Bragg Gratings

This work characterizes holographic polymer dispersed liquid crystals (HPDLC) composite material based on a new monomer, urethane trimethacrylate, by fabricating switchable diffraction grating. The highest diffraction efficiency achieved was 90.3%. Details of the fabrication and preliminary results of electro-optical switching of the HPDLC diffraction gratings are presented and discussed based on the functionality of the monomer. These experimental results are explained by means of morphological scanning electron microscopy analyses.

ABSTRACT form only given. Complex coupling (CC) in distributed feedback (DFB) lasers can lead to high-quality modal properties such as high monomode yield, stable narrow linewidth, high side-mode suppression ratio (SMSR) and strong immunity to feedback without the use of AR coatings. We fabricate second order DFB lasers with strong vertical emission to create the complex coupling by a simple and reliable method. The vertical radiation also presents the potential advantage of high power, high brightness and low diffraction angles. In this paper, we use a 2-dimensional model of the laser cavity to describe the relations between the facet phases and the vertical radiation profile of as-cleaved second order DFB lasers. We demonstrate a method that uses the radiation profile to derive the left and right facet phases. Previously, Morthier et al. (1995) proposed a method based on numerical fits of subthreshold spectra to determine the coupling coefficients and the facet phases. However, this method requires high-resolution spectra and precise relative intensity measurements of the modal peaks below threshold. It is preferential to measure the facet phases under actual lasing conditions. Our new method requires only one measurement of the surface near-field emission profile.

A CMOS-compatible plasmonic multimode filter capable of working in the O, E, S, C, L, and U optical communication bands is analysed. The device consists of a hybrid plasmonic waveguide with metal segments. By properly designing the segments, it is possible to pass a particular mode and diffract the others. The results of the analysis show that the device has an extinction ratio over 20 dB and an insertion loss of less than 1.6 dB across the mentioned optical communication bands.

In this project integration of Bragg grating structures to silicon-on-insulator (SOI) waveguides was studied. An efficient quasi-rigorous computational method was developed for analysis of waveguide gratings and applied to SOI structures. Phase masks for Bragg grating exposure experiments on the proximity mask aligner were designed and fabricated. A new method was found to eliminate the harmful zeroth diffraction order of a phasemask grating. Investigations on photonic bandgap structures by rigorous diffraction theory were ...

Fabrication of nanoscale optical Fiber Bragg Gratings (FBGs) is one of the key manufacturing processes for fiber optics, which has many important applications in data communication and distributed remote sensing at a distance up to hundreds of kms. However, the fabrication of the FBGs is challenging. To meet such need, we propose a novel method to write the FBGs using high-flux synchrotron x-ray with a nanoscale gold/Si gratings to modulate the x-ray flux and thus change the refractive index contrast of the optical fiber to form the FBGs. The nanoscale gold/Si with high aspect ratio has been fabricated at the Center for Nanoscale Materials (CNM) at Argonne National Laboratory (ANL) and the preliminary experiment of x-ray writing of the optical fiber FBGs has been carried out at the Advanced Photon Source (APS) of ANL. The preliminary experiment shows promising result of the x-ray writing method of the optical fiber FBGs.