Design and fabrication of SOI micro-ring resonators based on sub-wavelength grating waveguides

Abstract

Standard silicon photonic strip waveguides offer a high intrinsic refractive index contrast; this permits strong light confinement, leading to compact bends, which in turn facilitates the fabrication of devices with small footprints. Sub-wavelength grating (SWG) based waveguides can allow the fabrication of low loss devices with specific, engineered optical properties. The combination of SWG waveguides with optical micro-resonators can offer the possibility of achieving resonators with properties different from the traditional SOI rings. One important property that SWG rings can offer is decreased light confinement in the waveguide core; this improves the resonator's sensitivity to changes in the cladding refractive index, making the rings ideal for refractive index sensing applications. In this paper, we present the design and experimental characterization of SWG based rings realized on SOI chips without upper cladding (permitting their use as sensors). The fabricated rings offer quality factors in the range of ~1k-6k, depending on SWG parameters. Based on the comparison of experimental and simulated data we expect sensitivities exceeding 383 nm/RIU in water and 270 nm/RIU in air, showing excellent potential for use in sensing applications.

Subwavelength grating waveguide devices in silicon-on-insulators for integrated microwave photonics (Invited Paper)

“…Figures 2(c)-2(e) show the measured through responses for SWG MRRs with different ring radii. Our MRRs exhibit Q-factors of several hundred to ∼1200; higher values up to 6000 with an air cladding or 4000 with a fluidic cladding were also obtained [14] . We attribute irregularities in the measured responses of the MRRs (e.g., in the shape of the resonances) to fabrication and processing imperfections.…”

“…Recently, there has been growing interest in realizing integrated optical components based on subwavelength grating (SWG) structures [8][9][10][11][12][13][14][15][16][17] . As illustrated in Fig.…”

Grating-Assisted Fiber to Chip Coupling for SOI Photonic Circuits

“…Use of SWG structures allows for artificial engineering of a wide range of optical indices from high contrasting materials. SWG based structures have also been demonstrated for various other integrated applications like grating polarizers, multimode interference splitters and ring resonators [22,23].…”

Suspended Microracetrack Resonator with Lateral Sub-wavelength-Grating Metamaterial Cladding for Mid-infrared Sensing Applications

“…4. The fitting numerical model is specially developed based on the equivalent refractive index method [14,15,26,27]. As Pitch = 350 nm is small enough, the equivalent refractive index of the lateral SWG metamaterial can be written as:…”

“…Many efforts have been invested on the SOI based bio-chemical sensing in the nearinfrared (NIR) band, typically around 1.3-1.6 µm wavelength [1][2][3][4][5][6]. Various structures and methods have been utilized to achieve high sensitivity [7][8][9][10][11][12][13][14][15][16][17][18]. However, limited work has been reported on mid-infrared (MIR) sensors based on the SOI platform.…”