This letter reports a design for high-power single-mode operation in vertical-cavity surface-emitting lasers by means of modal gain control using two different sized current apertures to shape the injection-current profile. A smaller current aperture is located several mirror-pairs away from the active region in the p-mirror and a larger current aperture is located in the first n-mirror-pair next to the active region. Both theoretical modeling and experimental test results show substantial improvement in the optical mode behavior using this approach when compared to a traditional single-aperture design. A clear trend of the spectral purity in the modal behavior under continuous wave and pulsed conditions is demonstrated and is in good agreement with theoretical predictions. The best design tested demonstrated a room-temperature continuous wave power output of 7.5mW with a side mode suppression ratio of 20dB.
IntroductionThere have recently been several clinical studies suggesting that brief periods of exposure to red light (repeated low‐level red light, ‘RLRL’) may produce a dramatic anti‐myopia effect, calling for further investigations into its therapeutic parameters. Unfortunately, many experimental species used in refractive studies develop myopia in response to this wavelength. Tree shrews are the only animal model other than rhesus monkeys that consistently exhibit hyperopic responses to ambient red light. Here, tree shrews were used to study the influence of the spectral purity, duty cycle and intensity of red light on its anti‐myopic effect.MethodsJuvenile tree shrews (Tupaia belangeri) were raised from 24 to 35 days after eye opening under ambient lighting that was: standard white colony fluorescent light; pure narrow band red light of either 600, 50–100 or 5 lux; red light that was diluted with 10% white light (by lux) or 50% white and 2 s of pure red light that alternated with 2 s of pure white light (50% duty cycle). Refractive measures were taken with a NIDEK ARK‐700 autorefractor and axial dimensions with a LenStar LS‐900 Axial Biometer.ResultsThe pro‐hyperopia effect of ambient red light was greatly reduced by even small amounts of concurrent white light ‘contamination’, but remained robust if 2‐s periods of pure white light alternated with 2 s of red. Finally, the hyperopic effect of red light was maintained at reduced luminance levels in the 50–100 lux range and only failed at 5 lux.ConclusionsThese results have implications for understanding the mechanisms by which ambient red light affects refractive development, and possibly also for clinical therapies using RLRL. Nevertheless, it remains to be determined if the mechanism of the current clinical RLRL therapy is the same as that operating on tree shrews in ambient red light.
We propose using electronic equalization technology to allow components typically used in 2.5Gb/s systems to be used at 10Gb/s. We simulate the performance of links exploiting this concept and study the effect of receiver bandwidth on equalized systems in general. Links utilizing transmitters designed for 2.5Gb/s rates are experimentally demonstrated. Experiments also show that photo-receivers with 2.5 GHz bandwidths add minimal penalty when post-detection electronic equalization is employed.
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