Annular Diffuser Lens With Graded Index for Uniform VCSEL Beams
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Solution Overview
Problem
Existing diffusor lenses for VCSELs suffer from diffraction losses and inhomogeneities in the beam profile due to their small size and stepwise discontinuities, which are difficult to integrate into semiconductor chips.
Innovation Solution
A diffusor lens comprising concentric annular lens segments with varying refractive index profiles, where the first sub-profile transitions to the second sub-profile at an interface with slopes of opposite signs, reducing lens sag and optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If small diffusor lenses are used to achieve good homogeneity of the rectangular beam profile, then the beam profile homogeneity is improved, but diffraction losses increase and reduce the quality of sensing applications
Solution Approach 1:
The diffusor lens is divided into multiple concentric annular segments with different refractive index profiles. Each segment is optimized to control light propagation in specific radial zones, allowing the lens to achieve both small aperture and reduced diffraction losses through distributed optical control.
Solution Approach 2:
Different annular segments of the lens are assigned different refractive index profiles tailored to their specific radial positions. The inner segments have different optical properties than outer segments, allowing each region to be optimized for its local function in shaping the beam profile while minimizing overall diffraction effects.
2Loss of energy
If larger lenses are used to avoid diffraction losses, then diffraction losses are reduced, but the lens sag (height difference along optical axis) increases making integration into semiconductor chips difficult
Solution Approach 1:
The lens is segmented into concentric annular regions that can be fabricated separately and then assembled. This segmentation allows each segment to have a smaller, more manageable height while collectively providing the optical function of a larger lens, thereby reducing overall lens sag for semiconductor integration.
Solution Approach 2:
Instead of increasing lens aperture in a single dimension which increases sag, the solution uses multiple segments arranged in concentric rings. This transforms the problem from a single large curved surface to multiple smaller surfaces distributed radially, reducing the maximum height difference while maintaining optical functionality.
3Device complexity
If Fresnel lenses are used to reduce lens sag, then lens sag is reduced, but stepwise discontinuities cause losses and inhomogeneities in the beam profile
Solution Approach 1:
Each annular segment is assigned a specific refractive index profile optimized for its radial position. The transition between segments is designed to be smooth and continuous in terms of optical path length, eliminating the abrupt discontinuities that cause diffraction and inhomogeneities in conventional Fresnel lenses.
Solution Approach 2:
The refractive index parameter is varied continuously across different annular segments rather than using discrete steps. This continuous parameter change through graded refractive indices smooths out optical transitions between regions, eliminating the stepwise discontinuities that plague conventional Fresnel lens designs.
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 achieves a homogeneous rectangular beam profile, enhancing the quality of sensing applications by minimizing diffraction losses and integrating seamlessly into semiconductor chips.
Implementation Method 1
A refractive index of the first and second lens segments in a cross-section along a plane including an optical axis of the diffusor lens is described by a refractive index profile which varies in a direction perpendicular to the optical axis
Implementation Method 2
the small size of these diffusor lenses however results in diffraction losses as the lens array is typically illuminated homogenously
Data Source
AI summary
A diffuser lens includes a first annular lens segment and a second annular lens segment. The first and the second lens segments are concentric. A refractive index of the first and second lens segments in a cross-section along a plane including an optical axis of the diffusor lens is described by a refractive index profile which varies in a direction perpendicular to the optical axis. The refractive index profile includes a first sub-profile, which describes the refractive index profile of the first lens segment, and a second sub-profile, which describes the refractive index profile of the second lens segment. The first sub-profile transitions to the second sub-profile at an interface. These first and second sub-profiles have slopes with opposite signs.