Nonlinear integrated photonics on silicon and gallium arsenide substrates

Silicon photonics is nowadays a mature technology and is on the verge of becoming a blossoming industry. Silicon photonics has also been pursued as a platform for integrated nonlinear optics based on Raman and Kerr effects. In recent years, more futuristic directions have been pursued by various groups. For instance, the realm of silicon photonics has been expanded beyond the well-established near-infrared wavelengths and into the mid-infrared (3 - 5 µm). In this wavelength range, the omnipresent hurdle of nonlinear silicon photonics in the telecommunication band, i.e., nonlinear losses due to two-photon absorption, is inherently nonexistent. With the lack of efficient light-emission capability and second-order optical nonlinearity in silicon, heterogeneous integration with other material systems has been another direction pursued. Finally, several approaches have been proposed and demonstrated to address the energy efficiency of silicon photonic devices in the near-infrared wavelength range. In this dissertation, theoretical and experimental works are conducted to extend applications of integrated photonics into mid-infrared wavelengths based on silicon, demonstrate heterogeneous integration of tantalum pentoxide and lithium niobate photonics on silicon substrates, and study two-photon photovoltaic effect in gallium arsenide and plasmonic-enhanced structures. Specifically, performance and noise properties of nonlinear silicon photonic devices, such as Raman lasers and optical parametric amplifiers, based on novel and reliable waveguide technologies are studied. Both near-infrared and mid-infrared nonlinear silicon devices have been studied for comparison. Novel tantalum-pentoxide- and lithium-niobate-on-silicon platforms are developed for compact microring resonators and Mach-Zehnder modulators. Third- and second-harmonic generations are theoretical studied based on these two platforms, respectively. Also, the two-photon photovoltaic effect is studied in gallium arsenide waveguides for the first time. The effect, which was first demonstrated in silicon, is the nonlinear equivalent of the photovoltaic effect of solar cells and offers a viable solution for achieving energy-efficient photonic devices. The measured power efficiency achieved in gallium arsenide is higher than that in silicon and even higher efficiency is theoretically predicted with optimized designs. Finally, plasmonic-enhanced photovoltaic power converters, based on the two-photon photovoltaic effect in silicon using subwavelength apertures in metallic films, are proposed and theoretically studied

Silicon-on-nitride waveguides for mid- and near-infrared integrated photonics

Silicon-on-nitride ridge waveguides are demonstrated and characterized at mid-and near-infrared optical wavelengths. Silicon-on-nitride thin films were achieved by bonding a silicon handling die to a silicon-on-insulator die coated with a low-stress silicon nitride layer. Subsequent removal of the silicon-on-insulator substrate results in a thin film of silicon on a nitride bottom cladding, readily available for waveguide fabrication. At the mid-infrared wavelength of 3.39 mu m, the fabricated waveguides have a propagation loss of 5.2 +/- 0.6 dB/cm and 5.1 +/- 0.6 dB/cm for the transverse-electric and transverse-magnetic modes, respectively

Noise Figure In Near-Infrared Amorphous And Mid-Infrared Crystalline Silicon Optical Parametric Amplifiers

The noise figures (NF) of near-infrared (near-IR) amorphous silicon (a-Si) and mid-infrared (mid-IR) crystalline silicon (c-Si) optical parametric amplifiers (OPA) are numerically investigated. The impact of nonlinear losses, i.e., two-photon absorption (TPA) and TPA-induced free carrier absorption (FCA), as well as Raman-effect-induced complex nonlinear coefficient are taken into account in a-Si OPAs. The amplified spontaneous emission (ASE) of Erbium-doped fiber amplifiers (EDFA) and the relative intensity noise (RIN) of the pump laser are considered as the dominant pump noises when simulating the pump transferred noise (PTN) of near-IR a-Si and mid-IR c-Si OPAs, respectively. It is shown that in typical near-IR a-Si OPAs, the NF is ∼5 dB on the Stokes side but increases sharply to above 10 dB at the gain edge on the anti-Stokes side. In high-gain mid-IR c-Si OPAs, the NF is dominated by the PTN and is well above 10 dB at the gain edge. These results indicate that both near-IR a-Si OPAs and mid-IR c-Si OPAs are promising alternatives to near-IR c-Si OPAs, but they both have limitations in broadband operation. © 1983-2012 IEEE

Subwavelength Plasmonic Apertured Waveguides For Integrated Photonics Applications

Optical transmission properties of subwavelength apertured waveguides on semiconductor substrates, particularly silicon, are studied. The waveguide design is optimized for maximum power throughput at telecommunication wavelengths. © 2010 IEEE

Submicron optical waveguides and microring resonators fabricated by selective oxidation of tantalum

Submicron tantalum pentoxide ridge and channel optical waveguides and microring resonators are demonstrated on silicon substrates by selective oxidation of the refractory metal, tantalum. The novel method eliminates the surface roughness problem normally introduced during dry etching of waveguide sidewalls and also simplifies fabrication of directional couplers. It is shown that the measured propagation loss is independent of the waveguide structure and thereby limited by the material loss of tantalum pentoxide in waveguides core regions. The achieved microring resonators have cross-sectional dimensions of similar to 600 nm x similar to 500 nm, diameters as small as 80 mu m with a quality, Q, factor of 4.5 x 10(4), and a finesse of 120

Micro-Ring Optical Resonators Fabricated By Selective Oxidation Of Refractory Metals (Sorm)

A novel platform for integrated photonic circuits is proposed based on selective oxidation of refractory metals (SORM). Low-loss tantalum pentoxide coupled micro-ring optical resonators and high-index contrast ridge waveguides are demonstrated based on this platform. © 2013 OSA

Low-Loss And High Index-Contrast Tantalum Pentoxide Microring Resonators And Grating Couplers On Silicon Substrates

A platform for high index-contrast integrated photonics based on tantalum pentoxide submicrometer waveguides on silicon substrates is introduced. The platform allows demonstration of microring resonators with loaded quality factor, Q, of 67,000 and waveguides with a propagation loss of 4.9 dB/cm. Grating couplers, with an insertion loss of ~6 dB per coupler and 3 dB bandwidth of ~50 nm, are also demonstrated and integrated with microring resonators

High-contrast, all-silicon waveguiding platform for ultra-broadband mid-infrared photonics

Suspended silicon-membrane ridge waveguides are fabricated and characterized on a single-material photonic device platform. By using direct bonding, a thin layer of silicon is fused to a bulk silicon substrate, which is patterned with narrow trenches. Waveguides are etched on the resulting suspended membranes and are characterized at mid-and near-infrared wavelengths. Transverse magnetic-mode propagation losses of 2.8 +/- 0.5 and 5.6 +/- 0.3 dB/cm at 3.39 and 1.53 mu m wavelengths are measured, respectively. This all-silicon optical platform is capable of continuous low-loss waveguiding from wavelengths of 1.2-8.5 mu m, enabling numerous applications in frequency conversion and spectral analysis

High-Q Lithium Niobate Microring-Resonators On Silicon

Submicron lithium niobate waveguides and resonators are demonstrated on silicon by a novel and reliable ion implantation and wafer bonding technique. Waveguide ridges are formed by selective oxidation of tantalum to avoid etching lithium niobate. © 2013 The Optical Society

Micro-Ring Optical Resonators Fabricated By Selective Oxidation Of Refractory Metals (Sorm)

A novel platform for integrated photonic circuits is proposed based on selective oxidation of refractory metals (SORM). Low-loss tantalum pentoxide coupled micro-ring optical resonators and high-index contrast ridge waveguides are demonstrated based on this platform. © 2013 OSA