It has been shown that a fundamental mode adiabatically launched into a multimode SOI waveguide with submicron grating offers well-defined flat-top bandpass filter characteristics in transmission. The transmitted spectral bandwidth is controlled by adjusting both waveguide and grating design parameters. The bandwidth is further narrowed down by cascading two gratings with detuned parameters. A semi-analytical model is used to analyze the filter characteristics (1500 nm ≤ λ ≤ 1650 nm) of the device operating in transverse-electric polarization. The proposed devices were fabricated with an optimized set of design parameters in a SOI substrate with a device layer thickness of 250 nm. The pass bandwidth of waveguide devices integrated with single-stage gratings are measured to be ∼24 nm, whereas the device with two cascaded gratings with slightly detuned periods (ΔΛ 2 nm) exhibits a pass bandwidth down to ∼10 nm. © 2018 Optical Society of America.

Bijoy Krishna Das

Department of Electrical Engineering

Parimal Sah

Bandpass filters

Bandwidth

Waveguides

CASCADED GRATINGS

Design parameters

Filter characteristics

Fundamental modes

Semi-analytical model

SPECTRAL BANDWIDTH

TRANSVERSE ELECTRIC POLARIZATIONS

WAVEGUIDE DEVICE

Waveguide filters

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IIT Madras

Photonic bandpass filter characteristics of multimode SOI waveguides integrated with submicron gratings.

Applied Optics

An integrated optical design of a rectangular-edge filter device in 250-nm silicon-on-insulator platform is proposed and demonstrated experimentally. The device is designed with a multimode waveguide (supporting at least two modes) with asymmetric side-wall grating, which is adiabatically interfaced with input/output single-mode waveguides. The input/output access waveguides are terminated with grating couplers for optical characterizations. Design parameters are optimized for a sharp-edge or nearly rectangular-edge filter response in optical C-band (1530 nm ≤ λedge ≤ 1565 nm). The submicron features and the entire footprint of the devices were defined with a single-step e-beam lithography process by using negative-tone resist and subsequent dry etching of ∼ 100 nm by using an inductively coupled reactive ion etching system. All the fabricated devices exhibit a rectangular-edge filter response at λedge ∼ 1560 nm with an edge-extinction of &gt; 40 dB at the rate of 118 dB/nm. The rectangular-edge is followed by a broad pass-band of ∼ 40 nm till the first-order Bragg reflected wavelength of λ B00 ∼ 1600 nm in the transmission characteristics obtained for 1520 nm ≤ λ ≤ 1620 nm. Tunability of a rectangular-edge filter is verified with cladding refractive index change and the observed refractive index sensitivity of the edge is ∼ 18 nm/RIU. The limit of detection for 1-dB transmitted power extinction at λedge of a typical fabricated device is estimated to be 5.3 ×, 10-4 RIU. © 1983-2012 IEEE.

Journal of Lightwave Technology

Integrated optical rectangular-edge filter devices in SOI

It is shown that the dispersion in transmission characteristics of a ring resonator designed with silicon-on-insulator waveguides in all-pass configuration can be enhanced significantly by increasing interaction length of the directional coupler. This in turn helps to single-out highly extinct resonance(s) at and around the critically coupled wavelength. Such a device is found to be useful for a wide range of refractive index sensing for the cladding materials/analytes (1.0 &lt; nc ≤ 2.0). As a proof of concept, the sensor devices were fabricated and characterization results are shown to be consistent with theoretical prediction. The fabricated devices have been also used successfully to determine unknown refractive index of a given analyte (Newport F-IMF-150) with an error limit of δn ∼ 1.67 × 10-2 RIU. Analyzing experimental results, it is shown that the limit of detection can be further reduced (≤ 10-3 RIU), if the perimeter of the ring is increased without compromising the round-trip waveguide loss. The superiority of such a sensor device lies in its simpler design rule, easier operation, wider range, and nearly accurate detection mechanism. © 2016 IEEE.

IEEE Journal of Selected Topics in Quantum Electronics

Dispersion Enhanced Critically Coupled Ring Resonator for Wide Range Refractive Index Sensing

A filter device with a flat-top passband of Δλpb &gt; 40 nm is demonstrated using multi-mode SOI waveguide with a side-wall grating. The passband is bounded by highly extinguished sidebands of Δλsb &gt; 10 nm. © 2017 OSA.

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Photonic bandpass filter characteristics of multimode SOI waveguides integrated with submicron gratings

Journal	Data powered by TypesetApplied Optics
Publisher	Data powered by TypesetOSA - The Optical Society
ISSN	1559128X
Impact Factor	1.230
Open Access	No
Citation Style	unsrt
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