We study nonlinear far-field propagation of Kerr spatial solitons along a graphene monolayer embedded planar dielectric waveguide. The volumetric permittivity approach model of graphene is introduced to incorporate this carbon atoms layer into our optical simulations, which mathematically approximate graphene by a very thin layer with a finite thickness. A remarkably large third-order nonlinear optical susceptibility of graphene measured in previous experiment is considered in the numerical simulations. We demonstrate numerically that the TE-polarized beam forms Kerr spatial solitons at high beam intensity, due to the nonlinearity of graphene compensates diffraction losses. It’s very interesting that the Kerr optical solitons can adjust the beam width when propagating to become narrower. We suppose that it’s the selfregulation of the solitons after separating a portion of energy during the transmission process to become more compact. Our simulation results also reveal that the optical field distribution of Kerr optical solitons exhibits obvious periodic oscillation along the propagating path. This is a novel phenomenon that the dynamic regulation of the light field causes spatial oscillation of the solitons and a periodic change in the effective refractive index of graphene monolayer, forming a Kerr-induced index grating in the waveguide. We emphasize that the spatial oscillation of the solitons is due to the dynamic regulation of the light field, with a process of alternating self-focusing and defocusing. We predicate that the transmittance will be improved due to the nonlinear phase modulation by the Kerr-induced index grating through the waveguide.
Compressive imaging（CI）can offer a versatile improvements for imaging systems, such as smaller compressed data volume and super-resolution. Among various methods to realize Compressive imaging, pushing encoding mask has attracted the most attention with its compatibility to the space remote sensing. However, complex pre- calibrations are usually needed for calibrating the encoding mask to achieve the measurement matrix for the image reconstruction. Herein, we design a pushing compressive imaging system which fixed with the function of situ calibration of the encoding mask. The pushing compressive imaging system was constructed, and the experimental results confirmed that the system had the ability for data compression and super-resolution. And above all, the system can avoid the complex pre-calibration, which makes the on-orbit calibration feasible. In the simulations, twice, three times and four times resolutions higher than the captured image’s resolution are performed respectively, which confirm that the method can improve the target image resolution based on the relative low resolution raw captured target images. Furthermore, by pushing the mask precisely which can be considered equivalent to the real pushing imaging, we have reconstructed the true super-resolution target image accurately based on the mask calibration and 6 captured pushing imaging frames.
One of the most important branches in the development trend of the traditional fiber optic physical sensor is the miniaturization of sensor structure. Miniature fiber optic sensor can realize point measurement, and then to develop sensor networks to achieve quasi-distributed or distributed sensing as well as line measurement to area monitoring, which will greatly extend the application area of fiber optic sensors. The development of MEMS technology brings a light path to address the problems brought by the procedure of sensor miniaturization. Sensors manufactured by MEMS technology possess the advantages of small volume, light weight, easy fabricated and low cost. In this paper, a fiber optic extrinsic Fabry-Perot interferometric underwater acoustic probe utilizing micromachined diaphragm collaborated with fiber optic technology and MEMS technology has been designed and implemented to actualize underwater acoustic sensing. Diaphragm with central embossment, where the embossment is used to anti-hydrostatic pressure which would largely deflect the diaphragm that induce interferometric fringe fading, has been made by double-sided etching of silicon on insulator. By bonding the acoustic-sensitive diaphragm as well as a cleaved fiber end in ferrule with an outer sleeve, an extrinsic Fabry-Perot interferometer has been constructed. The sensor has been interrogated by quadrature-point control method and tested in field-stable acoustic standing wave tube. Results have been shown that the recovered signal detected by the sensor coincided well with the corresponding transmitted signal and the sensitivity response was flat in frequency range from 10 Hz to 2kHz with the value about -154.6 dB re. 1/μPa. It has been manifest that the designed sensor could be used as an underwater acoustic probe.
A high coupling efficiency silicon grating which serves both as a high extinction ratio polarization beam splitter and
a vertical coupler for silicon photonic circuits at the wavelength of 1550nm is presented. The design is based on the
Bragg diffraction condition and the phase matching equation by using the rigorous coupled wave analysis (RCWA).
For TE-polarized light, the computing coupling efficiency is as high as 69%, and the extinction ratio can reach -
20dB. The efficiency of TM-polarized wave is better than 53% and the extinction ratio is approximately -11dB. The
device has compact structure, high TE to TM extinction ratio, low excess loss and wide operation bandwidth.
Moreover, the simple fabrication method involves only single etch step and good compatibility with complementary
metal oxide semiconductor (CMOS) technology.
Model of non-line-of-sight (NLOS) UV transmission was introduced, NLOS UV transmission was simulated using
Monte-Carlo method. Impact of visibility, rainfall, wind speed, light source radiation power, detector sensitivity on
transmission range was debated. Results showed that visibility and rainfall had relative impact on transmission range,
while wind speed hardly had any influence, it was a main way to improve range by enhancing detector sensitivity, and it
weren't very effective to increase source radiation power.