Optical Waveguide Theory

Infrared and visible image fusion methods and applications: A survey

By exploiting the interaction between light and phonons in a silica microsphere resonator it is possible to generate Brillouin scattering induced transparency, which is akin to electromagnetically induced transparency but for acoustic waves.

Non-reciprocal Brillouin scattering induced transparency

Absorption, scattering, and color distortion are three major degradation factors in underwater optical imaging. Light rays are absorbed while passing through water, and absorption rates depend on the wavelength of the light. Scattering is caused by large suspended particles, which are always observed in an underwater environment. Color distortion occurs because the attenuation ratio is inversely proportional to the wavelength of light when light passes through a unit length in water. Consequently, underwater images are dark, low contrast, and dominated by a bluish tone. In this paper, we propose a novel underwater imaging model that compensates for the attenuation discrepancy along the propagation path. In addition, we develop a robust color lines-based ambient light estimator and a locally adaptive filtering algorithm for enhancing underwater images in shallow oceans. Furthermore, we propose a spectral characteristic-based color correction algorithm to recover the distorted color. The enhanced images have a reasonable noise level after the illumination compensation in the dark regions, and demonstrate an improved global contrast by which the finest details and edges are enhanced significantly.

Contrast enhancement for images in turbid water

The flexibility of microwave photonics provides advantages over electronic circuitry, yet the lack of integrated chip-scale devices limits its practical application. This study presents microwave filters based on photonic crystal waveguides with controllable delays as a step towards intregable circuits.

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Integrable microwave filter based on a photonic crystal delay line

Many dehazing methods have proven to be effective in removing haze out of the hazy image, but few of them are adaptive in handling the dense haze. In this paper, based on the angle of polarization (AOP) distribution analysis we propose a kind of polarimetric dehazing method, which is verified to be capable of enhancing the contrast and the range of visibility of images taken in dense haze substantially. It is found that the estimating precision of the intensity of airlight is a key factor which determines the dehazing quality, and fortunately our method involves a high precision estimation inherently. In the experiments a good dehazing performance is demonstrated, especially for dense haze removal. We find that the visibility can be enhanced at least 74%. Besides, the method can be used not only in dense haze but also in severe sea fog.

Polarimetric dehazing method for dense haze removal based on distribution analysis of angle of polarization.

A new kind of polymer porous fiber with elliptical air-holes is designed for obtaining high birefringence in the terahertz (THz) frequency range in this paper. Using the finite element method, the properties of this kind of fiber are simulated in detail including the single-mode propagation condition, the birefringence, and the loss. Theoretical results indicate that the single-mode THz wave in the frequency range from 0.73 to 1.22 THz can be guided in the fiber; the birefringence can be enhanced by rotating the major axis of the elliptical air-hole and there exists an optimal rotating angle at 30°. At this optimal angle a birefringence as high as 0.0445 can be obtained in a wide frequency range. Low-loss THz guidance can be achieved owing to the effective reduction of the material absorption in such a porous fiber. This research is useful for polarization-maintaining THz-wave guidance.

High-birefringence, low-loss porous fiber for single-mode terahertz-wave guidance

Broadband, low-loss, dispersion flattened porous-core photonic bandgap fiber for terahertz (THz)-wave propagation

A novel polarimetric dehazing method is proposed based on three linear polarization images (0°, 45°, and 90°). The polarization orientation angle of the light scattered by the haze particles is introduced in the algorithm. No additional image-processing algorithm is needed in the postprocessing. It is found that the dehazed image suffers from little noise and the details of the objects close to the observer can be preserved well. In addition, this algorithm is also proved to be useful for preserving image colors. Experimental results demonstrate that such an algorithm has some universality in handling all kinds of haze. We think that this robust algorithm might be very suitable for real-time dehazing.

Method for enhancing visibility of hazy images based on polarimetric imaging

We demonstrate that slow light with large group-index, wideband, and low dispersion can be realized in a silicon-on-insulator w1-type photonic crystal waveguide by simply shifting the first two rows of air-holes adjacent to the waveguide to specific directions. keeping the group index at 46, 60, 86, 111, 151, and 233, respectively, while restricting its variation within a +/- 10% range, we accordingly obtain a slow light bandwidth of 9.0 nm, 6.7 nm, 4.6 nm, 3.3 nm, 2.4 nm, and 1.7 nm, respectively. the normalized delay-bandwidth product keeps around 0.25 for all cases. moreover, we obtain ultraflat slow light with bandwidths over 3.0 nm, 2.4 nm, 1.6 nm, 1.3 nm, 0.93 nm, and 0.6 nm, respectively, where the group index variation is in a range of only +/- 0.8%. numerical simulations are performed, utilizing the 2d plane wave expansion method and the finite-difference time-domain method. (c) 2011 american institute of physics. [doi:10.1063/1.3634074]

Jian Liang

Papers

Polarimetric dehazing method for dense haze removal based on distribution analysis of angle of polarization.

High-birefringence, low-loss porous fiber for single-mode terahertz-wave guidance

Broadband, low-loss, dispersion flattened porous-core photonic bandgap fiber for terahertz (THz)-wave propagation

Method for enhancing visibility of hazy images based on polarimetric imaging

Wideband ultraflat slow light with large group index in a W1 photonic crystal waveguide