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.

Coupled-mode theory for light propagation through deep nonlinear gratings.

Abstract: In ordinary coupled-mode theory, the standard tool to analyze optical grating structures in both linear and nonlinear regimes, the grating is usually assumed to be shallow. Here we generalize this theory in a systematic way to include deep gratings. We do so by expanding in the exact eigenfunctions of the linear structure (the Bloch functions) rather than simply in the forward and backward propagating modes. We show that the resulting equations for deep gratings are qualitatively similar to those for shallow ones, except that the value of some of the coefficients is different and that some additional nonlinear terms arise. We also discuss solutions to these equations and point out differences from solutions of the conventional theory. \textcopyright{} 1996 The American Physical Society.

Efficient reflective multiplexer arrangement

Abstract: The efficiency and freedom from cross-talk achieved by transmissive multiplexer/demultiplexer devices is achieved in a reflective multiplexer/demultiplexer device. The reflective geometry avoids the large size devices necessitated by transmissive geometries handling a large number of optical channels. The reflective geometry also avoids long bends in waveguides used in optical gratings in high efficiency transmissive geometries. Integrated optical multiplexers/demultiplexers in accordance with this invention comprise a plurality of waveguides for carrying unmultiplexed optical signals interleaved with a plurality of waveguides for carrying multiplexed optical signals. The two pluralities of waveguides are connected to the boundary of a free space region. The pluralities of waveguides communicate through the free space region with an optical grating comprising a plurality of waveguides each terminated in a reflective element. The length of each waveguide in the grating differs from the lengths of adjacent waveguides in the grating by a predetermined amount to introduce predetermined path length differences for the optical signals traveling in the waveguides of the grating. Unmultiplexed optical signals, introduced into one or more of the input waveguides for carrying unmultiplexed optical signals, travel through those waveguides into the optical grating and are reflected towards one or more of the output waveguides for carrying multiplexed optical signals. When the device is used as a multiplexer in this fashion, it causes the optical signals introduced into the device to be multiplexed together and appear in a predetermined one or more of the waveguides for carrying multiplexed signals. Multiplexed optical signals introduced into one or more of the waveguides for carrying multiplexed signals are directed through the free space region to the optical grating and are reflected toward one or more of the output waveguides for carrying unmultiplexed optical signals. When the device is used as a demultiplexer in this manner, input signals which comprise a mixture of optical frequencies are demultiplexed so that the individual optical frequencies are separated from one another and appear at one or more predetermined waveguides for carrying unmultiplexed optical signals.

Polarization and switching properties of holographic polymer-dispersed liquid-crystal gratings. I. Theoretical model

Abstract: Polarization properties and electro-optical switching behavior of holographic polymer-dispersed liquid-crystal (HPDLC) reflection and transmission gratings are studied. A theoretical model is developed that combines anisotropic coupled-wave theory with an elongated liquid-crystal-droplet switching model and includes the effects of a statistical orientational distribution of droplet-symmetry axes. Angle- and polarization-dependent switching behaviors of HPDLC gratings are elucidated, and the effects on dynamic range are described. A new type of electro-optical switching not seen in ordinary polymer-dispersed liquid crystals, to the best of the author’s knowledge, is presented and given a physical interpretation. The model provides valuable insight to the physics of these gratings and can be applied to the design of HPDLC holographic optical elements.

Singlemode laser source tunable in wavelength with a self-aligned external cavity

Abstract: This invention relates to a singlemode laser source tunable in wavelength with a self-aligned external cavity, comprising: a resonant cavity having an output face that is partially reflecting (331) and a retroreflecting dispersive device (31, 39), defining a main collimating axis (351) and a secondary collimating axis (381), an amplifier wave guide (33) placed in position inside the resonant cavity The retroreflecting dispersive device comprises a plane diffraction grating (31) having dispersion planes and an orthogonal reflecting dihedral (39) whose line of intersection (391)is parallel to the dispersion plane of the diffraction grating containing the collimating axes (351, 352)

Enhanced type IIA gratings for high-temperature operation

Abstract: The inscription of type IIA fiber Bragg gratings in standard boron-codoped germanosilicate fiber has been demonstrated to show marked differences from that reported in the literature. These gratings were subjected to high temperatures, and their decay behavior was evaluated. Gratings resistant to heat up to 800 °C for a moderate length of time are demonstrated.