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Preliminary results on absolute frequency stabilization of Distributed Bragg Reflector (DBR) diode-lasers with emission wavelength at 852 nm will be reported. Saturated absorption D2 lines of cesium atom have been adopted as a frequency reference and the nonlinear spectroscopy method of Modulation Transfer has been used to lock the laser frequency against the resonance. From the preliminary results on the beat signal between two independent laser systems a relative frequency stability of 10-11 has been reached at an integration time of 0.1 s. The analysis on the obtained signal to noise ratio shows a frequency noise floor in the order of approximately 10-12 which should be achieved in an integration time of 1 s.

The results of an international comparison between the He-Ne lasers stabilized to 127I2 at 633 nm of the IMGC (Istituto di Metrologia "G. Colonnetti", Turin, Italy) and the IFA-IFTAR (Institute of Atomic Physics-IFTAR, Department of Lasers, Bucharest, Romania) are reported. The mean frequency difference, considering the hyperfine structure components d, e, f and g of the R(127) 11-5 transition, was Δν = νRO.2 - νIMGCA4/5 = 3,8 kHz, standard uncertainty u = 5,7 kHz, or Δν/ν0 = 0,8 × 10-11, standard uncertainty u = 1,2 × 10-11. The frequency stability, expressed as the relative Allan standard deviation of the beat note between the two lasers, resulted 3,7 × 10-12 for a 100 s sampling time.

An interferometric force balance (Nanobalance) for space micro-thruster qualification is presented. A new generation of space micro-thrusters is under development aiming at thrust resolution and accuracy below one micronewton. Nanobalance has been conceived and developed for ground calibration of thrust time profile and noise with sub-micronewton accuracy.

Preliminary results of an international comparison between the He-Ne lasers stabilized to 127I2 at 633 nm of the Instituto di Metrologia G. Colonnetti (IMGC) and the Institute of Atomic Physics-IFTAR (IFA-IFTAR), Department of Lasers are reported. The mean frequency difference, considering the hyperfine structure components d, e, f and g, resulted as (Delta) (nu) equals (nu) IMGC4/5 - (nu) R0.2 equals (-3.8 +/- 5.7) kHz, or as relative value reported to the laser frequency as (Delta) (nu) /(nu) o equals (0.8 +/- 1.2) X 10-11. The frequency stability, expressed as the Allan variance of the beat note between the two lasers, resulted 3.65 X 10-12 for 100 s sampling time.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The stabilization of a He-Ne (Helium-Neon) laser to hyper-fine structure (HFS) components of the P(48) 11-3 transition of 127I2 at 612 nm observed in an external iodine cell, may give a frequency reproducibility of ±5 kHz or ±1 × 10-11·? and a stability of 1.4 × 1013·? for an observation time ? = 100 s. From 3He-22Ne lasers stabilized to HFS components of 127I2 observed in an intracavity cell, both at 612 and 640 nm wavelengths, a reproducibility of ±2 × 10-10· ? can be expected. Common and convenient operating conditions have been found at both wavelengths.

Two 127I 2 transitions coincident with the 20Ne emission at 605 nm have been identified. One of them is sufficiently intense for locking the laser frequency to one isolated hyperfine structure (HFS) component. The performances presently achieved are: a stability of 6 ∗ 10−13 ∗ ν for an integration time τ = 1000 s and a reproducibility of 200 kHz(4 ∗ 10−10 ∗ ν).

In November 1981, a comparison between BIPM and IMGC He-Ne lasers stabilized to saturated absorption lines of 127I2, at the wavelengths ? = 633 nm and ? = 612 nm has been made at the BIPM. At 633 nm, a repeatability and a reproducibility within +1 × 10-11 · ? have been obtained. At 612 nm, a repeatability within a few 10-11 · ? only for one laser and a reproducibility of ± 2 × 10-10 · ? have been obtained.

The dispersion signal, observed with sub-Doppler spectroscopic techniques using a phase modulation of the probe beam, is antisymmetric and shows a remarkable slant at the central zero-crossing. Because of these characteristics, it is particularly suitable as an error signal for stabilizing the laser frequency using as a reference an atomic or molecular transition in a low-pressure gas. At IMGC the fitness of this method for the achievement of optical frequency standards has been tested using two He-Ne lasers, independently stabilized to the hyperfine structure component “b 15 ” of the P (48) 11–3 iodine transition at 612 nm.

Preliminary results for the implementation of modulation transfer technique using a He-Ne laser at 612 nm are given. The performances are presently limited by the noise of the detector, which was designed to be operated at a frequency higher than the one used for modulating the saturating beam.

Using FM spectroscopy as the detection method in an experiment of optical saturation absorption, a fractional stability (Allan variance) of 5/spl times/10/sup -14/ has been observed for an integration time of 10/sup 3/ s,and a reproducibility better than 1 part in 10/sup 11/ has been achieved. >