Molecular iodine laser optically pumped at 521 nm and 531 nm

We report the observation and identification of over 50 new cw laser lines belonging to the B³∏?X¹∑ system of I₂ optically pumped by a single mode krypton ion laser. When pumping at 531 nm, simultaneous oscillation was achieved on up to 16 lines in the range 540 nm to 650 nm. This system offers considerable potential as a multi-wavelength laser source in interferometry.     

Metal plasma induced by the bombardment of 308 nm excimer and 585 nm dye laser pulses at low pressure

The characteristics of the plasma induced by the bombardment of laser pulses (4–6 mJ, 10–15 ns) on a metal surface kept in the pressure range (0.1–10 Torr) is studied. The laser induced plasma consists of two distinct regions. One is a small-region plasma (primary plasma), which emits an intense continuous emission spectrum for a few tenths of 0.1 μs. The other is a plasma (secondary plasma) spreading out with time, which emits intense atomic emission spectra. It was found that the displacement length of the front of the secondary plasma is proportional to the two-fifths power of time. This fact indicates that the blast wave plays an important role in the mechanism of forming the luminuous secondary plasma. The primary plasma is considered as the source of the blast wave.     

Precision frequency measurement of visible intercombination lines of strontium

We report the direct frequency measurement of the visible 5s(2) 1S0-5s5p 3P1 intercombination line of strontium that is considered a possible candidate for a future optical-frequency standard. The frequency of a cavity-stabilized laser is locked to the saturated fluorescence in a thermal Sr atomic beam and is measured with an optical-frequency comb generator referenced to the SI second through a global positioning system signal. The 88Sr transition is measured to be at 434 829 121 311 (10) kHz. We measure also the 88Sr-86Sr isotope shift to be 163 817.4 (0.2) kHz.     

Dual-wavelength Nd:YAP laser at 930 and 1341 nm and sum-frequency mixing for an emission at 549 nm

A dual-wavelength continuous-wave (CW) diode end-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser that generates simultaneous laser action at the wavelengths 930 and 1341 nm is demonstrated. A total output power of 778 mW for the dual-wavelength was achieved at the incident pump power of 17.8 W. Furthermore, intracavity sum-frequency mixing at 930 and 1341 nm was then realized in a LBO crystal to reach the yellow-green range. We obtained a total CW output power of 103 mW at 549 nm.     

基于椭偏光谱仪的石英晶体1310nm处双折射率的精密测量

为了对石英晶体在通讯波段1 310 nm处的双折射率进行精密测量,基于椭偏光谱仪对P和S两方向上偏振光相位差的精密测量原理,在透射模式下,通过对琼斯矩阵的分析,设计了一种精密测量晶体双折射率的方法,并在室温(22℃)下对通讯波段1 310 nm处石英晶体的双折射率进行了精密测量,测量结果和对误差的分析显示,此方法给出的...     

Absolute frequency measurement of iodine lines with a femtosecond optical synthesizer

We have used a single laser femtosecond optical frequency synthesizer together with a widely tunable Nd:YAG laser to measure the absolute frequency of several absorption lines in molecular iodine around 532 nm. The use of two different repetition frequencies allows us to determine the number of modes used for the frequency measurement unambiguously. The lines also provide data for the determination of improved ro-vibrational constants of the iodine molecule. Received: 3 July 2001 / Published online: 19 September 2001     

Frequency stability and reproducibility of iodine stabilised He-Ne laser at 633 nm

The frequency of a 633 nm He-Ne laser is stabilised on a hyperfine-structure-component of natural iodine vapour. The third harmonic component of an applied modulation frequency is detected and a servosystem is used to lock the laser frequency to the zero-crossing of the third harmonic component. The stability and the reproducibility of the laser are determined by beat frequency experiment.     

Iodine hyperfine structure and absolute frequency measurements at 565, 576, and 585 nm

The hyperfine structure splittings of the P(10)14-1, R(15)14-1, and R(99)15-1 transitions at 585 nm, P(62)17-1 at 576 nm, and P(80)21-1 at 565 nm in ¹²⁷I₂ are measured by heterodyne spectroscopy using two dye lasers. In addition, the absolute frequencies of the hyperfine components P(10)14-1 a₁₅ and P(80)21-1 a₁₀ are determined using a self-referenced frequency comb. These frequencies are used in an experiment testing relativistic time dilation by laser spectroscopy on a fast ion beam.     

Collisional broadening and shifting of ammonia absorption lines at 790 nm

By using a diode laser spectrometer based on a commercial heterostructure diode laser operating in free-running mode, line shape parameters of some ammonia ro-vibrational overtones at 790 nm have been measured at room temperature. These weak absorption lines have been detected by using the wavelength modulation spectroscopy technique with second-harmonic detection. The broadening and shifting coefficients have been obtained for ten absorption lines by fitting the collected second-harmonic absorption features and varying the pressure of different buffer gases. Received 13 February 2002 / Received in final form 18 September 2002 Published online 17 December 2002 RID="a" ID="a"e-mail: alex@ifam.pi.cnr.it     

Absolute frequency measurements and comparisons in iodine at 735 nm and 772 nm

We report frequency measurements at the rovibronic transition P(42)1-14 (772 nm) and R(114)2-11 (735 nm) from the electronic transition of the iodine molecule ¹²⁷I₂ with the help of a frequency comb as a reference. By using Doppler-free saturation spectroscopy a frequency precision in the 7 × 10⁻¹⁰ region is reached and two iodine cells both operated at 550-600 °C are compared. To relate our results to other measurements, the absolute transition frequency of the hyperfine structure line P(148)1-14 a₁ at 780 nm with an already known transition frequency was also determined.     

