[en] A novel master oscillator/power amplifier architecture for optical parametric conversion of high pulse energy from 1.064 μm to 1.572 μm in KTiOPO₄ crystal is presented. A high gain of more than 80 at 1.572 μm pumped by a high energy Q-switched pulse laser is realized. With a seeding signal energy of 1 mJ, and 400 mJ pump pulse at 100 Hz, an amplified signal pulse energy of over 80 mJ is obtained. The total optical-optical conversion efficiency reaches 21%

[en] A frequency stabilizing system for a pulsed injection seeded 1550nm optical parametric oscillator (OPO) at 20 Hz repetition rate is demonstrated. The optical heterodyne method is used to measure the frequency difference between the seed laser and the OPO output. Using the frequency difference as the error signal, a proportionalintegral controller in combination with a scanner is applied to stably match the OPO cavity length to the seed laser frequency. The root-mean-square (rms) error of the frequency discrimination method is <0.07MHz according to a ‘frequency shifting-chopping-beat’ evaluation. The frequency fluctuation of the frequency-stabilized OPO is 0.29MHz (rms), and the Allan deviation is less than 20 kHz for averaging time of more than 3 s. (paper)