Directional Coupler Phase Shift via Mechanical Displacement
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Solution Overview
Problem
Existing methods for changing the phase or time delay in optical paths, such as altering the refractive index or using mechanical movement, face limitations in achieving large changes without substantial stretching of waveguide materials, which is difficult to integrate with waveguide paths.
Innovation Solution
The approach involves a directional coupler configuration where waveguides are bent rather than stretched, allowing for large changes in optical path length by displacing the interaction region longitudinally, thereby reducing or increasing the optical path length without stretching the waveguides, using mechanical displacement techniques like flexures and electrostatic comb drives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If refractive index of material is changed to alter phase or time delay, then phase modulation is achieved, but only small changes in refractive index can be made limiting the phase change range
Solution Approach 1:
The patent replaces refractive index modulation (optical/electrical method) with mechanical displacement of the retroreflector along the optical path. By physically moving the retroreflector position, large optical path length changes are achieved without relying on limited refractive index variations, thus expanding the phase change range while maintaining precise phase control.
Solution Approach 2:
The system transitions from static phase control (fixed refractive index) to dynamic phase control (movable retroreflector). The retroreflector can be positioned at different locations along the optical path, enabling continuous adjustment of optical path length and providing versatile phase modulation capabilities.
2Manufacturing precision
If materials with large refractive index changes are used, then larger phase changes can be achieved, but optical absorption increases restricting usefulness
Solution Approach 1:
The patent eliminates the need for high-refractive-index materials by using mechanical displacement of the retroreflector. This substitution avoids optical absorption losses entirely, as the phase control is achieved through geometric path length adjustment rather than material property modification.
3Length of moving object
If waveguide material is stretched to change optical path length, then large path length changes can be made, but stretching waveguides substantially is difficult to integrate
Solution Approach 1:
Instead of stretching the waveguide to change optical path length, the patent inverts the approach by keeping the waveguide fixed and moving the retroreflector along the optical path. This allows large optical path length changes without deforming or reconfiguring the waveguide structure, maintaining ease of integration.
Solution Approach 2:
The patent replaces waveguide stretching (deformation of optical component) with retroreflector displacement (movement of mechanical component). This substitution preserves waveguide integrity and simplifies integration while achieving the desired optical path length modulation.
4Length of moving object
If retroreflector is moved to change optical path length, then large phase changes can be achieved, but integration with waveguide paths becomes difficult
Solution Approach 1:
The patent inverts the conventional approach by keeping the waveguide fixed and moving the retroreflector along the optical path instead. This allows the retroreflector to be integrated with waveguide paths through precise positioning mechanisms, achieving both large optical path length changes and waveguide compatibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables significant changes in optical path length and phase delay in waveguide structures without stretching, facilitating their integration in technologies like silicon photonics, while maintaining minimal power loss and optical coupling efficiency.
Implementation Method 1
electrostatic comb drives
Implementation Method 2
directional coupler configuration where waveguides are bent
Data Source
AI summary
A modified directional coupler structure is used to provide a controllable time delay or phase shift for radiation propagating through the structure. A longitudinal displacement of the interaction region of the directional coupler relative to one or both of the waveguides of the directional coupler provides this effect. Double flexure arrangements can be used to provide longitudinal displacement with substantially no corresponding lateral displacement (or vice versa). In some embodiments, lateral and longitudinal displacement of the waveguides of the directional coupler are independently adjustable to provide full control of the power splitting and phase shift/time delay of the directional coupler.