title: Performance characteristics of narrow linewidth fiber laser pumped mid-IR difference frequency mixing light source for methane detection.
abstract: A high-power, narrow-linewidth Yb fiber laser with a fiber Bragg grating (FBG) pumped difference frequency generation (DFG) in a periodically poled lithium niobate (PPLN) crystal was investigated in detail. A mid-IR power of approximately 2.3 microW at 3.3 micrometers with a slope efficiency of 0.85 mW/W2 was achieved. A Doppler-broadened absorption spectrum of CH4 at 3038.497 cm-1 (3.2911 micrometers) was obtained with a 0.1-m long-gas cell at a pressure of 133 Pa. The linewidth of the DFG source was evaluated to be less than 96 MHz from the observed spectral linewidth. Real-time monitoring of CH4 (approximately 1.78 ppm) in ambient air in a multipass cell which has an optical path length of 10 m was also demonstrated.
authors.affiliation: Department of Physics, School of Science, Tokai University, Hiratsuka, Kanagawa, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ashizawa
authors.forename: Shinobu
authors.initials: S
authors.lastname: Ohara
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Masao
authors.initials: M
authors.lastname: Takahashi
authors.forename: Masamori
authors.initials: M
authors.lastname: Endo
authors.forename: Kenzo
authors.initials: K
authors.lastname: Nanri
authors.forename: Tomoo
authors.initials: T
authors.lastname: Fujioka
authors.forename: Frank K
authors.initials: FK
authors.lastname: Tittel
mesh_terms: D000388:Air / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods; D005069:Evaluation Studies as Topic; D007834:Lasers; D008697:Methane / Q000032:analysis*; D009556:Niobium; D010087:Oxides; D013055:Spectrophotometry, Infrared; D015018:Ytterbium
chemical_list: D010087:Oxides; D009556:Niobium; C091692:lithium niobate; D015018:Ytterbium; D008697:Methane