Vertical-cavity electrically driven lasers with three GaInAs
quantum wells and diameters of several μm exhibit room-temperature pulsed current thresholds as low as 1.3mA with 958 nm output wavelength.

Low-Threshold Electrically Pumps Vertical-Cavity Surface-Emitting Microlasers

Semiconductors provide some of the most promising materials for nonlinear optics, because of large resonant nonlinearities, control of recombination time (from milliseconds to femtoseconds), well-developed fabrication technologies, and compatibility with other optoelectronic devices. The paper reviews some of the concepts and results that have come from the study of nonlinear optics in semiconductors. The emphasis is on nonlinear absorption and the refractive index that arises from the photo-induced excitation of free carriers. Mechanisms described include state-filling, carrier transport, and photorefractivity. Devices include optical bistability, reflective asymmetric Fabry-Perot all-optical absorptive switches, optically addressed spatial light modulators, and real-time holography. The paper's approach is to provide a basic engineering understanding of the principles, some of the historical details, and a snapshot of the state of the field today.

Resonant optical nonlinearities in semiconductors

Optical bistable behavior in a unidirectional ring cavity (or a Fabry–Perot cavity) containing a semiconductor quantum well, described as a three-level ladder-type system with similar transition energies, has been studied The system interacts with a strong driving field which is in two-photon resonance with the intersubband transition and thus simultaneously drives all three levels into phase-locked quantum coherence The threshold for switching to upper branch of the bistable curve is found to be reduced due to the presence of quantum interference Such system can be used for making efficient and fast all-optical switching devices

Optical bistability in a three-level semiconductor quantum-well system

Enhancement of optical nonlinearity in one-dimensional photonic-crystal structures with a defect is considered theoretically. It is shown that a large enhancement can be obtained for absorption saturation and degenerate four-wave mixing efficiency as a result of large optical field amplitude of the localized photonic-defect mode at the defect layer. The figure of merit of the use of the photonic-crystal structure is derived especially for systems in which the concentration of the nonlinear optical material can be arbitrarily adjusted. Optical bistability is also predicted for optically dense samples. They can be applied in real photonic devices because of their simple structure and the large enhancement obtained.

/pdf/analysis-of-optical-nonlinearity-by-defect-states-in-one-4lwv4oa3i5.pdf

Analysis of optical nonlinearity by defect states in one-dimensional photonic crystals

We have grown a very high finesse microcavity using distributed Bragg reflectors of AlxGa1−xAs and AlAs. The measured Fabry–Perot mode has a linewidth of 0.84 A at 930 nm. This implies a finesse in excess of 5500 and an effective (mirror corrected) finesse greater than 1450. Comparison with theoretical calculations for such a structure shows that (i) the growth rates are stable to 0.25% over 14 h and (ii) the internal losses are less than 1 cm−1.

Ultrahigh finesse microcavity with distributed Bragg reflectors

We report on a novel monolithic all‐optical bistable device operating at 980 nm, based on the dispersive optical nonlinearity of strained InGaAs/GaAs quantum wells located at the antinodes of the microcavity optical field. This design maximizes the interaction with the intracavity field and allowed to use only twelve quantum wells of 10 nm thickness. The first observation of all‐optical bistability with strained InGaAs/GaAs quantum wells is reported, with a contrast ratio of 7:1 and a threshold intensity of 1 kW/cm2. The operating wavelength offers key advantages such as the substrate transparency and compatibility with vertical cavity surface emitting lasers.

Optical bistability at 980 nm in a strained InGaAs/GaAs multiple quantum well microcavity with resonant periodic nonlinearity

The saturation behavior of the nonlinear index δnNL in the band tail of GaAs/AlGaAs multiple quantum wells is experimentally studied in quasi‐steady state and in a low absorption region (below 300 cm−1), where dispersive optical bistability is observed. Measurements at different detunings from the exciton resonance allow us to study the absorption dependence of the saturation parameters. The saturation intensity IS is found inversely proportional to the linear absorption coefficient, while the saturating nonlinear index δnS is approximately constant. This evidences that the nonlinear index saturation is due to a saturation of the carrier density versus light intensity, due to the saturation of the band tail absorption itself.

Origin of the nonlinear index saturation in the band tail absorption region of GaAs/AlGaAs multiple quantum wells

Epitaxial microcavity devices, such as surface emitting lasers [1,2], vertical cavity modulators [3,4], and all-optical bistable microresonators [5,6], are currently subject to a lot of interest for their potential application in photonic switching Due to their small active volume and their optical access perpendicular to the surface, they can be integrated as two-dimensional arrays, with a device density of 106 devices/cm2 or larger Such arrays of all-optical bistable devices could be useful as opto-optical modulators, wavelength converters, optical logic gates, or fast access digital optical memories

D. Pellat

Papers

Optical bistability at 980 nm in a strained InGaAs/GaAs multiple quantum well microcavity with resonant periodic nonlinearity

Origin of the nonlinear index saturation in the band tail absorption region of GaAs/AlGaAs multiple quantum wells

Optical Bistability in Quantum Well Semiconductor Devices