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

Measurement of Zn Doping Level in InGaAsP/InP DH Lasers

The focussing effect of Hyperbolic-type Gas Lens which was proposed by the authors for light beam waveguide is examined experimentally. Six types of experimental gas lens with different separation of poles 2a are made, and the temperature distribution on the heat conductive poles and in the gas medium is measured. The focussing characteristics of these types of gas lens are examined using the Gaussian light beam from a He-Ne gas laser. It is concluded that the focussing power is limited by the natural convection of the gas when the temperature difference between the poles is increased, and it is found that the critical temperature difference 2ΔTc above which the gas lens does not work normally is determined only by the separation 2a between the poles. The relation between them is formulated experimentally as follows; ΔT_c\cong42/a^1.34, 20\gtrsima\gtrsim5 (mm)ΔT_c\cong83/a^1.74, 2\lesssima\lesssim5 (mm). This formulation serves as the data for the design of the waveguide using this tpye of gas lens.

Experimental Studies on the Limitation of Focussing Power of Hyperbolic-Type Gas Lens

A new GaInAsP/InP injection laser with buried heterostructure fabricated by single-step epitaxial growth on a mesa substrate is reported. Single longitudinal-mode operation up to 1.4 times the threshold current Ith and linear light-output/current characteristics up to 3Ith are observed at 1.27 ?m.

Mesa-substrate buried heterostructure GaInAsP/InP injection lasers

PURPOSE:To contrive the improvement of life time and reliability and enable the laser oscillation in a wide range of wavelengths including yellow to red and further near infrared by a method wherein a double hetero-junction is formed of five element mixed crystal compound semiconductor. CONSTITUTION:A clad layer 2 constituted of (Alz'Ga1-z')x'In1-x'ASy'P1-y' as the five element mixed crystal has a structure of crystal growth on a substrate 1 constituted of (100)GaAs as two element mixed crystal so as to take lattice alignment therewith, and further an active layer 3 constituted of (AlxGa1-z)x In1-xASyP1-y as the five element mixed crystal has a structure of crystal growth on this clad layer 2 so as to take lattice alignment therewith in the same manne. Besides, a clad layer 4 constituted of (Alx'Ga1-z')x'In1-x'ASy'P1-y' has a structure of crystal growth on the active layer 3 so as to take lattice alignment therewith. Since Al, Ga, In, and P are contained, and As is contained in the five- element mixed crystal, the problem of meltback, miscibility gap, etc. do not occur in the process of crystal growth.

Yasuharu Suematsu

Papers

Measurement of Zn Doping Level in InGaAsP/InP DH Lasers

Experimental Studies on the Limitation of Focussing Power of Hyperbolic-Type Gas Lens

Mesa-substrate buried heterostructure GaInAsP/InP injection lasers

Visible light semiconductor laser

Contributors, Aug. 1972