Reconfigurable fiber-to-waveguide coupling module enabled by phase-change material incorporated switchable directional couplers

Abstract

In silicon photonics, grating-assisted fiber-to-waveguide couplers provide out-of-plane coupling to facilitate wafer-level testing; however, their limited bandwidth and efficiency restrict their use in broadband applications. Alternatively, end-fire couplers overcome these constraints but require a dicing process prior usage, which makes them unsuitable for wafer-level testing. To address this trade-off, a reconfigurable fiber-to-waveguide coupling module is proposed and designed to allow for both grating-assisted and end-fire coupling in the same photonic circuit. The proposed module deploys a switchable directional coupler incorporating a thin layer of phase-change material, whose state is initially amorphous to render the coupler activated and hence facilitate grating-assisted coupling for wafer-level testing. The state can be altered into crystalline through a low-temperature annealing process to deactivate the directional coupler, thus facilitating broadband chip-level coupling through end-fire couplers. All the components encompassing conjoined switchable directional couplers as well as the grating and end-fire couplers were individually designed through rigorous simulations. They were subsequently assembled to establish the proposed reconfigurable coupling module, which was simulated and analyzed to validate the selective coupling operation. The proposed module gives rise to a low excess loss below 1.2 dB and a high extinction ratio over 13 dB throughout the C-band, when operating either under grating-assisted or end-fire input. The proposed reconfigurable coupling module is anticipated to be a practical solution for flexibly expediting the inspection of integrated photonic circuits on a wafer scale.

Investigation of Optical-Switching Mechanism Using Guided Mode Resonances

“…Similarly, diverse time domain mathematical approaches, i.e., Finite Difference Time Domain (FDTD) [7], Coupling method [8], Finite Integral Time Domain (FITD) [9], Plane Wave Expansion (PWE) [10], along with frequency domain methods such as the Finite Elements Method (FEM) [11], Method of Moments [12], Transfer Matric Method (TMM) [13] and Fast Multi-pole Method (FMM) [14], are being used to design these components. Mainly dielectrics and semiconductors have been utilized for the design of optical components, which in turn can be modified into different forms to achieve various functionalities, such as optical waveguides [15], directional couplers [16] and Photonic Crystals (PhCs) [17]. By definition, PhCs are dielectric material-based nanostructures that are capable of controlling light at the wavelength scale.…”