Segmented VCSEL LiDAR Module With On-Chip Power Feedback
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Solution Overview
Problem
Current illumination modules for 3D sensing and LiDAR applications face challenges in achieving compact design, high efficiency, and fast pulse rise times due to high inductance between VCSELs and drivers, as well as limitations in monitoring and controlling output power, which affects the reliability and miniaturization of VCSEL-based systems.
Innovation Solution
The implementation of multi-junction VCSELs with integrated heterojunction bipolar transistors (HBTs) and segmented VCSEL arrays with a common anode driver design, along with the integration of photodetectors onto the VCSEL chip for monitoring output power and incorporating optics into the chip substrate, reduces inductance and enables independent modulation of VCSEL segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If VCSEL arrays are used with common anode and common cathode connections, then high optical power can be achieved, but inductance between VCSELs and drivers increases
Solution Approach 1:
The VCSEL array is divided into multiple independently controllable segments or groups, each with its own driver circuit. This segmentation reduces the inductance by creating shorter current paths and allowing parallel driving of multiple segments, thereby achieving high optical power while minimizing inductive effects that limit pulse rise times.
2Power
If VCSEL arrays are used for 3D sensing and LiDAR applications, then high optical power can be achieved, but module size increases
Solution Approach 1:
Multiple VCSELs are integrated onto a single semiconductor chip to form a VCSEL array, combining multiple light sources into one compact unit. This merging approach achieves high optical power through the collective emission of multiple VCSELs while maintaining a small module footprint, as the entire array occupies the area of a single chip rather than requiring separate mounting of individual VCSELs.
3Power
If VCSEL arrays are used for 3D sensing and LiDAR applications, then high optical power can be achieved, but pulse rise time increases
Solution Approach 1:
The VCSEL array is divided into multiple independently controllable segments or groups, each with its own driver circuit. This segmentation reduces the inductance by creating shorter current paths and allowing parallel driving of multiple segments, thereby achieving high optical power while minimizing inductive effects that limit pulse rise times.
4Power
If VCSEL arrays are used for 3D sensing and LiDAR applications, then high optical power can be achieved, but monitoring and controlling output power becomes difficult
Solution Approach 1:
A feedback mechanism is implemented where a portion of the light emitted by the VCSEL array is directed to a photodetector that converts the optical signal back to an electrical signal. This electrical signal is then used to monitor the actual output power and provide feedback to the driver circuit, enabling real-time control and adjustment of the optical power to maintain desired performance levels.
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 approach results in improved output power efficiency, faster rise times, and compact packaging, enhancing the performance and reliability of VCSEL-based illumination modules for 3D sensing and LiDAR applications while maintaining eye safety and reducing the overall size of the modules.
Implementation Method 1
Vertical cavity surface emitting lasers (VCSELs) and VCSEL arrays... are important technologies for applications within a variety of markets... Power conversion efficiency (PCE) of 30-60% may be achieved at wavelengths in the 660-1000 nanometer (nm) range
Implementation Method 2
The array of VCSELs may be individually modulated or modulated in segments... Each VCSEL or segment may be driven with a common anode driver array... Incorporating HBTs in to the VCSEL array to facilitate high speed switching
Implementation Method 3
incorporating HBTs in to the VCSEL array to facilitate high speed switching of the VCSEL segments... integrating monitor diodes onto a VCSEL chip for monitoring the output power
Data Source
AI summary
The present invention relates to a Vertical-Cavity Surface-Emitting Laser (VCSEL) die comprising a VCSEL array configured for flip chip bonding to a substrate with the VCSEL array being designed for emission from a substrate side of the chip, integrated beam shaping optics and electrical contacts including a top surface contact and an etched metal connection through a top mirror structure to a bottom n-mirror, or to an n-doped buffer layer under the bottom n-mirror or to the substrate. The invention further relates to an assembly comprising the above VCSEL die and a photodetector in which the VCSEL die is attached to a circuit board or sub-mount with a solder or bump bonds on the VCSEL die and the photodetector is placed on a same circuit board or sub-mount right next to the VCSEL die.