58 research outputs found
Experimental demonstration of a high quality factor photonic crystal microcavity
Sub-threshold measurements of a photonic crystal (PC) microcavity laser
operating at 1.3 microns show a linewidth of 0.10 nm, corresponding to a
quality factor Q ~ 1.3x10^4. The PC microcavity mode is a donor-type mode in a
graded square lattice of air holes, with a theoretical Q ~ 10^5 and mode volume
Veff ~ 0.25 cubic half-wavelengths in air. Devices are fabricated in an
InAsP/InGaAsP multi-quantum well membrane and are optically pumped at 830 nm.
External peak pump power laser thresholds as low as 100 microWatts are also
observed
Unidirectional mode selection in bistable quantum cascade ring lasers
Ideal ring resonators are characterized by travelling-wave counterpropagating
modes, but in practice travelling waves can only be realized under
unidirectional operation, which has proved elusive. Here, we have designed and
fabricated a monolithic quantum cascade ring laser coupled to an active
waveguide that allows for robust, deterministic and controllable unidirectional
operation. Spontaneous emission injection through the active waveguide enables
dynamical switching between the clockwise and counterclockwise states of the
ring laser with as little as 1.6% modulation of the electrical input. We show
that this behavior stems from a perturbation in the bistable dynamics of the
ring laser. In addition to switching and bistability, our novel coupler design
for quantum cascade ring lasers offers an efficient mechanism for outcoupling
and light detection.Comment: 13 pages, 6 figures, submitted to journa
High-Power Directional Emission from Microlasers with Chaotic Resonators
High-power and highly directional semiconductor cylinder-lasers based on an
optical resonator with deformed cross section are reported. In the favorable
directions of the far-field, a power increase of up to three orders of
magnitude over the conventional circularly symmetric lasers was obtained. A
"bow-tie"-shaped resonance is responsible for the improved performance of the
lasers in the higher range of deformations, in contrast to
"whispering-gallery"-type modes of circular and weakly deformed lasers. This
resonator design, although demonstrated here in midinfrared quantum-cascade
lasers, should be applicable to any laser based on semiconductors or other
high-refractive index materials.Comment: Removed minor discrepancies with published version in the text and in
Fig.
Thermoheliodome Testing: Evaluation Methods for Testing Directed Radiant Heat Reflection☆
Abstract The Thermoheliodome is a prototype experimental pavilion that produces comfort through the manipulation of the mean radiant temperature generated by a combination of evaporative cooling and radiant heat reflection. We present the development of a sensing and analysis method for measuring the impact on radiant temperature and other performance data for the space, along with the initial system measurements. This is an environmental control station through which low cost microcontrollers enable distributed networked nodes to take measurements of relevant system parameters. The system measurements show a reduction of mean radiant temperature by 2-3 °C using evaporative cooling and strategic reflection
Lasing mode pattern of a quantum cascade photonic crystal surface-emitting microcavity laser
The identification of the lasing mode within a quantum cascade photonic crystal microcavity laser emitting at λ ~8 µm is presented. The symmetry of the lasing mode is determined by the position of nodal lines within micro-bolometer camera measurements of its polarized spatial distribution. Full three-dimensional finite-difference time-domain simulations are also performed, and the resulting vertically emitted radiation field pattern is seen to follow the experimental results closely
Quantum Cascade Surface-Emitting Photonic Crystal Laser
We combine photonic and electronic band structure engineering to create a surface-emitting quantum cascade microcavity laser. A high-index contrast two-dimensional photonic crystal is used to form a micro-resonator that simultaneously provides feedback for laser action and diffracts light vertically from the surface of the semiconductor surface. A top metallic contact allows electrical current injection and provides vertical optical confinement through a bound surface plasmon wave. The miniaturization and tailorable emission properties of this design are potentially important for sensing applications, while electrical pumping can allow new studies of photonic crystal and surface plasmon structures in nonlinear and near-field optics
Quantum cascade photonic-crystal microlasers
We describe the realization of Quantum Cascade photonic-crystal microlasers. Photonic and electronic bandstructure engineering are combined to create a novel Quantum Cascade microcavity laser source. A high-index contrast two-dimensional photonic crystal forms a micro-resonator that provides feedback for laser action and diffracts light vertically from the surface of the semiconductor chip. A top metallic contact is used to form both a conductive path for current injection as well as to provide vertical optical confinement to the active region through a bound surface plasmon state at the metal-semiconductor interface. The device is miniaturized compared to standard Quantum Cascade technology, and the emission properties can in principle be engineered by design of the photonic crystal lattice. The combination of size reduction, vertical emission, and lithographic tailorability of the emission properties enabled by the use of a high-index contrast photonic crystal resonant cavity makes possible a number of active sensing applications in the mid- and far-infrared. In addition, the use of electrical pumping in these devices opens up another dimension of control for fundamental studies of photonic crystal and surface plasmon structures in linear, non-linear, and near-field optics
Mid-IR quantum cascade lasers and amplifiers: recent developments and applications
This talk will give an overview of the most recent results on the realization of new quantum cascade laser devices and the perspective of their innovative applications in the mid-infrared range of the spectrum
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