Cascaded third-harmonic generation approaching full efficiency through an unconventional pathway

Nuno Castanheira; Noah Flemens; Jeffrey Moses

doi:10.1117/12.2651978

14 March 2023 Cascaded third-harmonic generation approaching full efficiency through an unconventional pathway

Nuno Castanheira, Noah Flemens, Jeffrey Moses

Proceedings Volume 12405, Nonlinear Frequency Generation and Conversion: Materials and Devices XXII; 124050G (2023) https://doi.org/10.1117/12.2651978
Event: SPIE LASE, 2023, San Francisco, California, United States

Abstract

Third harmonic generation (THG) achieved by the simultaneous phase matching of multiple quadratic nonlinear processes in a single crystal has been studied previously both theoretically and experimentally, achieving modest conversion efficiencies. As opposed to the common practice of using second harmonic generation (SHG) and sum frequency generation (SFG) stages in series, performing these processes in parallel results in a narrow material parameter range in which the transfer of energy to the third harmonic can be fully efficient, even under conditions of perfect phase matching. This is largely due to the presence of back-conversion in the conversion dynamics, which limits the efficiency for spatio-temporally non-uniform beams. Here we demonstrate an unconventional method of THG where the fundamental wave is first frequency-quadrupled through cascaded SHG before being down-converted to the third harmonic. When the three associated phase matching conditions are met simultaneously, we find that energy is transferred robustly and efficiently from the fundamental wave to the third harmonic with inhibited back-conversion. This is an example of convergent dynamical behavior emerging from hybridized nonlinear optical processes as recently observed in hybridized parametric amplification. These dynamics are achievable over a broad parameter range that correspond to common nonlinear crystals. Using a spatio-temporal numerical investigation, we find that 25-ps CO₂ laser pulses with Gaussian spatio-temporal profiles and 10-μm wavelength can be converted to their third harmonic with over 80% conversion efficiency in a realizable monolithic orientation-patterned GaAs device. High performance realizable domain-poled KTP and LNB devices are also investigated.

Conference Presentation

Citation Download Citation

Nuno Castanheira, Noah Flemens, and Jeffrey Moses "Cascaded third-harmonic generation approaching full efficiency through an unconventional pathway", Proc. SPIE 12405, Nonlinear Frequency Generation and Conversion: Materials and Devices XXII, 124050G (14 March 2023); https://doi.org/10.1117/12.2651978

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