Sum-frequency generation surpasses 200 nJ with CLBO crystals

Researchers from the Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy (Berlin, Germany) and the Kogakugiken Co. Ltd., (Kanagawa, Japan) have used a 150-mm-thick cesium lithium borate (CLBO) crystal to achieve sum-frequency generation on a femtosecond time scale. The researchers produced 100-fs pulses that were tunable between 175 and 180 nm and at energy levels from 200 to 400 nJ with a 1-kHz repetition rate. The 100-fs pulses were supplied by a 1-kHz Ti:sapphire regenerative amplifier. Sequential fourth-harmonic generation took place in three barium borate crystals. A continuum-seeded, near-infrared, traveling-wave optical parametric amplifier was used to satisfy the phase-matching conditions for CLBO. The results achieved presented a fivefold improvement in output energy over lithium borate, due to the higher effective nonlinearity of CLBO, according to the researchers. They also expect to improve wavelength range and energy output further by cutting CLBO samples at larger angles. Contact Valentin Petrov at[email protected].