Search

We initiated a multi-technique campaign to understand the physics an d properties of the massive binary systemMWC 314. Our observations included optical high-resolution spectr oscopy and Johnson photometry, near-infrared spectrophotometry, and K 0 band long-baseline interferometry with the CHARA Array. Our resu ltsplace strong constraints on the spectroscopic orbit, along with re asonable observations of the phase-lockedphotometric variability. Our interferometry, with input from the sp ectrophotometry, provides information onthe geometry of the system that appears to consist of a primary s tar lling its Roche Lobe and loosing massboth onto a hidden companion and through the outer Lagrangian po int, feeding a circumbinary disk. While themulti-faceted observing program is allowing us to place some constra ints on the system, there is also a possibilitythat the outow seen by CHARA is actually a jet and not a circumbinar y disk.Keywords: stars: early-type { binaries: close { stars: individual (MWC 314) { m ethods: observational {techniques: high angular resolution, spectroscopic

Ultrafast intraband carrier dynamics strongly influence many important characteristics in bulk and quantum well lasers and amplifiers through Spectral-Hole Burning (SHB) leading to nonlinear gain effects. In Quantum Dot (QD) devices, where the inter-level relaxation times can be even longer than the intraband relaxation times in conventional devices, SHB effects should also be substantial. A number of promising applications of QD amplifiers in high-speed optical processing (Cross-Gain Modulation, for instance) are based on features of the carrier dynamics in QD structures. In the present paper, based on a density matrix approach, we develop a theory of SHB-based nonlinear gain in QD lasers and amplifiers, which can affect such important characteristics as the modulation bandwidth in QD lasers and the saturation power and pulse energy in QD amplifiers. We give an expression for the nonlinear gain in QD devices, and show how it depends, particularly, on the capture/escape and relaxation/excitation rates.

We analyse the sensitivity of quantum dot semiconductor lasers to optical feedback. While bulk and quantum well semiconductor lasers are usually extremely unstable when submitted to back reflection, quantum dot semiconductor lasers exhibit a reduced sensitivity. Using a rate equation approach, we show that this behaviour is the result of a relatively low but nonzero line-width enhancement factor and strongly damped relaxation oscillations.

We analyse the sensitivity of quantum dot semiconductor lasers to optical. While bulk and quantum well semiconductor lasers are usually extremely unstable when submitted to back reflection, quantum dot semiconductor lasers exhibit a reduced sensitivity. Using a rate equation approach, we show that this behaviour is the result of a relatively low but nonzero line-width enhancement factor and of strongly damped relaxation oscillations.

Universal self-organisation on surfaces of semiconductors upon deposition of a few non-lattice-matched monolayers using MOCVD or MBE lead to the formation of quantum dots. Their electronic and optical properties are closer to those of atoms than of solids. We have demonstrated for QD-lasers a record low transparency current density of 6A/cm2 per dot layer at 1.16 μm, high-power of 12W, an internal quantum efficiency of 98%, and an internal loss below 1.5 cm-1. Relaxation oscillations indicate the potential for cut-off frequencies larger than 10 GHz. GaAs-based QD-lasers emitting at 1.3 μm exhibit output power of 5 W and single transverse mode operation up to 300 mW. At 1.5 μm again an output power of 5 W has been obtained for first devices showing a transparency current of 700 A/cm2. Single mode lasers at 1.16 and 1.3 μm show no beam filamentation, reduced M2, sensitivity to optical feedback by 30 db and α-parameter as compared to quantum well lasers. Passive mode locking of 1.3 μm lasers up to 20 GHz is obtained. Thus GaAs-lasers can now replace InP-based ones at least in the range up to 1.3 ´m, probably up to 1.55 μm.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

There are a number of optical systems being considered for aircraft. These include communication systems, surveillance systems, and other pointing and tracking systems. The angular vibration of the vehicle is usually the primary disturbance that degrades the optical system performance. Boeing is involved in a project to measure and analyze the angular vibration of several different aircraft. This report will show a comparison of the angular vibration spectrums of large transport aircraft and smaller fighter aircraft over a range of flight conditions.