Various embodiments of the present technology provide a novel architecture for optical frequency conversion in a waveguide which can be applied to any suitable nonlinear waveguide material and any wavelength. In accordance with some embodiments, phase-matched bends can be used to increase the nonlinear interaction length. For example, the device can begin with a straight waveguide section with a width designed for phase-matching. When the straight waveguide section approaches the end of the chip, a bending waveguide section allows the waveguide to meander back in the opposite direction. Various embodiments of the bend can have a wider or narrower width to eliminate phase-matching for second harmonic generation (SHG) and instead provide a 2π phase-shift between the pump and signal light. Therefore, at the end of the bend, the pump and signal light are in-phase and a phase-matched width will continue the SHG process.
A novel architecture for optical frequency conversion in a waveguide is proposed, which increases the conversion efficiency compared to existing architectures. It consists of several straight sections of phase-matched nonlinear optical waveguides linked by dispersion-engineered bends to allow continuous build-up of the generated light. The architecture applies to any suitable nonlinear waveguide material and any wavelength. The main advantages are: (I) higher conversion efficiency, (2) lower power requirements, (3) greater manufacturability due to significantly reduced chip dimensions and higher yield.
The figure below is a cross-sectional view of a waveguide 400 in accordance with various embodiments of the technology. Waveguide 400 may include cladding 410 surrounding waveguide core 420 built on a substrate 430. Some embodiments of the waveguide 400 may have a waveguide core 420 (e.g., gallium arsenide) and one or more cladding layers (e.g., silicon dioxide) that include a uniform or composite material. For example, the cladding layers 410 may include sub-layers of quantum wells that form an effective medium. There are many other embodiments of a nonlinear waveguide in which this technology can be implemented.
In some embodiments, the waveguide core 420 and/or cladding layers 410 may be formed by deposition techniques (e.g., epitaxial growth or chemical-vapor deposition, or by wafer bonding techniques). The waveguide core 420 may have a higher refractive index than the waveguide cladding 410 in various embodiments. The cladding 410 surrounding the waveguide may include a gaseous medium, such as air, or vacuum in some embodiments. In addition, the waveguide may be suspended via mechanical tethers that are the same material or a different material as the waveguide core.
In some embodiments, the waveguide may include an intermediate layer (not shown) formed between the waveguide core 420 and the waveguide cladding 410. The waveguide core layer 420 formed by direct bonding or adhesive bonding from a secondary substrate material to a primary substrate material. In addition, the waveguide core layer 420 may be formed using selective die, selective area bonding, or full wafer-scale bonding.
This invention could enable rapid wavelength agility for optical communication systems on a low power budget, and in a form factor sufficiently compact for autonomous vehicle integration.