Cryogenic, high power, near diffraction limited, Yb:YAG slab laser

Efficient, low threshold, cryogenic Ho:YAG laser

“…The compact resonator and the bulk of the cryostat prevented us from making interferometric studies while lasing. However such measurements have been performed previously for a similarly mounted Yb:YAG slab [17] where no pump-induced stress was observed at thermal loads much larger than those reported here. These observations are ascribed to the significantly improved thermo-optic properties of YAG at cryogenic temperatures.…”

“…A key design criterion for cryogenic laser operation is the minimization of the applied stress that could lead to wave-front distortion and induced birefringence from differential thermal contraction when the laser gain medium is cooled to 77 K. In this work the mechanical laser head architecture is similar to that described elsewhere [17,25] and uses an indiummolybdenum-aluminium design to maximize thermal conductivity to the cold finger, while minimising the mechanical stress applied to the laser crystal. The laser crystal used was a 2 mm thick, 3 mm wide, 49 mm long 0.7% wt.…”

“…To mount the laser slab we followed the approach described in [17] and [26]. To ensure optimal stress-free mechanical mounting the slab was monitored interferometrically (with a 632.8 nm HeNe laser) at RT and when cooled to 77 K. The resulting interferograms are shown in Fig.…”

“…Furthermore, operating at CTs dramatically increases the thermal conductivity and decreases both the thermal expansion coefficient and dn/dT in the crystalline YAG host [12][13][14]. Several liquid nitrogen (LN) cooled Yb:YAG lasers have demonstrated these advantages with high average power and good beam quality using disk [15], rod [16] and slab [17] gain media. However these thermo-opto-mechanical properties have yet to be exploited in Ho:YAG.…”

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

“…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.…”