Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium for managing beam shaping in gradient refractive index (GRIN) media are provided. In one aspect, a method includes specifying a field evolution throughout a gradient-index (GRIN) medium and generating a refractive index profile of the GRIN medium based on the specified field evolution in the GRIN medium. Diffraction effects are considered in solving for the refractive index profile. The index profile is found by specifying a desired beam transformation throughout the GRIN medium and solving a series of phase retrieval problems. The GRIN medium can be two-dimensional (2D) or three-dimensional (3D).

Abstract: The present invention includes a method and system for compensating for cross-talk interference in communication systems. The method includes estimation of the interfering signals. Further, the method includes performing a compensation operation on at least one interfering signal.

Abstract: An infrared photodetector structure with voltage-tunable and -switchable photoresponses constructed of superlattices and blocking barriers. The photoresponses of the double-superlattice structure are also insensitive to the operating temperature changes. By using GaAs/AlxGa1-xAs system, the feasibility of this idea is verified. In the embodiment, the photoresponses can be switched between 6˜8.5 and 7.5˜12 m by the bias polarity and are also tunable by the bias magnitude in each detection wavelength range. In addition, the photoresponses are insensitive to operating temperatures ranging from 20 to 80 K. For the SLIP with few periods, the responsivity may be higher than the one with many periods and the operational temperature is higher. These results show the invention can be useful in the design of multicolor imaging systems.

Abstract: An infrared photodetector structure with voltage-tunable and -switchable photoresponses constructed of superlattices and blocking barriers. The photoresponses of the double-superlattice structure are also insensitive to the operating temperature changes. By using GaAs/AlxGa1-xAs system, the feasibility of this idea is verified. In the embodiment, the photoresponses can be switched between 6˜8.5 and 7.5˜12 m by the bias polarity and are also tunable by the bias magnitude in each detection wavelength range. In addition, the photoresponses are insensitive to operating temperatures ranging from 20 to 80 K. For the SLIP with few periods, the responsivity may be higher than the one with many periods and the operational temperature is higher. These results show the invention can be useful in the design of multicolor imaging systems.

Abstract: A method of forming a phase shift mask is disclosed. After providing a substrate with a shifter layer and a Cr layer, a first photoresist layer is formed on the Cr layer. Thereafter, a position of a shifter pattern is defined by using E-beam writing process and then a develop process is performed. After that, a first Cr pattern is formed by using an etching process to etch the Cr layer. After removing the first photoresist layer, the shifter pattern is formed by using an etching process to etch the shifter layer. After forming a second photoresist layer, an exposure process of conventional photolithography is performed by means of a boarder mask to define a position of a second Cr pattern. After performing a develop process, the second Cr pattern is formed by using an etching process to etch the first Cr pattern.