Tunable active chirped-corrugation waveguide filters

A novel tunable semiconductor waveguide reflection filter is proposed and analyzed. The filter is based on spatially selective gain pumping of a chirped-corrugation waveguide. This active chirped-corrugation waveguide filter (ACF) is considered for monolithic broadband tuning of semiconductor lasers

Saturable nonlinear dielectric waveguide with applications to broad-area semiconductor lasers

Self-focusing in a passive dielectric waveguide with a saturable nonlinearity is studied. The eigensolutions constitute a good approximation to the lateral modes of broad-area semiconductor lasers under low-duty-cycle pulsed conditions. The laser modes are predicted to consist of adjacent filaments coupled in phase, leading to a single-lobed far field, and to be stable with increased current injection above saturation intensity. The ultimate filament spacing is inversely proportional to the threshold gain, and thus wider filaments are expected in low-threshold broad-area lasers

Self-stabilized Nonlinear Lateral Modes of Broad Area Lasers

The lateral modes of broad area lasers are investigated theoretically. The nonlinear interaction between optical field and effective refractive index leads to a saturable nonlinearity in the governing field equation, so that self-modulated solutions are found to be stable with increased current injection above saturation intensity. We derive approximate analytical solutions for traveling wave fields within the broad area laser. The field amplitude consists of a small ripple superimposed on a large dc value. Matching fields at the boundary determines the modulation depth and imparts an overall phase curvature to the traveling wave mode. There are multiple lateral modes for a given set of operating conditions, and modes with successively more lobes in the ripple have greater overall phase curvature. In contrast to the linear problem, several lateral modes can achieve the same modal gain, for a given injected current density, by saturating the gain to different extent. Thus, these modes would exhibit slightly different optical powers

Broadband tunability of gain-flattened quantum well semiconductor lasers with an external grating

Quantum well lasers are shown to exhibit flattened broadband gain spectra at a particular pumping condition. The gain requirement for a grating-tuned external cavity configuration is examined and applied to a semiconductor quantum well laser with an optimized length of gain region. The predicted very broadband tunability of quantum well lasers is confirmed experimentally by grating-tuning of uncoated lasers over 85 nm, with single longitudinal mode output power exceeding 200 mW

Ultralow Threshold Quantum Well Lasers For Computer Interconnects

Optical computer interconnects appear very attractive when integration of state of the art technology of quantum well GaAs/GaA1As lasers is considered. These ultralow threshold lasers provide the very high transmission rates and the inherent simplicity required for such systems. A detailed design is presented for a 5 Gbit s-1 transmission rate, suppression of pattern effects, and a system power supply of approximately 25 mW per laser. Existing experimental data show that little extrapolation is required to reach that kind of performance from state of the art technology

Ultralow Threshold Quantum Well Lasers For Computer Interconnects

Optical computer interconnects appear very attractive when integration of state of the art technology of quantum well GaAs/GaA1As lasers is considered. These ultralow threshold lasers provide the very high transmission rates and the inherent simplicity required for such systems. A detailed design is presented for a 5 Gbit s-1 transmission rate, suppression of pattern effects, and a system power supply of approximately 25 mW per laser. Existing experimental data show that little extrapolation is required to reach that kind of performance from state of the art technology

Selective Ablation of Cancer Cells with Low Intensity Pulsed Ultrasound

Ultrasound can be focused into deep tissues with millimeter precision to perform noninvasive ablative therapy for diseases such as cancer. In most cases, this ablation uses high intensity ultrasound to deposit nonselective thermal or mechanical energy at the ultrasound focus, damaging both healthy bystander tissue and cancer cells. Here, we describe an alternative low intensity (I_(SPTA) 20 ms causes selective disruption of a panel of breast, colon, and leukemia cancer cell models in suspension without significantly damaging healthy immune or red blood cells. Mechanistic experiments reveal that the formation of acoustic standing waves and the emergence of cell-seeded cavitation lead to cytoskeletal disruption, expression of apoptotic markers, and cell death. The inherent selectivity of this low intensity pulsed ultrasound approach offers a potentially safer and thus more broadly applicable alternative to nonselective high intensity ultrasound ablation