Vertically Coupled LiDAR Transceivers With Turning Mirrors
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Solution Overview
Problem
Current LiDAR systems face challenges in efficiently coupling light out of and into waveguides within photonic integrated circuits (PICs) for optical transceiver arrays, leading to inefficiencies in scanning and depth mapping.
Innovation Solution
The use of diagonally disposed turning mirrors within optical transceivers on PICs, combined with tapered waveguides and collimating lenses, to manage light transmission and reception, reducing back-reflections and enhancing beam collimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional waveguide coupling is used in LiDAR systems, then device complexity is reduced, but light coupling efficiency deteriorates
Solution Approach 1:
Turning mirrors are introduced as intermediary elements between the waveguides and the external environment. These mirrors mediate the light coupling process by receiving light from the waveguides and directing it at specific angles, thereby improving coupling efficiency without requiring complex direct coupling structures.
Solution Approach 2:
The patent utilizes vertical coupling by directing light at angles (e.g., 45 degrees) relative to the waveguide plane. This transitions the light propagation from a two-dimensional waveguide confinement to a three-dimensional coupling configuration, enabling efficient vertical light extraction and coupling while maintaining planar device integration.
2Productivity
If high-channel density is implemented, then scanning efficiency is improved, but back-reflections increase
Solution Approach 1:
The patent converts harmful back-reflections into beneficial effects by strategically positioning turning mirrors and utilizing angle-dependent reflection. Light that would normally reflect back harmfully is instead directed at specific angles to enhance the forward-coupled light extraction, thereby transforming the harmful back-reflection into a useful light extraction mechanism.
Solution Approach 2:
The turning mirrors are positioned and oriented asymmetrically relative to the waveguides, with specific angular orientations (e.g., 45 degrees) that break symmetry in the light path. This asymmetric configuration ensures that light is coupled efficiently in the desired direction while minimizing symmetric back-reflections that would cause interference or loss.
3Manufacturing precision
If diagonally disposed turning mirrors are used, then light coupling precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the turning mirror function with the waveguide structure by integrating the mirror as a planar element that can be fabricated using standard photolithographic processes. This combination approach allows the diagonally disposed mirror to be created as part of the integrated circuit fabrication, achieving precise light coupling while avoiding the need for separate, complex optical component assembly.
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 configuration enables high-channel density and precise light coupling, improving scanning efficiency and depth map resolution in LiDAR systems.
Implementation Method 1
at least one turning mirror having a reflective surface disposed diagonally relative to the substrate
Implementation Method 2
Each optical transceiver includes a photodetector... The light reflected from the target scene is mixed with a sample of the transmitted light and detected by a photodetector
Implementation Method 3
multiple waveguides disposed parallel to the substrate... a transmit waveguide, which is coupled to convey outgoing light from a coherent light source to the at least one turning mirror
Implementation Method 4
the photodetector includes a balanced pair of photodiodes, and wherein each optical transceiver includes a splitter coupled to divide the light received through the receive waveguide between the photodiodes
Implementation Method 5
a mixer which is coupled to mix the fraction of the coherent light with the incoming light received through the receive waveguide for input to the photodetector
Implementation Method 6
a quarter-wave plate, which is configured to rotate a polarization of both the outgoing and the incoming light that is reflected from the at least one turning mirror
Implementation Method 7
the waveguides include at least one spot size converter, which is configured to reduce a mode diameter of the outgoing light before incidence of the outgoing light on the at least one turning mirror
Implementation Method 8
the device includes at least one lens, which is configured to collimate the outgoing light following reflection from the at least one turning mirror and to focus the incoming light before reflection via the at least one turning mirror into the receive waveguide
Data Source
AI summary
An optical sensing device includes a planar substrate and an array of optical transceivers disposed on the planar substrate. Each optical transceiver includes a photodetector, at least one turning mirror having a reflective surface disposed diagonally relative to the substrate, and multiple waveguides disposed parallel to the substrate. The waveguides include a transmit waveguide, which is coupled to convey outgoing light from a coherent light source to the at least one turning mirror for output from the optical transceiver, and a receive waveguide, which is coupled to receive incoming light reflected by the at least one turning mirror and to convey the incoming light to the photodetector.