Optical detection and spatial modulation of mid-infrared surface plasmon polaritons in a highly doped semiconductor

Highly doped semiconductors (HDSCs) are promising candidates for plasmonic applications in the mid-infrared (MIR) spectral range. This work examines a recent addition to the HDSC family, the dilute nitride alloy In(AsN). Post-growth hydrogenation of In(AsN) creates a highly conducting channel near the surface and a surface plasmon polariton detected by attenuated total reflection techniques. The suppression of plasmonic effects following a photo-annealing of the semiconductor is attributed to the dissociation of the N-H bond. This offers new routes for direct patterning of MIR plasmonic structures by laser writing

Quantum Cascade Lasers in the InAs/AlSb Material System

International audienceWe review the current state of the InAs/AlSb quantum cascade laser (QCL) technology. These materials have brought significant progress in short wavelength QCL due to the high-conduction band offset. The first QCLs emitting below 3 mu m have been demonstrated in this system. The short wavelength limit of QCL operation has further been moved down to 2.6 mu m. This system is also well suited for far-infrared QCLs because high intersubband gain can be achieved at low transition energies due to the small electron effective mass in InAs. Room temperature operation has been demonstrated in InAs-based QCLs to a wavelength of 21 mu m, for the first time for any semiconductor laser emitting above 16 mu m. Both short-and long-wavelength single-frequency distributed feedback InAs/AlSb QCLs have been realized, as well as widely tunable external cavity sources for the 3-3.5 mu m spectral range

Long Wavelength (λ > 17 µm) Distributed Feedback Quantum Cascade Lasers Operating in a Continuous Wave at Room Temperature

The extension of the available spectral range covered by quantum cascade lasers (QCL) would allow one to address new molecular spectroscopy applications, in particular in the long wavelength domain of the mid-infrared. We report in this paper the realization of distributed feedback (DFB) QCLs, made of InAs and AlSb, that demonstrated a continuous wave (CW) and a single mode emission at a wavelength of 17.7 µm, with output powers in the mW range. This is the longest wavelength for DFB QCLs, and for any QCLs or semiconductor lasers in general, operating in a CW at room temperature

InAs-Based Quantum Cascade Lasers with Extremely Low Threshold

We report InAs-based quantum cascade lasers (QCLs) operating near 14 µm with a threshold current density Jth as low as 0.6 kA/cm2 at room temperature. The threshold obtained is lower than the Jth of the best reported InP-based QCLs to date without facet treatment. The achieved performance improvement is partially due to an increased separation between the upper transition level and the next one in the active quantum wells of the employed QCL design

InAs-Based Quantum Cascade Lasers with Extremely Low Threshold

We report InAs-based quantum cascade lasers (QCLs) operating near 14 µm with a threshold current density Jth as low as 0.6 kA/cm2 at room temperature. The threshold obtained is lower than the Jth of the best reported InP-based QCLs to date without facet treatment. The achieved performance improvement is partially due to an increased separation between the upper transition level and the next one in the active quantum wells of the employed QCL design

Nanotransistor based THz plasma detectors: low tempeatures, graphene, linearity, and circular polarization studies

Nanometer size field effect transistors can operate as efficient resonant or broadband terahertz detectors, mixers, phase shifters and frequency multipliers at frequencies far beyond their fundamental cut-of frequency. This work is an overview of some recent results concerning the low temperatures operation, linearity, and circular polarization studies of nanometer scale field effect transistors for the detection of terahertz radiation. Also first results on graphene transistors are discussed

Short Duplex Module Coupled to G-Quadruplexes Increases Fluorescence of Synthetic GFP Chromophore Analogues

Aptasensors became popular instruments in bioanalytical chemistry and molecular biology. To increase specificity, perspective signaling elements in aptasensors can be separated into a G-quadruplex (G4) part and a free fluorescent dye that lights up upon binding to the G4 part. However, current systems are limited by relatively low enhancement of fluorescence upon dye binding. Here, we added duplex modules to G4 structures, which supposedly cause the formation of a dye-binding cavity between two modules. Screening of multiple synthetic GFP chromophore analogues and variation of the duplex module resulted in the selection of dyes that light up after complex formation with two-module structures and their RNA analogues by up to 20 times compared to parent G4s. We demonstrated that the short duplex part in TBA25 is preferable for fluorescence light up in comparison to parent TBA15 molecule as well as TBA31 and TBA63 stabilized by longer duplexes. Duplex part of TBA25 may be partially unfolded and has reduced rigidity, which might facilitate optimal dye positioning in the joint between G4 and the duplex. We demonstrated dye enhancement after binding to modified TBA, LTR-III, and Tel23a G4 structures and propose that such architecture of short duplex-G4 signaling elements will enforce the development of improved aptasensors

Semiconductor nanowire field-effect transistors: towards high-frequency THz detectors

We report about fabrication and characterization of semiconductor nanowire-based field effect transistor devices which can act as detectors for electromagnetic radiation in the THz frequency range. The detection mechanism is based on the nonlinear transfer characteristic of the transistor, which is used to realize signal rectification; the small capacitance related to the nanowire small cross section is beneficial in allowing a good device sensitivity up to 1.5 THz at room temperature. Due to the extreme flexibility with which semiconductor nanowires can be grown, we discuss how the basic, homogeneous InAs or InSb nanowire FETs can be improved to realize smarter devices and functionalities