An integrated optical Mach-Zehnder interferometer comprised of a sensing arm of sub-wavelength grating waveguide and a reference waveguide arm insensitive to cladding refractive index change has been proposed and demonstrated in silicon-on-insulator platform for lab-on-chip application. The device is designed to operate at an operating wavelength of λ ∼ 1550 nm and its sensitivity is estimated as high as ∼ 931 rad/RIU/mm, which is again linearly scalable with the sensing length. © 2017 IEEE.

Bijoy Krishna Das

Department of Electrical Engineering

R. Sumi

Nandita das Gupta

Interferometers

MACH-ZEHNDER INTERFEROMETERS

Refractive index

Semiconductor quantum wells

Silicon on insulator technology

Waveguides

1550 NM

Lab on chip

Operating wavelength

REFRACTIVE INDEX CHANGES

SENSING ARM

SILICON-ON-INSULATOR PLATFORMS

Sub-wave length grating

Diffraction gratings

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IIT Madras

Integrated optical Mach-Zehnder interferometer with a sensing arm of sub-wavelength grating waveguide in SOI

Proceedings of IEEE Sensors

An ultrabroadband add-drop filter/switch circuit is designed and demonstrated by integrating a pair of subwavelength grating waveguides in a 2\times 2 Mach-Zehnder interferometer configuration using silicon photonics technology. The subwavelength grating is designed such that its stopband and passband are distinguished by a band-edge wavelength \lambda -{\text{edge}} \sim1565 nm, separating C and L bands. The stopband (\lambda < lambda {\text{edge}}) is filtered at the drop port of the device, whereas the passband ( \lambda >\lambda -{\text{edge}}) is extracted either in cross port or in bar port. The device is designed to operate only in TE polarization. Experimental results exhibit a nearly flat-Top band exceeding 40 nm for both stopband and passband. The stopband extinction at cross-and bar ports are measured to be > 35 dB with a band-edge roll-off exceeding 70 dB/nm. Wavelength independent directional coupler design and integrated optical microheaters at different locations of the Mach-Zehnder arms for thermo-optic phase detuning are the key for stopband filtering at the drop port and switching of passband between cross-and bar ports with flat top response. Though the insertion loss of fabricated subwavelength grating waveguides are negligibly small, the observed passband insertion loss is \sim 2 dB, which is mainly due to the combined excess loss of two directional couplers. Experimental results also reveal that the passband switching between cross-and bar ports of the device has been possible with an extinction of >15 dB by an electrical power consumption of P-\pi \sim 54 mW. A switching time of 5 \mus is estimated by analyzing the transient response of the device. The passband edge could also be detuned thermo-optically at a rate of 22 pm/mW. © 1995-2012 IEEE.

IEEE Journal of Selected Topics in Quantum Electronics

Ultra-Broadband Add-Drop Filter/Switch Circuit Using Subwavelength Grating Waveguides

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.

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

Optics Letters

Slow light Mach–Zehnder interferometer as label-free biosensor with scalable sensitivity

Optics Express

Porous silicon ring resonator for compact, high sensitivity biosensing applications

Sensors and Actuators B: Chemical

Intensity modulated refractive index sensor based on optical fiber Michelson interferometer

Highly sensitive Mach–Zehnder interferometer biosensor based on silicon nitride slot waveguide

Journal	Data powered by TypesetProceedings of IEEE Sensors
Publisher	Data powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
ISSN	19300395
Open Access	No