Diffraction grating

About: Diffraction grating is a research topic. Over the lifetime, 24884 publications have been published within this topic receiving 372437 citations. The topic is also known as: grating.

Single-mode operation of terahertz quantum cascade lasers with distributed feedback resonators

Abstract: Single-mode operation at 4.4 THz is obtained from distributed-feedback quantum-cascade lasers with complex-coupling metallic gratings. The emission shows a stable side-mode suppression of more than 20 dB at all injection currents and operating temperatures

Compact slanted grating couplers

Abstract: We present a compact and efficient design for slanted grating couplers (SLGC's) to vertically connect fibers and planar waveguides without intermediate optics. The proposed SLGC employs a strong index modulated slanted grating. With the help of a genetic algorithm-based rigorous design tool, a 20microm-long SLGC with 80.1% input coupling efficiency has been optimized. A rigorous mode analysis reveals that the phase-matching condition and Bragg condition are satisfied simultaneously with respect to the fundamental leaky mode supported by the optimized SLGC.

Optical low coherence method for characterizing silica-based arrayed-waveguide grating multiplexers

Abstract: We describe a powerful method for the precise measurement of optical path phase errors and power-distribution coefficients in silica-based arrayed-waveguide grating multiplexers through the use of Fourier transform spectroscopy. The theoretical accuracies for measuring these parameters are /spl plusmn/1/spl deg/ and /spl plusmn/5%, respectively, when the geometrical step increment of the arrayed waveguides is greater than 48 /spl mu/m. The method reveals the random distributions of optical path phase errors in two multiplexers with channel spacings of 100 and 10 GHz, and proves that these distributions are the main origins of the channel crosstalk. The method predicts that when optical path phase errors are sufficiently reduced, the channel crosstalk values will decrease to -39 and -29 dB, respectively, and these limits are due to slightly deformed power distributions.

Fabrication of ultrahigh aspect ratio freestanding gratings on silicon-on-insulator wafers

Abstract: The authors report a silicon-on-insulator (SOI) process for the fabrication of ultrahigh aspect ratio freestanding gratings for high efficiency x-ray and extreme ultraviolet spectroscopy. This new grating design will lead to blazed transmission gratings via total external reflection on the grating sidewalls for x rays incident at graze angles below their critical angle (about 1°–2°). This critical-angle transmission (CAT) grating combines the alignment and figure insensitivity of transmission gratings with high broadband diffraction efficiency, which traditionally has been the domain of blazed reflection gratings. The required straight and ultrahigh aspect ratio freestanding structures are achieved by anisotropic etching of ⟨110⟩ SOI wafers in potassium hydroxide (KOH) solution. To overcome structural weakness, chromium is patterned as a reactive ion etch mask to form a support mesh. The grating with period of 574nm is written by scanning-beam interference lithography (SBIL) which is based on the interfer...

Plane wave scattering and absorption by resistive-strip and dielectric-strip periodic gratings

Abstract: The problems of plane wave scattering by resistive- and dielectric-strip gratings are considered. The formulation involves a set of resistive-type boundary conditions that characterizes nonzero jumps in tangential field components. The method of solution is based on analytical inversion of the static part of the full-wave equations and results in a rapidly convergent numerical algorithm. The dependences of the transmitted, reflected, and absorbed power fractions on the electrical and material parameters are presented.