Diffractive Optical Element Aberration Correction in Wavelength Switches
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Solution Overview
Problem
Wavelength selective switch (WSS) devices experience significant optical aberrations, particularly off-axis curvature, spherical aberration, and optical coma, which limit their performance in high numerical aperture systems and make it difficult to maintain spot quality across all wavelengths, especially with larger and more asymmetric beam profiles.
Innovation Solution
A wavelength dispersive optical system comprising a diffractive optical element (DOE) with a substrate and an array of diffraction elements having predefined spacing and curvature, combined with an optical focusing element, to spatially separate wavelength components and impose phase changes that correct for optical aberrations and provide wavelength-dependent focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beams are propagated off-axis to achieve advanced optical functions in WSS devices, then beam shaping capability and switching functionality are improved, but optical aberrations (off-axis curvature, spherical aberration, optical coma) increase significantly
Solution Approach 1:
A diffractive optical element (DOE) is introduced as an intermediary component between the off-axis beam propagation path and the switching engine. The DOE imposes predefined phase changes on the wavelength components to correct optical aberrations while maintaining the off-axis beam configuration needed for advanced switching functionality
Solution Approach 2:
The patent changes the phase parameters of the optical beam by using a DOE with specifically designed diffraction elements that have predefined spacing and curvature. This modifies the wavefront phase to compensate for aberrations introduced by off-axis propagation, allowing both off-axis beam shaping and aberration correction
2Productivity
If larger and more asymmetric beam profiles are used to switch many wavelength channels simultaneously, then switching capacity is improved, but optical aberrations increase
Solution Approach 1:
The diffractive optical element applies local phase corrections to different regions of the asymmetric beam profile. Each region of the beam receives tailored phase modulation to correct local aberrations, enabling the system to handle large asymmetric beams with high switching capacity while maintaining beam quality
3Object-affected harmful factors
If diffraction grating with diffraction elements is used to correct optical aberrations, then aberration correction is achieved, but wavelength-dependent focusing issues persist in high numerical aperture systems
Solution Approach 1:
The diffractive optical element incorporates curved diffraction elements with predefined curvature across their surface. This curvature is specifically designed to counteract the off-axis curvature of the focal plane and provide wavelength-independent focusing, ensuring consistent spot quality across all wavelengths in high numerical aperture systems
4Measurement precision
If the push for smaller beam spots at the switching plane is increased to achieve sharper channels, then channel resolution is improved, but aberrations become more limiting
Solution Approach 1:
The diffractive optical element applies preliminary phase corrections to the beam before it reaches the switching plane. By pre-compensating for the optical coma and other aberrations that would otherwise limit small beam spot performance, the system achieves both sharp channel resolution and maintains beam quality at the reduced spot size
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 corrects optical aberrations, improving the focusing of wavelength components and reducing wavelength-dependent focal displacement, resulting in sharper channel profiles and more symmetric beam spots, even in high numerical aperture systems.
Implementation Method 1
a diffractive optical element (DOE) including a substrate and an array of physical diffraction elements, wherein the diffraction elements have a predefined spacing and/or curvature across a length of the DOE and wherein the diffraction elements are collectively adapted to: i) spatially separate the individual wavelength components within the input optical beam to be formed into the one or more output optical beams
Implementation Method 2
impose predefined phase changes to the wavelength components to at least partially correct for optical aberrations to the input optical beam
Implementation Method 3
an optical focusing element having optical focusing properties complementary to the DOE to modify the optical focusing of the wavelength components imparted by the DOE
Data Source
AI summary
Described herein is a wavelength dispersive optical system (10). The system (10) comprises at least one optical input (12, 14, 16) for projecting an input optical beam comprising a plurality of individual wavelength components and at least one optical output (18) for receiving one or more output optical beams. The system (10) also includes a diffractive optical element (DOE) (1) including a substrate (2) and an array of physical diffraction elements (3). The diffraction elements (3) have a predefined spacing and/or curvature across a length of the DOE (1) and are collectively adapted to: i) spatially separate the individual wavelength components within the input optical beam to be formed into the one or more output optical beams; ii) impose predefined phase changes to the wavelength components to at least partially correct for optical aberrations to the input optical beam; and iii) impose predefined phase changes to the wavelength components to apply a wavelength dependent optical focusing to at least some of the wavelength components. The system (10) further includes an optical focusing element (5) having optical focusing properties complementary to the DOE (1) to modify the wavelength-dependent optical focusing of the wavelength components by the DOE (1).