Comparison of ^127I_2-stabilized frequency-doubled Nd:YAG lasers at the Bureau International des Poids et Mesures

Abstract

A frequency comparison was carried out between iodine-stabilized Nd:YAG lasers at 532 nm from the Bureau International des Poids et Mesures, the Centre for Metrology and Accreditation, the Czech Metrology Institute, and the Bureau National de Métrologie-Institut National de Métrologie. The frequency differences between lasers, as well as the frequency reproducibility of each system,were investigated. Pressure-, modulation-, and power-induced shifts were studied. A frequency dispersion (1 sigma) of 3.5 kHz (6.2 x 10(-12) in relative terms) with an average reproducibility for each laser of the order of 0.4 kHz (7.1 x 10(-13) in relative terms) was observed over the duration of the comparison. Relative stabilities better than 1 x 10(13) at 1 s were demonstrated for the third-harmonic systems.

Comparison of 10 cm and 50 cm Long Iodine Cells in Iodine-Stabilized Diode Laser-Pumped Nd:YAG Laser at 532 nm

“…These two parameters are believed to have the effects significantly on the frequency stability of the iodine-stabilized diodepumped Nd:YAG laser system developed in this study. The lowest Allan standard deviation of 0.6643×10 obtained at -5°C for 50 cm long iodine cell is quite high compared with previous values as reported in the literatures (Cordiale et al, 2000;Picard et al, 2003;Hong et al, 2003;1998;Arie and Byer, 1994;Döringshoff et al, 2012;Rovera et al, 2002;Robertsson et al, 2001;Eickhoff and Hall, 1995;Bitou et al, 2003). Therefore, the developed iodinestabilized diode laser-pumped Nd:YAG laser is not suitable to be used as a primary wavelength standard, However, the uncertainty of the iodine-stabilized laser system is acceptable to be used with a gauge block interferometer for the length calibration of the gauge block which is the main work of NIMT.…”

Investigation of Short-term Amplitude and Frequency Fluctuations of Lasers for Interferometry

“…The linewidth of the laser is below the 10 kHz level (integration time 0.1-1 s). Both L1(L2) and L3 are primarily intended for saturated subdoppler spectroscopy in iodine vapor at 532 nm wavelength and are designed to operate as laser optical frequency standards [32][33][34][35][36][37][38] with long-term frequency stability at 1*10 -14 level. L4 laser is simple DPSSL (diode pumped solid state laser) with alignment-free monolithic resonator equipped with slow thermal frequency tuning option which allows the linear absorption spectroscopy frequency stabilization technique.…”

“…This frequency stability is fully sufficient for measurements that are done on air conditions -the influence of the refractive index of air fluctuations is in the order of 10 -7 or can be compensated up to this level [23][24][25][26][27][28][29][30][31]. Next, the relative frequency stability of frequency doubled Nd:YAGs stabilized by some more sophisticated technique like saturated subdoppler spectroscopy in iodine vapor can be in the range close to the 10 -14 level for 100 s integration times [32][33][34][35][36][37][38]. Furthermore, not only long-term but also short-term frequency stability is important, especially in cases of high-speed interferometric systems.…”

Methods for Measurement and Verification of Purity of Iodine Cells for Laser Frequency Stabilization

“…The most suitable seems the 502 nm wavelength coinciding with absorption lines in iodine characterized by a high sensitivity to collisional quenching that is caused by a long lifetime of the excited level [4]. The strongest absorption line within the spectral width of the laser is the R(26) 62-0 of the 127 I 2 which contributes predominantly to the fluorescence measured.…”

“…With the stability that can be reached with iodine stabilized frequencydoubled Nd:YAG lasers the chance to compare the purity investigation with measured frequency shifts could go even below the kHz level [4], [5], [6].…”