FMCW LiDAR Light Source with Tunable External Cavity Linewidth
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Solution Overview
Problem
Existing FMCW LiDAR devices face challenges in achieving a narrow linewidth for accurate distance and velocity measurements, particularly in applications like autonomous driving, due to manufacturing tolerances and the need for complex electronic drivers, which affect production yield and reliability.
Innovation Solution
A photonic integrated circuit (PIC) light source with a variable attenuator and optical phase modulator is used to control the intensity and phase of light within an external cavity, allowing for calibration during production to ensure a stable linewidth, reducing the need for complex electronic drivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external cavity lasers are used to reduce linewidth, then measurement precision is improved, but manufacturing precision deteriorates due to variability from one device to another
Solution Approach 1:
The patent replaces mechanical adjustment mechanisms with a photonic integrated circuit solution. The external cavity laser is integrated onto a chip with precise optical paths defined by waveguides, eliminating mechanical variability. The variable optical attenuator and phase modulator are also integrated photonic components, ensuring consistent performance across manufacturing batches while maintaining the narrow linewidth required for accurate measurements.
Solution Approach 2:
The patent uses variable optical attenuators and phase modulators to dynamically adjust cavity parameters. By controlling the attenuation and phase shift electronically, the system can compensate for manufacturing variations and maintain consistent linewidth and measurement accuracy across different devices. This allows post-fabrication tuning to achieve uniform performance.
2Device complexity
If photonic integrated circuits are used to reduce device size, then device complexity is reduced, but manufacturing precision deteriorates due to tolerances affecting linewidth
Solution Approach 1:
The patent incorporates feedback mechanisms through the variable optical attenuator and phase modulator that can sense and correct for manufacturing variations. By monitoring the actual linewidth and adjusting the cavity parameters accordingly, the system compensates for tolerances introduced during photonic integrated circuit fabrication, maintaining narrow linewidth despite manufacturing variations.
Solution Approach 2:
The patent makes the cavity parameters dynamic rather than fixed. The variable optical attenuator and phase modulator allow real-time adjustment of cavity characteristics, enabling the system to adapt to manufacturing variations and maintain optimal performance. This dynamic control compensates for static manufacturing tolerances in the integrated photonic structure.
3Manufacturing precision
If variable attenuator and phase modulator are added to control cavity parameters, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the photonic integrated circuit. The variable optical attenuator, phase modulator, and external cavity laser are integrated onto a single chip rather than being separate components. This consolidation reduces overall device complexity while maintaining the precision benefits of having controllable cavity parameters. The integrated nature of the components eliminates additional alignment and connection complexities.
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
The solution achieves a narrow linewidth with high production yield, ensuring accurate and reliable range and velocity measurements in FMCW LiDAR devices, suitable for autonomous driving applications.
Implementation Method 1
an optical splitter connecting the input optical waveguide both to the output optical waveguide and to the cavity optical waveguide
Implementation Method 2
a reflector connected to the cavity optical waveguide
Implementation Method 3
a variable attenuator causing an attenuation of light guided in the cavity optical waveguide
Implementation Method 4
a semiconductor laser that is received in a recess etched into the multilayer structure and connected to the input optical waveguide
Implementation Method 5
the photodiode delivers a current that is proportional to the squared sum of the two optical waves ('self-mixing effect')
Data Source
AI summary
A light source for a frequency-modulated continuous-wave (FMCW) LiDAR device is formed by a photonic integrated circuit and comprises a substrate and a multilayer structure. Formed in the multilayer structure is a semiconductor laser that is received in a recess etched into the multilayer structure. An optical path between the semiconductor laser and a reflector forms an external cavity for the semiconductor laser. The external cavity includes a variable attenuator causing an attenuation of light guided in the cavity optical waveguide. The external cavity may also or alternatively include an optical phase modulator.