Towards automated design of quantum cascade lasers

We present an advanced technique for the design and optimization of GaAs/AlGaAs quantum cascade laser structures. It is based on the implementation of the simulated annealing algorithm with the purpose of determining a set of design parameters that satisfy predefined conditions, leading to an enhancement of the device output characteristics. Two important design aspects have been addressed: improved thermal behavior, achieved by the use of higher conduction band offset materials, and a more efficient extraction mechanism, realized via a ladder of three lower laser states, with subsequent pairs separated by the optical phonon energy. A detailed analysis of performance of the obtained structures is carried out within a full self-consistent rate equations model of the carrier dynamics. The latter uses wave functions calculated by the transfer matrix method, and evaluates all relevant carrier–phonon and carrier–carrier scattering rates from each quantized state to all others within the same and neighboring periods of the cascade. These values are then used to form a set of rate equations for the carrier density in each state, enabling further calculation of the current density and gain as a function of the applied field and temperature. This paper addresses the application of the described procedure to the design of lambda~9 µm GaAs-based mid-infrared quantum cascade lasers and presents the output characteristics of some of the designed optimized structures. © 2005 American Institute of Physic

Resonantly enhanced bound-continuum intersubband second harmonic generation in optimized asymmetric semiconductor quantum wells

A systematic procedure applied to a step-asymmetric quantum well in order to maximize intersubband bound–continuum second-order susceptibility is described. The possibility is explored of obtaining resonantly enhanced nonlinear optical susceptibilities in quantum wells with two bound and a continuum resonance state as the dominant third state. This would significantly extend the range of input radiation photon energies that may be frequency doubled under resonance conditions in realistic structures. Calculation for the AlxGa1−xAs alloy based wells designed for pump photon energies in range of ℏω=200–300 meV indicate a perspective of employing continuum states in resonant second harmonic generation at higher photon energies

Bound-continuum intersubband transition based optical nonlinearities in semiconductor quantum wells

The possibility is explored of obtaining resonantly enhanced nonlinear optical susceptibilities in semiconductor quantum wells with two bound states and the resonant state in continuum as the third state. This would significantly extend the range of input radiation photon energies that may be frequency-doubled under resonance conditions in realistic structures. Calculation for the AlGaAs alloy based wells designed for the second harmonic generation of 240meV radiation indicate the usefulness of this approache

The Innovative Human Resource Management Framework: Impact of Green Competencies on Organisational Performance

Scholars have emphasised the importance of green settings in today’s business paradigms. Studies on green behaviour have produced a plethora of noteworthy discoveries, whether focused on financial success, individual capabilities, or development. However, despite significant growth in interest in green business practices, the relationship between individuals’ willingness and green competencies has received little attention. This article used the customised green competencies conceptual model to investigate how green skills influence organisational performance and their relationship with the willingness moment. This article developed an innovative human resource management approach to address these difficulties. A questionnaire was used to perform empirical statistical research with 516 respondents from Serbian universities. Different mathematical and statistical methodologies were used to analyse the results. The findings corroborate the suggested theoretical model, and they suggest that green competencies will influence people’s willingness to participate in green activities. This article gives new information on human behaviour and organisational effectiveness in a green atmosphere. It includes managerial and practical consequences and recommendations for businesses looking to improve their social responsibility and environmental sustainability