Mid-infrared Suspended Membrane Waveguide and Ring Resonator on Silicon-on-Insulator

Theoretical and experimental studies of mid-infrared (mid-IR) suspended membrane waveguide (SMW) and suspended membrane ring (SMR) resonator are presented. An array of periodical holes beside the rib waveguide facilitates the local removal of buried oxide to form suspended membrane devices on silicon-on-insulator (SOI). The waveguide design is optimized in terms of hole size, etch depth, and bend radius to minimize device strain and optical loss. We calculate waveguide dimension to attain the wide low-dispersion ( $\pm$ 100 ps/nm/km) bandwidth for the wavelength range from 2.0 to 8.0 $\mu \hbox {m}$ , and optical nonlinearity is also studied. The SMWs are fabricated on a commercial SOI wafer and characterized by an $\hbox {Er}^{3+} - \hbox {Pr}^{3+}$ codoped fiber laser at 2.75 $\mu\hbox {m}$ . Negligible bending losses are measured for a 40- $\mu\hbox {m}$ radius bend. The minimum waveguide loss of 3.0 $\pm$ 0.7 dB/cm is measured experimentally. The SMR resonator has a quality factor ( $Q$ ) of $\sim$ 10 000 and an extinction ratio of $\sim$ 13 dB in near-IR. In mid-IR, the resonator has a $Q$ of $\sim$ 8100.