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We studied the photoelectromagnetic (PEM) effect induced by laser terahertz radiation in $\text{Pb}_{1_{-x}}\text{Sn}_{x}\text{Te}$ films in the composition range $x=(0.15-0.45)$ . A transition from the trivial phase to the topological crystalline insulator phase occurs within this composition interval at $x=0.35$ . The films had the crystallographic orientation $ $ , for which the appearance of topologically nontrivial surface states is expected. It was found that in the trivial phase, the amplitude of the PEM effect is determined by the power of the incident radiation, while in the topological phase, the amplitude is proportional to the flux of laser radiation quanta. Possible mechanism leading to the observed effect is discussed.

Here, we present the first vertical external cavity surface emitting lasers (VECSELs) based on quantum dot (QD) active regions and operating in the wavelength range above 2.8 μm.

Pump-probe transmission experiments have been performed on PbSe above the fundamental absorption edge near 4 μm in the temperature range 30 to 300 K, using the Dutch ps free-electron laser. For temperatures below 200 K and carrier densities above the threshold for stimulated emission, stimulated recombination represents the most efficient recombination mechanism with relatively fast kinetics in the 50–100-ps regime, in good agreement with earlier reports of photoluminescent emission. Above this temperature Auger recombination dominates, and the Auger coefficient C is determined from the pump-probe decay curves. In the low-temperature regime the Auger coefficient is determined from the decay curves at times beyond 100 ps. The Auger coefficient is approximately constant (with a value of about 8×10-28 cm6 s-1) between 300 and 70 K, and then drops a value of about 1×10-28 cm6 s-1 at 30 K, in good agreement with the theory for nonparabolic near-mirror bands and nondegenerate statistics. It is found that C for PbSe is between one and two orders of magnitude lower than for Hg1-xCdxTe of comparable band gap.

In this paper, we present a comparison between IV-VI vertical-cavity surface-emitting lasers (VCSELs) containing active regions of different dimensionality but with a nearly identical optical design of the cavity. In addition, the same optical set-up as well as pump source was used for laser excitation and characterization. This allows studying the influence of the dimensionality of the active material on the laser properties.

In this paper we present the fs time resolved two-color pump-probe experiments performed in the mid-infrared region. The pump beam was at a wavelength of 2 /spl mu/m well above the Bragg mirror and the probe beam was at 3.76 /spl mu/m. The transmission spectra measured by the weak probe beam are shown for various delay times in respect to the pump pulse.