The prospects of LEDs, diode detectors and negative luminescence in infrared sensing of gases and spectroscopy

Abstract

Infrared (IR) gas sensors are a minority of the general gas-sensing instrument market. They compete with devices based upon gas interaction with surfaces such as electrochemical sensors. They di¬er in that IR devices are selective, can`fail to safety' and are potentially intrinsically safe. However, they tend to be more expensive, using existing technology. We may expect that in due course the impact of all solid-state semiconductor mid-IR technology should revolutionize this situation and lead to signi cant growth in IR gas sensing.

Optical gas sensing: a review

“…NDIR gas sensing relies on the strength of optical absorption in the mid IR, which can be of the order of 100 times greater than that in the near IR. Thus, even with short pathlengths (3-10 cm), using relatively unsophisticated sources (microbulbs) and uncooled detectors (pyroelectric or thermopile), respectable limits of detection may be achieved (eg 10-50 ppm for CO 2 [82] ), and detection limits as low as 1 ppm can be obtained using more sophisticated benchtop equipment [83] . Figure 14.…”

“…Emission can be temperaturedependent, as Figure 19 shows. These devices are capable of much higher modulation rates than thermal sources, but have only been available at relatively low spectral power levels in comparison [83] .…”

A Novel Solid State Non-Dispersive Infrared CO2 Gas Sensor Compatible with Wireless and Portable Deployment

“…Moreover, the existence of the additional degree of freedom for the control of material electro-physical properties by changing its chemical composition becomes a significant advantage. This offers a new approach [23,24] to control optical confinement and carrier leakage as compared to previously reported work [17–21], offering advantages in lifetime and stability compared to previous LED/PD structures [19,22]. …”

“…Previous work describing the usage of LEDs for gas sensors [19,22], evaluated early stage LED devices from research sources with shortfalls in device reliability. Gas Sensing Solutions (GSS) Ltd (Glasgow, Scotland, UK) has implemented robust high volume throughput manufacturing process & device design with standard commercial semi-conductor processing techniques.…”

“…LED/PD offer the advantage of low power consumption, high source emittance, fast modulation rates, room temperature operation, fast stabilisation time and brings with it the cost benefits of semiconductor manufacturing techniques [22]. …”