Direct measurement of Fano-effect on Rb at 266 nm

Polarization of photoelectrons from Rb produced by circularly polarized light (λ = 266 nm) was measured to be 68 ± 5%. This value agrees with earlier indirect measurements of the Fano effect on Rb.     

Identification of hyperfine structure components of the iodine molecule at 640 nm wavelength

The frequencies and the relative intensities of rotation-vibration transitions of ¹²⁷I₂, ¹²⁹I₂ and ¹²⁷I¹²⁹I near the HeNe laser emission wavelength of 640 nm have been calculated. Interpolation formulas for the differences of the electric quadrupole constants ΔeQq and of the spin-rotation constants ΔC of ¹²⁷I₂ are given. Most of the weak saturated-aborption lines, elsewhere published, have been identified as cross-over and forbidden lines of the transitions P(10)8-5 and R(16)8-5.     

Precision measurement of neutrino oscillation parameters at INO-ICAL detector

A magnetized Iron CALorimeter (ICAL) detector at the India-based neutrino observatory (INO) is used to study neutrino oscillation sensitivity using atmospheric muon neutrino source. The ICAL detector will be able to detect muon tracks and hadron showers produced by neutrino interactions with the iron target. We have performed precision measurement analysis for the atmospheric neutrino oscillation parameters with the muon neutrino events, generated by Monte Carlo NUANCE event generator. A marginalized χ² analysis based on reconstructed neutrino energy and muon zenith angle binning scheme has been performed to determine the sensitivity for the atmospheric neutrino mixing parameters, \(\sin ^{2}\theta _{23}\) and \(| {\Delta } m^{2}_{23}|\).     

Double-edge molecular measurement of lidar wind profiles at 355 nm

We built a direct-detection Doppler lidar based on the double-edge molecular technique and made the what we believe to be the first molecular-based wind measurements using the eye-safe 355-nm wavelength. Three etalon bandpasses are obtained with step etalons on a single pair of etalon plates. We eliminate long-term frequency drift of the laser and the capacitively stabilized etalon by locking the etalon to the laser frequency. We use a low-angle design to avoid polarization effects. Wind measurements of 1-2-m /s accuracy are obtained to 10-km altitude with 5 mJ of laser energy, a 750-s integration, and a 25-cm telescope. Good agreement is obtained between lidar and rawinsonde measurements.     

Absolute frequency measurement of an acetylene-stabilized laser at 1542 nm

The absolute frequency of an acetylene-stabilized laser at 1542 nm is measured at its second harmonic (771 nm) by use of a femtosecond optical comb based on a mode-locked Ti:sapphire laser. Frequency stability and reproducibility of the acetylene-stabilized laser are evaluated by the femtosecond comb with a H maser as a frequency reference. The absolute frequency of a laser diode stabilized on the P(16) transition of 13C2H2 is determined to be 194 369 569 383.6(1.3) kHz. The acetylene-stabilized laser serves as an important optical frequency standard for telecommunication applications.     

Absolute optical frequency measurement of saturated absorption lines in Rb near 422 nm

We present absolute optical frequency measurements of the 5s² S _1/2–6p² P _1/2 hyperfine resolved transitions in both ⁸⁵Rb and ⁸⁷Rb near 422 nm. The frequency of each transition was measured by stabilizing a narrow-linewidth extended cavity diode laser to the transition under study and by measuring that frequency with a femtosecond laser frequency comb. A frequency-doubled 844 nm laser was used as a frequency link to connect the 422 nm probe laser to the near infrared part of the comb. The resulting uncertainties of <70 kHz in the Rb transition frequencies represent a four-order of magnitude improvement over previously published results. The frequencies reported in this paper are one of the most accurate series of measurements made in the violet region of the spectrum. PACS 06.30.Ft; 33.20.Kf; 43.62.Fi     

Absolute-frequency measurement of the iodine-based length standard at 514.67 nm

The absolute frequency of the length standard at 514.67 nm based on the molecular iodine (¹²⁷ I ₂) transition of the P(13) 43-0 component a₃ is measured using a self-referenced femtosecond optical comb. This frequency-based technique improves measurement precision more than 100 times compared with previous wavelength-based results. Power- and pressure-related frequency shifts have been carefully studied. The measured absolute frequency is 71.8±1.5 kHz higher than the internationally accepted value of 582490603.37±0.15 MHz, adopted by the Comité International des Poids et Mesures (CIPM) in 1997. Received: 7 March 2002 / Published online: 24 April 2002     

Hartmann wave-front measurement at 13.4 nm with lambdaEUV/120 accuracy

We report, for the first time to our knowledge, experimental demonstration of wave-front analysis via the Hartmann technique in the extreme ultraviolet range. The reference wave front needed to calibrate the sensor was generated by spatially filtering a focused undulator beam with 1.7- and 0.6-microm-diameter pinholes. To fully characterize the sensor, accuracy and sensitivity measurements were performed. The incident beam's wavelength was varied from 7 to 25 nm. Measurements of accuracy better than lambdaEUV/120 (0.11 nm) were obtained at lambdaEUV = 13.4 nm. The aberrations introduced by an additional thin mirror, as well as wave front of the spatially unfiltered incident beam, were also measured.     

Precision measurement of the muon momentum in pion decay at rest

A new series of precision measurements of the muon momentum p_μ⁺ in the decay π→μ⁺v_μ at rest have been made using a magnetic spectrometer. The result is p_μ⁺=(29.79139 ± 0.00083) MeV/c. The consequences of this value for the rest masses of the muon neutrino and of the charged pion are discussed.