ABSTRACT
We demonstrate a low-loss Ti:LiNbO(3) waveguide circuit for lambda = 1.55 microm that under voltage control can be used to combine two mutually coherent input beams of arbitrary relative amplitude and phase into a single-output waveguide while suffering only propagation losses.
ABSTRACT
Optical fiber is rapidly becoming the transmission medium of choice for new telecommunication systems. For a true lightwave network to evolve, however, optical control devices such as optical switches and multiplexer-demultiplexers will be essential. Optical guided-wave devices built with photolithographic fabrication techniques and electro-optic substrates are compact, low drive power devices that provide these functions. Research is particularly advanced on integrated-optic devices based on waveguides formed by titanium diffused into lithium niobate. Switch arrays, tunable filters, and high-speed modulators have been demonstrated and used in research systems experiments.
ABSTRACT
We propose and demonstrate a new integrated-optic TE/TM splitter using a polarization-selective Ti:LiNbO(3) directional coupler. By application of appropriate voltages, either polarization can be selected (cross talk will be below -30 dB) or both TE and TM modes can be simultaneously extracted (cross talk will be -24 dB).
ABSTRACT
By careful electrode design we have achieved a 1.7-GHz modulation bandwidth for a Ti:LiNbO(3) integrated-optic TE ? TM mode-converter modulator. Because of the wavelength selectivity of this modulator, it is an attractive device for simultaneously providing multiplexing and signal encoding in future wavelength-multiplexed single-mode light-wave systems.
ABSTRACT
We have achieved complete electro-optic TE <--> TM mode conversion in Ti-diffused lithium niobate waveguides with as little as a 2.5-V drive. Because, for birefringent substrates like lithium niobate, TE <--> TM conversion is wavelength dependent, our method is potentially useful for wavelength multiplexing and demultiplexing. Three independently controlled mode converters, each with a 15-A filter bandwidth and with center wavelengths separated by 80 A, have been fabricated on a single substrate.
ABSTRACT
The dependence of the coupling strength of titanium-diffused lithium niobate directional couplers upon fabrication parameters and guided wavelength has been investigated. Measurements of the coupling strength as a function of interguide separation have been made at He-Ne, GaAs, and Nd:YAG wavelengths. To good approximation, the coupling strength depends exponentially upon guide separation. Rather strong dependence upon the metal thickness diffused and the guided wavelength were observed. Good comparison was obtained with theoretical results calculated using an effective index method. Transfer lengths as short as 200 microm have been obtained. Fabrication parameters for which the coupling strength for the TE and TM modes are equal were determined.
