11-µJ picosecond-pulsed hollow-core-fibre-feedback optical parametric oscillator

Wu, Yudi, Liang, Sijing, Fu, Qiang, Poletti, Francesco, Richardson, David J. and Xu, Lin (2023) 11-µJ picosecond-pulsed hollow-core-fibre-feedback optical parametric oscillator. In 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. IEEE. 1 pp . (doi:10.1109/CLEO/EUROPE-EQEC57999.2023.10232710).

Abstract

High-energy, short-pulsed mid-infrared (MIR) lasers have many important applications such as spectroscopy, materials processing, and medical treatments. Optical parametric oscillators (OPOs), converting readily available near-infrared pulses to the MIR, are often used to service these applications. Temporal synchronization of pulses between the pump and the resonant signals is required in ultrashort-pulsed MIR OPOs. This becomes to be problematic for realising high-energy picosecond (ps) pulses at few-MHz repetition rates from the OPO because cavities with an optical length of hundreds of meters are impractical to implement. This problem can be mitigated using compact fibre-feedback OPO designs that incorporate a length of flexible optical fibre in the cavity. We have previously demonstrated a novel 1-MHz, 4-μJ-level, ps-pulsed OPO based on a fibre-laser-pumped periodically poled lithium niobate (PPLN) crystal cavity consisting of a 298-m-long hollow-core fibre (HCF) as a feedback fibre [1]. Use of HCF allows for significantly improved power scaling capability compared to a traditional solid-core-fibre-feedback OPO due to its vastly lower nonlinearity. Our previous results showed that the maximum achievable pulse energy from the HCF-feedback OPO was limited by the fibre master oscillator power amplifier (MOPA) pump source due to self-phase modulation (SPM) induced spectral broadening that exceeds the acceptance bandwidth of the PPLN crystal at high peak powers. Here we report the power scaling of a fibre MOPA source that provides 130-ps pulses at 1040 nm with a maximum peak power of 267 kW and present an HCF-feedback OPO that operates at 1-MHz repetition rate and generates pulse energies up to 11 μJ. These results represent, to the best of our knowledge, the highest pulse energy yet reported from a ps OPO.

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Contributors

Author: Francesco Poletti

Author: David J. Richardson

Author: Lin Xu

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