Search

Polyunsaturated fatty acids (PUFAs) are critical to nervous system function and structure, but their rates of incorporation from plasma into brain have not been evaluated. In the adult rat, calculations based on our model show that at least 3–5% of esterified brain arachidonic acid (AA) and 2–8% of esterified brain docosahexaenoic acid (DHA) are replaced daily by unesterified PUFAs in plasma. These rates, when related to unlabeled brain PUFA composition, give half-lives of 1–2 weeks for plasma-brain exchange of AA and DHA. In the human brain, the arachidonate replacement rate is 0.3% per day.Although unesterified plasma PUFA concentrations are low, their rates of incorporation into brain are sufficient to compensate for metabolic and efflux losses, so that PUFA transport from plasma into brain as a component of a lipoprotein is unnecessary. Dietary supplementation, by altering plasma unesterified PUFA concentrations, can regulate brain PUFA content and may help to treat brain diseases involving PUFA imbalance.

In contrast to absorbers, where the delay time via wave mixing saturates to its maximum with increasing device length due to decay of pump power along the device, in semiconductor optical amplifiers (SOAs) the delay time increases with the device length and is limited by the corresponding growth of the SOA gain, which can lead to unacceptable amplified stimulated emission in the SOA. The number of pulses which can be stored in an SOA, defined by the gain and group velocity dispersion, also is given ultimately by this SOA gain limitation, and is estimated between one and two. [ABSTRACT FROM PUBLISHER]

High-speed directly modulated diode lasers are important for optical communications and optical interconnects. In this work, we demonstrate greatly enhanced resonance frequency for vertical-cavity surface-emitting lasers, from 7 to 50 GHz, under ultrahigh injection-locking conditions. In addition, a 20-dB gain is achieved for small signal modulation below resonance frequency. [ABSTRACT FROM PUBLISHER]

We report injection-locked vertical-cavity surface-emitting lasers simultaneously achieving high extinction ratios of 20 dB, enhanced resonance frequency >30 GHz, and radio-frequency signal amplification of >10 dB, for the first time. [ABSTRACT FROM PUBLISHER]

We report an ultracompact label-free biosensor that uses a vertical-cavity surface-emitting laser (VCSEL)-based measurement system for the characterization of biomolecular interactions. It consists of a VCSEL, a plastic guided-mode resonant filter, and two p-i-n detectors. The system has demonstrated very high sensitivity to molecules on top of the sensor. [ABSTRACT FROM PUBLISHER]

We report the first experimental demonstration of a novel single-layer subwavelength grating (SWG) that has >500-nm-wide reflection spectrum from 1.12-1.62 μm and very high reflectivity (>98.5%). This SWG is scalable for different wavelengths by simply changing the grating dimensions, which, thus, facilitates monolithic integration of devices over a wide range of wavelengths. [ABSTRACT FROM PUBLISHER]

We study the temperature effects on injection-locked vertical-cavity surface-emitting lasers (VCSELs) for use in wavelength-division-multiplexed (WDM) transmitters. We show that injection locking can be used to lock an uncooled VCSEL to the WDM grid while improving its analog performance. [ABSTRACT FROM PUBLISHER]

We report a novel subwavelength grating that has a very broad reflection spectrum and very high reflectivity. The design is scalable for different wavelengths. It facilitates monolithic integration of optoelectronic devices at a wide range of wavelengths from visible to far infrared. [ABSTRACT FROM PUBLISHER]

Injection locking is demonstrated to improve the analog performance of long wavelength vertical-cavity surface-emitting lasers. The third-harmonic dynamic range was improved by ∼20 dB·Hz23/ to be ∼94 dB·Hz23/, and the modulation bandwidth was increased two fold. The locking conditions are studied and show that the improvement is present over a wide range of injection power and wavelength detuning. [ABSTRACT FROM PUBLISHER]

We demonstrate a novel buried oxide-grating structure formed by selectively oxidized AlxGa1-xAs grown on nonplanar substrates using low-pressure metal-organic chemical vapor deposition (MOCVD) for the first time. Localized aluminum content variation in AlGaAs is obtained with MOCVD growth on nonplanar substrate. Buried aluminum oxide/semiconductor-distributed-feedback structure is achieved with selective oxidation of these AlGaAs layers. We fabricated a resonant-cavity-enhanced photodetector with the imbedded buried-oxide structure and measured the photodetector responsivity spectrum. [ABSTRACT FROM PUBLISHER]