| 1. |
- Alnis, J, et al.
(författare)
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Sum-frequency generation with a blue diode laser for mercury spectroscopy at 254 nm
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:10, s. 1234-1236
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Tidskriftsartikel (refereegranskat)abstract
- Blue diode lasers emitting 5 mW continuous-wave power around 400 nm have recently become available. We report on the use of a blue diode laser together with a 30 mW red diode laser for sum-frequency generation around 254 nm. The ultraviolet power is estimated to be 0.9 nW, and 35 GHz mode-hop-free tuning range is achieved. This is enough to perform high-resolution ultraviolet spectroscopy of mercury isotopes. The possibility to use frequency modulation in the ultraviolet is demonstrated; however, at present the ultraviolet power is too low to give advantages over direct absorption monitoring. Mercury detection at atmospheric pressure is also considered which is of great interest for environmental monitoring. (C) 2000 American Institute of Physics. [S0003-6951(00)02810-2].
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| 2. |
- Gustafsson, U, et al.
(författare)
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Atomic spectroscopy with violet laser diodes
- 2000
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Ingår i: American Journal of Physics. - : American Association of Physics Teachers (AAPT). - 0002-9505 .- 1943-2909. ; 68:7, s. 660-664
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Tidskriftsartikel (refereegranskat)abstract
- Laser spectroscopy with laser diodes can now also be performed in the violet/blue spectral region. a 5 mW commercially available CW laser diode operating at 404 nm was used to perform spectroscopy on potassium atoms with signal detection in absorption as well as fluorescence when operating on a potassium vapor cell and with optogalvanic detection on a potassium hollow cathode lamp. The 4s(2)S(1/2)-5P(2)P(3/2,1/2) transitions were observed at 404.5 and 404.8 nm, respectively. The laser diode was operated with a standard laser diode driver, and with or without an external cavity. The 4s(2)S(1/2)-4p(2)P(1/2) transition at 770.1 nm was also observed with a different laser diode. Here, Doppler-free saturated-absorption signals were also observed, enabling the evaluation of the ground-state hyperfine splitting of about 460 MHz. The data recorded allows an experimental verification of the theory for Doppler broadening at two widely separated wavelengths. (C) 2000 American Association of Physics Teachers.
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| 3. |
- Gustafsson, U, et al.
(författare)
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Frequency-modulation spectroscopy with blue diode lasers
- 2000
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Ingår i: Applied Optics. - 2155-3165. ; 39:21, s. 3774-3780
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Tidskriftsartikel (refereegranskat)abstract
- 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 fitting procedure. Experimental signal-to-noise ratios: at different absorption levels are compared with theoretical signal-to-noise ratios and show good agreement. Detection sensitivities of 2 x 10(-6) and 5 x 10(-6) for wavelength and two-tone frequency-modulation spectroscopy, respectively, for a 120-Hz bandwidth are demonstrated. (C) 2000 Optical Society of America.
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| 4. |
- Sjöholm, Mikael, et al.
(författare)
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Analysis of gas dispersed in scattering media
- 2001
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Ingår i: Optics Letters. - 0146-9592. ; 26:1, s. 16-18
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring of free gas embedded in scattering media, such as wood, fruits, and synthetic materials, is demonstrated by use of diode laser spectroscopy combined with sensitive modulation techniques. Gas detection is made possible by the contrast of the narrow absorptive feature of the free-gas molecules with the slow wavelength dependence of the absorption and scattering cross sections in solids and liquids. An absorption sensitivity of 2.5 x 10(-4), corresponding to a 1.25-mm air column, is demonstrated by measurements of dispersed molecular oxygen. These techniques open up new possibilities for characterization and diagnostics, including internal gas pressure and gas-exchange assessment, in organic and synthetic materials. (C) 2001 Optical Society of America. OCIS codes: 300.6360, 290.7050, 290.5820, 170.3660, 020.3690, 160.4890.
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| 5. |
- Somesfalean, Gabriel, et al.
(författare)
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Concentration measurement of gas embedded in scattering media by employing absorption and time-resolved laser spectroscopy
- 2002
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Ingår i: Applied Optics. - 2155-3165. ; 41:18, s. 3538-3544
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Tidskriftsartikel (refereegranskat)abstract
- Diode-laser-based absorption spectroscopy for the evaluation of embedded gas concentrations in porous materials is demonstrated in measurements of molecular oxygen dispersed throughout scattering polystyrene foam, used here as a generic test material. The mean path length of light scattered in the material is determined with the temporal characteristics of the radiation transmitted through the sample. This combined with sensitive gas-absorption measurements employing wavelength-modulation spectroscopy yields an oxygen concentration in polystyrene foam of 20.4% corresponding to a foam porosity of 98%, which is consistent with manufacturing specifications. This feasibility study opens many possibilities for quantitative measurements by using the method of gas-in-scattering-media absorption spectroscopy. (C) 2002 Optical Society of America.
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| 6. |
- Somesfalean, Gabriel, et al.
(författare)
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Long-path monitoring of NO2 with a 635 nm diode laser using frequency-modulation spectroscopy
- 2005
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Ingår i: Applied Optics. - 2155-3165. ; 44:24, s. 5148-5151
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Tidskriftsartikel (refereegranskat)abstract
- In situ monitoring of traffic-generated nitrogen dioxide (NO2) emissions using long-path absorption spectroscopy is reported. High-sensitivity detection of NO2 is achieved by employing two-tone frequencymodulation spectroscopy at a visible absorption band using a tunable high-power diode laser operated around 635 nm. A real-time absorption spectrometer is accomplished by repetitively applying a rectangular current pulse to the diode-laser operating current, allowing detection of isolated NO2 absorption lines. A detection limit of 10 mu g/m(3) for NO2 at atmospheric pressure using a 160 m absorption path is demonstrated. Continuous monitoring of NO2 over a road intersection at peak traffic is performed.
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| 7. |
- Somesfalean, Gabriel, et al.
(författare)
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Violet diode laser in time-resolved stored-ion spectroscopy
- 2004
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; 69:2, s. 98-103
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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