Using nonlinear ring resonators for designing an all optical comparator

An all optical comparator is designed based on photonic crystals. The proposed structure was designed based on optical threshold switching that is realized using three nonlinear ring resonators. All nonlinear rings have the same optical characteristics, such that they can drop low intensity (as low as 0.5 W/μm2) optical waves at 1550 nm, but cannot drop the optical waves with optical intensity of 1 W/μm2. For the proposed structure the rise and fall time are about 2 and 1 ps, respectively. Therefore the bit rate is about 167 GHz and the ON/OFF contrast ratios for O1, O2, and O3 are 13.5, 13.6, and 13.3 dB, respectively.

A high speed all optical half adder using photonic crystal based nonlinear ring resonators

In this paper a high speed optical half adder is designed. The working mechanism of the proposed structure is based on optical threshold switching. Three nonlinear ring resonators are used for this purpose. These nonlinear ring resonators are created by adding doped glass based rods inside the resonant rings. The proposed structure works with optical waves with central wavelength and optical intensity equal to 1550 nm and 1 W/μm2 respectively. The rise time is 2 ps.

Optical Intensity Far-Field Distribution of MEMS Micro-mirror Arrays by Fraunhofer Diffraction

Compared with liquid crystal clad waveguide, MEMS mirror has some merits, such as high-er-transmissivity, lager-angle of scanning, faster scanning speed and so on. Furthermore, MEMS mirror arrays perform more superior than MEMS mirror when they steer laser beam, which make MEMS arrays much more suitable to be used in devising compact Lidar. Before assembling a Lidar with MEMS arrays, the optical intensity and distributions of the laser diffracted by MEMS arrays should be analyzed, but few published papers about this issue are available so far, this paper will focus on this issue about MEMS arrays. Firstly, the complex amplitudes of laser which is diffracted by 1-D and 2-D arrays are presented, respectively. Then the optical intensity and distributions on the observation plane are presented. Finally, the simulation diagrams of these distributions are shown, and the correctness of the results is indirectly verified by Young’s dou-ble-slit experiment. The results gotten in this letter are essential to design a compacted Lidar based on MEMS arrays.

Optical Coherence Tomography Biomarkers of Photoreceptor Degeneration in Retinitis Pigmentosa

Purpose: Several parameters on optical coherence tomography (OCT) have been suggested as biomarkers for photoreceptor degeneration in retinitis pigmentosa (RP). This study is to investigate which OCT parameters can serve as the earliest biomarkers in RP.Methods: OCT line scans of the horizontal meridian were conducted in 22 eyes of 22 RP patients and 30 eyes of 30 healthy controls. Longitudinal reflectance profiles were obtained using ImageJ at every 5 pixels. The following parameters on OCT were quantitatively measured: 1) relative optical intensity (ROI) of ellipsoid zone (EZ) and interdigitation zone (IZ); 2) thickness of outer nuclear layer (ONLT), photoreceptor (PRT), inner segment (IST) and outer segment (OST). The variations of these parameters across different regions were analyzed. Results: From fovea to peripheral retina, all the OCT biomarkers declined before disappeared, except IST and IZ-ROI. There was no identifiable declining zone for the IST and IZ-ROI between the normal and disappeared zones. The earliest biomarker was the shortening of OST and reduced IZ-ROI, followed by the shortening of PRT, EZ-ROI, then IST, and finally, ONLT. All these biomarkers had significant correlations with best-corrected visual acuity, except ONLT.Conclusion: In retinitis pigmentosa, EZ-ROI, IZ-ROI, PRT, OST, IST and ONLT are valuable biomarkers of photoreceptor degeneration. OST and IZ-ROI may serve as the earliest biomarkers.

Conjugate pulsating aurora and chorus waves: case study at high temporal resolution

<p>Studies have shown a broad correlation between pulsating aurora, chorus waves, and electron scattering, but most studies have used either low time resolution waveform data, high time resolution waveform data over short periods of time, or waveform data without direct crossover of an all sky camera field of view. For the present study, we analyze three nights in Oct 2016 with conjugate Van Allen Probe (VAP) chorus wave observations and HAARP all sky camera (ASC) pulsating aurora observations. We use VAP burst mode waveform data collected for about an hour at 16,000 samples/s during direct VAP crossover of the HAARP ASC FOV in Gakona, AK. Our high-resolution analysis indicates a more complicated relationship between individual aurora pulsations and chorus wave elements.</p><p>We show in previous study that for each VAP ASC crossover event on October 16 2016, the chorus wave elements observed by VAP do not correspond well to the detailed dynamics of the pulsating aurora. We compare the individual chorus wave elements to the extracted all sky camera optical intensity fluctuations along the mapped magnetic footpoint determined by four separate field line models. Our Poynting flux analysis shows chorus wave propagation towards the northern hemisphere. Based on previous results using THEMIS data, we would expect to see good correlation between the observed chorus waves above the magnetic equator and the pulsating aurora dynamics in the northern hemisphere. However, observed chorus waves may be distorted during propagation away from the generation region or non-linear wave effects may play a role.</p><p>In this study we extend our analysis to the VAP ASC crossover events on October 13 and 19 2016. We expand our methodologies for optical intensity extraction of ASC images. We seek to draw connections between the characteristics of the individual chorus wave elements and the correlation to pulsating aurora dynamics to better identify particular chorus wave electron resonance conditions.</p>