Multi-Junction Laser Module Beam Deflection for Fiber Coupling
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Solution Overview
Problem
Fiber-coupling multiple laser beams from a multi-junction laser diode is challenging due to propagation-direction discrepancies introduced by fast-axis collimation, which prevents high-brightness coupling into a single optical fiber.
Innovation Solution
A multi-junction laser-diode module that includes a transmissive beam-deflecting element to correct for propagation-direction discrepancies, using a fast-axis cylindrical lens for collimation and a slow-axis cylindrical lens, along with a transmissive beam-deflecting element to ensure laser beams emerge with parallel propagation directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If fast-axis collimation is performed with a cylindrical lens positioned close to the multi-junction laser diode, then each laser beam is collimated in the fast axis, but propagation-direction discrepancy is introduced between the laser beams
Solution Approach 1:
A transmissive beam-deflecting element is introduced as an intermediary component between the fast-axis cylindrical lens and the optical fiber. This element deflects the collimated laser beams to correct propagation-direction discrepancies, enabling all beams to emerge with mutually parallel propagation directions while maintaining the benefits of fast-axis collimation
2Device complexity
If multiple laser beams are coupled into an optical fiber without correcting propagation-direction discrepancy, then the system structure is simpler, but coupling efficiency and brightness are reduced
Solution Approach 1:
The transmissive beam-deflecting element serves as a relatively simple intermediary component that corrects beam propagation directions without requiring complex optical systems. This enables high-efficiency fiber coupling while maintaining reasonable device complexity
Solution Approach 2:
The beam-deflecting element operates in the angular dimension of beam propagation, correcting direction discrepancies without affecting the spatial positioning of beams. This dimensional approach allows parallel beam correction with minimal added complexity
3Device complexity
If a common laser resonator is formed around the full stack of laser junctions, then a single laser beam is emitted, but heat sinking constraints prevent this in high-power continuous-wave operation
Solution Approach 1:
The multi-junction laser diode is segmented into multiple independent laser junctions, each forming its own resonator. This segmentation allows independent heat management for each junction while maintaining a compact integrated structure, enabling high-power continuous-wave operation with effective heat sinking
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
Enables high-brightness fiber-coupling of multiple laser beams by ensuring they are fully collimated and parallel, allowing efficient coupling into an optical fiber with minimal loss and enabling frequency-locking capabilities.
Implementation Method 1
a fast-axis cylindrical lens configured to collimate each laser beam in the fast axis
Implementation Method 2
a slow-axis cylindrical lens configured to collimate each laser beam in the slow axis
Implementation Method 3
a transmissive beam-deflecting element configured to deflect all or all but one of the laser beams in a first plane, parallel to the fast axes of the laser beams, such that the laser beams emerge from the transmissive beam-deflecting element with mutually parallel propagation directions
Data Source
AI summary
A multi-junction laser-diode module includes (a) a multi-junction laser diode having a plurality of laser junctions stacked in a vertical dimension parallel to the fast-axes of the laser beams emitted by the laser junctions, (b) a fast-axis cylindrical lens collimating each laser beam in the fast axis, whereby the laser beams emerge from the fast-axis cylindrical lens with mutually nonparallel propagation directions, (c) a transmissive beam-deflecting element that deflects the laser beams in the fast-axis dimension after the fast-axis cylindrical lens to make their propagation directions parallel, and (d) a slow-axis cylindrical lens configured to collimate each laser beam in the slow axis. The transmissive beam-deflecting element corrects for the propagation-direction discrepancy between the laser beams, in the fast-axis dimension, caused by fast-axis collimation. The multi-junction laser-diode module can thereby produce a laser beam bundle suitable for high-brightness fiber-coupling.