Hollow Waveguide Gas Sensor for Mid-Infrared Trace Gas Analysis

Abstract

Abstract-A hollow waveguide mid-infrared gas sensor operating from 1000 cm -1 to 4000 cm -1 has been developed, optimized, and its performance characterized by combining a FT-IR spectrometer with Ag/Ag-halide hollow core optical fibers. The hollow core waveguide simultaneously serves as a light guide and miniature gas cell. CH 4 was used as test analyte during exponential dilution experiments for accurate determination of the achievable limit of detection (LOD). It is shown that the optimized integration of an optical gas sensor module with FT-IR spectroscopy provides trace sensitivity at the few hundreds of parts-per-billion concentration range (ppb, v/v) for CH 4 .

On-Chip Optical Gas Sensors Based on Group-IV Materials

“…The authors analyzed the LOD at a wavelength of 4.23 μm, and theoretically predicted 2 part per million (ppm) LOD. Moreover, Kim et al 81 developed a hollow-core waveguide sensor to detect methane (CH 4 ) gas with the LOD of 438 ppb. Later, Giraud-Carrier et al 74 demonstrated a perforated hollow-core waveguide for 85 Rb atomic vapor sensing, as shown in Figure 3a.…”

“…First, as the most commonly used structure, total-internal-refraction waveguides have been extensively studied for sensing applications, such as strip, ,,, rib, slot, , hollow-core, , and suspended-membrane waveguides. ,, In 2014, Huang et al comprehensively optimized and compared silicon-on-sapphire (SOS) strip, rib, and slot waveguides for carbon dioxide (CO 2 ) gas sensing applications. The authors analyzed the LOD at a wavelength of 4.23 μm, and theoretically predicted 2 part per million (ppm) LOD.…”

“…Explosive vapor analysis has tremendous applications in industry safety, public security, and counter-terrorism. , To date, on-chip optical gas sensors have been demonstrated to detect hydrogen (H 2 ), methane (CH 4 ), ,, and 2,4-dinitrotoluene (DNT) vapors . Due to the volatile and flammable nature of the gases, LODs of less than 4% and 5% are required for hydrogen (H 2 ) and methane (CH 4 ) sensors to meet the lower explosion limit. , Moreover, the trace detection of the 2,4-dinitrotoluene (DNT) vapor out of other usually volatile interferences is critical for security check purposes.…”

Laser-Based Trace Gas Detection inside Hollow-Core Fibers: A Review

“…Unfortunately, Zeeman spectroscopy can only be used for paramagnetic species (e.g., O 2 , NO, or NO 2 ), so its potential applications are limited. A similar hollow fiber was also used in [23], where a broad transmission bandwidth of the waveguide enabled methane transitions near 3.3 and 7.7 µm to be simultaneously recorded. More recently, laser-based gas sensing inside hollow waveguides has been demonstrated using quantum cascade lasers (QCLs) operating in the mid-infrared spectral region.…”

A comparison of spectroscopic techniques for human breath analysis

“…Reflective material can be coated in the inner surface to provide better light transmission. Hollow waveguide assisted LAS for methane gas analysis has been investigated by researchers and the LOD they have achieved is few hundreds of ppbv [22].…”