The development of optical gain in chemically synthesized semiconductor nanoparticles (nanocrystal quantum dots) has been intensely studied as the first step toward nanocrystal quantum dot lasers. We examined the competing dynamical processes involved in optical amplification and lasing in nanocrystal quantum dots and found that, despite a highly efficient intrinsic nonradiative Auger recombination, large optical gain can be developed at the wavelength of the emitting transition for close-packed solids of these dots. Narrowband stimulated emission with a pronounced gain threshold at wavelengths tunable with the size of the nanocrystal was observed, as expected from quantum confinement effects. These results unambiguously demonstrate the feasibility of nanocrystal quantum dot lasers.

http://science.sciencemag.org/content/sci/290/5490/314.full.pdf

Optical gain and stimulated emission in nanocrystal quantum dots.

Influences on the semiconductor laser properties of external optical feedback, i.e., return of a portion of the laser output from a reflector external to the laser cavity, have been examined. Experimental observations with a single mode laser is presented with analysis based on a compound cavity laser model, which has been found to explain essential features of the experimental results. In particular, it has been demonstrated that a laser with external feedback can be multistable and show hysteresis phenomena, analogous to those of non-linear Fabry-Perot resonator. It has also been shown that the dynamic properties of injection lasers are significantly affected by external feedback, depending on interference conditions between returned light and the field inside the laser diode.

External optical feedback effects on semiconductor injection laser properties

Slow light with a remarkably low group velocity is a promising solution for buffering and time-domain processing of optical signals. It also offers the possibility for spatial compression of optical energy and the enhancement of linear and nonlinear optical effects. Photonic-crystal devices are especially attractive for generating slow light, as they are compatible with on-chip integration and room-temperature operation, and can offer wide-bandwidth and dispersion-free propagation. Here the background theory, recent experimental demonstrations and progress towards tunable slow-light structures based on photonic-band engineering are reviewed. Practical issues related to real devices and their applications are also discussed. The unique properties of wide-bandwidth and dispersion-free propagation in photonic-crystal devices have made them a good candidate for slow-light generation. This article gives the background theory of slow light, as well as an overview of recent experimental demonstrations based on photonic-band engineering.

/pdf/slow-light-in-photonic-crystals-59fjoaj79v.pdf

Slow light in photonic crystals

1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

An overview of analog microwave photonics will be presented. The performance requirements for externally-modulated analog microwave photonic links will be reviewed with specific emphasis placed on modulator efficiency, laser noise, detected photocurrent, and link linearity.

http://ieeexplore.ieee.org/iel5/6387506/6403300/06403360.pdf

Microwave photonics

Transmission and reflection characteristics and wavelength chirping of a guided mode in a semiconductor intersectional optical switch-modulator are analyzed by considering the electric field-induced refractive index variation along with the absorption loss variation. The refractive index and absorption ratio, alpha /sub p/, is shown to determine the performance of the switch-modulator. A transmission port is suitable for a modulation with a high extinction ratio, low insertion loss, and small wavelength chirping. The insertion loss at the reflection port depends heavily on alpha /sub p/. A low insertion loss and high extinction ratio intersectional optical switch is possible when - alpha /sub p/ is higher than 10, which can be realized with a quantum box structure. >

Analysis of semiconductor intersectional waveguide optical switch-modulator

1.53 μm GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector (BH-DBR-ITG laser) was directly modulated with microwave modulation current superimposed on a DC bias which was fixed at 1.1 times the threshold current, and single-wavelength operation was experimentally confirmed with a modulation frequency up to 1 GHz and a modulation depth of 100%.

Single-wavelength operation of 1.53 μm gainasp/inp buried-heterostructure integrated twin-guide laser with distributed bragg reflector under direct modulation up to 1 ghz

A structure utilizing an exponential tapered active layer to improve the saturation output power and quantum efficiency of a traveling-wave semiconductor laser amplifier is discussed. Both the spatial distributions of the carrier density and the optical field are considered in the analysis. It is shown that an optimum taper geometry for maximizing the efficiency exists and that this structure provides simultaneous improvement in the saturation output power (7 dB) and the quantum efficiency (1.5 times) compared to a conventional device.<<ETX>>

A New Structure for High-Power TW-SLA

Conditions of LPE Growth for Lattice Matched GaInAsP/InP DH Lasers with (100) Substrate in the Range of 1.2–1.5 µm

The refractive-index variation with injected carrier density and temperature was measured for GaInAsP/InP b.h. lasers emitting at 1.6 μm. Values of dn/dN = -5.9 × 10-27 m3 and dn/dT = 3 × 10-4/°C resulted. The investigation was based on measurements of the wavelength shift of individual longitudinal modes in the spectra of the lasers.

Yasuharu Suematsu

Papers

Analysis of semiconductor intersectional waveguide optical switch-modulator

Single-wavelength operation of 1.53 μm gainasp/inp buried-heterostructure integrated twin-guide laser with distributed bragg reflector under direct modulation up to 1 ghz

A New Structure for High-Power TW-SLA

Conditions of LPE Growth for Lattice Matched GaInAsP/InP DH Lasers with (100) Substrate in the Range of 1.2–1.5 µm

Measurements of refractive-index variation with free carrier density and temperature for 1.6 μm GaInAsP/InP lasers