Doppler-free frequency-modulation spectroscopy of atomic erbium in a hollow-cathode discharge cell

Abstract

The erbium atomic system is a promising candidate for an atomic Bose-Einstein condensate of atoms with a non-vanishing orbital angular momentum (L = 0) of the electronic ground state. In this paper we report on the frequency stabilization of a blue external cavity diode laser system on the 400.91 nm laser cooling transition of atomic erbium. Doppler-free saturation spectroscopy is applied within a hollow cathode discharge tube to the corresponding electronic transition of several of the erbium isotopes. Using the technique of frequency modulation spectroscopy, a zero-crossing error signal is produced to lock the diode laser frequency on the atomic erbium resonance. The latter is taken as a reference laser to which a second main laser system, used for laser cooling of atomic erbium, is frequency stabilized.

Laser stabilization to neutral Yb in a discharge with polarization-enhanced frequency modulation spectroscopy

“…A reliable and cost-effective alternative to stabilize a UV laser is using atoms produced in the discharge of a hollow-cathode lamp (HCL). First demonstrated in 1970, 20 laser stabilization to a discharge has been extended to various atomic species, including neutral ytterbium, 21 erbium, [22][23][24] dysprosium, 25 chromium, 26 and strontium. 27 Several spectroscopy techniques using Yb have been reported in an atomic oven 28 or a discharge lamp including modulation transfer spectroscopy (MTS), 29 which uses non-linear four-wave mixing as well as dichroic atomic vapor laser locking (DAVLL).…”

Polarization spectroscopy of atomic erbium in a hollow cathode lamp

“…Thus, while vapor pressures compatible with laser spectroscopy may be achieved in alkali metal gas cells at or slightly above room temperature, extremely high temperatures ( 1250 K) would be necessary to achieve similar vapor pressures for the spectroscopy of atomic erbium. This has motivated the use of optogalvanic hollow cathode lamps (HCLs) for laser spectroscopy [15,16] on high density, non-thermal samples of erbium atoms produced by sputtering from an erbium cathode. As detailed in Section II, we employ such an HCL in our polarization spectroscopy experiments.…”

“…Beginning from the first theoretical study of erbium as a candidate for cooling and trapping [6], experimental studies on frequency stabilization using atomic transition lines in erbium have been performed. The techniques of frequency modulation spectroscopy [15], where multiple frequency components of a probe beam interfere and produce a demodulated error signal, and modulation transfer spectroscopy [16], where a background free error signal is generated by an induced four-wave mixing process [17], have been explored previously. For the near-ultraviolet (near-UV) transitions of the lanthanides, which feature very large natural linewidths, the technique of polarization spectroscopy offers a simplified, modulation-free alternative that can achieve the necessary levels of laser stability.…”

Isotope shift measurements in the 660 spectral lines of Er I covering the 340–605 nm wavelength region with a Fourier Transform Spectrometer

“…High-resolution spectroscopy of Er I with the help of conventional spectrometers like the Fabry-Perot spectrometer was used by a number of workers [17][18][19][20][21][22][23][24][25]. The specific problems associated with hyperfine structure and isotope shift (IS) measurements in the large number of spectral lines have been solved using laser spectroscopic techniques [26][27][28][29][30]. IS measurements in some more lines were performed to study the peripheral parameters like configuration mixing, crossed-secondorder effects, change in nuclear mean square charge radii effects, and segregation of normal mass, specific mass and field or volume shifts [31][32][33][34][35][36][37][38][39].…”