Impedance matching vertical optical waveguide couplers for dense high index contrast circuits

Abstract

We designed and demonstrated a compact, high-index contrast (HIC) vertical waveguide coupler for TE single mode operation with the lowest coupling loss of 0.20 dB +/- 0.05 dB at 1550 nm. Our vertical coupler consists of a pair of vertically overlapping inverse taper structures made of SOI and amorphous silicon. The vertical coupler can suppress power oscillation observed in regular directional couplers and guarantees vertical optical impedance matching with great tolerance for fabrication and refractive index variations of the waveguide materials. The coupler furthermore shows excellent broadband coupling efficiencies between 1460 nm and 1570 nm.

Photonic network-on-chip architectures using multilayer deposited silicon materials for high-performance chip multiprocessors

“…This technique is similar to what has recently been demonstrated with four cascaded crystalline silicon microring resonator filters demultiplexing a wavelength-parallel optical signal into geranium photodetectors with 19GHz bandwidths [Chen and Lipson 2009]. In the 3D-integrated configuration, the polycrystalline silicon microring photodetectors are coupled to a local polycrystalline silicon bus waveguide, which is vertically coupled to silicon nitride with a broadband vertical coupler [Sun et al 2008], assuming a 0.1dB optical loss per coupling.…”

“…The effective index of the microring resonator and waveguide must be matched to efficiently transfer optical power; therefore, we assume each modulator is coupled to a local polycrystalline silicon bus waveguide, which is then coupled to a silicon nitride waveguide with a broadband vertical coupler [Sun et al 2008], assuming a 0.1dB optical loss per coupling.…”

“…Monolithic Multilayer Silicon Device Integration. Experimental demonstrations of multilayer silicon photonic systems have involved crystalline silicon waveguides on one photonic plane vertically coupled to polycrystalline silicon microring resonators on another photonic plane [Preston et al 2007], and crystalline silicon waveguides vertically coupled to amorphous silicon waveguides in a low-loss and compact coupler [Sun et al 2008]. These are critical experimental validations of deposited silicon photonic devices that are monolithically integrated with low-loss silicon photonic waveguides.…”

Si-Photonics-Based Layer-to-Layer Coupler Toward 3D Optical Interconnection

“…The layer-to-layer directional coupler with linear tapers were demonstrated with an interlayer thickness of 200 nm [7]. However, as mentioned before, at least 1 µm was needed to reduce unwanted crosstalk.…”

“…If the interlayer thickness between the layers is relatively thin (< few hundred nm), a simple directional coupler type device with linear taper structure is sufficient [7]. However, such small interlayer thickness produces unwanted signal crosstalk between layers.…”