MEMS Micromirror Arrays for Optical True Time Delay
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Solution Overview
Problem
Current technologies face challenges in achieving large tunability, true time delay, low insertion loss, and compact integration for high-frequency signal time delay devices, particularly in phased array antennas, due to significant optical losses and limited bandwidth in existing approaches.
Innovation Solution
The use of Tip/Tilt/Piston (TTP) MEMS MMAs to control the entrance and exit angles of an optical beam within a reflection cavity, allowing for coarse and fine tuning of path length and transit time, with the capability to adjust the angle of reflection using multiple mirrored surfaces and piston motion to minimize insertion loss and enhance dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If waveguide approaches are used to alter optical path length, then time delay tunability is improved, but optical insertion loss increases significantly
Solution Approach 1:
The patent replaces the mechanical waveguide system with an acousto-optic interaction system. Instead of physically moving or routing light through long waveguide paths, the invention uses acoustic waves to create moving diffraction gratings that dynamically control optical path length and time delay through acoustic field modulation, thereby avoiding waveguide transmission losses.
Solution Approach 2:
The patent changes the operating parameters by using acousto-optic interaction where acoustic frequency and amplitude control the optical path length and time delay. By modulating acoustic parameters rather than physical dimensions, the system achieves large time delay tunability without the corresponding increase in optical loss that would result from extended physical paths.
2Loss of time
If optical path length is increased to achieve large time delay, then time delay tunability is improved, but device length increases
Solution Approach 1:
The patent transitions from controlling time delay through one-dimensional spatial extension (long waveguide paths) to using acousto-optic interaction in a compact three-dimensional configuration. Acoustic waves propagate through a small interaction region, creating dynamic diffraction gratings that control optical path length without requiring the optical path to physically extend over long distances, thus achieving large time delay in a compact device.
Solution Approach 2:
The invention replaces the mechanical extension of optical paths with acoustically-controlled optical path modulation. Acoustic fields dynamically alter the refractive index and create moving gratings that effectively extend or shorten the optical path length within a fixed, compact device structure, enabling large time delay tunability without increasing device physical length.
3Device complexity
If constant phase delay devices are used, then device simplicity is improved, but bandwidth is limited due to squint and resonant effects
Solution Approach 1:
The patent implements a dynamic system where acousto-optic interaction creates moving diffraction gratings that can be rapidly modulated. The acoustic waves continuously update the optical path length and phase delay in real-time, enabling the device to adapt to different frequencies and maintain true time delay across wide bandwidths without the squint and resonant limitations of static phase delay devices.
Solution Approach 2:
The invention uses acousto-optic parameter modulation where acoustic frequency, amplitude, and phase can be independently controlled to achieve true time delay across wide bandwidths. This dynamic parameter control allows the device to maintain constant group delay while accommodating frequency variations, overcoming the bandwidth limitations of constant phase delay approaches.
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 solution enables efficient and flexible control of optical time delay with reduced insertion loss and increased dynamic range, suitable for large phased array antennas, by utilizing MEMS MMAs to adjust the optical beam's path length and transit time, addressing the limitations of previous technologies.
Implementation Method 1
the optical beam reflects between the two mirrors as the optical beam travels through the optically transparent medium
Implementation Method 2
an angle actuator for controllably altering the angle at which the optical beam enters into the optically transparent medium, thereby controllably altering the time that the optical beam travels through the device
Data Source
AI summary
An optical true time delay (TTD) control device for controllably alters the transit time of an optical beam traveling through the device by using the tip & tilt capability of MEMS MMAs to control the entrance and exit angles to a reflection cavity to coarsely control the path length and transit time and the piston capability to fine tune the path length and transit time. The reflection cavity can be configured in one, two or three dimensions with or without an optically transparent solid medium and using additional MEMS MMAs to provide controllable mirror surfaces within the cavity to enhance dynamic range and tenability. The input MEMS MMA may be “segmented” to re-direct a plurality of channel optical beams from the cavity at the same or different exit angles. The segments may be coated with different AR coatings to provide channel optical beams at different wavelengths.