The authors propose and demonstrate a simple and novel method for fabrication of efficient Bragg grating reflectors at telecommunication wavelengths in titanium-indiffused lithium niobate single-mode channel waveguides. This technique is based on the patterned proton-exchanged process. The validity of the method is verified by the good agreement of the spectral responses and the Bragg phase-matching condition. Reflectivity as high as 94% at 1546 nm was measured with 4-mm distributed parameter waveguides in z-cut lithium niobate.

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Technological implementation of Bragg grating reflectors in Ti:LiNbO 3 waveguides by proton exchange

In this paper we propose an efficient technique for micromachining lithium niobate that is used in Ti-diffused waveguides. The use of Focused Ion Beam (FIB) etching allows obtaining homogeneous periodic microstructures. Bragg gratings with a period of 1.05 μm and an aspect ratio of 6:1 (depth-to-half period ratio) have been achieved. A reflectivity greater than 95 % associated with a bandwidth at half maximum of about 100 nm within a window centered at 1550 nm, is demonstrated for a Bragg grating of period Λ = 1.8 μm and a length of 144 μm, in good agreement with theoretical predictions.

/pdf/optical-performance-of-bragg-gratings-fabricated-in-ti-linbo-4q03n7lio2.pdf

Optical Performance of Bragg Gratings Fabricated in Ti:LiNbO $_3$ Waveguides by Focused Ion Beam Milling

Polarization dependence of grating-assisted waveguide Bragg reflectors is studied theoretically by use of a vectorial coupled-mode theory based on the ideal mode expansion. A criterion for choosing ideal waveguides is proposed. Experimental results obtained from an ion-exchanged waveguide with an etched grating agree well with the theory.

Polarization dependence of grating-assisted waveguide Bragg reflectors.

Quadratically nonlinear waveguides are studied in the presence of a Bragg grating resonant with one of the involved frequencies. In the case of second-harmonic generation and distributed feedback at the fundamental, we investigate the existence and features of two-color gap-solitary waves, focusing on controlling their propagation speed. This leads to the conception of optically controlled delay lines and retiming schemes for pulse streams in communication systems.

Optically controlled delay lines by pulse self-trapping in parametric waveguides with distributed feedback

A simple method is demonstrated to introduce phase shifts into holographic interferometry in such a way that no calibration of the phase shifter is required, and measurements are insensitive to the nonlinearity and drift of the phase shifter as well as to mechanical and/or thermal instabilities of the optical setup. Using a double-exposure, two-reference beam setup, we both introduce and measure the phase shifts a posteriori, in reconstructing a hologram. The phase shifts are monitored using a built-in Michelson interferometer, a trigger signal to activate the interferogram pick-up being generated as soon as the phase shift reaches the value predetermined by the algorithm employed in interferogram evaluation. Application of this technique combined with an advanced interferogram evaluation program to nondestructive testing of bioprosthetic heart valves is presented.

Narrow Band Width Interference Filter with Photorefractive LiNbO 3

The first demonstration of Bragg reflector grating filters in Ti:LiNbO/sub 3/ single mode channel guides is reported. Filter bandwidths as narrow as 0.14 nm centered at 1.476 mu m have been achieved for TE polarization in Y-cut (X-propagating) material. >

https://ieeexplore.ieee.org/iel3/1241/3061/00093644.pdf

J. Sochtig

Papers

Fabrication and characterization of Bragg reflector gratings in Ti:LiNbO/sub 3/ stripe waveguides