Ultra-broadband Optical Parametric Chirped Pulse Amplification By Two Broadband Pump Beams

Optical parametric chirped-pulse amplification (OPCPA) is suitable for a new approach to few-cycle, high-peak-power laser systems because of its broad gain bandwidth and large single-pass gain while maintaining negligible thermal load in a nonlinear crystal. In order to amplify ultrabroad bandwidth, various types of OPCPA schemes are proposed and demonstrated. Generally, non-collinear OPCPA (NOPCPA) has been used for broad-band amplification. NOPCPA is the way to set the crossing angle of generally over 2 degrees between pump and seed beam in non-linear crystal which is gain media. Far example, the calculated phase-matching bandwidth of a Type-I BBO crystal pumped by a monochromatic wavelength of 532 nm at crossing angle of 2.2° is obtained the range of 300nm. By using the broadband pump pulse from a Ti:sapphire laser, the enhancement of the amplified bandwidth was also obtained at degeneracy [1]. As another approach, OPA pumped by multiple pulses has been proposed and demonstrated [2]. In this scheme, each pump pulse which has a different incidence angle on the nonlinear crystal can achieve phase matching over different signal wavelength regions, respectively. In this paper, we demonstrated a Degenerate OPCPA with two pump beams. Using two beams, the amplified bandwidth extended more than 350 nm at a center wavelength of 1020 nm. This bandwidth is capable of producing less than 8.1 fs optical pulse duration, corresponding to the 2.5 optical cycles.