InAs quantum dot photonic crystal lasers and their temperature dependence

We report on the demonstration of optically pumped photonic crystal lasers with InAs quantum dot active regions operating at room temperature near 1310 nm. Absorbed threshold pump powers as low as 25 /spl mu/W are observed. We also extract a characteristic temperature of 17 K, which is attributed to limitations caused by surface recombination.     

Clustering irregular shapes using high-order neurons

This article introduces a method for clustering irregularly shaped data arrangements using high-order neurons. Complex analytical shapes are modeled by replacing the classic synaptic weight of the neuron by high-order tensors in homogeneous coordinates. In the first- and second-order cases, this neuron corresponds to a classic neuron and to an ellipsoidalmetric neuron. We show how high-order shapes can be formulated to follow the maximum-correlation activation principle and permit simple local Hebbian learning. We also demonstrate decomposition of spatial arrangements of data clusters, including very close and partially overlapping clusters, which are difficult to distinguish using classic neurons. Superior results are obtained for the Iris data.     

Strengthening of halides for infrared windows

The alkali halides are promising candidates for high-power carbon dioxide laser windows. However, their poor mechanical properties limit their application for windows. In this paper, several methods of strengthening these materials will be discussed. These methods include impurity addition, solid solution formation, use of systems with solid-solid immiscibility gaps and polycrystalline formation. Characterization will include both optical and mechanical properties. The studies indicate that solid solutions (KCl-KBr) can strengthen the halides about twofold without affecting optical properties. An eight-fold increase in hardness has been produced using the NaCl-KCl system but the optical properties are adversely affected. The results of impurity addition (CaCl₂) in KC1 are not clear, but the method does not look promising. Results of polycrystalline formation will also be discussed.     

Low-loss wavelength division multiplexing (WDM) devices for single-mode systems

We report here on single-mode microoptic wavelength division multiplexing (WDM) devices with two channels located at 1275 and 1345 nm, respectively. Data are presented for four multiplexers and four demultiplexers. The average insertion loss for the multiplexers was 0.5 ± 0.2 and 1.0 ± 0.3 dB for the short and long wavelength channels, respectively. For the demultiplexers, the average losses were 0.8 ± 0.2 dB and 1.0 ± 0.1 dB, respectively. The full channel widths of the demultiplexers for 0.5 dB of additional loss were about 22 nm. All measurements included the presence of prototype precision single-mode connectors. The multiplexers were based on interference filters and GRIN lenses with identical single-mode fibers used for inputs and output. The demultiplexers employed diffraction gratings and GRIN lenses with 50- μm core graded-index output fibers. In addition three of the demultiplexers included a third output channel centered at 1521 nm. The 28- dB dynamic range of the monochromator-based test appartus was insufficient to evaluate the crosstalk performance. Measurements on two demultiplexers, using a 1295-nm laser, yielded values of -33 and -38 dB, respectively for the crosstalk in the 1345-nm channel.     

Fourier fringe analysis with improved spatial resolution

The spatial resolution of the phase image derived from the interferogram by Fourier fringe analysis is limited by the necessity to isolate a first order in the Fourier plane. By use of the two complementary outputs of the interferometer, it is possible to eliminate the zero order and thus to improve the spatial resolution by a factor of approximately 2. The theory of this improvement is presented and confirmed experimentally.     

A 1-D Photonic Band Gap Tunable Optical Filter in (110) Silicon

In this paper, we describe an electrostatically tunable optical bandpass filter that is fabricated in (110) silicon. Deep reactive-ion etching is the main process that is used to fabricate the overall device structure. To create the highly parallel surfaces that are needed for the photonic band gap elements, electrochemical (KOH) etching of the vertical (111) planes is then used. Back etching is used to release the moving parts. Fiber pigtails are attached in etched alignment grooves, and fiber-fiber insertion loss below 11 dB was obtained. The measured passband width was 3 nm with a tuning range of 8 nm.     

Menopausal transition of Korean immigrant women: a literature review

The menopausal transition needs to be understood in terms of the multiple mediating factors within the context in which women experience it. For immigrant women especially, the menopausal experience is complicated by multiple transitions and social marginality, so it cannot be adequately explained without considering this complexity. In this paper we review the literature on the menopausal transition of a group of vulnerable immigrant women in two ways: describing the transitions themselves (menopause, immigration, and housewife to employee), and describing factors that mediate the menopausal transition experience (family norms, meaning of menopause and women's work, and health practices). We emphasize the context and suggest areas of needed research.