title: Difference frequency generation spectrometer for simultaneous multispecies detection.
abstract: A difference-frequency generation based spectrometer system for simultaneous ultra-sensitive measurements of formaldehyde (CH2O) and Methane (CH4) is presented. A new multiplexing approach using collinear quasi-phase-matching in a single grating period of periodically poled lithium niobate (PPLN) is discussed and demonstrated for two pairs of pump and signal lasers to generate mid-infrared frequencies at 2831.64 cm(-1) and 2916.32 cm(-1), respectively. The corresponding absorption signals are discriminated by modulating the DFB diode lasers at modulation frequencies of 40 kHz and 50 kHz, respectively, and using a computer based modulation and de-modulation scheme. In addition, simultaneous measurements of CH2O, CH4 and H2O are demonstrated utilizing both collinear and non-collinear quasi-phase-matching.
authors.affiliation: National Center for Atmospheric Research, Earth Observing Laboratory, Boulder, Colorado 80301, USA. weibring@ucar.edu
authors.forename: Petter
authors.initials: P
authors.lastname: Weibring
authors.forename: Dirk
authors.initials: D
authors.lastname: Richter
authors.forename: J G
authors.initials: JG
authors.lastname: Walega
authors.forename: Lars
authors.initials: L
authors.lastname: Rippe
authors.forename: Alan
authors.initials: A
authors.lastname: Fried
mesh_terms: D045424:Complex Mixtures / Q000032:analysis*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005557:Formaldehyde / Q000032:analysis*; D007834:Lasers; D008697:Methane / Q000032:analysis*; D013057:Spectrum Analysis / Q000295:instrumentation* / Q000379:methods*
chemical_list: D045424:Complex Mixtures; D005557:Formaldehyde; D008697:Methane