I. Gravé

Bio: I. Gravé is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Quantum well & Laser. The author has an hindex of 9, co-authored 17 publications receiving 271 citations.

Voltage‐controlled tunable GaAs/AlGaAs multistack quantum well infrared detector

Abstract: We describe a new type of intersubband GaAs/AlGaAs infrared detector consisting of three stacks of quantum wells; the quantum wells in a given stack are identical, but are different from stack to stack. Each stack is designed to yield an absorption and a photoresponse at a different peak wavelength. The resulting device is an infrared detector which can operate in a number of modes. Among the features of this device are a wide‐band detection domain, a tunable response and excellent responsivities and noise figures. The tunable operation includes a sharp peak‐switching response which follows the formation, expansion, and readjustment of electric field domains within the multiquantum well region.

Observation of phase conjugation at 10.6 μm via intersubband third‐order nonlinearities in a GaAs/AlGaAs multi‐quantum‐well structure

Abstract: We describe the observation of phase conjugation at 10.6 μm in a GaAs/AlGaAs multi‐quantum‐well‐doped structure. The responsible nonlinear susceptibility χ(3) is due to a nearly resonant intersubband transition. The magnitude of χ(3) is 7×10−5 esu and the phase conjugate reflectivity is a few tenths of a percent.

Observation of third‐order intersubband dc Kerr effect at the midinfrared wavelengths in GaAs quantum wells

Abstract: We report on the first observation of third‐order intersubband nonlinearities in a quantum well structure. We have measured the dc Kerr effect in a symmetric quantum well and found that the Kerr coefficients due to intersubband transitions are six orders of magnitude larger than that of bulk GaAs. To our best knowledge this is the largest value ever measured for the third‐order susceptibility. By including dc screening effects and evaluating the internal electric field in the well, a good agreement between the calculated coefficients and the experimental ones was found.

A Monolithic Integration of a Resonant Tunneling Diode and a Quantum Well Semiconductor Laser

Abstract: A monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported. Negative differential resistance and negative differential optical response are observed at room temperature. The device displays bistable electrical and optical characteristics which are voltage controlled. Operation as a two‐state optical memory is demonstrated.

Monolithic integration of a resonant tunneling diode and a quantum well semiconductor laser

Abstract: A monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported. Negative differential resistance and negative differential optical response are observed at room temperature. The device displays bistable electrical and optical characteristics which are voltage controlled. Operation as a two‐state optical memory is demonstrated.

Recent progress in quantum cascade lasers and applications

Abstract: Quantum cascade (`QC') lasers are reviewed. These are semiconductor injection lasers based on intersubband transitions in a multiple-quantum-well (QW) heterostructure, designed by means of band-structure engineering and grown by molecular beam epitaxy. The intersubband nature of the optical transition has several key advantages. First, the emission wavelength is primarily a function of the QW thickness. This characteristic allows choosing well-understood and reliable semiconductors for the generation of light in a wavelength range unrelated to the material's energy bandgap. Second, a cascade process in which multiple - often several tens of - photons are generated per electron becomes feasible, as the electron remains inside the conduction band throughout its traversal of the active region. This cascading process is behind the intrinsic high-power capabilities of the lasers. Finally, intersubband transitions are characterized through an ultrafast carrier dynamics and the absence of the linewidth enhancement factor, with both features being expected to have significant impact on laser performance. The first experimental demonstration by Faist et al in 1994 described a QC-laser emitting at 4.3 µm wavelength at cryogenic temperatures only. Since then, the lasers' performance has greatly improved, including operation spanning the mid- to far-infrared wavelength range from 3.5 to 24 µm, peak power levels in the Watt range and above-room-temperature (RT) pulsed operation for wavelengths from 4.5 to 16 µm. Three distinct designs of the active region, the so-called `vertical' and `diagonal' transition as well as the `superlattice' active regions, respectively, have emerged, and are used either with conventional dielectric or surface-plasmon waveguides. Fabricated as distributed feedback lasers they provide continuously tunable single-mode emission in the mid-infrared wavelength range. This feature together with the high optical peak power and RT operation makes QC-lasers a prime choice for narrow-band light sources in mid-infrared trace gas sensing applications. Finally, a manifestation of the high-speed capabilities can be seen in actively and passively mode-locked QC-lasers, where pulses as short as a few picoseconds with a repetition rate around 10 GHz have been measured.

