Efficient Ultrafast Frequency Conversion Sources for the Visible and Ultraviolet Based on BiB$_{3}$O$_{6}$

Abstract

Efficient frequency conversion of high-repetition-rate femtosecond and picosecond pulses with wide tunability throughout the visible, blue, and UV is demonstrated in the nonlinear optical crystal BiB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> (BIBO). Using direct single-pass second harmonic generation of Kerr-lens-mode-locked Ti:sapphire laser, average output powers close to 1 W at conversion efficiencies in excess of 50% are demonstrated with broad spectral coverage across 370-450 nm in the near-UV and blue spectral range. Output pulse durations of 220 fs and 2.8 ps have been obtained at a pulse repetition rate of 76 MHz. By implementing a synchronously pumped femtosecond optical parametric oscillator (OPO) based on BIBO, the generated spectral range is further extended to cover the entire visible spectrum, across the green-yellow-orange-red regions. Average output powers of up to 270 mW in pulses of 120 fs at 76 MHz repetition rate have been generated across the 480-710 nm range. Internal frequency doubling of the visible OPO signal pulses in the crystal of beta-BaB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> has permitted high-repetition-rate femtosecond pulse generation with wide tunability across 250-350 nm in the UV at up to 100 mW of average power. The potential of BIBO for efficient frequency conversion of high-intensity pulses is also demonstrated through third harmonic generation of amplified microjoule picosecond pulses at 1064 nm. Output pulse energies of 216 muJ in 29 ps duration at 25 Hz repetition rate have been obtained at 355 nm with overall conversion efficiencies of up to 50%.