A. A. Ukhanov

Comparison of the carrier induced refractive index, gain, and linewidth enhancement factor in quantum dot and quantum well lasers

The spectral dependence of the modal gain and linewidth enhancement factor is measured in an InAs/GaInAs/AlGaAs/GaAs quantum dot (QD) laser and a GaInAs/AlGaAs/GaAs quantum well laser of the same design lacking only the quantum dots. The material differential gain and material differential carrier induced refractive index are found to be about three times smaller in the quantum dot laser than in the quantum well laser. The linewidth enhancement factor is smaller in the QD laser and exhibits considerably less dispersion.

Orientation dependence of the optical properties in InAs quantum-dash lasers on InP

The anisotropy of the modal gain and the linewidth enhancement factor was experimentally measured in InAs/AlGaInAs/InP semiconductor lasers with an active region composed of quantum confined structures in the form of short wires called quantum dashes. This anisotropy is due to the polarization dependence of the transition matrix element in these quantum nanostructures. The spectral dependence of the gain and linewidth enhancement factor was investigated in a wavelength range from 1540 to 1640 nm at subthreshold current densities. The largest gain and the smallest linewidth enhancement factor were obtained when the quantum dashes were oriented perpendicular to the axis of the laser cavity.

Tip-enhanced stimulated Raman scattering with ultra-high-aspect-ratio tips and confocal polarization Raman spectroscopy for evaluation of sidewalls in Type II superlattices FPAs

Actoprobe team had developed custom Tip Enhancement Raman Spectroscopy System (TERS) with specially developed Ultra High Aspect Ratio probes for AFM and TERS measurements for small pixel infrared FPA sidewall characterization. Using this system, we report on stimulated Raman scattering observed in a standard tip-enhanced Raman spectroscopy (TERS) experiment on GaSb materials excited by 637-nm pump laser light. We explain our results by TERS-inherent mechanisms of enormous local field enhancement and by the special design and geometry of the ultrahigh-aspect-ratio tips that enabled conditions for stimulated Raman scattering in the sample with greatly enhanced resonance Raman gain when aided by a microcavity to provide feedback mechanism for the Raman emission. The approach has great potential for further, orders-of-magnitude, progress in TERS enhancement by significantly increasing its nonlinear component. We report development of novel class of probes for atomic force microscopy (AFM active optical probe - AAOP) by integrating a laser source and a photodetector monolithically into the AFM probe. The AAOPs are designed to be used in a conventional AFM and would enhance its functionality to include that of the instruments (NSOM, TERS, hybrid AFM).

Gain and linewidth enhancement factor in InAs-quantum-dot and InAs-quantum-dash laser heterostructures

Optical characteristics are investigated and compared of nanostructure semiconductor lasers with quantum dots and quantum dashes. Spectra of optical gain and of linewidth enhancement factor are obtained. Optical anisotropy in quantum dash structures is investigated.