Ref HAL: hal-00378539_v1
Ref Arxiv: 0901.2712
DOI: 10.1103/PhysRevB.80.121304
WoS: 000270383300007
Ref. & Cit.: NASA ADS
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29 Citations
Résumé:

The photovoltaic effect induced by terahertz radiation in a gatedtwo-dimensional electron gas in magnetic field is considered theoretically. Itis assumed that the incoming radiation creates an ac voltage between the sourceand gate and that the gate length is long compared to the damping length ofplasma waves. In the presence of pronounced Shubnikov-de Haas oscillations, animportant source of non-linearity is the oscillating dependence of the mobilityon the ac gate voltage. This results in a photoresponse oscillating as afunction of magnetic field, which is enhanced in the vicinity of the cyclotronresonance, in accordance with recent experiments. Another, smooth component ofthe photovoltage, unrelated to SdH oscillations, has a maximum at cyclotronresonance.

Commentaires: 4 pages, 3 figures

DOI: 10.1134/S1063782609050261
WoS: 000265835000026
1 Citation
Résumé:

Lasers that emit in the 1.3 mu m wavelength range and include the active region based on InAs quantum dots were grown by the method of molecular-beam epitaxy and have been studied. The cavity includes a multilayer interference reflector, which brings about the fact that a large factor of optical confinement and low leakage losses are obtained only for the light propagating at some angle and, consequently, having a strictly definite wavelength. It is shown that, due to the use of such a waveguide structure, the temperature shift of the lasing wavelength is 0.2 nm/K, which is 2.5 times smaller than this shift in the lasers with quantum dots and with a conventional structure of the waveguide. The lasers with the stripe-contact width W = 10 mu m exhibited the spatially single-mode emission, which verifies the advantages of the suggested nonconventional structure of the optical waveguide.

DOI: 10.1103/PhysRevB.80.085314
WoS: 000269639300075
5 Citations
Résumé:

The hole states in the valence band of a large class of semiconductors are degenerate in the projections of angular momentum. Here we show that the switching of a hole between the states can efficiently be realized by acoustic solitons. The microscopic mechanism of such a state conversion is related to the valence-band splitting by local elastic strain. The conversion is studied here for heavy holes localized at shallow and deep acceptors in silicon quantum wells.

Résumé:

We discuss wavelength stabilized all-epitaxial Tilted Cavity Lasers (TCLs). Optical cavity of a TCL favors propagation of only one tilted optical mode ensuring wavelength-selective operation. The possibility of full control of the thermal shift of the lasing wavelength d lambda/dT in TCL including positive, zero or negative shift, is proved theoretically. Broad-area (100 mu m) 970-nm-range devices have been fabricated showing a high temperature stability of the lasing wavelength (0.13 nm/K), a high power operation (>7 W in pulsed mode and >1.5 W in continuous wave (cw) mode), and a narrow vertical far-field beam divergence (FWHM similar to 20 degrees). Single transverse mode edge-emitting 4 mu m-wide-ridge TCLs demonstrated high-power spatial and spectral single mode cw operation with a longitudinal side mode suppression ratio (SMSR) up to 41.3 dB at 93 mW output power. Such a result is similar to the best values achieved for DFB lasers in the same spectral range, while no etching and overgrowth is used in present case.

DOI: 10.1088/0268-1242/22/9/014
WoS: 000249755900015
14 Citations
Résumé:

We address design and performance issues of a 975 nm range tilted cavity laser ( TCL) based on GaAs/GaAlAs waveguide and GaInAs quantum wells as an active medium. The all-epitaxial design of a TCL includes a cavity and a multilayer interference reflector (MIR). The cavity and the MIR are constructed as follows. The cavity confines one tilted optical mode, and the wavelength of this mode as a function of the tilt angle follows a first dispersion curve. The reflectivity spectrum of the MIR for tilted incidence of light has a well-pronounced stopband, and the stopband reflectivity maximum follows a second dispersion curve. The two dispersion curves intersect at one optimum tilt angle and one optimum wavelength lambda(0). At the wavelength lambda(0) the leakage loss of the optical mode through the MIR to the substrate has a minimum, which favors lasing at this optimum wavelength. The thermal shift of lambda(0) is governed by the shift of the intersection point. As the photon energy corresponding to the operation wavelength of the laser 975 nm is close to the resonance with the electronic energy gap in GaAs, the refractive index temperature coefficient dn/dT of GaA1As strongly increases at the GaAs side. This gives a tool to control the thermal shift of lambda(0) by replacing some layers of the cavity by a superlattice containing narrow insertions of GaAs. Such a superlattice may have the same averaged refractive index at room temperature, but significantly different values of dn/dT, thus affecting the thermal shift of lambda(0). Within this approach broad-area ( 100 mu m) devices have been fabricated showing a high temperature stability of the lasing wavelength ( 0.13 nm K-1), low threshold current density ( 300 A cm(-2)), a high power operation (> 7 W in pulsed mode and > 1.5 W in continuous wave mode), a high spectral stability at high output power, and a narrow vertical far-field beam divergence ( FWHM similar to 20 degrees).

Résumé:

We report the possibility to realize complete thermal stabilization of the lasing wavelength lambda(opt) in an all-epitaxial tilted cavity semiconductor laser, wherein the lasing wavelength is governed by the maximum resonance transparency of a lossy waveguide. When the positive temperature coefficient of the refractive index dn/dT is a non-linear function of the alloy composition, which is the case in most semiconductor alloys, there exists the possibility to achieve ultimate control of the resonance transparency wavelength. The thermal shift d lambda(opt)/dT can be positive, zero, or negative. An absolute thermal stabilization of the lasing wavelength is unique as compared to any conventional type of lasers.

DOI: 10.1088/0268-1242/22/4/014
WoS: 000246104100014
15 Citations
Résumé:

We report the possibility of realizing complete thermal stabilization of the resonance transparency wavelength lambda(char) in a planar multilayer tilted cavity waveguide. When the positive temperature coefficient of the refractive index dn/dT is a nonlinear function of the alloy composition, which is the case in most semiconductor alloys, there exists the possibility of achieving complete control of the resonance transparency wavelength. The thermal shift d lambda(char)/dT can be positive, zero or negative. Our result applies quite generally to optical waveguides, etalons, filters, semiconductor lasers and optical amplifiers, potentially extending the performance of the devices and their application range.