Divergence-reshaping array for laser diode beam collimation
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Solution Overview
Problem
Multimode laser diodes emit beams with significant asymmetry between fast and slow axes, leading to suboptimal collimation and brightness in applications, where traditional collimation methods result in residual divergence and compromises in beam size or power.
Innovation Solution
A divergence reshaping apparatus comprising specific optical elements with tailored optical powers and alignments along the fast and slow axes, including a fast axis collimator, slow axis magnifier, off-axis objective, and slow axis collimator, to collimate, compress, and shift the beam, reducing residual divergence and enhancing brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional collimation optics are used for laser diode arrays, then the beam can be collimated, but residual divergence remains and brightness is compromised
Solution Approach 1:
The optical system is divided into separate fast axis and slow axis optical paths with dedicated collimation and magnification elements for each axis, allowing independent optimization of each axis to eliminate residual divergence while maintaining brightness
Solution Approach 2:
The patent employs asymmetric optical design where the fast axis and slow axis have different optical powers and element configurations matched to the asymmetric emission characteristics of laser diodes, with the fast axis requiring higher magnification due to smaller emission area and larger divergence
2Adaptability or versatility
If the emitter to emitter pitch is decreased to accommodate larger bar to bar pitch, then the array geometry is improved, but the divergence in the fast axis becomes smaller than optimal and the slow axis becomes larger than optimal
Solution Approach 1:
The patent changes the optical parameters (optical power, focal length) of the collimation and magnification elements to match the specific array geometry and pitch dimensions, allowing the system to adapt to different emitter to emitter pitches while maintaining optimal divergence correction
3Manufacturing precision
If the focal length of the collimating lens is maximized to minimize residual divergence, then the divergence is reduced, but the distance from source to intersection of largest angle rays is increased
Solution Approach 1:
The patent introduces a second optical dimension by adding magnification elements that operate in the magnification direction, allowing the system to achieve divergence correction without requiring excessively long focal lengths in the collimation direction alone
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 slow axis residual divergence while increasing slow axis brightness, achieving higher symmetry and brightness in laser diode beams by trading off fast axis brightness, thus improving the performance of laser diode arrays.
Implementation Method 1
a fast axis collimator element having positive optical power in the fast axis and no optical power in the slow axis
Implementation Method 2
A slow axis magnifier element has no optical power in the fast axis and has positive optical power in the slow axis
Implementation Method 3
An objective element has positive optical power in the fast axis and no optical power in the slow axis, wherein the positive optical power of the objective element compresses the beam in the fast axis
Implementation Method 4
A slow axis collimator element has negative optical power in the fast axis and positive optical power in the slow axis, wherein the negative optical power of the slow axis collimator element collimates the compressed beam in the fast axis, and wherein the positive optical power of the slow axis collimator element collimates the beam in the slow axis
Data Source
Figure 1A~1B
Figure 2
Figure 3A
AI summary
A divergence reshaping apparatus for laser diodes having a fast axis and a slow axis includes a fast axis collimator element having positive optical power in the fast axis and no optical power in the slow axis. A slow axis magnifier element has no optical power in the fast axis and positive optical power in the slow axis. An objective element has positive optical power in the fast axis and no optical power in the slow axis. A slow axis collimator element has negative optical power in the fast axis and positive optical power in the slow axis. Every element is optically aligned down an optical axis, and wherein a beam travelling through every element is collimated, compressed and shifted in the fast axis and expanded and collimated in the slow axis.