Researchers from the University of New South Wales (Canberra, Australia), Montana State University (Bozeman, MT), and the National Institute of Chemical Physics and Biophysics (Tallinn, Estonia) have induced the “slow-light” phenomenon in emerald via the transient spectral-hole-burning (THB) process. The group was able to slow light within the emerald down to only 16 km/s. Potential applications include time-resolved spectroscopy, in which spectral-hole widths can be measured as a function of time.
In THB, laser light is used to excite some optical centers in the experimental material from the ground state to an excited state, producing a narrow spectral hole that produces high dispersion at the laser frequency (slow light is often associated with high dispersion). The researchers used a lab-grown pale-green emerald (cooled to 2.2 K) with a path length of 2.5 mm and a polarized external-cavity laser diode emitting at 682.30341 nm, along with a tungsten-halogen bulb, a monochromator, and a photomultiplier tube (PMT) to measure the polarized transmission spectrum. The spectral hole width was measured as a function of time; a pulse delay under a 15.2 mT magnetic field was measured to be 1.54 ±0.2 ns, corresponding to a hole 4.8 ±0.01 MHz wide. Contact Hans Riesen at [email protected].