Self-pulsation at 480 GHz from a two-color discrete mode laser diode

A discrete mode Fabry-Pérot laser is designed and fabricated to achieve two-color lasing. We demonstrate beating between the two laser modes and self-pulsation at 480 GHz

Inverse scattering approach to multiwavelength Fabry-Pérot laser design

A class of multiwavelength Fabry-Pérot lasers is introduced where the spectrum is tailored through a patterning of the cavity effective index. The cavity geometry is obtained using an inverse scattering approach and can be designed such that the spacing of discrete Fabry-Pérot lasing modes is limited only by the bandwidth of the inverted gain medium. A specific two-color semiconductor laser with a mode spacing in the THz region is designed, and measurements are presented demonstrating the simultaneous oscillation of the two wavelengths. The nonperiodic effective index profile of the particular two-color device considered is shown to be related to a Moiré or superstructure grating

New games, new rules: big data and the changing context of strategy

Big data and the mechanisms by which it is produced and disseminated introduce important changes in the ways information is generated and made relevant for organizations. Big data often represents miscellaneous records of the whereabouts of large and shifting online crowds. It is frequently agnostic, in the sense of being produced for generic purposes or purposes different from those sought by big data crunching. It is based on varying formats and modes of communication (e.g., texts, image and sound), raising severe problems of semiotic translation and meaning compatibility. Crucially, the usefulness of big data rests on their steady updatability, a condition that reduces the time span within which this data is useful or relevant. Jointly, these attributes challenge established rules of strategy making as these are manifested in the canons of procuring structured information of lasting value that addresses specific and long-term organizational objectives. The developments underlying big data thus seem to carry important implications for strategy making, and the data and information practices with which strategy has been associated. We conclude by placing the understanding of these changes within the wider social and institutional context of longstanding data practices and the significance they carry for management and organizations

Predicting oral anticoagulant response using a pharmacodynamic model

We developed a pharmacokinetic and pharmacodynamic model of warfarin absorption, metabolism, and anticoagulant action appropriate for guiding anticoagulant therapy. The model requires only two independently adjustable parameters to describe warfarin's effect on individual patients. For any given individual, these parameters are rapidly and inexpensively identified using a computer program based on the model. Test data were generated by superimposing Gaussian noise on dose-response curves calculated with the model. Then the computer program was applied to the test data. Future prothrombin complex activities (PCA's) and maintenance doses were predicted accurately early in the course of drug administration. In addition, the program accurately predicted PCA response in two groups of normal volunteers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44006/1/10439_2006_Article_BF02363455.pd

VALENCE BAND STRUCTURE OF STRAINED-LAYER Si-Si0.5Ge0.5 SUPERLATTICES

We calculate the valence subband dispersion of Si0.5Ge0.5 - Si strained layer structures grown on a Si (001) substrate and on a Si0.75Ge0.25 buffer. We use the 6x6 Luttinger-Kohn Hamiltonian, including the effects both of strain and of the split-off band. The heavy-hole zone centre states are separated by over 60meV from the light-hole states and the highest valence subband has a low zone-centre effective mass (m* ~ .15 - .18), suggesting such structures to be useful for high hole mobility applications. Away from the zone centre, the bands are strongly anisotropic. We predict little difference in electronic properties for p-type Si0.5Ge0.5-Si superlattices when grown on Si substrates or Si0.75Ge0.25 buffers

Microscopic theory for interband and intersubband optical responses of quantum well laser media

This work analyzes the influence of Coulomb effects with increasing degree of complexity, starting with the Hartree-Fock limit, and evolving to the screened Hartree-Fock case and further on to beyond Hartree-Fock corrections, including non-diagonal dephasing contributions to both interband and intersubband transitions. Electron-electron, hole-hole and electron-hole transitions, correlation and scattering mechanisms are systematically included in our many body Greens functions formalism that consistently includes the nonparabolic electron and hole dispersion relations as well as independent transition dipole elements obtained from a rigorous solution of an 8 × 8 k.p Hamiltonian. The carrier-induced absorption/gain coefficient and refractive index change are directly calculated from the imaginary, χ" and real, χ' parts of the optical susceptibility function

Longitudinal mode grouping in InGaAs/GaAs/AlGaAs quantum dot lasers: origin and means of control

It is proposed that the recently observed quasi-periodic modulation of the emission spectra of quantum dot lasers is due to interference effects associated with waveguide leakage into the substrate. Such effects could be positively engineered to control laser spectra in such devices

Composition-dependent band gap and band-edge bowing in AIInN : a combined theoretical and experimental study

A combined experimental and theoretical study of the band gap of AllnN is presented, which confirms the breakdown of the virtual crystal approximation (VCA) for the conduction and valence band edges. Composition-dependent bowing parameters for these quantities are extracted. Additionally, composition-dependent band offsets for GaN/AllnN systems are provided. We show that local strain and built-in fields affect the band edges significantly, leading to optical polarization switching at a much lower In composition than expected from a VCA approach