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We demonstrate multi-layer silicon-oxy-nitride (SiON) waveguides as a platform for broadband tunable phase-matching of second-order nonlinear interactions arising at material interfaces. Second-harmonic generation (SHG) is measured with a 2 ps pulsed pump of 1515-1535 nm wavelength, where 6 nW power is generated by an average pump power of 30 mW in a 0.92 mm long device. The wavelength acceptance bandwidth of the SHG is as broad as 20 nm due to the low material dispersion of SiON waveguides. The waveguide structure provides a viable method for utilizing second order nonlinearity for light generation and manipulation in silicon photonic circuits. [ABSTRACT FROM AUTHOR]

Recent advancements in phase-matching second-order nonlinear processes by using matching-layer-enhanced Bragg reflection waveguides (ML-BRWs) in Al_xGa 1-xAs material system are discussed. The limitations on the choice of the Al_xGa1-xAs layers for applications that require high pump power operation are highlighted. Multilayer-core ML-BRWs are proposed as a new waveguide design with relaxed constraints over the choice of the Al _xGa1-xAs layers composition. The tradeoffs associated with material bandgap on the efficiency of second-order nonlinear processes are examined by using this novel structure. The interplay among the various factors, including the nonlinear overlap factor, the effective second-order nonlinearity, and the third-order nonlinear effects result in the presence of an optimum detuning of the core bandgap from the operating wavelength for maximum conversion efficiency. Two different wafer structures are examined by using second-harmonic generation to elucidate these tradeoffs. The conversion efficiency is examined by using 30-ps, 2-ps, and 250-fs pulses at various pump average power levels. [ABSTRACT FROM PUBLISHER]

Wavelength conversion by difference frequency generation is demonstrated in domain-disordered quasi-phase-matched waveguides. The waveguide structure consisted of a GaAs/AlGaAs superlattice core that was periodically intermixed by ion implantation. For quasi-phase-matching periods of 3.0–3.8 \mum, degeneracy pump wavelengths were found by second-harmonic generation experiments for fundamental wavelengths between 1520 and 1620 nm in both type-I and type-II configurations. In the difference frequency generation experiments, output powers up to 8.7 nW were generated for the type-I phase matching interaction and 1.9 nW for the type-II interaction. The conversion bandwidth was measured to be over 100 nm covering the C, L, and U optical communications bands, which agrees with predictions. [ABSTRACT FROM PUBLISHER]

A comprehensive study of the far-field diffraction pattern of Bragg reflection waveguides is presented. Using a Gaussian approximation of the near-field profile, an analytical formula for the far-field pattern of the fundamental Bragg mode is obtained. The proposed closed-form representation offers a powerful technique for examining the far-field characteristics, which provides insight into the design optimization of Bragg reflection waveguides. [ABSTRACT FROM PUBLISHER]

Bragg reflection waveguides (BRWs) with matching layers placed between the core and claddings are proposed and analyzed as a means of enhancing the effective second-order optical nonlinearity. The addition of matching layers to conventional BRW structures provides extra degrees of freedom, which enable further optimization to enhance the nonlinear conversion efficiency. Pertinent parameters including overlap between modal profiles of the interacting waves, the group velocity mismatch and group velocity dispersion are examined. The structures studied in this work are designed using the GaAs-AlxGa1-xAs material system. It is shown that, in comparison to phase-matched BRWs with no matching layers, the proposed structure benefits from relaxing the constraint over the phase-matched core thickness. For typical designs, it is shown that the new structure can provide over an order of magnitude enhancement in nonlinear coupling efficiency and 30% decrease in group velocity mismatch. It is also shown that the group velocity dispersion of the first and second harmonics are reduced by 10% and 52%, respectively. [ABSTRACT FROM AUTHOR]

Second-harmonic generation in a quasi-phase matched waveguide produced using a domain-disordered GaAs-AlAs superlattice is modeled including the effects of group velocity mismatch, nonlinear refraction, two-photon absorption, and linear loss. The model predicts our experimentally observed second-harmonic powers within an order of magnitude. Self-phase modulation and two-photon absorption led to reduced conversion efficiencies of up to 33% at input peak powers >50 W. Group velocity mismatch results in a reduction of 23% in conversion efficiency using estimated group velocities calculated from the measured effective refractive index. The modeling also shows that the conversion efficiency peaks at propagation lengths longer than the pulse walk off length and that duty cycle variations induced shifts in the tuning curves. Group velocity mismatch also increased the conversion bandwidth by ~30%. Incomplete modulation of X(2) in disordered regions reduced the output conversion efficiency by up to two orders of magnitude. Grating-assisted phase matching led to a 7% efficiency drop for a Δn of 0.045 at the second-harmonic and 0.0! at the fundamental. This model serves as a valuable tool to provide insight into the optimization of these devices. [ABSTRACT FROM AUTHOR]