Gratings with an aperiodic basis: single-mode emission in multi-wavelength lasers

We propose a new class of gratings having multiple spatial frequencies. Their design relies on the use of small aperiodic grating sequences as unit cells whose repetition forms a superlattice. The superlattice provides well-defined Fourier components, while the choice of the unit cell structure enables the selection, modulation or suppression of certain Fourier components. Using these gratings to provide distributed feedback in mid-infrared quantum cascade lasers, we demonstrate simultaneous lasing on multiple well-defined and isolated longitudinal modes, each one having a sidemode suppression ratio of about 20 dB.United States. Air Force Office of Scientific Research (MURI 67N-1069926)Harvard University (Nanoscale Systems and Engineering Center)United States. Air Force (‘Deterministic Aperiodic Structures for Onchip Nanophotonic and Nanoplasmonic Device Applications’ under award no. FA9550-10-1- 0019)National Science Foundation (U.S.) (NSF CAREER Award ECCS-0846651)Georgia Institute of Technology (Steve W. Chaddick Endowed Chair of OptoElectronics

From Dynamic State Machines to Promela

Dynamic State Machines (DSTM) is an extension of Hierarchical State Machines recently introduced to answer some concerns raised by model-based validation of railway control systems. However, DSTM can be used to model a wide class of systems for design, verification and validation purposes. Its main characteristics are the dynamic instantiation of parametric machines and the definition of complex data types. In addition, DSTM allows for recursion and preemptive termination. In this paper we present a translation of DSTM models in Promela that can enable automatic test case generation via model checking and, at least in principle, system verification. We illustrate the main steps of the translation process and the obtained Promela encoding