Intersubband transitions in quantum wells

Abstract: The potential energy profile in semiconductor heterostructures can now be controlled in a fascinating way that could barely be dreamed of twenty years ago 1. When dealing with interband optical transitions, additional features related to electron-hole interactions (see for instance exciton descriptions in this book) are coming into play and the one-electron wavefunctions and energy levels may fail to describe or predict experimental results. Moreover, the quantization energy is usually small compared to the forbidden band gap, so that typical interband transitions always occur in the same energy range for a given materials pair. On the contrary, intersubband transitions (ISBT) are very sensitive to the exact potential profile and transitions have been observed at wavelengths between lμm and 100μm. In addition, they can be quantitatively described by a simple formalism based on one-electron approaches and many-body effects usually appear as small corrections only. Since 19852, many devices have been designed according to this quantum engineering and have shown unsurpassed properties3. Various materials have been successfully used for these quantum well (QW) heterostructures: GaAs/AlGaAs, InP/InGaAs/InAlAs, Si/SiGe, D/VI compounds…We will focus here on the GaAs/AlGaAs system which has been the most widely studied. First, the calculation of the ISBT matrix element will evidence two major characteristic properties: the optical transitions take advantage of giant dipoles but must verify in the same time a rather drastic selection rule. Then, examples will be given in different fields of application: detection, modulation and emission. Some interesting aspects of coupling and propagation in these structures involve a photon mode density alteration. Finally, a detailed study of second order non linearities will exemplify the beauty of quantum engineering for improving optical properties.

Non-linear dynamics of semiconductor superlattices

Abstract: In the last decade, non-linear dynamical transport in semiconductor superlattices (SLs) has witnessed significant progress in theoretical descriptions as well as in experimentally observed non-linear phenomena. However, until now, a clear distinction between non-linear transport in strongly and weakly coupled SLs was missing, although it is necessary to provide a detailed description of the observed phenomena. In this review, strongly coupled SLs are described by spatially continuous equations and display self-sustained current oscillations due to the periodic motion of a charge dipole as in the Gunn effect for bulk semiconductors. In contrast, weakly coupled SLs have to be described by spatially discrete equations. Therefore, weakly coupled SLs exhibit a more complex dynamical behaviour than strongly coupled ones, which includes the formation of stationary electric field domains, pinning or propagation of domain walls consisting of a charge monopole, switching between stationary domains, self-sustained current oscillations due to the recycling motion of a charge monopole and chaos. This review summarizes the existing theories and the experimentally observed non-linear phenomena for both types of semiconductor SLs.

Progress in long-wavelength strained-layer InGaAs(P) quantum-well semiconductor lasers and amplifiers

Abstract: The progress in long-wavelength compressively and tensile-strained InGaAs(P) quantum-well semiconductor lasers and amplifiers is reviewed. By the application of grown-in strain, the device performance is considerably improved such that conventional bulk and unstrained quantum-well active-layer devices are outperformed, while a high reliability is maintained. >

New frontiers in quantum cascade lasers and applications

Abstract: Recent advances and new directions in quantum cascade (QC) lasers are discussed. Invented in 1994 following many years of research on band-structure engineered semiconductors and devices grown by molecular beam epitaxy, this fundamentally new laser has rapidly advanced to a leading position among midinfrared semiconductor lasers in terms of wavelength agility as well as power and temperature performance. Because of the cascaded structure, QC lasers have a slope efficiency proportional to the number of stages. Devices with 100 stages having a record peak power of 0.6 W at room temperature are reported. QC lasers in the AlInAs-GaInAs lattice matched to InP material system can now be designed to emit in the whole midinfrared range from 4 to 20 /spl mu/m by appropriately choosing the thickness of the quantum wells in the active region. Using strained AlInAs-GaInAs, wavelengths as short as 3.4 /spl mu/m have been produced. New results on QC lasers emitting at 19 /spl mu/m, the longest ever realized in a III-V semiconductor laser, are reported. These devices use innovative plasmon waveguides to greatly enhance the mode confinement factor, thereby reducing the thickness of the epitaxial material. By use of a distributed feedback (DFB) geometry, QC lasers show single-mode emission with a 30-dB side-mode suppression ratio. Broad continuous single-mode tuning by either temperature or current has been demonstrated in these DFB QC lasers at wavelengths in two atmospheric windows (3-5 and 8-13 /spl mu/m), with continuous-wave linewidths <1 MHz when free running and /spl sim/10 KHz with suitable locking to the side of a molecular transition. These devices have been used in a number of chemical sensing and spectroscopic applications, demonstrating the capability of detecting parts per billion in volume of several trace gases. Sophisticated band-structure engineering has allowed the design and demonstration of bidirectional lasers. These devices emit different wavelengths for opposite bias polarities. The last section of the paper deals with the high-speed operation of QC lasers. Gain switching with pulse widths /spl sim/50 ps and active modelocking with a few picosecond-long pulses have been demonstrated. Finally, a new type of passive modelocking has been demonstrated in QC lasers, which relies on the giant and ultrafast optical Kerr effect of intersubband transitions.