Diode-pumped single-frequency Tm:LiLuF(4) ring laser

We report a room-temperature single-frequency Tm:LiLuF(4) laser with a maximum output power of 120 mW, a slope efficiency of 13%, and a wavelength tunability range from 1875 to 1895 nm. Both frequency and relative intensity noise have been investigated, showing an emission linewidth of ~300 kHz over 1 ms observation time and an intensity noise spectrum limited by quantum noise for Fourier frequencies larger than 5 MHz.     

Primary gas thermometry by means of laser-absorption spectroscopy: determination of the Boltzmann constant

We report on a new optical implementation of primary gas thermometry based on laser-absorption spectrometry in the near infrared. The method consists in retrieving the Doppler broadening from highly accurate observations of the line shape of the R(12) nu1+2nu2(0)+nu3 transition in CO2 gas at thermodynamic equilibrium. Doppler width measurements as a function of gas temperature, ranging between the triple point of water and the gallium melting point, allowed for a spectroscopic determination of the Boltzmann constant with a relative accuracy of approximately 1.6 x 10(-4).     

Noise characteristics of a high-power ytterbium-doped fibre amplifier at 1083 nm

Experimental results are reported for the noise characteristics of an Yb-doped fibre amplifier pumped at 975 nm, used as a booster of a low-noise narrow-linewidth single-frequency 1083-nm wavelength laser diode. The maximum output power of the amplifier is 1.2 W with a gain larger than 30 dB. An increase of the intensity-noise spectral density relative to the signal, by approximately 6.5 dB, is introduced by the amplification process, due to signal-amplified spontaneous-emission (ASE) beat noise. A remarkable increase of the noise level with decreasing frequency is observed below ≈35 kHz, probably due to technical noise of the amplifier pump diodes. The spectral broadening due to amplifier phase noise was measured to be less than 300 Hz with a 5-kHz-linewidth Nd:YAG laser and that for the 300-kHz-linewidth diode laser at 1083 nm is therefore expected to be in the same range. Received: 5 October 1999 / Revised version: 2 December 1999 / Published online: 24 March 2000     

Frequency-stabilized seed laser system for dial applications around 0.94 μm

Absolute frequency stabilization of an extended-cavity diode laser at 0.94 μm is reported. The diode laser was frequency locked against rovibrational absorption lines of water vapour by using the frequency modulation spectroscopy technique. The stabilized oscillator shows a short-term frequency stability level of 40 kHz for integration times of 1 s and a long-term frequency drift lower than 10 MHz for observation times longer than 10³ s. The frequency-stabilized oscillator system is mounted on a compact breadboard (75 cm×50 cm) and constitutes the seed laser system for the injection of a high-energy DIAL laser transmitter operating in the 0.94-μm spectral region.     

J/ψ strong couplings to vector mesons

We present a study of the cross sections J/ψX→D^(*)D̄^(*) (X=ρ, Φ) based on the calculation of the effective tri- and four-linear couplings J/ψ X D^(*) D̄^(*) within a constituent quark model. In particular, the method for the calculation of the four-linear couplings is illustrated. The results obtained have been used in a recent analysis of J/ψ absorption by the hot hadron gas formed heavy-ion collisions at SPS energies. PACS 12.38.Mh; 12.39.-x; 25.75.-q     

Two-step laser activation of hematoporphyrin derivative

A new photoactivation mechanism of hematoporphyrin derivative is presented. This process, based on the sequential absorption of two photons, leads to the production of cytotoxic radicals of HpD. The cytocidal efficiency is demonstrated by in vitro experiments.     

Passive mode-locking of a diode-pumped Tm:GdLiF4 laser

We propose an optical near-field assisted sputtering method for repairing scratches on the surface of polycrystalline ceramics in a self-assembling manner. An Al₂O₃ source was sputtered on substrates with laser radiation of wavelength 473 nm. The average depth of the scratched grooves on polycrystalline Al₂O₃ ceramic substrate decreased from 3.2 nm to 0.79 nm. Using a Hough transform, we also confirmed the selective repair of scratches.     

LC–UV Method with Pre-Column Derivatization for the Determination of Ciclopirox Olamine in Raw Material and Topical Solution

A rapid, simple and sensitive liquid chromatographic method has been developed to assay ciclopirox olamine in raw material and topical solution. The analysis used a reversed-phase C₁₈ end-capped column, with UV detection at 305 nm and pre-column derivatization with dimethyl sulphate. A linear response (r ² > 0.999) was observed in the range of 0.4–200 μg mL⁻¹. The method showed good recoveries for the raw material and topical solution and the relative standard deviation intra and inter-day were ≤2.00%. Validation parameters such as specificity and robustness were also determined. The proposed method provided an accurate and precise analysis of ciclopirox olamine in raw material and topical solution.