Modeling the Electro-Optical Performance of High Power Mid-Infrared Quantum Cascade Lasers

Performance modeling of the characteristics of mid-infrared quantum cascade lasers (MIR QCL) is an essential element in formulating consistent component requirements and specifications, in preparing guidelines for the design and manufacture of the QCL structures, and in assessing different modes of operation of the laser device. We use principles of system physics to analyze the electro-optical characteristics of high power MIR QCL, including thermal backfilling of the lower laser level, hot electron effects, and Stark detuning during lasing. The analysis is based on analytical modeling to give simple mathematical expressions which are easily incorporated in system-level simulations of defense applications such as directed infrared countermeasures (DIRCM). The paper delineates the system physics of the electro-optical energy conversion in QCL and the related modeling. The application of the performance model to a DIRCM QCL is explained by an example

Mid-infrared quantum cascade detectors for applications in spectroscopy and pyrometry

In this paper, we give an overview of quantum cascade detector technology for the near- and mid-infrared wavelength range. Thanks to their photovoltaic operating principle, the most advanced quantum cascade detectors offer great opportunities in terms of high detection speed, reliable room temperature operation, and excellent Johnson noise limited detectivity. Besides some important features dealing with their fabrication and their general characteristics, we will also briefly present some possibilities for performance improvement. Elementary theoretical considerations adopted from photoconductive detectors confirm that optimization of such devices always involves various trade-offs

InGaAs/AlAsSb quantum cascade detectors operating in the near infrared

NRC publication: Ye

Buried-heterostructure quantum cascade lasers fabricated using a sacrificial layer and a two-step regrowth process

We report various aspects related to the selective area growth of thick InP:Fe layers by metal organic vapor deposition and their application to buried-heterostructures. In particular, we focus on the development of planar buried-heterostructure quantum cascade lasers using selective wet chemical etching for ridge mesa preparation and versatile regrowth processes. After describing the optimization of the insulating properties of InP:Fe layers, we expose our approach to circumvent the difficulties inherent to the selective area growth on non-planar structures. By adding an InGaAs/InP layer stack (where, the InGaAs layer is used as a sacrificial layer) on the top of the active region, reproducible regrowths have been successfully carried out with good optical, electrical and crystalline quality. Using this method, buried-heterostructure quantum cascade lasers characterized in TM00 mode, exhibited output powers in the range of 2.5 W and wall plug efficiencies of about 13% at room temperature

A bio-inspired, one-step but versatile coating onto various substrates with strong antibacterial and enhanced osteogenesis

It is of great interest to prepare osteogenic and antibacterial coatings for successful implants. Current coating techniques suffer from being time-consuming, substrate material or shape dependence, expensive equipment, environmental pollution, low stability, processes that are difficult to control, etc. Herein, inspired by mussels, we report a one-step and versatile method to fabricate a dual functional coating. The coating is finished in minutes independently of materials or dimensions of substrates. Thus, our coatings exhibit strong antibacterial ability against both Gram-positive bacteria S. aureus, and Gram-negative bacteria E. coli, support the proliferation of dental pulp stem cells (DPSCs), and are powerful for inducing osteogenic differentiation. The universality, facility, rapidness, and mildness of our coating process, which is also environmentally-friendly and cost-effective, points towards potential applications in bone or dental implants

Simulation and Analysis of Wind Pressure Coefficient of Landslide-Type Long-Span Roof Structure

This article carries out a numerical simulation of a landslide-type long-span roof structure, Harbin Wanda Cultural Industry Complex. The maximum span of the landslide-type roof is 150 m and the minimum span is 90 m, with a minimum height of 40 m and a maximum height of 120 m, and the roof area is divided into three different parts. The large eddy simulation (LES) method is used to simulate and record the wind pressure coefficient of the roof. The distribution law and cause of the mean wind pressure coefficient of the roof are firstly analyzed, and the comparison with the existing wind tunnel test data proves the validity of the numerical simulation. Secondly, a qualitative analysis is made on the distribution of root mean square (RMS) fluctuating coefficients. Subsequently, the non-Gaussian characteristics of the roof are briefly discussed, and the peak factor distribution is calculated. Finally, based on the total wind pressure coefficient, a simple evaluation method for judging favorable and unfavorable wind direction angles is proposed, and only the shape of the roof and wind angle need to be known

Broadly tunable hetero-cascading quantum cascade lasers: Design, growth, and external cavity operation

Design and growth characteristics of broadly tunable hetero-cascading quantum cascade lasers are discussed. We show the influence of electric field variation, and interface roughness on the gain spectra. Interface roughness is shown to play an important role for these broadband lasers. External cavity configuration has been used to extract narrow-band emission, thus rendering wide tuning range of the device. We achieve a single-chip tuning range of 400 cm−1 (from 1030 cm−1 to 1430 cm−1, namely 7.0–9.7 µm in wavelength) by using tri-stack active regions