Accession Number : ADP008214
Title : GHz Velocity-Matched, Broad Wavelength LiNbO3 Modulator with Multimode Active Section,
Corporate Author : HEWLETT-PACKARD LABS PALO ALTO CA
Personal Author(s) : Dolfi, David W. ; Ranganath, T. R.
Report Date : APR 1992
Pagination or Media Count : 4
Abstract : Improved velocity matching in LiNbO3 modulators has been achieved by several workers using a combination of relatively thick (greater than or = to 1 micrometer) S1O2 buffer layers and thick (typically greater than or = to 10 micrometers) plated electrodes. Utilizing this combination, microwave indices less than or = to 2.5 have been achieved. However, increase in electrode thickness lowers device impedance, which raises drive power requirements and causes mismatch to most common 50 omega sources. This decrease is partially compensated by the thicker buffer layer and by employing large gaps (typically 15 micrometers) between the hot and ground electrode(s), both of which maintain the impedance at a high value. They also increase the drive voltage, however, resulting in a larger voltage-length product relative to conventional modulators. To achieve closer velocity matching would require additional increases in electrode/buffer thicknesses, resulting in even higher voltages. Here we describe a device which also utilizes a thick electrode/buffer layer geometry. However, it also introduces two novel features, resulting in a device which achieves almost exact velocity matching to the optical index, maintains high impedance, and has a voltage-length product which is as good or better than previous devices of this type. In addition, it maintains this performance over the whole range of wavelengths from 1.3 to 1.55 micrometers. This latter property is very important for optical measurement applications such as network analysis and optical sampling.
Descriptors : *LITHIUM NIOBATES, *MICROWAVE OPTICS, BUFFERS, ELECTRODES, GEOMETRY, IMPEDANCE, LAYERS, MATCHING, MICROWAVES, NETWORKS, THICKNESS, VELOCITY, VOLTAGE, MULTIMODE, LIGHT MODULATORS, OPTICAL WAVEGUIDES.
Subject Categories : Electrooptical and Optoelectronic Devices
Distribution Statement : APPROVED FOR PUBLIC RELEASE