A CEP-stable, femtosecond 8.5 μm source based on intrapulse DFG of 2.1 μm pulses

Abstract

Few-cycle carrier-envelope phase (CEP) stable laser pulses enable the precise control of strong-field electron dynamics, such as high-harmonic generation in gases and solids or electron emission in nano-structures [1]. The intrapulse difference-frequency generation (DFG) pumped by a broadband pulse is a reliable method of producing passively CEP-stable pulses. Mid-infrared (mid-IR) pulse generation via intrapulse DFG has been demonstrated with near-IR pump pulses. For example, the intrapulse DFG of Ti:sapphire laser pulses can generate ∼2 μm [2] or ∼5 μm pulses [3], while spectrally broadened and compressed pulses of Yb:YAG laser were used to cover the region from 6.8 to 16.4 μm [4]. Since the efficiency and output pulse energy is rather low for intrapulse DFG, these pulses typically seed further optical parametric amplifiers. If the pump wavelength is shifted to ∼2 μm region, the mid-IR intrapulse DFG at >5 μm becomes more efficient due to a lower quantum defect and the excellent phase matching characteristics of mid-IR nonlinear crystals based on non-oxide materials.