Vertical cavity lasers for telecom applications

The authors review the development of long-wavelength vertical cavity lasers (VCLs) for telecommunications applications. Long-wavelength VCLs provide an attractive choice for inexpensive fiber optic communication. The different designs of such lasers are presented, along with the advantages and disadvantages of each. System requirements and experiments are also presented at 2.5 Gb/s over 200 km of optical fiber     

Room-temperature continuous-wave operation of 1.54-μmvertical-cavity lasers

We report on the room-temperature continuous-wave operation of vertical-cavity lasers operating at 1.54 μm. The devices use a 7 strain-compensated quantum-well active layer sandwiched between two Al(Ga)As-GaAs quarter-wave mirrors joined by wafer fusion. Five device sizes between 8 and 20 μm were found to operate continuously at room temperature (23°C), The lowest room-temperature continuous-wave threshold current of 2.3 mA was measured on an 8-μm diameter device, while the highest continuous-wave operating temperature of 33°C was measured on a 12-μm device     

On demonstrating unconscious perception: Comment on Draine and Greenwald (1998).

S. C. Draine and A. G. Greenwald (see record 1999-10824-004) have described a methodology based on regression analysis for demonstrating unconscious perception. They have suggested that their methodology represents a major improvement over existing methodologies. An analysis of their methodology reveals that it is closely related to the classic dissociation paradigm. As such, interpretation of their results is compromised by the same issues concerning the measurement of awareness that have plagued all previous attempts to use the dissociation paradigm to demonstrate unconscious perception in the complete absence of conscious perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cryogenic scanning tunneling spectroscopy studies of inhomogeneous superconductors

We applied scanning tunneling microscopy and spectroscopy, combined with magnetic susceptibility measurements and Mossbauer spectroscopy, in studies of three superconducting materials. Two belong to a new class of high T_c magnetic-superconductor systems, R_1.4Ce_0.6RuSr₂Cu₂O_10-δ (R=Eu and Gd), which are magnetically ordered at T_N≪T_c. The third is a granular normal-superconductor system, where the superconducting phase is YNi₂B₂C. In this paper we focus on the tunneling measurements, which exhibit large spatial variations of the local electronic properties for all three materials. Albeit, these local measurements also reveal pronounced differences between the third and the first two systems, which will be discussed in view of their macroscopic properties.     

Synthesis and characterization of broad-band polarization-mode dispersion equalizers

A synthesis algorithm for the design of a finite impulse response polarization-mode dispersion (PMD) equalizer is described and used for characterization of the filter. Defined in terms of the residual maximum differential group delay, the performance of the equalizer is characterized as a function of the equalizer order and period. The synthesis algorithm uses spectral factorization to analytically find estimated equalizer control variables. The control variables are then used as initial guess for an optimization procedure that minimize the maximum differential group delay in the frequency range of interest.     

3-D curve matching using splines

A machine vision algorithm to find the longest common subcurve of two 3-D curves is presented. The curves are represented by splines fitted through sequences of sample points extracted from dense range data. The approximated 3-D curves are transformed into 1-D numerical strings of rotation and translation invariant shape signatures, based on a multiresolution representation of the curvature and torsion values of the space curves. The shape signature strings are matched using an efficient hashing technique that finds longest matching substrings. The results of the string matching stage are later verified by a robust, least-squares, 3-D curve matching technique, which also recovers the Euclidean transformation between the curves being matched. This algorithm is of average complexity O(n) where n is the number of the sample points on the two curves. The algorithm has applications in assembly and object recognition tasks. Results of assembly experiments are included.