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.

A theoretical analysis of etched grating couplers for integrated optics

Abstract: Grating couplers provide an attractive method for the excitation of optical thin-film waveguides. We present here a perturbation analysis of etched or deposited grating couplers based upon both the transmission line and the Green's Function approaches, which predict the coupling efficiency, the output radiation beamwidth, the angular dependence of excitation, and the intensities of the other orders of the diffracted beams as functions of the grating periodicity, grating groove depth, and excitation direction. It is found that the maximum excitation efficiency is 81 percent, that high efficiency can be achieved by excitation from the substrate, and that higher efficiency is obtained when the radiation leakage to the side orders is minimized.

Generalized expression for the growth of long period gratings

Abstract: Experimental results have shown that the peak loss wavelength of long period gratings can shift in the direction of either shorter or longer wavelengths as the induced index change of the grating increases. An expression, which the authors believe to be novel, is derived and verified experimentally, to explain this phenomena. It is shown that the waveguide dispersion characteristics of the core and clad effective indices play a key role in the evolution of the transmission characteristics of the grating.

Numerical analysis of polarization gratings using the finite-difference time-domain method

Abstract: We report the first full numerical analysis of polarization gratings (PGs), and study their most general properties and limits by using the finite-difference time-domain (FDTD) method. In this way, we avoid limiting assumptions on material properties or grating dimensions (e.g., no paraxial approximations) and provide a more complete understanding of PG diffraction behavior. We identify the fundamental delineation between diffraction regimes (thin versus thick) for anisotropic gratings and determine the conditions for $\ensuremath{\approx}100%$ diffraction efficiency in the framework of the coupled-wave $\ensuremath{\rho}$ and $Q$ parameters. Diffraction characteristics including the efficiency, spectral response, and polarization sensitivity are investigated for the two primary types of PGs with linear and circular birefringence. The angular response and finite-grating behavior (i.e., pixelation) are also examined. Comparisons with previous analytic approximations, where applicable, show good agreement.

Fiber gratings in lasers and amplifiers

Abstract: The emergence of UV-written fiber gratings, both short and long period, as a reliable fiber technology has revolutionized the field of active fiber devices. The advantageous properties of spectral selectivity, low insertion loss, and component ruggedness have made devices possible that would not be viable without their use. The use of fiber gratings in conjunction with erbium-doped fiber amplifiers (EDFAs), fiber lasers, and with semiconductor diode lasers is reviewed.

Modeling and performance analysis of a fiber Bragg grating interrogation system using an acousto-optic tunable filter

Abstract: The performance of a fiber grating interrogation system using an acousto-optic tunable filter (AOTF) is analyzed. An equivalent linear circuit is presented to describe the system, which tracks the wavelength of a fiber Bragg grating (FBG) sensor in a FBG sensor array. From the model, the tracking resolution of a shot-noise-limited system has been determined for both transmissive and reflective interrogation of FBGs. An optimum ratio between the bandwidths of the FBG and the AOTF has been derived. Experimental results of a tracking system are presented to validate the theoretical predictions. The theory should also be suitable for interrogation systems using other forms of tunable bandpass filters for tracking the FBG wavelength.