Spatial Light Modulator with Diffractive Aberration Correction
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Solution Overview
Problem
Existing LCOS spatial light modulators used for wavelength selective switches face challenges in providing spatially varying phase control and beam shaping, which compromises phase availability for switching and fine-tuning individual wavelength channels.
Innovation Solution
A spatial light modulator incorporating a diffractive optical element with sub-wavelength gratings between electrodes, allowing for position-dependent wavefront correction and enhanced reflectivity, which includes a two-dimensional array of independently controllable pixels and a diffractive optical element with varying spatial periods to apply phase changes and beam steering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase modulation is used for wavefront correction in LCOS spatial light modulators, then wavefront correction capability is improved, but phase availability for switching and fine-tuning wavelength channels is reduced
Solution Approach 1:
The spatial light modulator is divided into two functionally independent components: a diffractive optical element (DOE) with sub-wavelength gratings dedicated to wavefront correction, and an LCOS layer with pixelated electrodes dedicated to wavelength channel switching. This segmentation allows each component to specialize in its respective function without competing for the same phase modulation resources, thereby resolving the contradiction between wavefront correction capability and phase availability for switching.
Solution Approach 2:
The diffractive optical element acts as an intermediary component between the incident light and the LCOS layer. It pre-corrects the wavefront aberrations before the light reaches the LCOS layer, so that the LCOS layer only needs to perform switching operations without being burdened by wavefront correction requirements. This intermediary approach enables both functions to coexist effectively.
2Illumination intensity
If sub-wavelength grating structures are incorporated to enhance reflectivity, then device reflectivity is improved, but spatially varying phase control capability is lost
Solution Approach 1:
The invention merges two previously separate concepts into a single integrated device: the high-reflectivity sub-wavelength grating structure and the spatially controllable LCOS layer. The DOE provides enhanced reflectivity and polarization independence, while the LCOS layer with its pixelated electrodes provides spatially varying phase control for switching. The combination of these elements in one device achieves both high reflectivity and spatial control capability simultaneously.
3Device complexity
If a single LCOS layer is used for both wavefront correction and switching, then device complexity is reduced, but performance optimization for wavelength selective switches is compromised
Solution Approach 1:
The device is segmented into functionally distinct layers: a diffractive optical element layer for wavefront correction and an LCOS layer for switching control. This segmentation, while adding structural complexity, enables each layer to be optimized for its specific function, thereby improving overall device reliability and performance for wavelength selective switching applications.
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 provides improved wavefront correction and beam steering capabilities without detracting from the phase required for switching, enhancing reflectivity and optimizing performance for wavelength selective switches.
Implementation Method 1
A liquid crystal material, first and second electrodes. The first and second electrodes are disposed on opposing sides of the liquid crystal material and are connected to an electric circuit for applying an electric potential across the liquid crystal material
Implementation Method 2
The diffractive optical element has an array of diffracting formations formed from sub-wavelength structures. The array of diffracting formations defines a phase profile adapted to modify the incident wavefront of light reflected off the second electrode and to apply a position-dependent wavefront correction to the reflected wavefront of light
Implementation Method 3
the second electrode is reflective and divided into a two-dimensional array of independently electrically controllable pixels
Data Source
AI summary
A spatial light modulator (100) comprises a liquid crystal material (104), first and second electrodes (106, 108) disposed on opposing sides of the liquid crystal material (104), and a diffractive optical element (120) disposed between the electrodes (106, 108) and extending laterally across the modulator (100). The diffractive optical element (120) comprises an array of diffracting formations (122) formed from sub-wavelength structures. The array of diffracting formations (122) defines a phase profile adapted to modify the incident wavefront of light reflected off the second electrode and to apply a position-dependent wavefront correction to the incident wavefront of light.