1,720,993 research outputs found
Single-shot detection of bacterial spores with Yb-laser-based CARS spectroscopy
Full text linkWe present a system based on a high-energy femtosecond ytterbium laser seeding an optical parametric amplifier and a photonic crystal hollow core fiber (PCHCF) compressor for coherent anti-Stokes Raman scattering (CARS) spectroscopy. The PCHCF provides spectral broadening of the Stokes pulse which is then compressed to a duration matched to that of the pump pulse. In these conditions, the excitation efficiency of vibrational levels in the target molecules is largely improved, as the time gating effect due to the mismatch between the durations of the pump and Stokes pulses is avoided. Experiments are presented along with a theoretical model to quantify expected improvement of sensitivity. The system is used to detect bacterial spores deposited on a surface with a single laser shot at unprecedented signal-to-noise ratio
High-efficiency diode-pumped Tm:GdLiF4 laser at 1.9 μa
No full textContinuous-wave laser action of a Tm-doped GdLiF4 (GLF) crystal pumped by a laser diode is reported at room temperature. A comparative analysis of laser performance using GLF crystals with doping concentrations of 8 at. % and 12 at. % of Tm3+ has been carried out. A maximum output power of 1.47 W with 57% slope efficiency and a wide tunability range from 1826 to 2054 nm have been obtained at 8% Tm doping level. © 2009 Optical Society of America
Broadband fourier-transform coherent raman spectroscopy with an ytterbium fiber laser
No full textWe demonstrate a Fourier transform (FT) coherent anti-Stokes Raman scattering (CARS) spectroscopy system based on fiber technology with ultra-broad spectral coverage and high-sensitivity. A femtosecond ytterbium fiber oscillator is amplified and spectrally broadened in a photonic crystal fiber to synthesize pulses with energy of 14 nJ at 1040 nm, that are compressed to durations below 20 fs. The resulting pulse train is coupled to a FT-CARS interferometer enabling measurement of high-quality CARS spectra with Raman shifts of ∼3000 cm−1 and signal to noise ratio up to 240 and 690 with acetonitrile and polystyrene samples, respectively, for observation times of 160 μs; a detection limit of one part per thousand is demonstrated with a cyanide/water solution. The system has the potential to detect trace contaminants in water as well as other broadband high-sensitivity CARS spectroscopy applications
Tunability range of 245 nm in a diode-pumped Tm : BaY2F8 laser at 1.9 mu m: a theoretical and experimental investigation
No full textExtremely wide wavelength tuning ranges of up to similar to 300 nm around 1.9 mu m are theoretically predicted in a Tm-doped BaY2F8 crystal, on the basis of near-infrared measurements of emission and absorption cross sections. A tunability interval of 245 nm, from 1849 nm to 2059 nm, has been demonstrated by room-temperature laser experiments using a 8% Tm-doped crystal
Comparative analysis of Tm-Ho : KYF4 laser crystals
No full textA spectroscopic characterization of Tm-Ho:KYF4 crystals with different doping levels is presented. A comparative investigation based on diode-pumped 2-mu m laser experiments shows that the best trade-off in terms of cw output power characteristics and wavelength tuning ranges is obtained with 5% Tm-0.5% Ho active crystal
High-resolution mid-infrared spectroscopy based on ultrafast Cr:ZnSe laser
Full text linkHigh-resolution broadband direct frequency comb spectroscopy in the mid-infrared spectral region is an extremely powerful and versatile experimental technique that allows study of the molecular structure of gaseous compounds with multiple applicative and scientific implications. Here we present the first implementation of an ultrafast Cr:ZnSe mode-locked laser covering more than 7 THz at around the emission wavelength of 2.4 um, for direct frequency comb molecular spectroscopy with a frequency sampling of 220 MHz and a frequency resolution of 100 kHz. This technique is based on a scanning micro-cavity resonator with a Finesse of 12,000 and a diffraction reflecting grating. We demonstrate its application in high-precision spectroscopy of the acetylene molecule by retrieving line center frequencies of more than 68 roto-vibrational lines. Our technique paves the way for real time spectroscopic studies as well as for hyperspectral imaging techniques
Room-temperature diode-pumped Yb3+-doped LiYF4 and KYF4 lasers
No full textWe present a comparative analysis on the growth, the spectroscopic features, and the cw laser action of room-temperature Yb(5%):LiYF4 (YLF) and Yb(10%):KYF4 (KYF) crystals. Optical slope efficiencies of 33% and 52% have been demonstrated for Yb:YLF and Yb:KYF crystals, respectively. A remarkable wide wavelength tunability from 1.01 to 1.07 mu m has been obtained for both laser crystals
CW and femtosecond operation of a diode-pumped Yb:BaY(2)F(8) laser
No full textWe report for the first time on laser action of a diode-pumped Yb:BaY(2)F(8) crystal. Both CW and femtosecond operations have been demonstrated at room-temperature conditions. A maximum output power of 0.56 W, a slope efficiency of 34%, and a tunability range from 1013 to 1067 nm have been obtained in CW regime. Transform-limited pulse trains with a minimum duration of 275 fs, an average power of 40 mW, and a repetition rate of 83 MHz have been achieved in a passive mode-locked regime using a semiconductor saturable absorber mirror. (C) 2010 Optical Society of Americ
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