We report on mid-infrared optical parametric generation in the 4–5 μm and 9–12 μm bands by pumping custom-designed orientation-patterned gallium arsenide (OP-GaAs) rib waveguides with an ultrafast femtosecond fiber laser system. This pump source is seeded by a mode-locked fluoride fiber laser with 59 MHz repetition rate and can be tuned between 2.8 and 3.2 μm using a soliton self-frequency shifting stage. The single TE and TM modes OP-GaAs crystals feature quasi-phase-matched grating periods of 85 and 90 μm and different transverse sizes thus allowing a wide spectral tunability.
A new process to produce orientation-patterned gallium phosphide (OP-GaP) on GaAs with almost perfectly parallel domain boundaries is presented. Taking advantage of the chemical selectivity between phosphides and arsenides, OP-GaP is processed into suspended shallow-ridge waveguides. Efficient second-harmonic generation from telecom wavelengths is achieved in both Type-I and Type-II polarisation configurations. The highest observed conversion efficiency is 200% W −1 cm −2 , with a bandwidth of 2.67 nm in a 1 mm-long waveguide. The variation of the conversion efficiency with wavelength closely follows a squared cardinal sine function, in excellent agreement with theory, confirming the good uniformity of the poling period over the entire length of the waveguide.
Heteroepitaxial growth of orientation-patterned (OP) GaP (OP-GaP) on wafer-bonded OP-GaAs templates is investigated by low-pressure hydride vapor phase epitaxy for exploiting the beneficial low two-photon absorption properties of GaP with the matured processing technologies and higher-quality substrates afforded by GaAs. -First, GaP homoepitaxial selective area growth (SAG) is conducted to investigate the dependence of GaP SAG on precursor flows and temperatures toward achieving a high vertical growth rate and equal lateral growth rate in the [110] and [110]-oriented openings. Deteriorated domain fidelity is observed in the heteroepitaxial growth of OP-GaP on OP-GaAs due to the enhanced growth rate on domain boundaries by threading dislocations generated by 3.6% lattice matching in GaP/GaAs. The dependence of dislocation dynamics on heteroepitaxial growth conditions of OP-GaP on OP-GaAs is studied. High OP-GaP domain fidelity associated with low threading dislocation density and a growth rate of 57 μm h À1 are obtained by increasing GaCl flow. The properties of heteroepitaxial GaP on semi-insulating GaAs is studied by terahertz time-domain spectroscopy in the terahertz range. The outcomes of this work will pave the way to exploit heteroepitaxial OP-GaP growth on OP-GaAs for frequency conversion by quasi-phase-matching in the mid-infrared and terahertz regions.
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