We report the design and fabrication of a PT-symmetric coupled-cavity AlGaAs MQW laser for THz beat frequency generation. The optical source consists of two PT-symmetric coupled-cavity resonators and an amplifying waveguide section, producing a beat frequency in the THz band. When the beat frequency is fed into a photomixing cell, a coherent THz signal is produced. The THz frequency can be tuned by varying the gain contrast between the two individual resonators.
This paper will report on some features of a platform for the realization of an anti parity-time (anti-PT) symmetric system in a pair of time-delay coupled semiconductor lasers, with special emphasis on the delay induced dynamics in the system. The system is modeled by a modified Lang-Kobayashi rate equations model, augmented to include delayed coupling. The role of a phase accumulation factor that arises from the delayed coupling is elucidated. Finally, the novel exceptional point(s) behavior that is characteristic of the time-delay is investigated via numerics as well as analytically via the Lambert W function.
The purpose of this paper is to examine the behavior of exceptional points (EPs) in a time delayed anti-parity-time symmetric system composed of two delay-coupled semiconductor lasers (SCLs). Starting from a pseudo-2x2 rate equation model for the lasers’ electric fields we analyze the eigenvalues and eigenvectors of the system’s effective Hamiltonian and numerically search for EPs. Recent experimental work has suggested that the EP landscape in this system may be significantly different from the typical anti-PT dimer due to the time delay. Exceptional points in these PT dimers mark global phase changes from overall oscillatory behaviour to exponential growth/decay; in contrast, the time delay renders our effective Hamiltonian infinite-dimensional and allows for more than one EP. Specifically, we numerically demonstrate that by tuning the delay time or coupling strength our time delayed system may exhibit one, two, or zero EPs.
This paper describes our work on the realization of a non-hermitian Hamiltonian system in time-delay coupled semiconductor lasers consisting of two identical lasers, operated with a small frequency detuning between them, and bidirectionally coupled to each other through optical injection. The effective Hamiltonian for this system is non-hermitian, and, under some assumptions and conditions, reminiscent of two-site paritytime (PT) symmetric Hamiltonians, a topic that is under intense investigation. The dynamical response of the intensity of the lasers as a function of the detuning between them reveals characteristics of a PT symmetric system, and our emphasis is on the features that arise from the delayed coupling. Experimental measurements are in good agreement with numerical simulation of the nonlinear rate equation model that describes the coupled system.
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