Multilayer 3-D Photonics in Silicon

California Univ., Los Angeles
Optics Express (Impact Factor: 3.49). 11/2007; 15(20):12686-91. DOI: 10.1364/OE.15.012686
Source: PubMed


Three-dimensionally (3-D) integrated photonic structures in multiple layers of silicon are reported. Implantation of oxygen ions into a silicon-on-insulator substrate with a patterned thermal oxide mask, followed by a high temperature anneal, creates photonic structures on 3-D integrated layers of silicon. This process is combined with epitaxial growth to achieve devices on three vertically integrated layers of silicon. As a demonstration vehicle, we report a multistage optical filter that comprises of coupled microdisks on two subsurface silicon layers with bus waveguides on the surface (3rd) layer. The optical filter shows extinction ratios in excess of 14 dB, with excess insertion loss of less than 1 dB.

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    • "The field of silicon photonics [1] [2] holds promise for 3-D integration [3] [4] with compact, high-contrast dielectric optical waveguides at different levels of photonic chips. This might concern small vertical distances, such that evanescent coupling between overlapping components becomes possible, but just as well optically well separated waveguides at larger vertical separations. "
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    ABSTRACT: We show how to optically connect guiding layers at different elevations in a 3-D integrated pho-tonic circuit. Transfer of optical power carried by planar, semi-guided waves is possible without reflections, without radiation losses, and over large vertical distances. This functionality is realized through simple step-like folds of high-contrast dielectric slab waveguides, in combination with oblique wave incidence, and fulfilling a resonance condition. Radiation losses vanish, and polarization conversion is being suppressed, for TE wave incidence beyond certain critical angles. This can be understood by fundamental arguments resting on a version of Snell's law. The two 90-degree corners of a step act as identical partial reflectors in a Fabry-Perot-like resonator setup. By selecting the step height, i.e. the distance between the reflectors, one realizes resonant states with full transmission. Rigorous quasi-analytical simulations for typical silicon/silica parameters demonstrate the functioning. Combinations of several step junctions can lead to other types of optical on-chip connects, e.g. u-turn-or bridge-like configurations.
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    ABSTRACT: We propose a design of an optical switch on a silicon chip comprising a 5 × 5 array of cascaded waveguide-crossing-coupled microring resonator-based switches for photonic networks-on-chip applications. We adopt our recently demonstrated design of multimode-interference (MMI)-based wire waveguide crossings, instead of conventional plain waveguide crossings, for the merits of low loss and low crosstalk. The microring resonator is integrated with a lateral p-i-n diode for carrier-injection-based GHz-speed on-off switching. All 25 microring resonators are assumed to be identical within a relatively wide resonance line width. The optical circuit switch can employ a single wavelength channel or multiple wavelength channels that are spaced by the microring resonator free spectral range. We analyze the potential performance of the proposed photonic network in terms of (i) light path cross-connections loss budget, and (ii) DC on-off power consumption for establishing a light path. As a proof-of-concept, our initial experiments on cascaded passive silicon MMI-crossing-coupled microring resonators demonstrate 3.6-Gbit/s non-return-to-zero data transmissions at on-and off-resonance wavelengths.
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