Injection-Locked Laser Phase Control for Coherent Multi-Frequency Output
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Solution Overview
Problem
Injection-locked laser systems face challenges in achieving high phase-coherence, especially at high frequencies, due to limitations in active phase-control and the introduction of residual phase noise, particularly at low frequencies and during optical field transmission.
Innovation Solution
An injection-locked laser system is designed with a master laser generating continuous-wave output fields that are modulated to produce seed optical fields at specific frequencies, which are used to injection-lock optical amplifiers. Phase lock control loops provide feedback to modulators to ensure high phase-coherence between the output fields of the amplifiers and the master laser, reducing noise and maintaining phase-locking across the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active phase-control is used to phase match two optical fields, then phase-coherence can be maintained within the control frequency range, but phase-coherence deteriorates at high frequencies beyond the control range and servo-bump noise is introduced
Solution Approach 1:
The patent introduces a mode-locked master laser as an intermediary that generates multiple optical modes which are then used to injection-lock multiple slave lasers. This intermediary approach allows phase-coherence to be extended to high frequencies through the correlated phase fluctuations of the master laser modes, bypassing the limitations of direct active phase-control between slave lasers.
Solution Approach 2:
The patent segments the single high-power laser system into multiple slave lasers that are each injection-locked to different modes of the master laser. This segmentation allows each slave laser to operate at its optimal frequency while maintaining phase-coherence through the common master laser source, avoiding the need for a single complex active phase-control system.
2Loss of energy
If injection-locking is used to achieve single-frequency operation of high-power lasers, then power efficiency is improved compared to using etalons, but residual phase noise remains particularly at low frequencies
Solution Approach 1:
The patent implements feedback control loops that detect phase fluctuations in the slave laser outputs and use this information to adjust the injection-locking conditions. This feedback mechanism actively suppresses residual phase noise, particularly at low frequencies, while maintaining the power efficiency benefits of injection-locking without intracavity elements.
Solution Approach 2:
The patent combines multiple slave laser outputs that are each injection-locked to the master laser. By merging these outputs, the system achieves both the power efficiency of injection-locking and reduced phase noise through the averaging effect and correlated phase fluctuations of the master laser modes.
3Reliability
If a single master laser is used to injection-lock multiple slave lasers at different frequencies, then phase-coherence is achieved across all outputs, but the frequency range is limited by the mode spacing of the master laser
Solution Approach 1:
The patent employs a mode-locked master laser with dynamically adjustable mode spacing and a tunable frequency comb structure. This allows the system to adapt to different frequency requirements by changing the operating conditions of the master laser, thereby extending the usable frequency range while maintaining phase-coherence across all slave laser outputs.
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 system achieves high phase-coherence between the output fields of the optical amplifiers and the master laser, effectively reducing residual phase noise and maintaining phase-locking, even at high frequencies and during transmission, thereby improving the overall performance of the injection-locked laser system.
Implementation Method 1
a master laser that generates a continuous-wave output field
Implementation Method 2
one or more optical modulators employed to produce from the continuous-wave output field a first seed optical field having a first frequency (f1) and a second seed optical field having a second frequency (f2)
Implementation Method 3
Injection-locking is achieved by injecting the output of the master laser into the cavity of the slave laser. As the frequency of the master laser approaches one of the axial mode frequencies of the slave laser, light from the master laser is regeneratively amplified to higher intensities
Implementation Method 4
a first phase lock control loop that provide a first feedback signal to one of the one or more optical modulators to phase lock the continuous-wave output field, produced at the first frequency (f1), of a first optical amplifier to the continuous-wave output field
Data Source
Figure 1
Figure 2(a)~2(b)
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AI summary
A method and system for injection-locking multiple optical amplifiers is disclosed. A master laser is employed to generate a continuous-wave output field. Optical modulators then produce first and second seed optical fields from the continuous-wave output field. The first and second seed optical fields provide an input to injection lock one or more optical amplifiers, optionally at different operating frequencies. Since the first and second seed optical fields are generated from the continuous-wave output field then the output fields of the optical amplifiers exhibit a high phase-coherence with each other and with the continuous-wave output field. Employing the first and second optical fields reduces the requirement to induce large frequency shifts on a single optical field. Techniques for phase-locking the output of the injection-locked laser systems are also provided to further reduce phase noise within the systems.