Sub-Nanosecond Infrared Optical Parametric Pulse Generation in Periodically Poled Lithium Niobate Pumped by a Seeded Fiber Amplifier

摘要

A ytterbium-doped, polarization maintaining PM double-clad fiber was seeded at one end and pumped at the other end, using dichroic filters to protect the pump and seed lasers, creating a fiber amplifier. The seed laser was a passively Q-switched Nd:YAG microchip laser operating at 1064 nm, polarized 99:1, 7.14 kHz repetition rare, 0.5 nsec pulse width, average power of 38 mW, and 5.3 microjoule pulse energy. The pump laser was a 915 nm diode laser coupled to a fiber pigtail, operating at a maximum of 6 W with 7 A of operating current. The 3.56-m-long FC connectorized fiber was the active element and had a 25 micron core diameter and a 248 micron inner cladding diameter with 400- micron-diameter spliced silica end-caps to prevent damage polished at 8 to prevent back reflections. The PPLN crystal was an uncoated 1 x 14 x 49-mm-long multigrating crystal with approximate parallelism of the front and back surfaces. The domain grating period used was 29.5 micron, converting the 720 mW (over 100 microjoule pulse energy) fiber amplifier beam to a 1.507 micron signal beam and a 3.619 m idler beam, with 24% of the pump energy going to the signal and idler outputs.