Variable Feedback Control for Dense Wavelength Beam Combining
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Solution Overview
Problem
Dense wavelength beam combining (DWBC) techniques face challenges in maintaining spectral stability due to variations in feedback provided to individual emitters, leading to increased beam parameter product (BPP) and reduced performance in applications requiring high beam quality.
Innovation Solution
An external cavity laser apparatus with a variable feedback system utilizing polarizing beam splitting, birefringent optics, and high reflectivity mirrors to adjust the effective reflectivity of the external resonator, ensuring consistent wavelength stabilization across multiple emitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed feedback is provided to individual emitters in DWBC, then wavelength locking can be achieved, but spectral stability deteriorates due to variations in feedback levels
Solution Approach 1:
The patent implements a variable feedback system where the reflectivity of the external resonator is dynamically adjustable. By replacing fixed feedback with adjustable feedback, the system can compensate for variations in feedback levels across different emitters, maintaining consistent wavelength locking while improving spectral stability. The adjustable resonator allows real-time optimization of feedback conditions for each emitter.
Solution Approach 2:
The patent changes the feedback parameter from fixed to variable by introducing an adjustable external resonator. This parameter change enables the feedback level to be tuned and optimized for each emitter, resolving the contradiction between achieving wavelength locking and maintaining spectral stability. The variable feedback mechanism allows the system to adapt feedback conditions to match the specific characteristics of each emitter.
2Measurement precision
If wavelength filtering elements are used to remove non-desired wavelengths, then wavelength locking fidelity improves, but device complexity increases
Solution Approach 1:
The patent employs feedback mechanisms within the external resonator to suppress non-desired wavelengths. By using the adjustable resonator to provide wavelength-selective feedback, the system achieves wavelength locking fidelity without requiring additional wavelength filtering elements. The feedback loop naturally filters out non-desired wavelengths through constructive and destructive interference, simplifying the overall system architecture.
Solution Approach 2:
The adjustable external resonator acts as an intermediary that provides wavelength-selective feedback without requiring separate filtering elements. The resonator mediates between the emitters and the output, automatically selecting desired wavelengths through its adjustable resonant conditions. This intermediary approach achieves wavelength filtering functionality while maintaining system simplicity.
3Power
If individual emitters emit radiation at non-desired wavelengths, then total power output increases, but beam quality deteriorates due to increased BPP
Solution Approach 1:
The patent uses dynamic feedback control through the adjustable external resonator to suppress non-desired wavelengths from individual emitters. By adjusting the resonator conditions, the system selectively enhances desired wavelengths while suppressing unwanted ones, maintaining beam quality (low BPP) while preserving total power output. The dynamic adjustment allows optimization of wavelength selection without sacrificing overall power.
Solution Approach 2:
The patent changes the feedback parameter to be variable and tunable, allowing selective enhancement of desired wavelengths and suppression of non-desired wavelengths. This parameter change enables the system to maintain beam quality by controlling the spectral composition of each emitter's output, while still achieving high total power through the combined output of multiple emitters operating at optimized wavelengths.
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 adjustable feedback system enhances spectral stability, reduces BPP, and improves beam quality, enabling the production of high-power, high-quality combined laser beams suitable for applications like laser cutting of sheet metal.
Implementation Method 1
an angular dispersive optic disposed in the optical path of the plurality of primary component emitted beams and configured to combine the plurality of primary component emitted beams into a combined input beam
Implementation Method 2
a first polarizing optic disposed in the optical path of the combined input beam and configured to rotate a polarization of each of the plurality of component beams of the combined input beam
Implementation Method 3
a polarized beam splitter configured to direct the first combined feedback system output beam as a combined output beam, and direct the second combined feedback system output beam to the angular dispersive optic as a first combined feedback beam and back to the plurality of beam emitters
Implementation Method 4
DWBC techniques achieve wavelength-locking by providing feedback to each individual emitter that stimulates emission of radiation at wavelengths within the narrow spectrum
Data Source
AI summary
An external cavity laser apparatus according to an embodiment of the invention is provided. The external cavity laser apparatus includes a plurality of beam emitters that collectively emit a plurality of emitted beams that each includes a primary component emitted beam. A first reflective element is configured to reflect the plurality of primary component emitted beams and a first polarizing optic disposed in the optical path of the plurality of primary component emitted beams is configured to rotate a polarization of each primary component emitted beam to produce a first rotated primary component beam having a first linear polarization and a second rotated primary component beam having a second linear polarization. A polarized beam splitter is configured to direct first feedback system output component beams into an output beam, and to direct second feedback system output component beams to the plurality of beam emitters as feedback beams.