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.

Achromatic interferometric lithography for 100‐nm‐period gratings and grids

Abstract: For the fabrication of periodic structures with spatial periods of 100 nm or less, achromatic interferometric lithography is preferred over other lithographic techniques. We report on processes we have developed, using achromatic interferometric lithography, to fabricate large‐area coherent gratings and grids with spatial periods of 100 nm.

Dispersion-tailored few-mode fibers: a versatile platform for in-fiber photonic devices

Abstract: In-fiber devices enable a vast array of critical photonic functions ranging from signal conditioning (amplification, dispersion control) to network management (add/drop multiplexers, optical monitoring). These devices have become mainstays of fiber-optic communication systems because they provide the advantages of low loss, polarization insensitivity, high reliability, and compatibility with the transmission line. The majority of fiber devices reported to date are obtained by doping, designing, or writing gratings in the core of a single-mode fiber (SMF). Thus, these devices use the fiber only as a platform for propagating light-the device effect itself is due to some extraneously introduced material or structure (dopants for amplification, gratings for phase matching, etc.) There exists another, relatively less explored degree of freedom afforded by fibers-the ability to copropagate more than one mode. Each mode may have a uniquely defined modal dispersion and propagation characteristic. In this paper, we will describe the variety of fiber devices enabled by few-mode fibers-fibers that typically support two to four modes with suitably tailored dispersive properties. We will show that the unique dispersive properties of various modes, in conjunction with the ability to couple between them with gratings, leads to devices that offer novel solutions for dispersion compensation, spectral shaping, and polarization control, to name a few.

Continuously tuned external cavity semiconductor laser

Abstract: Continuous tuning (no mode hops) of a grating-tuned external-cavity semiconductor laser by rotation of the grating about a carefully selected point is analyzed and demonstrated using a laser containing a prism beam expander. The analysis predicts the continuous tuning range as a function of pivot-point position and is used to select the point for maximum continuous tuning range. Because dispersive optical elements in the cavity were found to limit the continuous tuning range, the model was modified to include dispersion to first order. The dispersion correction improved the maximum observed tuning range of the 1300-nm-wavelength laser from 600 GHz to nearly 3000 GHz. Details of the cavity and mechanical design as well as pivot-point tolerances are also included. >

A modal analysis of lamellar diffraction gratings in conical mountings

Abstract: A rigorous modal analysis of lamellar grating, i.e., gratings having rectangular grooves, in conical mountings is presented. It is an extension of the analysis of Botten et al. which considered non-conical mountings. A key step in the extension is a decomposition of the electromagnetic field in the grating region into two orthogonal components. A computer program implementing this extended modal analysis is capable of dealing with plane wave diffraction by dielectric and metallic gratings with deep grooves, at arbitrary angles of incidence, and having arbitrary incident polarizations. Some numerical examples are included.

Single-step writing of Bragg grating waveguides in fused silica with an externally modulated femtosecond fiber laser

Abstract: For the first time to our knowledge, high-strength (>30 dB) first-order Bragg grating waveguides were fabricated in bulk fused silica glass in a single-scanning step by modulating a high-repetition-rate femtosecond fiber laser with an external acousto-optic modulator. The modulation induced a waveguide segmentation by delivering controlled bursts of laser pulses to define an array of partially overlapped refractive index voxels. With appropriate choice of modulation frequency and sample scanning speed, low loss waveguides could be formed at high writing speeds to yield sharp Bragg spectral resonances tunable over the 1300 to 1550 nm telecom band. Effects of acousto-optic modulation duty cycle on propagation loss and grating strength are characterized. This modulation method offers facile control and integration of multiwavelength Bragg grating devices to enhance overall functionality of optical circuits in three-dimensional geometries.