Ring Resonator Laser Phase Matching for Unidirectional Output
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Solution Overview
Problem
In ring resonator lasers, thermally induced aberrations and refractive index variations lead to unequal power and spatial distribution between counter-propagating beams, resulting in reduced beam quality and suboptimal power extraction efficiency due to unequal losses and non-resonant phase distributions.
Innovation Solution
Redirecting one beam to propagate in the same direction as the other and using a beam modifier to match the spatial phase distribution of both beams, thereby minimizing losses associated with non-resonance and enhancing beam quality through a combination of beam splitters, reflectors, and phase distortion rectifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beam propagation is made unstable using magnifying optics to achieve unidirectional propagation, then beam quality and power extraction efficiency are improved, but device complexity and manufacturing costs increase
Solution Approach 1:
The patent introduces a corner cube retroreflector that creates asymmetric optical paths for clockwise and anticlockwise beams. The retroreflector returns only the clockwise beam to the cavity while the anticlockwise beam is directed to the output coupler, creating unidirectional lasing without requiring magnifying optics. This asymmetric configuration achieves stable unidirectional propagation while maintaining simple optical design.
2Ease of operation
If a polarising beam splitter is used to couple out beams and redirect one beam, then unidirectional propagation is achieved, but device complexity increases
Solution Approach 1:
The patent combines the beam splitting and beam redirecting functions into a single corner cube retroreflector component. The retroreflector inherently separates the counter-propagating beams through its geometric optics properties, eliminating the need for separate polarising beam splitters and redirecting mirrors. This merging of functions reduces the number of optical components while achieving the same unidirectional propagation control.
3Power
If both counter-propagating beams are allowed to propagate with equal power, then beam brightness is maximized, but beam quality deteriorates due to non-resonant phase distribution
Solution Approach 1:
Instead of allowing both beams to propagate equally and then trying to match their phases, the patent inverts the approach by using the corner cube retroreflector to selectively return only one beam (the clockwise beam) to the cavity. This inversion of the beam selection process ensures that only resonant beams with proper phase distribution are amplified, while the other beam is directed to the output coupler for extraction.
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 approach ensures that the combined beam is naturally resonant with the resonator, reducing losses and improving beam brightness and radiance by equalizing power and phase distribution between the beams, thus optimizing power extraction efficiency.
Implementation Method 1
a corner cube retroreflector (CCRR) 4. When lasing, clockwise Ic and anticlockwise Ia travelling beams propagate from the gain medium. The polarising beam splitter couples out the two beams: Ia forms the useful output and Ic is coupled back into the cavity by a corner cube retroreflector (CCRR) 4 as an anticlockwise travelling, clockwise beam, Ica.
Implementation Method 2
a polarising beam splitter (PBS) 3. The polarising beam splitter couples out the two beams: Ia forms the useful output and Ic is coupled back into the cavity
Implementation Method 3
a beam modifier adapted to modify the spatial distribution of the phase across the aperture of the first beam such as to cause it to become more similar or substantially match that of the spatial distribution of phase across the aperture of the second beam
Implementation Method 4
a laser gain medium (for example Nd:YAG) 2. When lasing, clockwise Ic and anticlockwise Ia travelling beams propagate from the gain medium
Data Source
AI summary
A laser system having an optical ring resonator, a beam splitter that directs a first beam travelling in a first direction around the ring resonator, out of the resonator towards a reflector that reflects the first beam back into the resonator to travel in an opposite direction around the optical ring resonator that is in the same direction as a second beam travelling around the optical ring resonator; and a beam modifier configured and adapted to modify a spatial distribution of phase across an aperture of the first beam such as to cause it to become more similar or substantially match that of a spatial distribution of phase across an aperture of the second beam.