Saturated Absorption Spectrometer Research Articles

Widely tunable, single-mode optical frequency synthesizer with a 100 kHz uncertainty

A tunable cw Ti:sapphire laser is locked to a self-referenced femtosecond frequency comb generated by an erbium-doped fiber laser thereby creating a single-frequency optical frequency synthesizer. This synthesizer has a tuning range of 760-820 nm with an absolute frequency uncertainty less than 100 kHz. We demonstrate the precision of this cw optical frequency synthesizer by measuring the optical frequency of several transitions on the D2 lines of 85Rb and 87Rb using a saturated absorption spectrometer.

Measurement of acetylene-d absorption lines with a self-referenced fiber laser frequency comb

A self-referenced optical frequency comb, derived from a mode-locked fiber laser, and a cavity-enhanced diode-laser-based saturated absorption spectrometer were employed to measure the absolute frequency of 55 absorption lines of the P and R branches of the 2ν1 band of 12C2HD at 1.5 μm with a one standard deviation uncertainty of better than 2.5 kHz for all lines measured. The shift sensitivities of the P(16) line to changes in power, pressure, and modulation amplitude have been studied in detail. Improved values of the ground-state molecular constants are obtained.

Precise measurement of hyperfine structure in the 6P1/2 state of 133Cs

We have measured hyperfine structure in the 6P1/2 state of 133Cs using a frequency-stabilized diode laser and acousto-optic modulators that produce calibrated frequency offsets. We check for errors due to radiation-pressure and optical-pumping effects by repeating the measurements at different values of pump power in a saturated-absorption spectrometer. We obtain a precise value of the magnetic-dipole constant, A = 291.9135(15) MHz, representing an improvement of more than an order of magnitude.

Precise measurement of hyperfine structure in the 52P1/2 state of Rb

We have measured hyperfine structure in the 5 2P1/2 state of Rb using a frequency-stabilized diode laser, which is locked to one hyperfine transition, and an acousto-optic modulator, whose frequency is locked to the interval of interest. We check for optical-pumping errors by repeating the measurement at different values of pump power in the saturated-absorption spectrometer. We obtain precise values of the hyperfine constant: A=120.645(5) MHz for 85Rb and A=406.119(7) MHz for 87Rb. The values resolve a large discrepancy between two earlier high-accuracy measurements on this state.

Frequency Stabilization of Diode Laser Using Dichroic-Atomic-Vapor Laser Lock Signals and Thin Rb Vapor Cell

We report the frequency stabilization of a diode laser by applying the dichroic-atomic-vapor laser lock (DAVLL) method to a thin Rb vapor cell. A 1-mm-long Rb vapor cell is used to obtain a sub-Doppler spectrum that is required for frequency locking, which is easier than in the case of using a saturated absorption spectrometer. A 794-nm diode laser is tuned to the Rb D1 line, and sub-Doppler signals are observed by introducing a pumping beam and a probe beam in a perpendicular direction. We obtain error signals by subtracting the signals of σ+ polarized beams from that of σ- polarized beams in the presence of a magnetic field and stabilized the 794 nm diode laser frequency without modulating laser parameters. The stability of the 794-nm diode laser is evaluated using other independently stabilized diode laser.

Development and study of a 1.5 μm optical frequency standard referenced to the P(16) saturated absorption line in the ( ν1+ ν3) overtone band of 13C 2H 2

We describe a recently developed saturated absorption spectrometer realizing an optical frequency standard based on the P(16) transition of the ( ν 1+ ν 3) band of 13C 2H 2. Studies of stability, reproducibility and sensitivity to various parameters were performed. The current stability of the system has been measured to reach 4×10 −13 for an averaging time of 100 s. To our knowledge, we report the first results on the parameter shifts of the Doppler-free P(16) line. A modulation amplitude shift of 4700 ± 300 Hz/MHz pp, an intracavity power shift of −11.4 ± 0.6 Hz/mW, and a pressure shift of −230 ± 20 Hz/mTorr were measured for standard operating conditions of: 1.0 MHz pp modulation excursion, 120 mW intracavity power, and 20 mTorr gas pressure. Control of these parameters should allow kilohertz reproducibilities of this device in the long term.

Modulation-free laser frequency stabilization and detuning

We have developed a modulation-free technique for stabilizing a laser to a Doppler-free saturated absorption spectrometer without the need for phase sensitive detection. By using two acousto-optic modulators, we can lock, with variable offset, to atomic resonances. The new technique works equally well with both vapor and discharge reference cells. We demonstrate the technique using rubidium and metastable argon as references.

High-contrast saturated absorption spectrometer with a grating reflector as an optical frequency locker

By optical feedback of signals obtained with a high-contrast saturated absorption spectrometer as a reference frequency selector, diode laser frequency has been locked to the hyperfine transition line of a Cs atom. We used a grating instead of a mirror for optical feedback to avoid feedback of unwanted modes, because such modes cause mode hopping or generate another frequency component, whose intensity does not decrease even after it passes through an atomic cell twice. Long-term frequency stability has been improved by compensating the cavity length for phase fluctuations.

A narrow-band tunable diode laser system with grating feedback, and a saturated absorption spectrometer for Cs and Rb

Detailed instructions for the construction and operation of a diode laser system with optical feedback are presented. This system uses feedback from a diffraction grating to provide a narrow-band continuously tuneable source of light at red or near-IR wavelengths. These instructions include machine drawings for the parts to be constructed, electronic circuit diagrams, and prices and vendors of the items to be purchased. It is also explained how to align the system and how to use it to observe saturated absorption spectra of atomic cesium or rubidium.