title: Vibrational mid-infrared photothermal spectroscopy using a fiber laser probe: asymptotic limit in signal-to-baseline contrast.
abstract: We report on a mid-infrared photothermal spectroscopy system with a near-infrared fiber probe laser and a tunable quantum cascade pump laser. Photothermal spectra of a 6 μm-thick 4-octyl-4'-cyanobiphenyl liquid crystal sample are measured with a signal-to-baseline contrast above 103. As both the peak photothermal signal and the corresponding baseline increase linearly with probe power, the signal-to-baseline contrast converges to an asymptotic limit for a given pump power. This limit is independent of the probe power and characterizes the best contrast achievable for the system. This enables sensitive quantitative spectral characterization of linear infrared absorption features directly from photothermal spectroscopy measurements.
authors.forename: Atcha
authors.initials: A
authors.lastname: Totachawattana
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.forename: Alket
authors.initials: A
authors.lastname: Mertiri
authors.forename: Mi K
authors.initials: MK
authors.lastname: Hong
authors.forename: Shyamsunder
authors.initials: S
authors.lastname: Erramilli
authors.forename: Michelle Y
authors.initials: MY
authors.lastname: Sander
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry; D007259:Infrared Rays; D007834:Lasers; D050866:Liquid Crystals / Q000737:chemistry; D009570:Nitriles / Q000737:chemistry; D055100:Optical Fibers; D055620:Optical Phenomena; D059629:Signal-To-Noise Ratio; D013057:Spectrum Analysis / Q000295:instrumentation*; D013696:Temperature; D014732:Vibration
chemical_list: C495061:4'-octyl-4-cyanobiphenyl; D001713:Biphenyl Compounds; D009570:Nitriles