Mid-Infrared Serial Microring Resonator Array for Real-Time Detection of Vapor-Phase Volatile Organic Compounds

Abstract

Chip-scale infrared spectrometers consisting of a microring resonator array (MRA) were developed for volatile organic compound (VOC) detection. The MRA is serially positioned to serve as a wavelength sorting element that enables wavelength demultiplexing. Unlike conventional devices operated by a single microring, our MRA can perform multiwavelength mid-infrared (mid-IR) sensing by routing the resonant wavelength light from a broadband mid-IR source into different sensing channels. Miniaturized spectrometer devices were fabricated on mid-IR transparent silicon-rich silicon nitride (SiN x ) thin films through complementary metal–oxide-semiconductor (CMOS) processes, thus enabling wafer-level manufacturing and packaging. The spectral distribution of the resonance lines and the optimization of the microring structures were designed using finite-difference time-domain (FDTD) modeling and then verified by laser spectrum scanning. Using small microring structures, the spectrum showed a large free spectral range (FSR) of 100 nm and held four spectral channels without crosstalk. Unlike near-infrared microrings using refractive index sensing, our MRA can detect hexane and ethanol vapor pulses by monitoring the intensity variation at their characteristic mid-IR absorption bands, thus providing high specificity. Applying multiwavelength detection, the sensor module can discriminate among various VOC vapors. Hence, our mid-IR MRA could be an essential component to achieve a compact spectroscopic sensing module that has the potential for applications such as remote environmental monitoring and portable health care devices.

Enhancement of Refractive Index Sensitivity Using Small Footprint S-Shaped Double-Spiral Resonators for Biosensing

“…VOCs are also known as biomarkers to discover diseases at an early stage [33,34]. Monitoring a low concentration of VOCs in air and solution with a simple real-time measurement system has been well studied [35][36][37]. IPA and acetone are popular VOCs with high vapor pressure and evaporate quickly.…”

Biosensing with Silicon Nitride Microring Resonators Integrated with an On-Chip Filter Bank Spectrometer

“…However, when the spectral feature is comparatively broad, such as the drop spectrum of an add/drop ring resonator, the resonance wavelength may be identified using fewer, sparsely placed channels (Figure 1). Narrowband filters such as microring filter banks 17,18 have been used extensively for spectral analysis and signal processing but, as far as we are aware, have not been integrated with transducers in a biosensing context. In this paper, we demonstrate this concept for bulk sensing of sucrose solutions and specific detection of C-reactive protein (CRP) in serum at biologically relevant concentrations.…”