External Cavity Perturbation Structures for Narrow Linewidth Laser
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Solution Overview
Problem
Current LIDAR systems face challenges in achieving narrow linewidths necessary for accurate distance and velocity measurements due to the impracticality of using Distributed FeedBack (DFB) or External Cavity Lasers, as they are costly and complex, while Discrete Mode Fabry-Perot (DMFP) lasers cannot provide the required 1-10 kHz linewidths.
Innovation Solution
A laser system with a resonant cavity and a utility waveguide that includes perturbation structures external to the cavity, which provide optical feedback to enhance the laser signal, effectively converting a Fabry-Perot laser cavity into a single-mode, narrow-linewidth light source without increasing the cavity length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DFB laser with ultra long cavity or ECL is used to achieve narrow linewidth, then linewidth is improved, but fabrication cost and complexity increase
Solution Approach 1:
The patent introduces an external cavity with perturbation structures as an intermediary element that provides optical feedback to the laser diode. This external cavity acts as a mediator to narrow the linewidth without requiring modifications to the laser diode's internal structure, thus avoiding the fabrication complexity of DFB or ECL while achieving the desired narrow linewidth performance
Solution Approach 2:
The patent employs optical feedback from an external cavity with perturbation structures to selectively enhance desired wavelengths and suppress unwanted emissions. The feedback mechanism allows the system to achieve narrow linewidth by reinforcing specific modes through the perturbation structures, eliminating the need for complex internal laser design
2Manufacturing precision
If DFB laser with ultra long cavity or ECL is used to achieve narrow linewidth, then linewidth is improved, but device cost increases
Solution Approach 1:
The external cavity with perturbation structures serves as a separate, independently fabricable component that provides the necessary wavelength selection and linewidth narrowing. This intermediary approach allows standard laser diodes to be used with a relatively simple external cavity, significantly reducing fabrication costs compared to integrating complex DFB or ECL structures
Solution Approach 2:
The patent uses a relatively simple external cavity design with perturbation structures that can be fabricated using standard techniques. This approach replaces expensive, complex DFB or ECL lasers with a more economical solution that achieves the same functional result through a different architectural approach
3Ease of manufacture
If Fabry-Perot laser is used for LIDAR chip, then ease of manufacture is improved, but linewidth is insufficient
Solution Approach 1:
The external cavity with perturbation structures acts as an intermediary that enhances the linewidth performance of simple Fabry-Perot lasers. By adding this external component, the system maintains the ease of manufacture of FP lasers while achieving the narrow linewidth necessary for LIDAR applications through optical feedback and mode selection
4Manufacturing precision
If external cavity length is increased to achieve narrow linewidth, then linewidth is improved, but device complexity increases
Solution Approach 1:
Instead of increasing the entire cavity length, the patent introduces localized perturbation structures at specific positions within the external cavity. These localized perturbations create wavelength-selective feedback that narrows the linewidth without requiring a long cavity, thus reducing overall device complexity while achieving the desired spectral precision
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 the production of a practical and affordable light source for LIDAR systems, improving signal-to-noise ratios and enhancing the performance of LIDAR systems by achieving narrow linewidths, thus enabling more accurate distance and velocity measurements.
Implementation Method 1
The perturbation structures are selected to provide optical feedback to the resonant laser cavity such that a power versus wavelength distribution in the laser beam is different from the power versus wavelength distribution that would be in the laser signal in the absence of the perturbation structures. The optical feedback can be a result of reflection of light from the perturbation structures back into the laser cavity.
Data Source
AI summary
A laser system includes a resonant laser cavity configured to output a laser signal. The system also includes a utility waveguide configured to receive the laser signal from the laser cavity. The utility waveguide includes a perturbation region that is external to the laser cavity and receives the laser signal from the laser cavity and outputs a laser beam. The perturbation region includes one or more perturbation structures that each causes one or more perturbation(s) in the index of refraction of the utility waveguide. The perturbation structures are selected to provide optical feedback to the resonant laser cavity such that a power versus wavelength distribution in the laser beam is different from the power versus wavelength distribution that would be in the laser signal in the absence of the perturbation structures.