anup ray - Academia.edu (original) (raw)
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Variable Energy Cyclotron Centre
The University of Nottingham Malaysia Campus
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Papers by anup ray
Applied Physics B-lasers and Optics, 2004
A near-infrared tunable diode laser absorption spectrometer is set up to measure the air-induced ... more A near-infrared tunable diode laser absorption spectrometer is set up to measure the air-induced broadening coefficients and the line-strength parameters of water-vapour overtone transitions within the (2,1,1)←(0,0,0) band in the 822–832 nm wavelength region. A Hitachi HL8311 E double hetero-junction structure diode laser is used as a probe. The diode laser controller is home-built and stable within ±10 μA and ±10 mK, respectively. The laser-head mount has a simple design and provides easy access whenever changing of the laser head is required. The diode laser emission wavelength is thermally tuned between 50 °C and 12 °C. Thermal tuning of the diode laser emission wavelength is used to reveal the mode structure of the diode laser and to probe the overtone-band transitions of water vapour within its operating wavelength range. Current tuning of the diode laser is used at a fixed laser temperature to study the transitions one at a time. A balanced detector is used to improve the S/N ratio of the spectrum. A phase sensitive detection technique is followed to obtain the first-derivative spectra of the overtone transitions. The first-derivative spectra have been recorded at different air pressures inside the sample cell while the water-vapour pressure is kept fixed. The first-derivative spectrum is numerically integrated to obtain the original line shape. The original line shape is fitted with a Voigt profile by using a nonlinear least-squares fit program to extract the air-broadening coefficient and the line-strength parameter. The data obtained in our work is compared with the results of the HITRAN database.
Chemical Physics Letters, 2004
Velocity-selective resonance dips in the probe absorption spectra of Rb D 2 transitions induced b... more Velocity-selective resonance dips in the probe absorption spectra of Rb D 2 transitions induced by a pump laser.
Iee Proceedings-optoelectronics, 2004
An inexpensive GaAlAs single mode semiconductor diode laser operating in the 822 nm wavelength re... more An inexpensive GaAlAs single mode semiconductor diode laser operating in the 822 nm wavelength region is frequency stabilised at the line centre of a transition in the (2,1,1) vibrationrotation band of water vapour. A balanced photodetector is used for recording to improve the signal/noise (S/N) ratio. The laser frequency is locked at the line centre by using a simple currentfeedback servocircuit. A long-term laser frequency stability of , 4 MHz is attained, which is more than a hundred-fold improvement over the performance provided by the free running semiconductor diode laser. The corresponding Allan-variance measurement reaches s(t) ¼ 8.0 £ 10 212 for an integration time of 100 s.
Applied Physics B-lasers and Optics, 2004
A near-infrared tunable diode laser absorption spectrometer is set up to measure the air-induced ... more A near-infrared tunable diode laser absorption spectrometer is set up to measure the air-induced broadening coefficients and the line-strength parameters of water-vapour overtone transitions within the (2,1,1)←(0,0,0) band in the 822–832 nm wavelength region. A Hitachi HL8311 E double hetero-junction structure diode laser is used as a probe. The diode laser controller is home-built and stable within ±10 μA and ±10 mK, respectively. The laser-head mount has a simple design and provides easy access whenever changing of the laser head is required. The diode laser emission wavelength is thermally tuned between 50 °C and 12 °C. Thermal tuning of the diode laser emission wavelength is used to reveal the mode structure of the diode laser and to probe the overtone-band transitions of water vapour within its operating wavelength range. Current tuning of the diode laser is used at a fixed laser temperature to study the transitions one at a time. A balanced detector is used to improve the S/N ratio of the spectrum. A phase sensitive detection technique is followed to obtain the first-derivative spectra of the overtone transitions. The first-derivative spectra have been recorded at different air pressures inside the sample cell while the water-vapour pressure is kept fixed. The first-derivative spectrum is numerically integrated to obtain the original line shape. The original line shape is fitted with a Voigt profile by using a nonlinear least-squares fit program to extract the air-broadening coefficient and the line-strength parameter. The data obtained in our work is compared with the results of the HITRAN database.
Chemical Physics Letters, 2004
Velocity-selective resonance dips in the probe absorption spectra of Rb D 2 transitions induced b... more Velocity-selective resonance dips in the probe absorption spectra of Rb D 2 transitions induced by a pump laser.
Iee Proceedings-optoelectronics, 2004
An inexpensive GaAlAs single mode semiconductor diode laser operating in the 822 nm wavelength re... more An inexpensive GaAlAs single mode semiconductor diode laser operating in the 822 nm wavelength region is frequency stabilised at the line centre of a transition in the (2,1,1) vibrationrotation band of water vapour. A balanced photodetector is used for recording to improve the signal/noise (S/N) ratio. The laser frequency is locked at the line centre by using a simple currentfeedback servocircuit. A long-term laser frequency stability of , 4 MHz is attained, which is more than a hundred-fold improvement over the performance provided by the free running semiconductor diode laser. The corresponding Allan-variance measurement reaches s(t) ¼ 8.0 £ 10 212 for an integration time of 100 s.