Efficient generation of mid-infrared few-cycle pulses by the intrapulse difference-frequency generation in YCOB

Yttrium calcium oxyborate (YCOB) crystals have been widely applied for generating intense near-infrared laser pulses by optical parametric amplification. Here, we show that the YCOB crystals oriented in both the XZ and XY prin-cipal planes possess broadband phase-matching property of intrapulse difference-frequency generation in the mid -infrared region. Few-cycle pulses tunable from 2 to 4 mu m are experimentally produced by using a 7.5-fs pump laser at 800 nm, in which the conversion efficiency can be as high as 2.5%. With a large-size crystal and high-power pump laser, intrapulse difference-frequency generation based on YCOB may provide a new route for directly producing intense few -cycle mid-infrared pulses. (c) 2022 Optica Publishing Group