Mikhail N Skvortsov

Absolute frequency measurement of the In + clock transition with a mode-locked laser

The absolute frequency of the In(+) 5s(2) (1)S(0)5s5p (3)P(0) clock transition at 237 nm was measured with an accuracy of 1.8 parts in 10(13). Using a phase-coherent frequency chain, we compared the (1)S(0)(3)P(0) transition with a methane-stabilized HeNe laser at 3.39 microm, which was calibrated against an atomic cesium fountain clock. A frequency gap of 37 THz at the fourth harmonic of the HeNe standard was bridged by a frequency comb generated by a mode-locked femtosecond laser. The frequency of the In(+) clock transition was found to be 1,267,402,452,899.92 (0.23) kHz, the accuracy being limited by the uncertainty of the HeNe laser reference. This result represents an improvement in accuracy of more than 2 orders of magnitude over previous measurements of the line and now stands as what is to our knowledge the most accurate measurement of an optical transition in a single ion.s.

Frequency Comparison and Absolute Frequency Measurement of I2-stabilized Lasers at 532 nm

We present a frequency comparison and an absolute frequency measurement of two independent I2-stabilized frequency-doubled Nd:YAG lasers at 532 nm, one set up at the Institute of Laser Physics, No vosibirsk, Russia, the other at the Physikalisch-Technische Bundesanstalt, Braunschweig, Germany. The absolute frequency of the I2-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:a10 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.

Tunable single-frequency diode-pumped Nd:YAG ring laser at 1064/532 nm for optical frequency standard applications

We demonstrate a simple design for an infrared/green tunable unidirectional traveling-wave Nd:YAG laser consisting of only two intracavity components: a Nd:YAG gain medium and a KTP doubling crystal. The spectral linewidth of less than 10 kHz, and a widely tunable (∼400 GHz) green output up to 250 mW make this laser convenient for spectroscopy and frequency stabilization. We also demonstrate the results of long-term frequency stability of our laser stabilized onto the hyperfine luminescent peaks of molecular iodine.

Absolute frequency measurement of the 115In+ 5S2 1S0-5S5p 3P0 transition

Abstract We have measured the absolute frequency of the 115 In+ 5s 2 1 S0–5s5p 3 P0 clock transition at 236.5 nm with an accuracy of 3.3 parts in 1011. For this measurement, a frequency synthesis chain was used which links the indium clock transition to a methane-stabilized He–Ne laser at 3.39 μm and a Nd:YAG laser at 1064 nm whose second harmonic was locked to a hyperfine component in molecular iodine. A frequency gap in the chain of 1.43 THz at 850 nm was bridged with the help of an optical frequency comb generator. The frequency of the 115 In+ clock transition was determined to 1 267 402 452 914 (41) kHz, where the accuracy is limited by the uncertainty of the iodine reference. This measurement represents an improvement of more than three orders of magnitude in accuracy compared to previous measurements of the line.

Tunable single-frequency diode-pumped Nd:YAG ring laser at 946 nm

A simple design for a quasi-three-level diode-pumped tunable unidirectional traveling-wave Nd:YAG laser operating at 946 nm is demonstrated using a cavity consisting of two intracavity components, a Nd:YAG gain medium, and a KTP crystal. 280 GHz of tuning up to 160 mW of single-frequency output has been obtained by inserting a temperature controlled birefringent filter into the cavity.

Second-order Zeeman effect of theX−B transition in molecular iodine

Saturated absorption spectroscopy was applied to study the line shape of the molecular iodineX(ν″ = 0,J″ = 13,15) →B(ν′ = 43,J′ = 12, 16) transition (λ = 514.5 nm) in a transversal magnetic field as high as 0.51 T. The Zeeman structure of several hyperfine structure (hfs) components was completely resolved and a detailed study of the second-order Zeeman shift and splitting was made. The anisotropic Magnetic Susceptibility (MS) of the molecular iodine both in theB(43) (X′ = 7.3 ± 1 × 10−34 J/Oe2) and theX(0) [χ″ = (0.6 ± 1) × 10−34 J/Oe2] states as well as the isotropic MS difference [χ′0 −χ″o = (2 ± 0.2) × 10−34 J/Oe2] was measured.

Hybrid highly nonlinear fiber for spectral supercontinuum generation in mobile femtosecond clockwork

We have proposed and tested a novel design of a short-length dispersion-managed hybrid highly nonlinear fiber (HNLF), which is intended for low-noise spectral supercontinuum generation with controlled intensity distribution over the range 1?2??m. It is shown experimentally that such a HNLF facilitates development of a mobile femtosecond optical clockwork, which is based on a fiber-optic femtosecond laser system and an original fiber-coupled Nd?:?YAG/I2 optical frequency standard with a long-term instability lowered to 3???10?15.

Precise modulation of laser radiation by an acousto-optic modulator for stabilisation of the Nd : YAG laser on optical resonances in molecular iodine

A system of precise frequency modulation of laser radiation by an acousto-optic modulator, which makes it possible to stabilise the radiation power and simultaneously suppress the residual amplitude modulation to a level of 10-8 of the total laser power at the third harmonic of modulation frequency (~500 Hz), is presented. The use of this system for the Nd : YAG/I2 optical frequency standard and application of digital signal synthesis and processing methods provided a level of frequency standard instability as small as ~10-15 for ~6 × 104 s.

Femtosecond optical clock with the use of a frequency comb

The principles of precision measurement of frequency intervals in optical range with the help of femtosecond lasers are described. An experimental scheme of femtosecond optical clock is described. The characteristics of the basic elements and units of the setup are presented. The results of a broadened spectrum researches with the help of tapered fibers are reported.

Direct observation of the second-order Stark effect of theX-B transition in molecular iodine

The second-order Stark shift of the components of the hyperfine structure of the transition1∑g+(υ″ = 0,j″ = 13, 15) →3∏ou+(υ′ = 43,j′ = 12, 16) (of molecular iodine have been studied by means of saturated absorption spectroscopy in an external cell with the I2 vapour located in an electric field. The anisotropic polarizabilities of the upper and lower levels together with the difference between the isotropic polarizabilities of the levels of the transition have been obtained.