B.G. Whitford

Absolute frequency measurements of N2O laser transitions

Abstract The absolute frequencies of 33 P- and R-branch lines of the N 2 O, 00°1–10°0 laser band have been measured by heterodyning with known CO 2 laser frequencies of the 00°1 – 10°0 band in a tungsten-nickel diode. These measurements were used to calculate more precise values for the band centre and for the rotational constants.

Heterodyne frequency measurements of CO2 laser sequence-band transitions

Abstract The absolute frequencies of 93 lines of the 00°2-[10°1, 02°1]I, II and 00°3-[10°2, 02°2]I CO2 laser bands have been measured by heterodyning with the well known CO2 laser frequencies of the 00°1-[10°0]I,II band in a tungsten-nickel diode. The measured frequencies were used to calculate the band centre frequencies and the rotational constants. Line frequencies computed from the new constants are given and compared with the measured values.

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.

Heterodyne frequency measurements of CO2 laser hot-band transitions

Careful measurements by means of stabilized CO2 lasers are presented for the frequencies of 28 lines in the P-branch of the 01 0 0-(11 1 0, 03 1 0)I band of (C-13)(0-16)2, observed in laser emission, and three lines in the R-branch, observed in absorption with a diode laser. A significant improvement in the ro-vibrational constants has been obtained from a least squares fit to these data, demonstrating that the laser lines stabilized by natural absorption techniques provide convenient, accurate frequency references near 11.7 microns with an uncertainty of less than 0.1 MHz.

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.

A Tm:YAG laser for optical frequency measurements: mixing 148 THz light with CO2 laser radiation

Abstract A single-mode, diode-pumped Tm:YAG laser which is tunable from 2005 to 2035 nm and has an output power of 90 mW at 148 THz (2022 nm) is described. The beat between the frequency of this laser and the fifth harmonic of a CO2 laser transition has been observed using a tungsten-nickel point-contact diode. A signal to noise ratio of up to 20 dB in a 100 kHz bandwidth has been obtained. The Tm:YAG laser will be used as an intermediate frequency source in a chain between a visible frequency and a cesium standard.

Measurement of the Absolute Frequencies of CO2 Laser Transitions by Multiplication of CO2 Laser Difference Frequencies

It is verified experimentally that frequency differences between CO2 laser lines and the harmonics of these differences can be used as intermediate frequencies to bridge the gap between microwave frequency standards and infrared frequencies. Criteria for the design of a microwave to 30-THz frequency chain are discussed, and experimental details of the measurement of five CO2 isotope laser frequencies to an accuracy of ±2 parts in 109 are presented. The values obtained for the CO2 isotope transitions are 26334.776614 GHz for P(40) of 13C16O2, 27979.469512 GHz for R(6) of 13C18O2, 28665.704581 GHz for P(6) of 12C16O2, 29442.483293 GHz for R(30) of 12C16O2 and 33328.991337 GHz for R(8) of 12C18O2.

Confirmation of the currently accepted value 299 792 458 metres per second for the speed of light

Abstract The speed of light has been determined from a completely independent measurement of the wavelength and frequency of the CH4-stabilized He-Ne laser. The wavelength is 3 392 231.40 ± 0.02 pm, the frequency 88 376 181.57 ± 0.20 MHz, and the speed of light 299 792 458.1 ± 1.9 m/s.

Absolute frequency measurements of 12C16O and 13C16O laser transitions

Abstract The absolute frequencies of one 5.2 μm 12C16O laser line and one 5.3 μm 13C16O laser line have been measured against 10 μm band transitions of the CO2 laser by heterodyning in a tungsten-nickel diode. The frequencies, wavelengths and wave numbers of these lines are reported to an accuracy of one part in 107.

Absolute frequencies of CO2 laser transitions by multiplication of CO2 laser difference frequencies

Abstract Frequencies of CO 2 laser transitions have been compared to the Cs standard by a four-step frequency chain using difference-frequencies from five CO 2 isotope lasers. A tungsten-nickel diode generates the differences and their harmonics. Measurement of the 10.71 μm R(6) transition of 13 C 18 O 2 is described. The absolute frequency was found to be 27 979 469.512(65) MHz. Simultaneously, the four other CO 2 frequencies in the chain were also determined.