High harmonic generation (HHG) in a Kagome-type hollow-core photonic crystal fiber (HC-PCF)

Hollow-core photonic crystal fibers (HC-PCF) offer a combination of long effective interaction length and small mode areas which has resulted in several major breakthroughs in low-power nonlinear optics. Recently, it was shown numerically that such fibers offer unique properties in terms of efficiency and low threshold for high harmonic generation. In addition to the substantial decrease in pump threshold, the efficiency is expected to be significantly enhanced by guiding and improved phase-matching using optimized dispersion engineering in PCFs. This paper presents the high harmonic generation (HHG) in a HC-PCF. An extremely low threshold pulse energy for HHG of 440 nJ is observed.