Optical Feedback Circuit for Narrow Laser Linewidth Control
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Solution Overview
Problem
Existing methods for narrowing the linewidth of lasers suffer from drawbacks such as the need for multiple lasers, bulky assemblies, high optical losses, high-speed electronic control, and sensitivity to vibrations and reflections, limiting their performance and efficiency.
Innovation Solution
A method involving optical feedback with electronic control using an integrated photonic circuit to redirect a fraction of the laser beam back into the laser, with adjustable amplitude and phase to minimize linewidth, utilizing components like a splitter/combiner, optical attenuator, and phase shifter, without high-speed electronic control and significant optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electro-optical phase locked loops are used to narrow linewidth, then linewidth suppression is improved, but device complexity increases due to need for multiple lasers and bulky assembly
Solution Approach 1:
The patent combines the reference laser and main laser into a single integrated photonic circuit, merging multiple laser functions into one compact device. This eliminates the need for separate laser assemblies while maintaining the phase-locked loop functionality for linewidth suppression.
Solution Approach 2:
The patent implements a nested structure where the optical feedback path is integrated within the photonic circuit itself, with the feedback loop nested inside the laser structure. This allows the reference cavity to be embedded within the main laser body, reducing overall assembly complexity.
2Manufacturing precision
If optical feedback techniques are used to reduce linewidth, then linewidth reduction is improved, but stability deteriorates due to sensitivity to vibrations and reflections
Solution Approach 1:
The patent creates a localized feedback path within the integrated photonic circuit, confining the optical feedback to a specific controlled region. This localizes the feedback interaction away from external environmental disturbances, improving stability while maintaining linewidth reduction performance.
Solution Approach 2:
The patent introduces an intermediary integrated photonic circuit structure that mediates the optical feedback process. This intermediary structure provides a controlled interface between the laser and the feedback path, isolating the system from external vibrations and reflections while enabling precise linewidth control.
3Manufacturing precision
If electrical feedback techniques are used to narrow linewidth, then linewidth suppression is improved, but loss of energy increases due to high-speed electronic control requirements
Solution Approach 1:
The patent replaces high-speed electronic control systems with an all-optical feedback mechanism implemented in the integrated photonic circuit. This substitution eliminates the need for high-speed electronic components and their associated energy consumption, while maintaining effective linewidth suppression through optical path control.
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
Achieves narrow linewidth laser output with reduced optical losses and stability against environmental variations, maintaining performance across different conditions.
Implementation Method 1
redirect a fraction of the light of the beam of coherent light back into the coherent light emitter as an optical feedback signal
Implementation Method 2
The phase and amplitude of the optical feedback signal are controlled to reduce an optical linewidth of the beam of coherent light
Implementation Method 3
an optical attenuator, and phase shifter
Implementation Method 4
an integrated photonic circuit to redirect a fraction of the laser beam back into the laser, with adjustable amplitude and phase
Data Source
AI summary
An integrated optical linewidth reduction system based on optical feedback and a low-speed electronic control loop to control the optical feedback. Light is tapped and reflected back to the laser with an amplitude, phase or both amplitude and phase adjustment such that the linewidth of the laser is lower than the free-running laser linewidth. The amplitude of the feedback signal may be controlled using an optical attenuator. The phase of the feedback signal may be controlled using a phase shifter. The amplitude of the optical feedback may be monitored by means of a filter and a photodetector, or just a photodetector. The amplitude and/or phase of the optical feedback is monitored by means of a frequency/phase noise discriminator. The phase shifter can be an endless phase shifter.