A practical direct current discharge helium absorption cell for laser frequency locking at 1083 nm

Abstract

We report the construction of a low pressure (∼0.5 Torr) helium direct current discharge cell to lock a 1083 nm InGaAs diode laser to the 2 3S–2 3P transition in helium using saturated absorption spectroscopy. The direct current discharge cell has the advantage of being radio frequency noise free.

Interferometric, modulation-free laser stabilization

“…The laser linewidth of our diodes is measured to be 5 MHz. This linewidth is consistent with measurements made with our old locking techniques 9 and is not due to the tilt-locking mechanism. The bandwidth of our servo-locking circuit is 100 Hz, providing good low-frequency control of the central laser frequency, but has no effect on fast dynamics, which determine the laser linewidth.…”

A rf discharge cell for saturated absorption spectroscopy of metastable argon

“…Lu et al recently described the construction of a direct current discharge for saturated absorption spectroscopy in helium. 2 In this Note, we detail how we fabricated and operate a rf discharge cell for saturated absorption spectroscopy in argon.…”

Electron scattering from laser-excited He atoms

“…The number density of the metastable atoms in the collision region is about 5×10 7 cm −3 , whilst the electron current, at an incident beam energy of 9.2 eV, is about 10 µA. Details of the apparatus have been discussed previously (Jacka et al 1995(Jacka et al , 1996 in connection with measurements of superelastic electron scattering from the metastable states. The interaction region formed by the above beams is also irradiated by light from a diode laser (SDL 6702-H1), tuned close to the 2 3 S 1 → 2 3 P 2 transition at 1.083 µm.…”

“…The interaction region formed by the above beams is also irradiated by light from a diode laser (SDL 6702-H1), tuned close to the 2 3 S 1 → 2 3 P 2 transition at 1.083 µm. The laser is locked to this transition by use of the saturated absorption signal obtained by double-passing a small amount of the light split from the main beam through a low-pressure helium discharge cell (Lu et al 1996). The metastable beam has a transverse Doppler width of about 300 MHz while the laser has a bandwidth of a few MHz.…”