Methane detection of chirped laser dispersion spectroscopy using DSB-SC modulation
- University of Pittsburgh
This paper discusses the use of double-sideband suppressed-carrier (DSB-SC) modulation and radio frequency mixer as phase detector to extract phase information for methane detection in chirped laser dispersion spectroscopy (CLaDS). The 1.66 μm light from narrow-linewidth laser was modulated by electro-optic modulator (EOM) working on DSB-SC mode. These two sidebands passed through gas chamber and formed interference on photodetector. The phase change from gas absorption in beating signal can be extracted by using passive RF mixer with another input as reference signal which is achieved by doubling RF drive signal of EOM. In RF mixer, two inputs with identical frequency but various phase shift corresponds to DC bias voltage variation of output. The phase change is proportional to refractive index change and can be referred to gas concentration by using Kramers-Kronig relations. The advantage of phase sensitive CLaDS is wide dynamic range for gas detection. It compensates the deficiency of wavelength modulation spectroscopy (WMS) on high concentration circumstances. And the passive scheme pushes the system requirement to the lowest level.
- Research Organization:
- University of Pittsburgh
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE)
- DOE Contract Number:
- FE0029063
- OSTI ID:
- 1870136
- Report Number(s):
- DE-PITT-FE0029063-8
- Journal Information:
- Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XII, Journal Name: Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XII
- Country of Publication:
- United States
- Language:
- English
Similar Records
A surface acoustic wave oscillator-based modulator/mixer for frequency-modulated electron nuclear double resonance spectroscopy
Extension of wavelength-modulation spectroscopy to large modulation depth for diode laser absorption measurements in high-pressure gases