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.

Design of broadband subwavelength grating couplers with low back reflection

Abstract: We present a methodology to design broadband grating couplers using one-dimensional subwavelength gratings. Using the presented method, we design subwavelength grating couplers (SWGCs) with 1-dB bandwidths ranging from 50 to 90 nm. Our designed SWGCs have competitive coupling efficiency, as high as -3.8 dB for the fundamental TE mode, and state-of-the-art back reflections, as low as -23 dB.

Tunable long-period optical grating device and optical systems employing same

Abstract: A device and method for dynamically tuning a long-period grating of an optical fiber is disclosed. The grating is made tunable by using a controlled strain imposed on the fiber adjacent the grating, wherein the strain comprises an electromechanical force, magnetostrictive force, magnetic force, or a thermally-induced force. An improved optical communication system comprising a dynamically gain-equalized amplifier device, a wavelength feedback device, and the tunable long-period grating device is also disclosed. In the communications system, the grating device is reconfigured to have a desired broadband filtering frequency, thus equalizing the amplifier gain, in response to feedback from the wavelength detector.

Display element and observation apparatus having the same

Abstract: A display element includes a substrate and a display pattern formed on the substrate, the display pattern including a diffraction grating. The width in the direction perpendicular to the grating lines of the diffraction grating of the display pattern is selected so as to prevent re-diffraction of the light diffracted by the one diffraction grating. An observation apparatus includes the afore-said display element, but the display pattern has a first diffraction grating structure and a second diffraction grating structure. An illuminating system and an observation system are added so as to allow for observation of the display pattern. The direction of the grating lines of the first diffraction grating structure differs from that of the grating lines of the second diffraction grating structure, thereby preventing the occurrence of a rainbow-like image.

Temperature compensation of long-period fiber grating for refractive-index sensing with bending effect

Abstract: In this letter, we show that by properly mounting a bent long-period fiber grating (LPFG) on a suitable material, the temperature dependence of the resonance wavelength of the LPFG can be largely eliminated. With this method, we reduced the temperature sensitivity of the resonance wavelength of a typical LPFG by two orders of magnitude from -0.933 nm//spl deg/C to 0.008 nm//spl deg/C. The principle of using this mounted LPFG as a temperature-insensitive chemical concentration or refractive-index sensor is demonstrated.

Numerical solution of diffraction problems: a method of variation of boundaries. II. Finitely conducting gratings, Padé approximants, and singularities

Abstract: We recently introduced a method of variation of boundaries for the solution of diffraction problems [ J. Opt. Soc. Am. A10, 1168 ( 1993)]. This method, which is based on a theorem of analyticity of the electromagnetic field with respect to variations of the interfaces, has been successfully applied in problems of diffraction of light by perfectly conducting gratings. We continue our investigation of diffraction problems. Using our previous results on analytic dependence with respect to the grating groove depth, we present a new numerical algorithm that applies to dielectric and metallic gratings. We also incorporate Pade approximation in our numerics. This addition enlarges the domain of applicability of our methods, and it results in computer codes that can predict more accurately the response of diffraction gratings in the resonance region. In many cases results are obtained that are several orders of magnitude more accurate than those given by other methods available at present, such as the integral or differential formalisms. We present a variety of numerical applications, including examples for several types of grating profile and for wavelengths of light ranging from microwaves to ultraviolet, and we compare our results with experimental data. We also use Pade approximants to gain insight into the analytic structure and the spectrum of singularities of the fields as functions of the groove depth. Finally, we discuss some connections between Pade approximation and another summation mechanism, enhanced convergence, which we introduced in the earlier paper. It is argued that, provided that certain numerical difficulties can be overcome, the performance of our algorithms could be further improved by a combination of these summation methods.