Lasers and photodetectors for mid-infrared 2–3 μm applications

This paper presents an overview of the recent developments in III–V semiconductor lasers and detectors operating in the 2–3 μm wavelength range, which are highly desirable for various important applications, such as military, communications, molecular spectroscopy, biomedical surgery, and environmental protection. The lasers and detectors with different structure designs are discussed and compared. Advantages and disadvantages of each design are also discussed. Promising materials and structures to obtain high performance lasers and detectors operating in the 2–3 μm region are also suggested.Thanks are due to Australian Research Council for the financial support

The state of commercial augmentative biological control: plenty of natural enemies, but a frustrating lack of uptake

Augmentative biological control concerns the periodical release of natural enemies. In com- mercial augmentative biological control, natural enemies are mass-reared in biofactories for release in large numbers to obtain an immediate control of pests. The history of commercial mass production of natural enemies spans a period of roughly 120 years. It has been a successful, environmentally and eco- nomically sound alternative for chemical pest control in crops like fruit orchards, maize, cotton, sugar cane, soybean, vineyards and greenhouses. Currently, aug- mentative biological control is in a critical phase, even though during the past decades it has moved from a cottage industry to professional production. Many efficient species of natural enemies have been discovered and 230 are commercially available today. The industry developed quality control guidelines, mass production, shipment and release methods as well as adequate guidance for farmers. However, augmentative biological control is applied on a frustratingly small acreage. Trends in research and application are reviewed, causes explaining the limited uptake are discussed and ways to increase application of augmentative biological control are explored

Intermixing of InGaAs/GaAs quantum wells and quantum dots using sputter-deposited silicon oxynitride capping layers

Various approaches can be used to selectively control the amount of intermixing in III-Vquantum well and quantum dotstructures. Impurity-free vacancy disordering is one technique that is favored for its simplicity, however this mechanism is sensitive to many experimental parameters. In this study, a series of silicon oxynitride capping layers have been used in the intermixing of InGaAs/GaAs quantum well and quantum dotstructures. These thin films were deposited by sputter deposition in order to minimize the incorporation of hydrogen, which has been reported to influence impurity-free vacancy disordering. The degree of intermixing was probed by photoluminescence spectroscopy and this is discussed with respect to the properties of the SiOxNyfilms. This work was also designed to monitor any additional intermixing that might be attributed to the sputtering process. In addition, the high-temperature stress is known to affect the group-III vacancy concentration, which is central to the intermixing process. This stress was directly measured and the experimental values are compared with an elastic-deformation model.This work has been made possible with access to the ACT Node of the Australian National Fabrication Facility and through the financial support of the Australian Research Council

Semiconductor Nanolasers

Recent progress in the field of semiconductor nanolasers is discussed. New designs have emerged that eliminate the need for a conventional Fabry-Perot cavity, bringing down the physical dimensions of the lasers below the diffraction limit. Semiconductor nanolasers are critical components for nanophotonics and offer possible integration with Si nanoelectronics

Analysis of optically pumped compact laterally coupled distributed feedback lasers with three symmetric defect regions

This article analyzes compact laterally coupled distributed feedback DFB lasers with three defect regions. These devices are more flexible and smaller than conventional DFB lasers, having typical lengths between 20 and 50 m and a width less than 1 m lateral gratings are inserted in a single-mode waveguide . We optimize the defect regions to achieve an improved performance. In other words, an adequate choice of phase shifts may lead to single-mode operation, lower threshold optical power, higher quantum differential efficiency, and more uniform field distribution. This device is designed to operate under optical pumping

Integration of an InGaAs Quantum-Dot Laser with a Low-Loss Passive Waveguide using Selective-Area Epitaxy

An InGaAs quantum-dot (QD) laser integrated with a low- losswaveguideisdemonstrated. Selective-areaepitaxy isusedto simultaneously form the QDs that form the active region of the laser and quantum wells (QWs) that form the waveguide section of the integrated devices.Thelosses in the activeand passive sections of the integrated devices are 6 and 3 cm-1, respectively. Very low losses in the waveguide section are due to a large difference of 200 meV in the bandgap energies of the selectively grown QDs and QWs

