Integrated End Mirror Assembly for High-Speed Fiber Ring Cavity Control
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Solution Overview
Problem
Fiber-based lasers are sensitive to vibrations and acoustics due to imperfections in fiber splices, temperature and pressure fluctuations, and the lack of high-speed actuators that can control cavity length at high frequencies, leading to spurious intra-cavity back reflections and limited dynamic range.
Innovation Solution
A cavity adjuster with a circulator element and a mirror mounted on an actuator that adjusts the relative distance between the mirror and the circulator, ensuring unidirectional lasing and allowing for high-speed adjustments of the ring cavity length using a PZT actuator, thereby reducing sensitivity to vibrations and acoustics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a ring laser with an intra-cavity isolator is built to enforce unidirectional lasing, then spurious back reflections are reduced, but it becomes difficult to incorporate a high-speed actuator for cavity length control
Solution Approach 1:
The laser cavity is segmented into distinct functional sections: a fiber-based section containing the isolator for unidirectional lasing, and a free-space section containing the PZT actuator and mirror for high-speed cavity length control. This segmentation allows each section to optimize its specific function without interfering with the other, resolving the contradiction between reducing back reflections and incorporating high-speed actuators.
2Adaptability or versatility
If fiber stretchers are used for cavity length control, then the system maintains fiber-based architecture, but the bandwidth is limited and dynamic range is restricted
Solution Approach 1:
A free-space optical path acts as an intermediary between the fiber-based laser cavity and the PZT actuator. The collimated beam travels through free space to the mirror mounted on the PZT actuator, enabling high-speed cavity length control (bandwidth >10 kHz) while maintaining compatibility with the fiber-based laser architecture. This intermediary interface resolves the contradiction between maintaining fiber architecture and achieving high bandwidth.
3Speed
If high-speed PZT actuators are incorporated behind a cavity end mirror in linear laser cavities, then cavity length can be controlled at high frequencies, but spurious intra-cavity back reflections and spatial hole burning occur
Solution Approach 1:
The laser cavity employs asymmetric design with unidirectional lasing enforced by the isolator in the fiber section. The free-space section contains the PZT actuator and mirror positioned to reflect light back through the circulator element, creating an asymmetric optical path that prevents spurious back reflections from entering the gain medium, thereby eliminating spatial hole burning while maintaining high-speed control capability.
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 solution effectively reduces sensitivity to vibrations and acoustics by ensuring unidirectional lasing and allowing for precise control of the ring cavity length, avoiding spurious back reflections and spatial hole burning, while providing a high-speed actuator with improved dynamic range.
Implementation Method 1
a circulator element optically coupled to the input and output ports and configured to establish unidirectional propagation of the laser light from the input port to the output port
Implementation Method 2
a mirror configured to receive the laser light in free-space from the circulator element and reflect the laser light such that the reflected laser light passes through the circulator element and into the output port
Implementation Method 3
an actuator physically coupled to the mirror where the actuator adjusts a relative distance between the mirror and the circulator element to change a length of the ring cavity
Data Source
AI summary
Embodiments herein describe a path length adjuster for, e.g., adjusting the length of an optical cavity of a laser. In one embodiment, the path length adjuster includes a circulator element for ensuring unidirectional lasing. The path length adjuster may also include one or more focusing elements such as a focusing lens and/or a collimator which directs received laser light at a mirror. The mirror is mounted on an actuator that moves the mirror in a direction parallel with the propagation of the laser light, thereby increasing or reducing the length of the ring cavity.