Stress-Optic Phase Controller Electrode Configuration
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Solution Overview
Problem
Existing phase control technologies for optical signals in surface waveguides, such as thermo-optic and stress-optic phase controllers, face challenges of being too slow, power-consuming, and requiring significant chip real estate.
Innovation Solution
The use of stress-optic phase controllers with a 'push-pull' operational mode, where one controller induces positive stress and the other induces negative stress, significantly reduces the stress required for a relative 2π phase shift, thereby improving speed, power efficiency, and space utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If thermo-optic phase controllers are used to control optical phase in surface waveguides, then phase control capability is achieved, but the response speed becomes too slow for many applications
Solution Approach 1:
The patent replaces the thermal field mechanism (thermo-optic effect) with a mechanical stress field mechanism (photo-elastic effect). Instead of using heaters to change refractive index through temperature changes, the invention uses piezoelectric actuators to apply mechanical stress directly to the waveguide, achieving phase modulation through stress-induced refractive index changes. This substitution eliminates the slow thermal diffusion process and achieves faster response times.
2Use of energy by moving object
If thermo-optic phase controllers are used, then phase control is achieved, but power consumption becomes excessively high
Solution Approach 1:
The patent replaces the high-power thermal heating mechanism with a low-power mechanical actuation mechanism. Piezoelectric actuators consume significantly less power than resistive heaters because they convert electrical energy directly to mechanical displacement without generating excessive heat. The stress-induced photo-elastic effect achieves the same phase modulation with much lower energy input, reducing both dynamic and static power consumption.
3Speed
If conventional stress-optic phase controllers are used, then faster response is achieved, but significant chip real estate is required
Solution Approach 1:
The patent merges the stress application mechanism with the waveguide structure itself. Instead of using separate, large-area actuators positioned beside the waveguide, the piezoelectric actuators are integrated directly onto the waveguide structure, applying stress locally at the interaction region. This integration allows the same functional elements to serve dual purposes: guiding light and applying stress, thereby reducing the total chip area required.
Solution Approach 2:
The patent applies stress locally at specific regions of the waveguide rather than requiring uniform stress across large areas. By concentrating the piezoelectric actuators and stress application zones directly over the waveguide core where light propagation occurs, the design achieves effective phase modulation with minimal interaction length and reduced chip footprint.
4Adaptability or versatility
If conventional stress-optic phase controllers are used, then phase control is achieved, but the structure requires significant space
Solution Approach 1:
The patent combines multiple functions into integrated structures. The piezoelectric actuators are deposited directly on the waveguide substrate, merging the actuation function with the guiding function. The upper and lower claddings serve both as optical confinement structures and as mechanical support structures for the piezoelectric actuators. This functional integration reduces the overall device volume while maintaining full phase control capability.
Data Source
AI summary
The present Specification is directed to devices for controlling the phase of a light signal in a surface waveguide of a planar-lightwave circuit by controlling a stress in the waveguide material. Phase controllers disclosed can impart stresses of opposite signs in a material such that a desired effect on the refractive index of an optical material can be accentuated. As a result, a greater change in the refractive index of the material can be realized in a phase controller that requires less chip real estate and/or at lower voltages. In some embodiments, a phase-control module includes a pair of complimentary stress-optic phase controllers, one having electrodes disposed on the top and bottom of a piezoelectric layer, while the other has electrodes disposed only on top of the piezoelectric layer. As a result, the phase controllers impart stress of opposite sign in the material beneath them.