L. Marmet

A laser frequency lock referenced to a single trapped ion

Abstract A frequency lock has been developed which frequency stabilizes a portion of the output from an ultrastable diode laser to the narrow 5s 2 S 1/2 –4d 2 D 5/2 transition at 445 THz (674 nm) of a single, trapped and laser cooled 88Sr+ ion. Digital processing is used to record quantum jump data and to servo the frequency applied to an acousto-optic modulator which is used to scan a portion of the laser output across two, symmetrically displaced Zeeman components. Stable locking has been obtained resulting in uncertainties in the ion transition referenced laser frequency of less than 150 Hz.

Precision frequency measurement of the /sup 2/S/sub 1/2/-/sup 2/D/sub 5/2/ transition of Sr/sup +/ with a 674-nm diode laser locked to an ultrastable cavity

We have measured the frequency of the 5s /sup 2/S/sub 1/2/-4d /sup 2/D/sub 5/2/ clock transition of a single Sr ion confined in a Paul trap. A diode laser locked to an ultrastable Fabry-Perot (F-P) cavity was used to probe the transition with a resolution of 3.5 kHz. The absolute frequency was determined from heterodyne measurements referenced to an iodine stabilized HeNe laser and a CO/sub 2/ laser yielding a value for the S-D transition of (444 779 043 963/spl plusmn/30) kHz. This work could lead to the development of a new optical frequency standard at 674 nm.

Absolute frequency measurement of a laser at 1556 nm locked to the 5S1/2-5D5/2 two-photon transition in 87Rb

Abstract The frequency of a diode laser system at 193 THz (1556 nm), which is frequency doubled and locked to a two-photon transition in rubidium at 385 THz (778 nm), has been measured with a Cs-based frequency chain and a single Sr + ion standard at 445 THz. The output frequency of the diode laser system was measured to be 192 642 283 183 700 ± 500 Hz. After applying corrections for systematic offsets in the rubidium spectrum, the frequency of the 87 Rb 5S 1/2 ( F g =2)−5D 5/2 ( F e =4) two-photon transition is found to be 385 284 566 370.4 ± 2 kHz.

Phase-locked optical divide-by-3 system for visible radiation

An optical divide-by-3 system has been developed to phase lock a diode-pumped Tm:YAG laser at 148 THz (2022 nm) to a frequency near 1/3 that of an ultrastable diode laser system at 445 THz (674 nm). The 148-THz radiation is frequency doubled in angle-tuned AgGaS(2) and frequency differenced with the 445-THz radiation in noncritically phase-matched LiNbO(3) , generating two signals at 297 THz, which are mixed on a photodiode. An electronic servo system is used to control the frequency of the Tm:YAG laser and to phase lock it to the visible diode laser output. Phase-locking periods of several minutes are routinely obtained.

Detailed description of FCs1: NRC’s cesium fountain primary standard

The first cesium fountain primary standard built at the National Research Council Canada is described in details. Dimensional measurements and functions of components of the standard are given. We expect the standard to perform with a short term stability of 7times10-14 at one second and have a relative inaccuracy below the 1times10-15 level.

Linking the 474 THz HeNe/I/sub 2/ standard to the 445 THz single Sr/sup +/ trapped ion standard: heterodyne frequency measurements using an OsO/sub 4/ stabilized 29 THz laser system

A 29 THz CO/sub 2/ laser system operating on the 10 /spl mu/m R(0) line has been developed, which is frequency-stabilized by third harmonic locking to a saturated absorption resonance of OsO/sub 4/. By difference frequency mixing this radiation and 474 THz radiation referenced to a HeNe/I/sub 2/ laser standard, sufficient 445 THz power is obtained for an absolute heterodyne measurement of the 445 THz radiation probing a /sup 88/Sr/sup +/ single ion reference transition. A new series of measurements give a value of 444779044086 kHz/spl plusmn/12 kHz for the /sup 88/Sr/sup +/, 5s/sup 2/S/sub 1/2/-4d/sup 2/D/sub 5/2/ center frequency.

Effect of counterintuitive time delays in nonlinear mixing.

The effect of varying the relative arrival time of the two laser pulses employed in doubly resonant four-wave sum mixing, enhanced by induced transparency, is studied with the aim of optimizing the efficiency of vacuum-ultraviolet generation. With atomic hydrogen as the nonlinear medium, pulsed radiation with wavelengths of 243 and 656 nm and durations of 8 and 14 ns, respectively, is mixed to generate 103-nm coherent radiation. It is shown that by delaying the arrival time of the ground-state pump beam (243 nm) by 2.5-3.5 ns relative to the arrival of the upper-state coupling beam (656 nm), it is possible to enhance the generated intensity by a factor of 2 or more.

Measurement of the 88Sr+ reference transition frequency with a new probe laser system

The authors have designed and implemented a new 674 nm (445 THz) laser system for probing the ultranarrow 5s²S_1/2-4d²D_5/2 reference (clock) transition of the trapped and laser-cooled ⁸⁸Sr⁺ ion. The authors describe briefly the double-stage probe laser system; linewidths of (50 plusmn 9) Hz FWHM were observed for the clock transition with this source. Results on the determination of the temperature of zero thermal expansion coefficient of the reference cavity were also presented. Preliminary measurement of the absolute frequency of the ⁸⁸Sr⁺ clock transition frequency gives a frequency of (444779044095472 plusmn 15) Hz

Progress towards NRC's fountain clock FCs1

Summary form only given. Systematic improvements of NRCs cesium fountain clock prototype have resulted in a stability reaching /spl sigma//sub y/(/spl tau/)=1.5/spl times/10/sup -12/ /spl tau//sup -1/2/, the best ever obtained at NRC for a Cs standard. We are in the process of completing the construction of the cesium fountain clock.

Mapping the magnetic field vector in a fountain clock

We show how the mapping of the magnetic field vector components can be achieved in a fountain clock by measuring the Larmor transition frequency in atoms that are used as a spatial probe. We control two vector components of the magnetic field and apply audio frequency magnetic pulses to localize and measure the field vector through Zeeman spectroscopy.