Design, fabrication and characterization of optical microring sensors on metal substrates

Abstract

Optical microring sensors can provide measurements with high spatial and temporal resolution along with immunity to electromagnetic interference, multiplexing capabilities and high rates of data collection. If these micro optical sensors can be fabricated on metals, tremendous benefits can be achieved for real industrial applications. In this paper, the principles of the optical microring resonator as temperature sensors were studied. A ring resonator with silicon nitride as the core layer and silica as the cladding layer was designed and fabricated on metal. A nonuniform taper was introduced and optimized to facilitate light coupling. Wafer-scale fabrication processes based on standard microfabrication and electroplating techniques were developed to fabricate the sensors on nickel substrates. Experimental characterization of those microring resonators as temperature sensors was carried out to investigate the feasibility and functionality of optical thin film sensors on metal substrates. The measured thermal sensitivity of microring sensors on the metal substrate was 22.5 pm °C−1, which is much higher than that of those sensors on silicon. This study paves a way to apply optical sensors on metal for manufacturing environments.