Frequency Noise Properties of Lasers for Interferometry  in Nanometrology

Hrabina, Jan; Lazar, Josef; Holá, Miroslava

doi:10.3390/s130202206

Cited by 25 publications

(12 citation statements)

References 48 publications

(41 reference statements)

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“…The concept presented here offers fast response to any change of the optical length in the refractometer beam path, as fast as the response of the interferometer output in case of calculated compensation [5] or as fast as it is offered by the control loop of a stabilized laser in a regime of stabilization of wavelength [6]. The spectral interpretation of the length noise associated with the fluctuating refractive index shows similar characteristics with the laser induced noise [7,8]. As expected the dominating bandwidth here lies in the low-frequency part, where the fluctuations gradually grow into drifts, thermal and pressure induced.…”

Section: Fluctuations Of the Refractive Index Of Airmentioning

confidence: 56%

Interferometry with Stabilization of Wavelength within a Fixed Measuring Range

et al. 2014

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We present an interferometric technique based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. One of the important limiting factors in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty traditionally compensated when the index is evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where a reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 10 -8 level. The technique allows to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. Stabilization of WavelengthProposed concept relies on direct stabilization of wavelength to a mechanical reference. The principal optical arrangement [1] consists of a set of two countermeasuring interferometers. The moving element, representing the displacement to be measured, moves within stable grid of fringes/wavelengths insensitive to the varying refractive index of air. The key improvement here is the ability to measure, or compensate, for the refractive index variations in the beam path identical with the position sensing. Concepts proposing referencing wavelength to external mechanical reference have been proposed before [2] but thermal gradients and inhomogeneity of the atmosphere results in a large uncertainty caused by measurement of the refractive index of air at a place different to the measuring beam. In this contribution we present a new version of this concept focused on a design applicable in real displacement measurements. The setup consists of three interferometers where each measures the specified part of the overall length (A, B, C, see Fig. 1).

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Section: Fluctuations Of the Refractive Index Of Airmentioning

confidence: 56%

Interferometry with Stabilization of Wavelength within a Fixed Measuring Range

et al. 2014

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“…These lasers stabilized by saturation spectroscopy can achieve long-term frequency stability better than 1*10 -14 for an integration time of 100 s, which means a more than two orders better result in comparison to traditionally used He-Ne-I 2 stabilized standards [6][7][8][9][10][11][12][13][14][15][16]. The short-term frequency noise of these lasers is also lower [17][18][19][20]. Further improvement in the short-term stability can be reached by means of prestabilization to a high-finesse passive optical cavity or by fiber based interferometer [21,22].…”

Section: Introductionmentioning

confidence: 91%

Comparison of Molecular Iodine Spectral Properties at 514.7 and 532 nm Wavelengths

Hrabina

Acef

Burck

et al. 2014

Measurement Science Review

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We present results of investigation and comparison of spectral properties of molecular iodine transitions in the spectral region of 514.7 nm that are suitable for laser frequency stabilization and metrology of length. Eight Doppler-broadened transitions that were not studied in detail before were investigated with the help of frequency doubled Yb-doped fiber laser, and three of the most promising lines were studied in detail with prospect of using them in frequency stabilization of new laser standards. The spectral properties of hyperfine components (linewidths, signal-to-noise ratio) were compared with transitions that are well known and traditionally used for stabilization of frequency doubled Nd:YAG laser at the 532 nm region with the same molecular iodine absorption. The external frequency doubling arrangement with waveguide crystal and the Yb-doped fiber laser is also briefly described together with the observed effect of laser aging.

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“…Fig. 7 shows that the resolution is limited by a constant voltage noise above 2 Hz, and by a 1/f current noise below 2 Hz coming from the laser optical power noise [30].…”

Section: Noise Budgetingmentioning

confidence: 99%

“…stage (two translations and two rotations) to adjust the position and the angle of the beams on the photodiodes. The length of the two arms (d 1 and d 2 ) are similar to minimize the impact of the laser frequency noise on the measurements [30]. Note that the He-Ne laser can be replaced by a pigtailed laser diode with a polarization-maintaining optical fiber [8] and a fiber collimator.…”

Section: Interferometric Sensormentioning

confidence: 99%