Room-temperature laser action from Cr(2+)-doped Cd(0.85)Mn(0.15)Te has been demonstrated for what is believed to be the first time. We achieved pulsed laser operation centered at ~2.5mu m by pumping into the mid-infrared absorption band of Cr(2+) ions by use of the 1.907- mum output of a H(2) Raman-shifted Nd:YAG laser. The output of the free-running Cr(2+):Cd(0.85)Mn(0.15)Te laser had a width of ~50 nm (FWHM), and the slope efficiency was calculated to be 5.5% under nonoptimum conditions.
A variety of approaches have been used for optical limiting in the past [1–6].A relatively new approach, an electro-optic power limiter (EOPL) has a simple and compact design, wavelength agile sensitivity, the ability to respond to coherent as well as incoherent radiation, low threshold and a large field of view (up to 15°). EOPL devices allow the transmission of low intensity background radiation while simultaneously blocking the damaging high intensity beam. We have demonstrated EOPL in the past using the II-VI semiconductors CdTe:In [7,8], CdTe:V [9] and ZnTe [10]. In this paper, we are reporting on EOPL using a new ternary II-VI semiconductor Cdl-xMnxTe:V. Cd0.55Mn0.45Te is capable of limiting optical radiation from visible (0.630.tm) to near infrared (1.5pm) wavelengths, which covers the wavelength ranges of both CdTe and ZnTe combined. Additionally, crystals of Cd0.55Mn0.45Te are relatively easier to grow than ZnTe. We report our preliminary results of optical limiting in Cd0.55Mn0.45Te:V at 0.780μm, 0.895μm, and 1.06μm, and we discuss the materials issues involved in improving and optimizing Cd1-xMnxTe for electro-optic power limiting.
We review recent experimental advances by the Buffalo group in performing far-infrared magnetospectroscopy under he tuning of applied high hydrostatic pressure. Experiments are reported for the effects of pressure on Si donors in modulation doped GaAs/AlGaAs quantum wells. We clearly observe pressure-mediated competition between free (i.e., Landau level) and bound electron states -the latter arising from both neutral (D 0 ) and charged (D -) donor species. With increasing pressure, there is a progression of the observed spectra from being dominated by cyclotron resonance and the D -singlet (or singlet-like bound magnetoplasmon) transitions, to showing the D0 is →2p+ line. The main reason for this evolution is the decrease in electrons due to the crossover of the Si levels associated with the F (well) and X (barrier) conduction minima. Indeed, for pressures above 30 kbar the Γ(well)-X(barrier) crossover quenches all the transitions. However, we find strong evidence that electrons are independently lost to a trap, which becomes active several kbar below this crossing. A possible candidate for this trap is residual Se impurities in the barriers. We present the results of detailed numerical calculation which are found to agree very well with the measured field dependencies of the cyclotron resonance, D0 and D -transition energies. In the sample with the highest doping, a new transition is observed for fields and pressures above 7.5 T and 5 kbar. Reasons for this apparent anomaly are discussed.
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