Search results for "diode laser"
showing 10 items of 23 documents
Broadband Fabry–Pérot Resonator From Zerodur for Laser Stabilisation Below 1KHZ Linewidth With < 100 HZ/S Drift and Reduced Sensitivity to Vibrati…
2015
Abstract Here we demonstrate the results of creating a two-mirror Fabry-Pérot resonator (FPR) that allows achieving the spectral width of a stabilised laser line below 1 kHz. It had low expansion Zerodur spacer and broadband high reflectance mirrors (99.85% in the range of 630 to 1140 nm). FPR was vertically mid-plane mounted for reduced sensitivity to vibrations and included in two shields inside a vacuum chamber to lower temperature fluctuations. Peltier element was used for temperature stabilisation at zero-expansion temperature. Pound-Drever-Hall (PDH) technique was applied. The signal from FPR was compared to ultra-stable signal (of about 1 Hz linewidth) to form a beat note signal. For…
Real-time measurements of Volcanic Gases based by Infrared Spectroscopy
2014
Near-infrared Tunable Diode Lasers have recently found increased usage in atmospheric chemistry and air monitoring research, but applications in Volcanology are still limited to a few examples. The Tunable Diode Laser Spectroscopy technique (TDLS) relies on measuring the absorbance at specific wavelengths due to the absorption of IR radiation by a target gas. Here, we report on the application of the GasFinder 2.0, a commercial infrared laser-receiver unit operating in the 1.3-1.7 m wavelength range, to measuring CO2 concentrations and fluxes in volcanic gas emissions. Our field tests were conducted at Campi Flegrei volcano (near Pozzuoli, Southern Italy), where the GasFinder was used (duri…
Frequency-modulation spectroscopy with blue diode lasers
2000
Frequency-modulation spectroscopy provides ultrasensitive absorption measurements. The technique is especially adaptable to diode lasers, which can be modulated easily, and has been used extensively in the near-infrared and infrared spectral regions. The availability of blue diode lasers now means that the accessible wavelength region can be increased. We successfully demonstrate wavelength-modulation spectroscopy and two-tone frequency-modulation spectroscopy for the weak second resonance line of potassium at 404.8 nm and for the transition at 405.8 nm in lead, starting from the thermally populated 6p(2) P-3(2) metastable level, information on the modulation parameters is obtained with a f…
Subpicosecond Laser Spectroscopy of Blue-Light-Induced Absorption in KNbO3 and LiNbO3
2000
Pulses of 427-nm light from am amplified Ti:sapphire frequency-doubled laser are absorbed in two-photon band-gap excitations of KNbO3 and LiNbO3. Induced absorption spectra measured in the visible and recently extended in the infrared have been recorded as a function of delay from 0 to 250 ps after two-photon blue excitation. Samples include stoichiometric as well as congruent LiNbO3. Comparison is made to transient absorption in the nanosecond and longer time range induced by electron pulses of~10 ns width and 270 keV energy. Parts of the absorption can be attributed to bound and free polarons, including the intrinsic electron polaron.
Violet Diode Laser in Time-Resolved Stored-Ion Spectroscopy
2004
Lifetime measurements of the metastable 3d D-2(3/2) level in singly charged calcium were performed using the newly developed violet diode laser operated in an external cavity arrangement. The laser was employed on stored ions at the CRYRING facility to optically pump the resonance line at 397 nm. In combination with laser probing at 866 nm this detection scheme gave the possibility to record the lifetime of this level. which has a radiative lifetime of about 1 s.
REAL-TIME MEASUREMENT OF VOLCANIC GASES BASED ON INFRARED SPECTROSCOPY
The interpretation of volcanic gas datasets offers key information to build/validate geological models relevant to a variety of volcanic processes and behaviours, including eruptions. Major efforts have therefore been spent in recent years to improve our ability to measure volcanic gas compositions and fluxes. In the last decades, near-infrared room-temperature diode lasers, though in an experimental phase, are finding applications in volcanic gas studies. In this PhD dissertation, I use the GasFinder 2.0, a commercial tunable diode infrared laser transmitter-receiver unit, operating in the 1.3-1.7 m wavelength range, in the attempt to measure CO2 mixing ratios and fluxes in volcanic gas e…
Photobiomodulation Therapy in the Management of Burning Mouth Syndrome: Morphological Variations in the Capillary Bed
2020
Burning mouth syndrome (BMS) is an idiopathic condition that manifests itself primarily with the onset of a burning sensation. The aim of this research was to perform photobiomodulation therapy (PBM) using a diode laser on the oral mucosa of BMS patients, followed by an objective evaluation of the morphological changes in the vascular bed underlying the mucosa using polarized light videocapillaroscopy. A group of 40 patients were included in the study. The patients were randomly divided into two groups (using simple randomization) as follows: 20 patients were assigned to the laser group and 20 patients were assigned to the placebo group. Each patient of the laser group received eight irradi…
Preliminary study about the efficiency of diode laser compared with retraction cords used for exposing the finishing lines of dental abutments before…
2016
Gingival displacement using diode laser or retraction cords: A comparative clinical study.
2018
PURPOSE: To compare two systems used for conditioning the gingival sulcus and exposing the finish line before the final impression for a fixed denture: retraction cords and diode laser. METHODS: All subjects participating in the study had healthy gingival and periodontal status before intervention for fixed prosthesis. 74 abutments for complete crown restoration were randomly divided into two groups for displacing the gingival sulcus before the final impression: gingival retraction cords (RC) and diode laser (DL). The height of the clinical crowns was measured by a blinded examiner in three points of the buccal surface (mesial, midline and distal) at four different times: after tooth prepar…
Volcanic CO_2 detection with a DFM/OPA-based lidar
2015
The DFM/OPA-based lidar BILLI was used to investigate the volcanic plume released by the hydrothermal vent of Pisciarelli, in the Campi Flegrei volcano. BILLI remotely measured CO2 concentrations in cross-sections of the nearvent plume using the differential absorption technique. To our knowledge, this is the first example of lidar-based measurement of volcanic CO2 . The spatial resolution was 1.5 m and the temporal resolution 20 s. © 2015 Optical Society of America.