A design study is presented for difference-frequency generation (DFG) in aluminum gallium arsenide (AlGaAs)- on-insulator waveguides. AlGaAs is a mature technology platform with large optical nonlinearities, a high refractive index contrast, and the presence of second-order susceptibility, making it interesting for chip-based frequency conversion. This work targets to efficiently down-convert single-photons to the telecom C-band by DFG. Modal phase-matching (PhM) is used, where the waveguide dimensions are optimized for an efficient and robust conversion of single-photons at 930 nm to around 1550 nm. This paves the way for a single-photon converter that can be integrated on a chip-platform with a single-photon emitters, along other photonic components with standard fabrication techniques. Furthermore, a thorough revision of the DFG theory provides insight into the particular case of a low-powered pump, which is relevant for quantum applications. Finally, a comparison is made with state of the art devices in periodically poled thin film lithium niobate (PPLN). This is, to the best of our knowledge, the first design of a single-photon converter operating in the telecom band that is realized with a III-V material.
Lasers emitting in the ultraviolet C-band (UVC) have recently attracted considerable attention for germicidal purposes. Combining diode lasers with nonlinear crystals used for second-harmonic generation (SHG) is a promising approach thanks to their relatively low cost, small footprint and long lifetime. The output power in the UVC is limited by the output power of the diode lasers and by the conversion efficiency in the nonlinear crystal. This work compares the SHG conversion efficiency using a bulk approach to values expected using guided modes in waveguides. It discusses the phase-matching (PhM) condition for different input polarizations, the effective nonlinearity, and the Poynting vector walk-off. This last effect is particularly detrimental as it reduces the effective length for the nonlinear interaction in bulk, which ultimately limits the conversion efficiency towards the UVC. Values for the walk-off angle are computed for barium borate (BBO), and a comparison is provided with other nonlinear crystals.
Optoelectronic oscillators (OEOs), realized on photonic integrated circuits (PICs), have the potential of producing millimeter-wave (mm-wave) clock signals with lower timing jitter and higher operating frequencies than their all-electronic counterparts. To have a proper design tool for these PIC-based OEOs, a novel, computationally efficient time-domain circuit simulation model is presented. It relies on describing the propagation, filtering and mixing of the spectral contents of the circulating optical and mm-waves. This work specifically targets OEOs consisting of building blocks offered by commercial PIC platforms, such as high-speed modulators, high-Q filters, semiconductor optical amplifiers (SOAs) and high-speed photodetectors (PDs). The model can simulate a wide range of OEO topologies, including OEOs that use an array of SOAs and PDs to boost the generated mm-wave signal power, or OEOs that employ modulator configurations other than the often-used Mach-Zehnder devices. The model also takes into account the saturation effects and noise of the SOAs and PDs, as well as all the propagation losses and delays experienced by the optical and mm-waves, which allows for investigating the effects of fabrication errors. As a test case, this model is applied to a proposed design of a hybridly integrated 20-GHz OEO, which relies on a combination of indium phosphide (InP) and silicon nitride (SiN) based PICs, using realistic parameters representative for these platforms. Timing jitters of almost 100 fs (10 kHz { 10 MHz) are demonstrated by optimising the SOA gain and the laser frequency detuning from the high-Q filter resonances.
We present the design of a photonic crystal-based multilayer structure that allows to experimentally demonstrate, using attenuated total reflectance experiments, the existence of the predicted transverse electric (TE) polarized excitation in graphene. We show that this mode can be excited in a single layer of graphene, even at room temperature. Furthermore, we prove that the observed mode in the reflection spectra corresponds to the TE- polarized graphene excitation and not the Bloch Surface Wave of the photonic crystal experiencing graphene- induced loss. Finally, we point out that adding an extra layer of dielectric material on top of the structure would ensure the unambiguous identification of the TE graphene mode even in the presence of fabrication errors.
In this paper, we numerically demonstrate the promise of silicon microdisks for Raman Stokes/anti-Stokes wavelength conversion. We design a silicon microdisk suitable for Raman wavelength conversion with “automatic” quasi-phase matching. We show that with this design and with a 2.5% incoupling efficiency for the pump and Stokes input, we can theoretically achieve wavelength conversion efficiencies up to 3.2 dB at input pump powers as low as 7.8 mW. Regarding fabrication tolerances of the design, we find that small deviations from the optimal cross coupling coefficient and from the condition for “automatic” quasi-phase matching are allowed without deteriorating the wavelength conversion efficiency.
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