Apodized focusing subwavelength grating couplers for suspended membrane waveguides

Abstract

We demonstrate an apodized focusing subwavelength grating (SWG) for suspended membrane waveguides on silicon-on-insulator. Finite-difference time-domain simulation predicts −1.7 dB coupling efficiency and a 3 dB bandwidth of ∼50 nm for the transverse-magnetic mode apodized SWG, which has 98% field overlap with propagation mode in the single mode fiber. A modified phase matching formula is proposed to design the focusing apodized SWG. Better than −3.0 dB coupling efficiency and a 3 dB optical bandwidth of ∼50 nm is demonstrated experimentally.

Mode-locked fiber laser using graphene on silicon waveguide

“…The light is coupled between the quasitransverse electric (TE) mode of the silicon waveguide and conventional single mode fiber (SMF) through focusing subwavelength grating (SWG) couplers with a coupling efficiency of ~30% at 1560 nm. The straight silicon waveguide length was 175 μm and the input and output focusing grating couplers were each 30 μm in length [11]. …”

Polarization dependent loss of graphene-on-silicon waveguides

“…Light was coupled into the 150 µm long SMW using an apodized focusing subwavelength grating which allowed high efficiency coupling [10], as shown in Fig. 1 (c).…”

“…1 (c). The silicon devices were fabricated using the CMOS compatible process [10]. The grating couplers had a peak coupling efficiency of -3.0 dB and ~50 nm 3 dB bandwidth for TM mode.…”

“…The grating coupling efficiency was not affected significantly by the graphene layer and the coupling profile is almost unchanged. As we did not use any long adiabatic taper in the focusing grating coupler, the possible TM mode to TE mode conversion is avoided [10]. Thus, the strong polarization dependent loss mainly comes from the graphene.…”

Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures

“…This technique suffers from high losses induced by both the large mode area mismatch and the large effective index mismatch between the conventional single mode fiber (SMF) and the silicon strip waveguides with submicron cross sections. One of the promising solutions for achieving efficient coupling is through using grating couplers [3][4][5][6][7][8][9][10][11]. Grating couplers have demonstrated impressive performance features, especially the feasibility of achieving inline testing capability, which distinguishes it from edge coupling solutions.…”