High-resolution Saturation Spectroscopy Research Articles

Spectroscopically in situ traceable heterodyne frequency-scanning interferometry for distances up to 50 m

High-resolution saturation spectroscopy of iodine transitions at 637 nm is used to generate physically stable frequency reference markers for an interferometric absolute distance measurement based on frequency-scanning interferometry. Both experiments are performed simultaneously, posing severe challenges to the in principle well-established experimental techniques. The software-based enhancement of the signal-to-noise ratio is discussed in detail, as well as the demodulation and separation of the heterodyne interferometer signals. Verification measurements up to fifty meters indicate a relative measurement uncertainty well below 10−6.

High-resolution saturation spectroscopy of singly-ionized iron with a pulsed UV laser

We describe the design and realization of a scheme for UV laser spectroscopy of singly-ionized iron (Fe II) with very high resolution. A buffer-gas cooled laser ablation source is used to provide a room-temperature plasma with a high density of Fe II. We combine this with a scheme for pulsed-laser saturation spectroscopy to yield sub-Doppler resolution. In a demonstration experiment, we have examined an Fe II transition near 260 nm, attaining a linewidth of about 250 MHz. The method is well suited to measure transition frequencies and hyperfine structure. It could also be used to measure small isotope shifts in isotope-enriched samples.

Wavelength selective charge accumulation in self-organized InAs/GaAs quantum dots

Wavelength selective charging of a QD sub-ensemble is demonstrated, presenting a basis of future wavelength dependent parallel optical memory. High-resolution saturation spectroscopy in two-colour photocurrent experiments is used to investigate the binding energy of the positively charged trion complex as well as the temperature dependence of the coupling to acoustic phonons.

High-resolution spectroscopy of the /sup 39/K transitions at 770 nm and /sup 13/C/sub 2/H/sub 2/ saturated lines by a solid-state laser at 1.54 μm: toward an accurate frequency standard in the optical communication band

A novel and compact Er-Yb:glass laser was developed with single-frequency output power >10 mW in a wavelength range from 1531 to 1547 nm. The laser output was efficiently frequency doubled at 770.1 nm in a single-pass periodically poled lithium niobate waveguide and a second harmonic power in excess of 15 /spl mu/W was achieved, with an internal conversion efficiency of /spl sim/220% W/sup -1/. This frequency-doubled beam was used for high-resolution saturated spectroscopy of the /sup 39/K 4S/sub 1/2 /-4P/sub 1/2 / absorption line. The best resolved crossover peak showed 16% line contrast and 10-MHz linewidth. In a second experiment, working at the fundamental frequency, saturation spectroscopy of /sup 13/C/sub 2/H/sub 2/ was achieved using a low-pressure gas cell inside a build-up cavity. The measured absorption dip has 3% line contrast and 1.2 MHz linewidth. Both the atomic and molecular saturated lines are very well suited for frequency locking in order to establish accurate frequency standards in the optical communication band.

Hyperfine structure and isotope shift of the 3s-3p transitions of atomic oxygen

Using high-resolution saturation spectroscopy, by means of both double heterostructure and multiple quantum-well AlGaAs diode lasers, we investigate the isotope shifts and the hyperfine structure in the 3s-3p transitions of the triplet and quintet systems of atomic oxygen. From the analysis of the signals from17O we can deduce precise values for the hyperfine structure magnetic dipole constants. A theoretical analysis allows us to bring into evidence core polarization effects in the hyperfine structure. By heterodyning two frequency locked lasers, we perform a direct frequency measurement of the isotope effect on the3S1→3P1,2,0 transitions. From the comparison with similar accuracy data on the corresponding quintet transitions, an upper bound to the size of the nuclear volume effect is given, and precise values for the specific mass contributions are consequently obtained.

High-resolution saturation spectroscopy of the H 2n = 3 triplet states

For measurements of the fine and hyperfine structure of the H 2 n = 3 complex of triplet states, laser saturation spectroscopy has been applied to a beam of metastable H 2 molecules. A spectral resolution of better than 20 MHz (fwhm) was achieved. The experimental arrangement is described in detail, and preliminary results are given.

Recent developments in high resolution saturation spectroscopy obtained by means of acousto-optic modulators

We present three applications of acousto-optic modulators to high resolution saturation spectroscopy. — First, an A/O modulator is used to improve both frequency and amplitude stabilization of Ar+ lasers outside the laser resonator. — Second, a new technique to detect saturation resonances is demonstrated. In this method the saturation beam is both frequency shifted and modulated and the induced modulation of the probe beam is detected resulting in a highly improved signal to noise ratio and a high degree of background cancellation. — Third, an auxiliary A/O modulator is used for line shape studies with a single laser.

Isotope shift and HFS ofD 1 lines in Na-22 and 23 measured by saturation spectroscopy

High resolution saturation spectroscopy was applied to measure the relative isotope shift of theD1 lines in radioactive22Na against23Na in vapour cells. The result,δν=758.5(7) MHz, combined with other known values, indicates that the field shift is negligible in sodium isotopes. The hyperfine coupling constant of the2P1/2 level in22Na was found to be 37.0(1) MHz. A frequency offset locking technique is described which renders an accurate frequency calibration and achieves a long-term frequency stabilization.

Pulsed laser saturation spectroscopy: Observation of power broadening by optical nutations

High-resolution saturation spectroscopy of atomic resonance lines with a pulsed tunable dye laser can be performed with a variable time delay between bleaching and probing. Measurements for the Na D 2 line reveal an anomalous time dependent power broadening which cannot be explained within a hole burning model, but is ascribed to a line splitting by optical nutations. The magnitude of the effect is in agreement with recent semiclassical calculations.