For some applications, resonant cavity infrared detectors (RCIDs) offer advantages over traditional broadband photodetectors. The addition of a resonant cavity allows for higher external quantum efficiency (EQE), faster response time, and narrower spectral response for enhanced selectivity. Recently, the US Naval Research Laboratory demonstrated RCIDs with EQE of 34% and D∗ of 7 × 109 at room temperature, centered at 4.0 μm (46 nm FWHM). Princeton University has demonstrated that these RCIDs can detect gas-phase nitrous oxide (N2O) at room temperature with only a broadband light source and no other optical components. The results imply that a simple RCID-LED pair manufactured on a semiconductor wafer would provide a viable gas sensor. The manufacturing process could be completely automated, resulting in mass-producible optical gas sensors. Progress has been made for developing RCIDs at other wavelengths. Based on the achieved detection limit of 4% N2O at 4.0 μm, with 3 cm path length, leak detection of percentage-level concentrations of gases is definitely viable. The potential for operating at a more optimal wavelength to attain high-precision measurements at part-per-million (ppm) levels is still under investigation.
Mid-infrared, interband-cascade, light-emitting devices (ICLEDs) have the potential to improve the performance of trace-gas sensors for air quality and greenhouse gas measurements. ICLEDs are broadband, incoherent, high-optical-power devices (up to ~5 mW continuous-wave at room temperature). We present an ICLED-based, methane sensor using a hollow-core fiber and direct absorption spectroscopy. A 1σ noise equivalent absorption of 0.17 ppmv CH4 at 1 Hz was achieved (1.13e-5 absorbance). Sub-ppmv methane detection is relevant for monitoring emissions near sources such as petrochemical infrastructure, agricultural activities, and wastewater treatment plants.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.