Sub-wavelength grating for enhanced ring resonator biosensor

Abstract

While silicon photonic resonant cavities have been widely investigated for biosensing applications, enhancing their sensitivity and detection limit continues to be an area of active research. Here, we describe how to engineer the effective refractive index and mode profile of a silicon-on-insulator (SOI) waveguide using sub-wavelength gratings (SWG) and report on its observed performance as a biosensor. We designed a 30 μm diameter SWG ring resonator and fabricated it using Ebeam lithography. Its characterization resulted in a quality factor, Q, of 7 · 10³, bulk sensitivity Sb = 490 nm/RIU, and system limit of detection sLoD = 2 · 10^-6 RIU. Finally we employ a model biological sandwich assay to demonstrate its utility for biosensing applications.

Disorder effects in subwavelength grating metamaterial waveguides

“…Since the first experimental demonstration of an optical waveguide with a subwavelength periodic core [4], these structures, also called subwavelength gratings (SWGs), have found many applications in integrated optics, for example as highly efficient fiber-chip couplers [3][4][5][6][7][8][9], low-loss waveguide crossings, evanescent field sensors [10,11], broadband directional couplers [12] and multimode interference (MMI) [13] couplers, polarization beam splitters [14][15][16], wavelength division [4] and mode division [17] multiplexers, delay lines [18], Fourier-transform spectrometers [19] and suspended (membrane) waveguides for mid-infrared applications [20]. Exhaustive reviews of SWG fundamentals and applications can be found in [21,22].…”

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.…”

Subwavelength metamaterial engineering for silicon photonics

“…1, 2 This principle, which was well known in free space optics, has now found widespread applications in waveguide devices, 3 with recent developments including wavelength filters, 4, 5 evanescent field sensors, 6,7 and highly efficient fiber-to-chip couplers. [8][9][10][11][12] Here we provide a short introduction on the general design of subwavelength waveguide devices (section 2), and then discuss two applications: suspended waveguides for the mid-infrared (section 3), and ultra-broadband couplers (section 4).…”