Search results for "optical pumping"

Counter-propagating difference frequency mixing in diamond with terahertz waves

2013

We investigate four-wave mixing between terahertz and optical pulses in diamond. We observe the occurrence of sum and difference frequency generation, with the latter being phase-matched for terahertz pulses counter-propagating to the optical field.

Nonlinear effects in optical pumping of a cold and slow atomic beam

2015

By photoionizing hyperfine (HF) levels of the Cs state $6{\phantom{\rule{0.16em}{0ex}}}^{2}{P}_{3/2}$ in a slow and cold atom beam, we find how their population depends on the excitation laser power. The long time (around $180\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s})$ spent by the slow atoms inside the resonant laser beam is large enough to enable exploration of a unique atom-light interaction regime heavily affected by time-dependent optical pumping. We demonstrate that, under such conditions, the onset of nonlinear effects in the population dynamics and optical pumping occurs at excitation laser intensities much smaller than the conventional respective saturation values. The ev…

Polarization-sensitive population trapping in an optically pumped laser

1994

Optical pumping and unstable nuclei

1985

The paper reviews the application of optical pumping to short-lived nuclei, where either the nuclear polarisation is detected by the β-decay asymmetry or the atomic polarisation by Stern-Gerlach-analyzer. Moreover the paper deals with collinear laser spectroscopy on beams of short-lived, mass-separated isotopes. The aim of the experiments is the systematic investigation of nuclear structure through the determination of spin, moments and charge radii from the hyperfine structure and isotopic shift of the atomic spectra. The impact of these experiments on the theory of nuclear forces and structure is discussed by means of a few examples.

1.3 µm GaInNAs optically-pumped vertical cavity semiconductor optical amplifier

2003

A GaInNAs/GaAs vertical cavity semiconductor optical amplifier (VCSOA) is reported. This is believed to be the first monolithic VCSOA operating at 1.3 mum. Under continuous-wave optical pumping in a singlemode fibre coupled format, gain figures of up to 17.7 dB were achieved. Amplification with 12 GHz bandwidth,was obtained at 12.8 dB peak gain.

Influence of pump coherence on the dynamic behavior of a laser

1988

The dynamic behavior of a coherently pumped single-mode unidirectional ring laser with a homogeneously broadened three-level active medium is studied. Our formulation is based on a set often real equations of the plane-wave, mean-field Maxwell–Bloch type. The instability domain in the main control parameters space is determined. Our numerical study of these equations for a parameter range of the type explored in the recent experiments by Weiss Brock [ Phys. Rev. Lett.57, 2804 ( 1986)] reveals some similarities, but striking differences between our theoretical predictions and their experimental observations are also noted.

Efficient polarization of high-angular-momentum systems

2016

We propose methods of optical pumping that are applicable to open, high-angular-momentum transitions in atoms and molecules, for which conventional optical pumping would lead to significant population loss. Instead of applying circularly polarized cw light, as in conventional optical pumping, we propose to use techniques for coherent population transfer (e.g., adiabatic fast passage) to arrange the atoms so as to increase the entropy removed from the system with each spontaneous decay from the upper state. This minimizes the number of spontaneous-emission events required to produce a stretched state, thus reducing the population loss due to decay to other states. To produce a stretched stat…

Saturated absorption spectroscopy: elimination of crossover resonances by use of a nanocell

2007

It is demonstrated that velocity selective optical pumping/saturation resonances of reduced absorption in a Rb vapor nanocell with thickness \textit{L=} $\lambda $, 2$\lambda $, and 3$\lambda $ (resonant wavelength $\lambda $ = 780 nm) allow the complete elimination of crossover (CO) resonances. We observe well pronounced resonances corresponding to the F$_{g}=3$ $\to $ F$_{e}=2,3,4$ hyperfine transitions of the $^{85}$Rb D$_{2}$ line with linewidths close to the natural width. A small CO resonance located midway between F$_{g}=3$ $\to $ F$_{e}=3$ and F$_{g}=3$ $\to$ F$_{e}=4$ transitions appears only for \textit{L} = 4$\lambda $. The D$_{2}$ line ($\lambda $ = 852 nm) in a Cs nanocell exhi…

Modelling of Laser Operation in RPE Nd3+:LiNbO3 Channel Waveguides

2006

In this work, laser action in RPE Nd3+:LiNbO3 is modelled by using the overlapping integrals method. Different pumping schemes, TE or TM, have been considered in order to reproduce the experimental measurements. Calculated results indicate that the slope efficiency remains basically independent on the pumping scheme while the threshold pump power increases for TE pumping.

Near-IR-to-visible emission in ytterbium-doped silica fiber at in-core 488-nm pumping

2008

We report near-IR-to-visible broadband emission in Ytterbium-doped silicate fiber (YF) at 488-nm in-core excitation. This emission is revealed to originate from Yb3+-Yb3+ pair clusters (900 – 1200-nm band), whose presence is proved by a separate study of cooperative processes in the fiber, and Yb2+ phototropic centers (600 – 900-nm band) provisionally accepted to be present in the YF.