RESUMEN
The near-infrared transmission of a semiconductor multiple quantum well is probed under intense terahertz illumination. We observe clear evidence of the intraexcitonic Autler-Townes effect when the terahertz beam is tuned near the 1s-2p transition of the heavy-hole exciton. The strongly coupled effective two-level system has been driven with terahertz field strengths of up to 10 kV/cm resulting in a Rabi energy of ≈0.6 times the transition energy. The induced near-infrared spectral changes at low intensities are qualitatively explained using a basic two-level model.
RESUMEN
Increased coupling is observed in distributed-feedback quantum cascade lasers when placing a shallow second order grating between a continuous surface-plasmon layer and the active region. The combined effect of an air cladding and a metallic layer on the opposite sides of the waveguide increases the overlap with the grating region resulting in calculated coupling coefficients up to 100 cm(-1). The waveguide design was implemented by Au thermo-compression bonding after grating formation and subsequent backside processing of ridges with air claddings. Lasers as short as 176 microm show single-mode behavior with a side-mode-suppression-ratio of 20 dB and thresholds (10 kA/cm(2)) as well as output powers (> 150 mW) close to Fabry-Pérot device performances are reached for 360 microm long devices.
Asunto(s)
Diseño Asistido por Computadora , Rayos Láser , Modelos Teóricos , Refractometría/instrumentación , Simulación por Computador , Diseño de Equipo , Análisis de Falla de Equipo , Retroalimentación , Rayos Infrarrojos , Teoría CuánticaRESUMEN
We present a novel approach for the reversible switching of the emission wavelength of a quantum cascade laser (QCL) using a halochromic cladding. An air-waveguide laser ridge is coated with a thin layer of polyacrylic acid. This cladding introduces losses corresponding to the absorption spectrum of the polymer. By changing the state of the polymer, the absorption spectrum and losses change, inducing a shift of 7 cm(-1) in the emission wavelength. This change is induced by exposure to acidic or alkaline vapors under ambient conditions and is fully reversible. Such lasers can be used as multi-color light source and as sensor for atmospheric pH.
Asunto(s)
Resinas Acrílicas/química , Rayos Láser , Modelos Teóricos , Puntos Cuánticos , Procesamiento de Señales Asistido por Computador/instrumentación , Transductores , Simulación por Computador , Diseño de Equipo , Análisis de Falla de Equipo , Concentración de Iones de Hidrógeno , Luz , Dispersión de RadiaciónRESUMEN
The authors use a quantum well intersubband photodetector fabricated into a two dimensional photonic crystal to investigate the optical defect modes of a single missing hole defect. The modes appear as a local enhancement in spectral photocurrent due to an increased in-coupling of surface incident light when a defect mode is present. The frequencies of these localized modes are tracked as they are varied by the defect geometry and compared to simulations.
Asunto(s)
Diseño Asistido por Computadora , Modelos Teóricos , Óptica y Fotónica/instrumentación , Fotometría/instrumentación , Resonancia por Plasmón de Superficie/instrumentación , Transductores , Simulación por Computador , Cristalografía/métodos , Conductividad Eléctrica , Diseño de Equipo , Análisis de Falla de Equipo , Luz , Fotometría/métodosRESUMEN
We demonstrate an In(0.635)Al(0.356)As/In(0.678)Ga(0.322)As strain compensated quantum cascade laser that employs heterogeneous injector regions for low voltage defect operation. The active core consists of interdigitated undoped and doped injectors followed by nominally identical wavelength optical transitions. The undoped injector regions are designed with reduced voltage defect while the doped injectors are of a more conventional design. The measured average voltage defect is less than 79 meV. At 80 K, a 2.3 mm long, back facet high reflectance coated laser has an emission wavelength of 4.7 mum and outputs 2.3 W pulsed power with a peak wall-plug efficiency of 19%.