We report on master-oscillator/power-amplifier (MOPA) systems featuring Yb-doped photonic crystal fiber (PCF) amplifiers and designed to generate high peak and average powers in beams of good spectral and spatial quality.
In the first setup, a 1064nm-wavelength Q-switched Nd:YAG micro-chip laser emitting 500ps pulses at pulse repetition frequency (PRF) ~13.5-kHz is amplified in a 40μm-core, Yb-doped PCF to obtain peak power ~1.1 MW in a diffraction-limited beam (M2 = 1.05) of peak spectral brightness ~ 10 kW/(cm2 sr Hz).
In the second setup, a 1ns-pulse Nd:LSB microchip laser (1062nm wavelength, single frequency, PRF = 9.6 kHz) is used to seed a dual-stage amplifier featuring the same 40μm-core Yb-doped PCF as the final stage. From this MOPA, we obtained diffraction-limited pulses of 1.1mJ energy, peak/average power ~1.1 MW/~10.2 W, and spectral linewidth ~9GHz.
In the third setup, a single-polarization, single-transverse-mode Yb-doped PCF was used as the final amplifier, which permitted to obtain high-peak-power, spectrally narrow, 100:1 linearly-polarized pulses directly usable for wavelength conversion. The PCF output was frequency doubled, tripled, and quadrupled in nonlinear crystals to generate peak power in excess of 400 kW in the visible and ~200 kW in the UV.
Finally, in the fourth setup, an Yb-doped, 70μm-core, intrinsically single-mode photonic-crystal rod (PCR) was used to generate near-diffraction-limited (M2 ~ 1.1) ~1ns pulses of 2.25mJ energy and peak-power >2.2 MW.