Chip-Scale LiDAR Waveguide Isolation via MEMS Grating Couplers
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Solution Overview
Problem
Active sensing systems like LiDAR face issues with signal loss and noise due to the use of 3 dB splitters, which increase system size and complexity, and require bulky off-chip components when using circulators for separating excitation and detection paths.
Innovation Solution
An integrated photonic chip with separate waveguides for excitation and return signals, utilizing MEMS-actuated grating couplers to selectively couple light in and out of the chip, allowing for spatial separation of excitation and detection paths without the need for splitters or circulators, enabling compact and efficient LiDAR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 3 dB splitter is used to separate excitation and detection paths, then the paths are separated, but signal loss increases and detector gating is required
Solution Approach 1:
The patent divides the optical path into separate excitation and detection waveguides on the photonic integrated circuit. The excitation waveguide carries the outgoing laser pulse while the detection waveguide receives the reflected signal, physically segmenting the paths to eliminate the need for 3 dB splitters and associated signal losses.
Solution Approach 2:
The patent introduces a movable mirror as an intermediary component that dynamically routes optical signals between different waveguides. This mirror acts as a mediator that directs the excitation pulse through the output waveguide and redirects the reflected signal to the detection waveguide, enabling path separation without energy loss.
2Reliability
If a circulator is used to route excitation and return signals, then path separation is achieved, but device size increases and off-chip components are required
Solution Approach 1:
The patent merges the excitation and detection paths onto a single photonic integrated circuit chip. Both waveguides are fabricated on the same substrate with integrated components, eliminating the need for bulky off-chip circulators and reducing overall system size while maintaining path separation functionality.
Solution Approach 2:
The patent replaces the mechanical circulator with a dynamically controllable mirror system actuated by piezoelectric elements. This substitution eliminates bulky mechanical rotating components while achieving the same signal routing function through controlled mirror positioning, reducing device complexity and enabling chip-scale integration.
3Reliability
If spatially separated modules are used for excitation and detection, then path isolation is improved, but parallax errors increase and device size grows
Solution Approach 1:
The patent combines both excitation and detection waveguides on the same photonic integrated circuit substrate, ensuring they share the exact same physical origin point. This merging approach eliminates parallax errors that would occur with spatially separated modules, as both optical paths originate from the identical location on the chip.
Solution Approach 2:
The patent implements local path separation through distinct waveguide routes on the integrated circuit while maintaining a common origin point. The excitation and detection paths are locally differentiated through separate waveguide structures and routing, but both originate from the same location, providing path isolation without introducing parallax errors.
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 reduces signal loss, eliminates noise, and allows for more compact LiDAR systems by isolating detectors from the excitation source, enabling detection of objects closer to the sensor and improving system performance.
Implementation Method 1
utilizing MEMS-actuated grating couplers to selectively couple light in and out of the chip
Implementation Method 2
utilizing MEMS-actuated grating couplers to selectively couple light in and out of the chip
Data Source
AI summary
Embodiments described herein improve the performance of active sensing systems, such as LiDAR systems, and enable detection of objects closer to the system's sensor. Illustrative embodiments enable spatial separation of the excitation and return signal on a photonic integrated chip (“PIC”) such that separate waveguides can be used for the excitation and return signals, enabling isolation of the system's detectors from the excitation source without the use of a splitter or circulator. For example, preferred embodiments avoid loss due to the use of splitters and the need for gating the detector, and are desirably compatible with chip-scale systems. Moreover, illustrative embodiments enable keeping the excitation and detection paths on the same PIC (e.g. in an interleaved configuration), which helps keep the system more compact and avoid issues introduced by parallax.