Beaming light from a subwavelength aperture.

Light usually diffracts in all directions when it emerges from a subwavelength aperture, which puts a lower limit on the size of features that can be used in photonics. This limitation can be overcome by creating a periodic texture on the exit side of a single aperture in a metal film. The transmitted light emerges from the aperture as a beam with a small angular divergence (approximately +/-3 degrees ) whose directionality can be controlled. This finding is especially surprising, considering that the radiating region is mainly confined to an area with lateral dimensions comparable to the wavelength of the light. The device occupies no more than one cubic micrometer and, when combined with enhanced transmission, suggests that a wide range of photonic applications is possible.

Enhanced light transmission through a single subwavelength aperture.

The optical transmission through a subwavelength aperture in a metal film is strongly enhanced when the incident light is resonant with surface plasmons at the corrugated metal surface surrounding the aperture. Conversely, the aperture acts as a novel probe of the surface plasmons, yielding useful insights for optimizing the transmission enhancement. For the optimal corrugation geometry, a set of concentric circular grooves, three times more light is transmitted through the central subwavelength aperture than directly impinges upon it. This effect is useful in the fabrication of near-field optical devices with extremely high optical throughput.

Holographic data storage in a DX-center material.

We report on the optical storage of digital data in a semiconductor sample containing DX centers. The diffraction efficiency and the bit-error-rate performance of multiplexed data images are shown to agree well with a simple model of the material. Uniform storage without an exposure schedule is demonstrated. The volume sensitivity is found to be ~10(3) times that of LiNBO(3):Fe. The importance of coherent addition of scattered light with diffracted light in holographic data storage is discussed.

VCSEL-array-based angle-multiplexed optoelectronic crossbar interconnects.

A large crossbar switch, which is a desirable building block for any low-latency interconnect network, is difficult to implement because of many practical problems associated with digital electronics. We propose a new method for implementing a large optoelectronic crossbar interconnect to take advantage of a unique principle of optics. Based on an emerging vertical-cavity surface-emitting laser (VCSEL) technology, a passive angle-multiplexed beam-steering architecture is proposed as a key component of the optoelectronic crossbar. Various optical system parameters are evaluated. Because there is no optical fan-out power loss, the interconnect capacity of the proposed system is determined by the diffraction-limited receiver power cutoff, and therefore interconnection of more than 1000 nodes with a per node bandwidth of 1 GHz is possible with today's technology. A 64-element VCSEL-array-based proof-of-principle optical system for studying the interconnect scalability has been built. Details of the features of the proposed system, its advantages and limitations, demonstration experimental results, and their analyses are presented.

Confirmation of the local nature of the plasma grating photorefractive effect.

Two-wave mixing measurements made during the encoding of plasma gratings in AlGaAs:Te indicate that there is no phase shift between the illumination intensity pattern and the encoded refractive-index grating. These results support our previously proposed photorefractive mechanism, which is based on persistent plasma gratings and does not require charge transport.

Planar-optical mesh-connected tree interconnects: a feasibility study.

The mesh-connected tree is a two-dimensional interconnect topology that combines aspects of a conventional tree network and a two-dimensional nearest-neighbor mesh network. Because of its topological features, a mesh-connected tree has the potential to be implemented with planar optoelectronic interconnect concepts. We examine the feasibility of employing vertical-to-surface-transmissionelectro-photonic optical array switches together with planar micro-optical components for the future implementation of an optoelectronic mesh-connected tree interconnect.

Thick plasma gratings using a local photorefractive effect in CdZnTe:In.

Diffraction gratings have been encoded in bulk Cd(0.8)Zn(0.2)Te:In samples by near-band-gap excitation. The photoinduced index change is associated with persistent photoconductivity resulting from ionization of DX centers. The gratings have a thickness of 1.7 mm, as evinced by Bragg selectivity during the readout process. Encoded grating are shown to be persistent for sufficiently low temperatures and are not erased by subsequent writing of more gratings.

Astronomical identification of the C3H radical.

The C3H radical, a linear carbon chain with a 2 pi electronic ground state, has been identified in the millimeter-wave spectra of two astronomical sources, IRC +10216 and TMC-1, and conclusively confirmed (accompanying Letter) in a laboratory glow discharge. In IRC +10216 four rotational transitions have been observed, three in the lower fine-structure ladder (2 pi 1/2) and one in the upper (2 pi 3/2), each a resolved or partially resolved lambda-doublet. In TMC-1, both lambda components of the lowest lying 3/2 --> 1/2 transition of the 2 pi 1/2 ladder have been observed, each with well-resolved hfs. In IRC +10216 the excitation of C3H is similar to that of SiCC: the rotational temperature Trot within the 2 pi 1/2 ladder is low (8.5 K), owing to rapid radiative decay, while Trot across the ladders is high (approximately 52 K) because interconnecting far-IR radiative transitions are only weakly permitted. The column density of C3H in IRC +10216 averaged over the estimated source diameter of 84" is 2.8 x 10(13) cm-2, an order of magnitude less than that of C2H and C4H. A determination of the spectroscopic constraints of C3H that permitted the entire radio spectrum of this molecule to be calculated to high accuracy has been derived from analysis of the combined astronomical and laboratory data presented in the accompanying Letter.

Survey on body image, weight, and diet of college students.

In this study, college students visiting a university health service were categorized according to various anthropometric measurements and completed a questionnaire. Fifty-five per cent of the men were realistic in their self-perception of body size, but 63 per cent of the women perceived themselves to be one category of weight higher than they actually were. Fifty-six per cent of the students sampled (but only 60 per cent of those who were dissatisfied with their body images) said they were modifying their eating practices. The majority of students were realistic in their goals for weight loss, but 46 per cent of the women wanted to be underweight or slightly underweight.