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

High Speed Pulse Modulation of Injection Lasers at Non-Bias Condition

Dynamic Single-Mode Semiconductor Lasers

Stabilization and control of the operating field mode in injection lasers are very important problems for wider application of the devices. This paper gives a theoretical analysis of the relation between transverse mode control and longitudinal mode behavior in the injection lasers which have undoped active regions. The guided modes are classified into three types, normal guided mode, active guided mode, and leaky mode, owing to guiding mechanism. Cutoff conditions for all types of modes are mentioned. Gain saturation was analyzed on the basis of the density matrix equation. The so-called weakly (partially) inhomogeneous property of the gain saturation was taken into account. The single longitudinal mode operation is expected when the transverse higher modes are in cutoff condition, because the suppression effect among the resonant modes is promoted. The normal guided mode is the most suitable for the single longitudinal mode operation, because the field profile and diffraction loss are invariable with increasing injection current. The transverse mode control is the most important characteristic in obtaining the single longitudinal mode operation in the injection lasers.

Relation between transverse mode control and longitudinal mode behavior in the injection laser

Parametric gain, the oscillation condition, and output efficiency of optical parametric oscillator are considered. Both the resonant idler case and nonresonant idler case are taken into account with the resonator configuration of a plane and a spherical mirror. A matrix analysis is introduced for this consideration. The gain factor thus reduced is commonly used both for resonant idler and nonresonant idler case. The optimum focusing conditions for maximum gain are derived. The oscillation output power and efficiency are estimated analytically. This treatment is extended to the degenerate four wave interactions. The differences in gains due to the focusing condition and in output efficiencies are compared.

Yasuharu Suematsu

Papers

High Speed Pulse Modulation of Injection Lasers at Non-Bias Condition

Dynamic Single-Mode Semiconductor Lasers

Relation between transverse mode control and longitudinal mode behavior in the injection laser

Focusing Effect on Optical Parametric Oscillations for Three and Four Wave Interactions

1.5-1.6μm Wavelength (100) GaInAsP/InP DH Lasers