse energy.…”

“…99 A system with a double-and single-pass amplifier was presented based on multiple thick Yb:YAG disks generating up to 15.2 μJ pulse energy with 760 W average power and 12 ps duration. 81 Another scheme to reduce thermally induced aberrations is a slab amplifier. The beam multipasses through the slab offering lower thermal aberration compared to rod-type designs, high small signal gain as well as a compact design.…”

Performance scaling of high-power picosecond cryogenically cooled rod-type Yb:YAG multipass amplification

“…On the other hand, Yb:YAG bulk amplifier at cryogenic temperature are available for scaling both energy and average power, combining the good thermo-optical properties of the Yb:YAG crystal and the advantage of high single-pass gain. Cryogenic cooling of the Yb:YAG gain medium [10][11][12] dramatically reduces the saturation fluence (~1.5 J/cm 2 at 77 K). Recently, Hong et al demonstrated a 40 mJ, ps cryogenic Yb:YAG bulk CPA laser system operating at 2 kHz repetition rate [13].…”