An efficient modeling workflow for high-performance nanowire single-photon avalanche detector

Single-photon detector (SPD), an essential building block of the quantum communication system, plays a fundamental role in developing next-generation quantum technologies. In this work, we propose an efficient modeling workflow of nanowire SPDs utilizing avalanche breakdown at reverse-biased conditions. The proposed workflow is explored to maximize computational efficiency and balance time-consuming drift-diffusion simulation with fast script-based post-processing. Without excessive computational effort, we could predict a suite of key device performance metrics, including breakdown voltage, dark/light avalanche built-up time, photon detection efficiency, dark count rate, and the deterministic part of timing jitter due to device structures. Implementing the proposed workflow onto a single InP nanowire and comparing it to the extensively studied planar devices and superconducting nanowire SPDs, we showed the great potential of nanowire avalanche SPD to outperform their planar counterparts and obtain as superior performance as superconducting nanowires, i.e., achieve a high photon detection efficiency of 70% with a dark count rate less than 20 Hz at non-cryogenic temperature. The proposed workflow is not limited to single-nanowire or nanowire-based device modeling and can be readily extended to more complicated two-/three dimensional structures

Engineering the side facets of vertical [100] oriented InP nanowires for novel radial heterostructures

In addition to being grown on industry-standard orientation, vertical [100] oriented nanowires present novel families of facets and related cross-sectional shapes. These nanowires are engineered to achieve a number of facet combinations and cross-sectional shapes, by varying their growth parameters within ranges that facilitate vertical growth. In situ post-growth annealing technique is used to realise other combinations that are unattainable solely using growth parameters. Two examples of possible novel radial heterostructures grown on these vertical [100] oriented nanowire facets are presented, demonstrating their potential in future applications

Dynamics and control of gold-encapped gallium arsenide nanowires imaged by 4D electron microscopy

Eutectic related reaction is a special chemical/physical reaction involving multiple phases, solid and liquid. Visualization of phase reaction of composite nanomaterials with high spatial and temporal resolution provides a key understanding of alloy growth with important industrial applications. However, it has been a rather challenging task. Here we report the direct imaging and control of the phase reaction dynamics of a single, as-grown free-standing gallium arsenide nanowire encapped with a gold nanoparticle, free from environmental confinement or disturbance, using four-dimensional electron microscopy. The non-destructive preparation of as-grown free-standing nanowires without supporting films allows us to study their anisotropic properties in their native environment with better statistical character. A laser heating pulse initiates the eutectic related reaction at a temperature much lower than the melting points of the composite materials, followed by a precisely time-delayed electron pulse to visualize the irreversible transient states of nucleation, growth and solidification of the complex. Combined with theoretical modeling, useful thermodynamic parameters of the newly formed alloy phases and their crystal structures could be determined. This technique of dynamical control and 4D imaging of phase reaction processes on the nanometer-ultrafast time scale open new venues for engineering various reactions in a wide variety of other systems

The effect of rapid thermal annealing to device performance of InGaAs/AlGaAs quantum well laser diodes

The effect of rapid thermal annealing to device performance of InGaAs/AlGaAs quantum well laser diode has been investigated using photoluminescence (PL), double-crystal X-ray diffraction (DCXRD), photo-response (PR) and lasing characteristic. X-ray measurement results show that there is an incorporation of carbon atom in lattice site of higly doped p++ GaAs contact layer. The photocurrent spectra at room temperature reveal that the relative intensity of 1e-1hh transition of annealed samples is much higher than that of as-grown samples and the peak became narrow. Stark shifts are much higher for the samples after annealing in comparison to the as-grown samples and this has been attributed to a decrease of the confining potential due to thermal interdiffusion. Characteristic of laser diodes shows that there is no significant degradation of lasing parameters after annealing has been observed and it has been found that the threshold current of annealed laser diodes are approximately four times less than as-grown laser diodes and this has been attributed to the electrical activation of carbon