Stabilized lasers

This interferometric dilatometer consists of a rather simple and small Michelson interferometer, in which the two arms are parallel, and of a 4He cryostat, in which the sample to be measured is hold. The sample is cooled to 4 K, and data are taken during the warm up of the cryostat. The optical path difference between the two arms depends on the sample length hence a variation of the sample length determines an interference signal. The Michelson interferometer consists of a He-Ne stabilized laser (A = 0.6328 xm), two cube corner prisms, a beam splitter, three mirrors and a silicon photodiode detector placed in the focal plane of a 25 mm focal length biconvex lens (see Fig. 13.1). 

M. Kremer, B. Fischer, B. Feuerstein, V.L.B. de Jesus, V. Sharma, C. Hofrichter, et al., Electron localization in molecular fragmentation of H2 by carrier-envelope phase stabilized laser pulses, Phys. Rev. Lett. 103 (21) (2009) 213003. 

The schematic view of the Mainz apparatus for collinear laser spectroscopy, installed at Isolde is given in fig 4. The 60 keV ion beam is set collinear with the laser beam, then accelerated (or decelerated) and finally neutralized in charge exchange cell. By Doppler tuning the atomic absorption is set resonnant with the stabilized laser frequency, and the fluorescence emitted is detected. 

Fig. 11. Outline of the frequency chain between the 2S — 12D hydrogen frequencies and the LD/Rb and CO2/OSO4 standards. The details are explained in the text (Ti-Sa titanium sapphire laser, LD/Rb rubidium stabilized laser diode, LD(int) intermediate laser diode, CO2/OSO4 osmium tetraoxyde stabilized CO2 laser, SHG second harmonic generation, SFG sum frequency generation)...

Another domain of fs comb accuracy confirmation was provided by comparison of the apparent measured frequency of a HeNe 12-stabilized laser, measured... 

Frequency Comparison and Absolute Frequency Measurement of 12-stabilized Lasers at 532 nm... 

Abstract. We present a frequency comparison and an absolute frequency measurement of two independent -stabilized frequency-doubled Nd YAG lasers at 532 nm, one set up at the Institute of Laser Physics, Novosibirsk, Russia, the other at the Physikalisch-Technische Bundesanstalt, Braunschweig, Germany. The absolute frequency of the l2-stabilized lasers was determined using a CH4-stabilized He-Ne laser as a reference. This laser had been calibrated prior to the measurement by an atomic cesium fountain clock. The frequency chain linking phase-coherently the two frequencies made use of the frequency comb of a Kerr-lens mode-locked Ti sapphire femtosecond laser where the comb mode separation was controlled by a local cesium atomic clock. A new value for the R.(56)32-0 aio component, recommended by the Comite International des Poids et Mesures (CIPM) for the realization of the metre [1], was obtained with reduced uncertainty. Absolute frequencies of the R(56)32-0 and P(54)32-0 iodine absorp tion lines together with the hyperfine line separations were measured. 

We present a frequency comparison of two independent -stabilized Nd YAG lasers at 532 nm and an absolute frequency measurement of the laser frequencies which were locked to different HFS components of the R(56)32-0 and P (54)32-0 iodine absorption line. The absolute frequencies have been determinded using a phase-coherent frequency chain which links the 12-stabilized laser frequency to a CH4-stabilized He-Ne laser at 3.39 pm. This laser had been calibrated before the measurements against an atomic cesium fountain clock. 

Although the lifetime of the 2S /2 state in Si13+ is much longer than that of the 2P3/2 state, it is still only 16 ns. For this reason, very high laser power (several kW or more) is required to obtain a reasonable transition rate to the 2P3/2 state [31], The required intensities may be obtained by using an extremely high finesse enhancement cavity to build up the output power from a frequency-stabilized laser [32]. 

A company dial micrometer linked via chained calibrations to a stabilized laser wavelength standard maintained by an NMI... 

The interaction of the Rydberg atoms with the thermal radiation field results in a small shift of the Rydberg levels (AC-Stark shift), which only amounts io Av/v 2 X 10 for rubidium. It has recently been measured with extremely well stabilized lasers [565]. In order to eliminate the influence of the thermal radiation field one has to enclose the interaction zone of the laser and atomic beam by walls cooled to a few degrees Kelvin. 

Even a well-stabilized laser, where all technical noise has been eliminated (Vol. 1, Sect. 5.4.5) still shows small fluctuations AEo of its amplitude and A(/> of its phase, because of quantum fluctuations. While technical fluctuations may be at least partly eliminated by difference detection (Fig. 1.9), this is not possible with classical means for photon noise caused by uncorrelated quantum fluctuations. 

F.R. Petersen, D.G. McDonald, F.D. Cupp, B.L. Danielson, Rotational constants of C 02 from beats between Lamb-dip stabilized laser lines. Phys. Rev. Lett. 31, 573 (1973), also in Laser Spectroscopy, ed. by R.G. Brewer, A. Mooradian (Plenum, New York, 1974), p. 555... 

In the field of metrology a big step forward was the use of frequency combs from cw mode-locked femtosecond lasers. It is now possible to directly compare the microwave frequency of the cesium clock with optical frequencies, and it turns out that the stability and the absolute accuracy of frequency measurements in the optical range using frequency-stabilized lasers greatly surpasses that of the cesium clock. Such frequency combs also allow the synchronization of two independent femtosecond lasers. 

We are indebted to H. P. Layer for providing us with a detailed design of the NBS He-Ne iodine stabilized laser, to J. L. Hall for informing us of his design of an acoustically isolated interferometer chamber, to K. L. Foster for assistance in all phases of their fabrication, and to F. Walls for help with ultra-stable crystal oscillators. This work is supported in part by the U.S. Office of Naval Research. 

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