Electronic band structures of GaInAsP/InP vertically stacked multiple quantum wires with strain-compensating barriers Dry etching and consequent burring regrowth of nanosize quantum wells stripes using an in situ ultrahigh vacuum multichamber system

No abstract

Bi-lateral force measurements on the supporting limbs in postural sway while standing still were carried out to evaluate postural stability of craniocerebral injured (CCI) patients. Brain pathology of these patients was characterised by CT scans and MRI, as well as by their cognitive and behavioural disturbances. Normal subjects of the same age group were tested as controls. From the force tracings obtained, three oscillation frequencies were identified, with orders of magnitudes of 6, 1.5 and 0.1 Hz, respectively, of which the middle frequency, i.e. that corresponding to 1.5 Hz, was selected for subsequent processing and analysis, which included the determination of relative sequence of the force vectors on both feet and evaluation of timings and amplitudes of the waveforms. Weight-bearing imbalance was defined in the vertical direction to express the difference between the average forces supported by each of the legs. In the horizontal plane, two parameters were defined: Sway Total Activity (sii), to represent the vector summation of the absolute values of the horizontal force components acting on both legs; and Asymmetry (ASYM), to express the difference in activities between the two legs. The results presented disclose the reactive force patterns acting on each of the legs of CCI individuals, in comparison with normal individuals. Although the'forces were shown to act synchronously on both legs, in most of the patients, they appeared to be asymmetrical in nature, with a typical vectorial pattern for every individual, which generally differed from that of normal subjects. Sway activity was found to be significantly higher in the CCI group as compared with that of the normal controls. These results justify the necessity to study the activity of each of the legs, rather than that corresponding to the resultant forces acting on the whole body, when treating the external forces involved in the stabilisation and regulation of the standing posture of these patients. An attempt to grade the patients according to ascending order of neurological deficits disclosed that their sway disturbances, as revealed by the magnirude of sway total activity and asymmetry, had a tendency to be related to the severity of neurobehavioural disturbances.

Simple switching scheme of frequency with precise feedback control of robust wavelength locker has been presented for a short-cavity DBR laser array. Switching time was less than 13 µsec within +/-2.5GHz from ITU grid. IntroductionNew network technologies such as optical packet switching and optical burst switching will be introduced to next generation network, to accommodate increasing traffic of internet services. These technologies realize transparent optical routing. For the optical burst switching, agile tunable wavelength converter is indispensable to avoid burst contention in optical region [1]. For this use, tuning speed of tunable lasers should be around a few microseconds, however, commercial tunable lasers based on multi-section DBR laser can not guarantee tuning speed of sub milliseconds. Experimentally, wavelength switching in the order of nanoseconds has been reported. under feed forward control without wavelength monitoring, however, both wavelength stability and reliability are not ensured over long period time because wavelength was affected by thermal relaxation process in the laser module. In addition, multi-section DBR lasers have been used, therefore, control circuits are considered to be rather complicated. There are only a few reports on fast wavelength locking for tunable lasers [2][3][4]. In this paper, we show simple control scheme for a stable wavelength switching by using both a short-cavity DBR tunable laser and a built-in wavelength locker packaged in a standard butterfly package, resulting in fast and stable wavelength switching time of approximately 10 microseconds. A short cavity DBR laser and integrated wavelength lockerWe have reported a short-cavity DBR tunable laser which realizes continuous wavelength tuning by changing only one DBR current without phase control. Integrating six lasers (DBR and gain sections), an MMI coupler and an SOA in one chip, continuous tuning range of 21 nm had been achieved as shown in fig. 1 [5]. Robust and compact laser module with built-in wavelength monitor was also developed [6]. In fig. 2, the laser module consists of the DBR laser array, a collimator lens, an optical isolator, a beam splitter, a Fabry-Perot etalon, and two photo-diodes. The hexagonal-shaped beam splitter splits collimated beam in three portions for wavelength monitoring, power monitoring, and fiber output. This monitor ensures the stable wavelength on the ITU grid over 30 nm. The module is potentially high-reliable packaging by the use of soldering and laser welding techniques. Dynamic switching characteristics of this module are investigated assemble onto control electronics.

No abstract