Abstract
A highly sensitive integrated photonic transducer is designed by utilizing asymmetric long-period gratings on a silicon waveguide. These gratings are formed by periodic perturbation of the waveguide width, leading to coupling between the fundamental mode and the 1st order asymmetric leaky mode. The coupled modes are studied via finite-element and finite-difference time-domain methods. Only a single fabrication step is required to realize this novel design. The device is utilized as a refractive index sensor in liquid, yielding a sensitivity of 5078 nm/RIU. The design is a unique combination of being highly sensitive, easily fabricated and highly compact.
Highlights
Over recent years an abundance of refractive index sensors has been developed in the field of integrated photonics
In this paper we present an integrated photonic component utilizing a long-period grating structure on the silicon-on-insulator (SOI) platform
The waveguides are patterned into the silicon layer using an inductively coupled plasma reactive-ion etching (ICP-RIE) system (Oxford Instruments) and a mixture of CHF3 and SF6 for an anisotropic and low-roughness etch. 2x2 μm polymer waveguides are utilized as spot-size converters in conjunction with inverted silicon tapers
Summary
Over recent years an abundance of refractive index sensors has been developed in the field of integrated photonics. These sensors often function by evanescent field sensing with a sensitivity which directly correlates to the magnitude of the evanescent field of the guided mode. Integrated photonic Mach-Zehnder interferometers (MZIs), for example, utilize an intensity-based sensing scheme where interference is caused by a relative phase shift between the two arms of the sensor. Optical ring resonators are several orders of magnitude more compact than MZIs and can be more multiplexed as they do not require continuous measurement of the transduction signal. The downsides are that the sensitivity is lower and the need to scan over a wavelength range
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