Optical Processes and χ⁽²⁾ Susceptibility Dispersion of LBO for Storage Media and Tunable Frequency Oscillator

Abstract

The increasing interest in the field of time-resolved spectroscopy has lead to a development of various tunable ultrashort pulse lasers of picosecond or femtosecond scale. The lithium triborate (LBO) crystal is one of new promising materials for nonlinear optics. The birefringence of LiB₃O₅ (LBO) allows phase-matching between the wave vectors of pump and the signal (idler) beams to be achieved for collinear as well as for noncollinear propagation directions. This LBO crystal is important because of its extensive use in parametric devices and harmonic converters. Despite its smaller nonlinearities compared to KTP and BBO, the LBO is a highly attractive crystal due to its noncritical phase-matching, small temporal walkaway and wide acceptance bandwidths. The LBO has very high damage threshold up to 25 GW/cm² for a 0.1 ns at 1064 nm, and small walk-off angle. When comparing to BBO, lithium triborate has a smaller nonlinear coefficient and a smaller birefringence, however this leads to narrower inherent linewidths and greater acceptance angle. This combined with superior chemical and mechanical properties makes LBO an interesting material for broadly tunable, line-narrowed, optical parametric oscillator (OPO).