Cascaded-crystal optical parametric amplifier for broadband near-infrared pulse generation

We experimentally demonstrate a robust optical parametric amplifier (OPA) designed for the efficient generation of ultrashort near-infrared (NIR) laser pulses. Utilizing hundred-fs narrowband pulses from a commercial pre-amplifier as the seed, the system employs a cascaded arrangement of nonlinear crystals with varying phase-matching angles to amplify adjacent frequency regions of the seed pulse. This approach realizes a broad signal gain bandwidth and significantly reduces the output pulse durations. The resulting pulses centered at 1400 nm are compressed to 5 optical cycles (23.3 fs) using only linear compression with fused silica, meanwhile achieving a high pump-to-signal conversion efficiency of 40.0%. Our novel scheme offers a straightforward and cost-effective method for simultaneously enhancing the pulse energy and broadening the pulse bandwidth within a single stage. This advancement could benefit a variety of research fields and applications that rely on ultrafast lasers, particularly those demanding ultrabroad bandwidths or few-optical- cycle pulse durations.