Laser System Optical Feedback Phase Control
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Solution Overview
Problem
Existing laser systems with optical feedback require precise control of the distance between the laser and resonant optical cavity to maintain phase alignment, which is challenging due to thermomechanical effects and limited by the bandwidth of mechanical adjustments, leading to slow and cumbersome adjustments for different laser emission frequencies.
Innovation Solution
Incorporating a fiber electro-optical modulator to phase-shift the source and counter-propagating waves, allowing for rapid and flexible adjustment of the relative phase between the laser and resonant optical cavity, enabling instantaneous phase correction and maximizing coupling efficiency regardless of wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If mechanical adjustment methods are used to control the distance between laser and resonant optical cavity, then phase alignment can be achieved, but the adjustment speed is slow and the response time is limited
Solution Approach 1:
The patent replaces the mechanical adjustment system (piezoelectric transducer moving a mirror) with an optical phase modulation system using an electro-optical modulator. This substitution eliminates mechanical moving parts and achieves phase control through electrical signals, thereby increasing adjustment speed to less than 0.1 nanoseconds while reducing mechanical complexity
Solution Approach 2:
The patent changes the control parameter from physical distance (mechanical parameter) to optical phase (electromagnetic parameter). By using an electro-optical modulator to directly modulate the phase of the optical wave, the system achieves rapid phase alignment without mechanical movement, resolving the contradiction between adjustment speed and device complexity
2Reliability
If the distance between laser and resonant optical cavity is controlled with great precision to maintain phase alignment, then optical feedback efficiency is improved, but the system can only be maintained passively for limited times due to thermomechanical effects
Solution Approach 1:
The patent implements an active feedback control system using a phase control device that continuously monitors and adjusts the phase relationship between the laser and resonant optical cavity. This feedback mechanism compensates for thermomechanical drifts and environmental variations, maintaining phase alignment stability indefinitely rather than passively for limited times
Solution Approach 2:
The patent transitions from passive static phase alignment to active dynamic phase control. The electro-optical modulator enables real-time phase adjustment in response to environmental changes, making the system adaptable and stable over extended periods despite thermomechanical effects
3Adaptability or versatility
If a mirror mounted on a piezoelectric transducer is used for fine adjustment of distance, then phase cancellation can be achieved, but the bandwidth is limited and adjustment for different frequencies requires several hours
Solution Approach 1:
The patent replaces the piezoelectric transducer and mirror mechanical adjustment system with an electro-optical modulator that controls phase through electrical signals. This substitution increases the bandwidth from limited mechanical response to electronic speeds, enabling frequency adaptation in less than 0.1 nanoseconds instead of several hours
Solution Approach 2:
The patent changes the control approach from mechanical position adjustment to optical phase modulation. The electro-optical modulator can rapidly adjust phase for different laser frequencies without mechanical movement, achieving high frequency adaptability with minimal time loss
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 almost instantaneous adjustment of the laser-cavity phase shift, improving the response time to less than 0.1 nanoseconds and allowing for rapid switching between different laser emission frequencies, enhancing the system's sensitivity and stability.
Implementation Method 1
a fiber electro-optical modulator to phase-shift the source and counter-propagating waves
Implementation Method 2
a resonant optical cavity, coupled by optical feedback to the laser, configured to generate an intra-cavity wave
Implementation Method 3
When the laser is sensitive to optical feedback, which is the case for example of semiconductor lasers, an optical feedback phenomenon occurs so that the frequency of the source wave is locked to that of the resonance mode of the resonant optical cavity
Data Source
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AI summary
The invention relates to a laser system with optical feedback, comprising an optical-feedback-sensitive laser (110) which emits, via an output optical fibre (111), a continuous, frequency-adjustable, propagating, source optical wave (L0p), known as the source wave; a resonant optical cavity (120) coupled by means of optical feedback to the laser and configured to generate an intra-cavity wave (L5), one fraction of which returns to the laser in the form of a counter-propagating optical wave (L0c); an electro-optic fibre modulator (115) placed on the optical path between the laser and the resonant optical cavity, said electro-optic modulator being configured to generate a phase-shifted source wave (L1p) by phase-shifting the source wave and, by phase-shifting the counter-propagating optical wave, to generate a phase-shifted counter-propagating wave (L0c), known as the feedback wave, which reaches the laser; a phase-control device (130) for generating a control signal (SC) for the electro-optic modulator from an error signal (SE) representative of the relative phase between the source wave (L0p) and the feedback wave (L0c), such as to cancel the relative phase between the source wave and the feedback wave.