Optical waveguides – Having nonlinear property
Patent
1998-08-03
2000-08-01
Bovernick, Rodney
Optical waveguides
Having nonlinear property
385123, 385129, 65429, 65430, G02B 616
Patent
active
060978678
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for the fabrication of electrooptically active fiber segments that can be readily integrated into optical fiber lines, with applications in high-speed modulators, electric field sensors, or optical mixers.
2. Description of the Related Art
This invention is related to U.S. Pat. Nos. 5,239,407, Method and Apparatus for Creating Large Second-Order Nonlinearities in Fused Silica and 5,247,601, Arrangement for Producing Large Second-Order Optical Nonlinearities in a Waveguide Structure including Amorphous SiO.sub.2. These patents are hereby incorporated by reference.
Packaging costs associated with opto-mechanical coupling of discrete optical components are a major part of the cost for advanced optoelectronic systems. For example, for many high-speed fiber communications systems, the output of a diode laser must be coupled into a single-mode optical fiber, the fiber must then be coupled to a LiNbO.sub.3 waveguide modulator whose output is again coupled into a fiber. Discrete optical components, e. g., graded-index lenses or micro-lenses are required at each coupling node to adapt the very different mode profiles and spatial extents of the diode laser and modulator waveguide modes to the fiber mode. Tolerances are fractions of a micrometer to ensure minimal coupling losses and extensive active alignment (optimizing coupling with the laser on) is typically required. Throughput and yield are both limited by the requirement of keeping the system stable while the bonding agents cure. If a modulator could be produced that was integrated into the fiber, the manufacturing and packaging costs associated with these high-speed fiber communications systems would be substantially reduced.
Electric field sensors are another potentially attractive application of electrooptically active fibers. The electric power industry has a need for remote sensors to monitor high voltage power systems. Integrating electrooptically active fiber sensors with Bragg reflector gratings is a very attractive alternative to currently available sensors that will have a major economic impact.
A third potential area of application of electrooptically active fibers is frequency mixing (i.e., second harmonic and sum frequency generation to reach shorter wavelengths than the starting wavelengths and difference frequency generation to reach longer wavelengths). This would enable the extension of the utility of high power diode lasers which are today confined to the wavelength range from roughly 700 nm to 1 micrometer. Applications include high-density optical recording, displays, and spectroscopic sensors. These nonlinear mixing processes require both a second-order nonlinearity, the same order nonlinearity that gives rise to the electrooptic effect, as well as a phase matching technique to ensure that the nonlinear mixing stays coherent along the active length of the fiber. Previous work (X.-C. Long, R. A. Myers and S. R. J. Brueck, Measurement of the linear electrooptic coefficient in poled amorphous silica, Optics Letters 19, 1820 (1994); X.-C. Long, R. A. Myers and S. R. J. Brueck, Measurement of linear electrooptic effect in temperature/electric-field poled optical fibers, Electronics Letters 30, 2162 (1994)) has shown that the second-order nonlinearity and the electrooptic effect induced in germanosilicate glasses arise from the same electronic processes and are closely related. The required phase matching is most conveniently achieved by quasi-phase matching in which the nonlinearity is alternately turned on and off each coherence length (i.e., the length over which the phases of the fundamental and second harmonic fields are shifted by .pi. because of their different velocities). More complex poling patterns may be desirable to tailor the phase matching bandwidth for specific applications.
There has been extensive work on integral fiber lasers involving doping the fiber with an appropriate chromophore (typically a rare earth element such as Er for the impor
REFERENCES:
patent: 4929050 (1990-05-01), Wilson
patent: 5076658 (1991-12-01), Hayden et al.
patent: 5239407 (1993-08-01), Brueck et al.
patent: 5351324 (1994-09-01), Forman
patent: 5617499 (1997-04-01), Brueck et al.
Brueck Steven R. J.
Long Xiang-Cun
Bovernick Rodney
Kim Ellen
The University of New Mexico
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