D. Lofgreen

High-quality factor optical microcavities using oxide apertured micropillars

An oxide aperture is used to confine optical modes in a micropillar structure. This method overcomes the limitations due to sidewall scattering loss typical in semiconductor etched micropillars. High cavity quality factors (Q) up to 48 000 are determined by external Fabry–Perot cavity scanning measurements, a significantly higher value than prior work in III-V etched micropillars. Measured Q values and estimated mode volumes correspond to a maximum Purcell factor figure of merit value of 72.

Superlattice barrier 1528-nm vertical-cavity laser with 85/spl deg/C continuous-wave operation

We report 85 C continuous wave operation of a 1528 nm VCSEL with an InP-InGaAsP active region and wafer fused GaAs-AlGaAs mirrors. A superlattice barrier was used to reduce defect density in the wafer fused active region.

Analysis of spatial relationships in three dimensions: tools for the study of nerve cell patterning

BackgroundMultiple technologies have been brought to bear on understanding the three-dimensional morphology of individual neurons and glia within the brain, but little progress has been made on understanding the rules controlling cellular patterning. We describe new matlab-based software tools, now available to the scientific community, permitting the calculation of spatial statistics associated with 3D point patterns. The analyses are largely derived from the Delaunay tessellation of the field, including the nearest neighbor and Voronoi domain analyses, and from the spatial autocorrelogram.ResultsOur tools enable the analysis of the spatial relationship between neurons within the central nervous system in 3D, and permit the modeling of these fields based on lattice-like simulations, and on simulations of minimal-distance spacing rules. Here we demonstrate the utility of our analysis methods to discriminate between two different simulated neuronal populations.ConclusionTogether, these tools can be used to reveal the presence of nerve cell patterning and to model its foundation, in turn informing on the potential developmental mechanisms that govern its establishment. Furthermore, in conjunction with analyses of dendritic morphology, they can be used to determine the degree of dendritic coverage within a volume of tissue exhibited by mature nerve cells.

Densely packed pie shaped vertical-cavity surface-emitting laser array incorporating a tapered one-dimensional wet oxidation

Wavelength-division-multiplexing (WDM) photonic integrated emitter (PIE) vertical-cavity surface-emitting laser (VCSEL) arrays are fabricated using a post growth wet oxidation technique. High-density integration of WDM VCSEL arrays is possible by combining the technique of one-dimensional oxidation and large-scale tapered oxidation. Eight channels are integrated into a circle of 60 /spl mu/m in diameter. Seven channels are found to operate as lasers. The lasing wavelengths range from 823 to 836 nm corresponding with the distance between the VCSEL mesa and the tuning trench. The successful demonstration of incorporating wet oxidation into the wavelength control of the PIE VCSEL array opens a new way of fabricating mask-defined densely packed WDM VCSEL arrays.

Al0.95Ga0.05As0.56Sb0.44 for lateral oxide-confinement layer in InP-based devices

We report a lateral oxide-confinement layer for InP-based devices using lattice-matched AlGaAsSb. The confinement-layer-induced excess loss at different widths was extracted after de-embedding the losses due to carrier diffusion, nonradiative recombination, and changes in internal injection efficiency. The results show that AlGaAsSb oxide acts as an excellent confinement layer, and shows no excess loss down to a width of 4 μm.

A diode laser chemical sensor utilizing an oxidized lower cladding layer for high sensitivity

We demonstrate a chemical sensor incorporating a self-aligned, symmetrically-clad high index contrast evanescent field sensing waveguide. Analyte overlap of 4.8% is obtained with a tightly confined mode, ideal for sensitive affinity assays.

A monolithic diode laser chemical sensor with a quasi-symmetrical sensing waveguide for improved sensitivity

We demonstrate a diode laser chemical sensor incorporating a self-aligned, symmetrically clad high index contrast evanescent field sensing waveguide. This is accomplished by selectively oxidizing the lower cladding layer of the sensing waveguide. An analyte overlap of 4.8% is obtained with a tightly confined mode, ideal for sensitive affinity assays.

Analyzing neuronal patterning in the developing brain in three dimensions

were chronically implanted with stimulating electrodes in the BLA and recording electrodes in the DG via stereotaxic surgery. A second group of rats which received no isolation treatment and which were not handled (NH) during the neonatal period underwent the same surgical procedures and served as the control group. Following a one-week postsurgical recovery period, either LTP (100-pulse, 5-Hz theta-burst stimulation, TBS) or LTD (900-pulse, 1-Hz low frequency stimulation, LFS) was induced in the DG of both groups. ISO rats (n = 16) showed significantly enhanced levels of both LTP and LTD compared to NH counterparts (n = 15). These results indicate that neonatal isolation stress alters synaptic plasticity in neural circuits involved in memory and emotional functions. These findings may help to clarify the development of neural mechanisms linking emotional and stress responses in the amygdala with memory consolidation and information processing in the hippocampus (Fig. 1). Acknowledgements

Active photonic integrated circuits

Recent advances in photonic integration technology on InP and related materials have enabled continued growth in the scale, performance and quality of active photonic integrated circuits. Complex widely-tunable transmitters, transceivers, and wavelength converters with state-of-the-art performance have been demonstrated.

Densely packed pie-shaped vertical cavity surface-emitting laser array incorporating a tapered one-dimensional wet oxidation

Summary form only given. Owing to their geometric advantage with respect to mass production, WDM VCSEL arrays have drawn attention as a low cost means of increasing data transmission rate for short haul communications. Recently, pie-shaped WDM VCSEL arrays were successfully fabricated by means of anodic etching followed by regrowth. In addition to this work, wavelength tuning of VCSEL emission has been demonstrated via postgrowth oxidation. In this paper, we present the results of applying postgrowth oxidation to the fabrication of mask-defined densely-packed WDM VCSEL arrays.