SAW Modulator Phase Selective Optical Coatings
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Solution Overview
Problem
Existing surface acoustic wave (SAW) modulators face limitations in efficient light coupling into leaky modes due to inefficient mode overlap, leading to restricted angular bandwidth and interference among guided modes, resulting in decreased light amplitude and increased stray light.
Innovation Solution
Applying coating layers to the SAW modulators, specifically tailored to adjust the phase shift of incoming plane waves, improves coupling into leaky modes by enhancing constructive interference and suppressing unwanted diffractive orders, thereby increasing the angular bandwidth and efficiency of light coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coating layers are applied to adjust phase shift of incoming plane waves, then coupling efficiency into leaky modes is improved over broader angular bandwidth, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies coating layers with specific optical properties (refractive index, thickness) to the SAW substrate surface to modify the phase shift of incoming plane waves. By changing these optical parameters, the coating enables constructive interference across broader angular bandwidth, improving coupling efficiency from guided modes to leaky modes without fundamentally altering the SAW modulator architecture.
Solution Approach 2:
The patent employs composite optical coatings composed of multiple layers with different refractive indices and thicknesses. These composite structures are designed to produce specific phase shifts that enhance mode coupling. The composite nature allows independent optimization of each layer's properties to achieve desired interference patterns across different angles.
2Object-generated harmful factors
If coating layers are applied to suppress unwanted diffractive orders, then stray light is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent converts the potentially harmful effect of multiple diffractive orders into a beneficial outcome by using coating layers to selectively suppress unwanted orders. The coating design exploits interference effects to cancel out stray light from higher-order diffraction while preserving the desired first-order diffraction, thereby reducing stray light through controlled destructive interference.
Solution Approach 2:
The coating layers are designed with spatially varying properties (different thicknesses, materials) at different locations on the substrate surface. This local variation in coating quality allows selective suppression of unwanted diffractive orders in specific angular ranges while maintaining high efficiency for desired orders, addressing stray light reduction with localized optimization.
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 enhances the coupling efficiency of guided modes into leaky modes over a broader range of angles with reduced variability, increasing the useful angular bandwidth and minimizing stray light, thus improving the performance of SAW modulators in light field generation.
Implementation Method 1
The proximal coating layer(s) are tailored to adjust the phase shift due to the reflection that more of the incoming plane waves experience by the one or more coating layers. The resulting adjustments in the standing wave improve constructive interference among the plane waves at the location where the interaction with the guided mode is strongest.
Implementation Method 2
the leaky mode is characterized as a standing wave formed by the interference between a plane wave incident on the top-face and its reflection, obeying the laws of Fresnel reflection
Implementation Method 3
In leaky mode SAW modulators, the SAW causes at least some of the light to be diffracted and change from a guided mode within the waveguides to a leaky mode that exits the waveguides at some deflection angle
Implementation Method 4
a SAW is generated in a piezoelectric substrate under radio frequency (RF) excitation
Data Source
AI summary
A system and method for improving spatial light modulator (SLM) devices such as Surface Acoustic Wave (SAW) modulators are disclosed. The SAW modulators can improved angular bandwidth and suppress unwanted diffractive orders. In one example, a coating layer(s) is applied to a proximal face of the SAW modulator to improve coupling of guided modes into leaky modes. Additionally, applying coating layers(s) such as a hybrid anti-reflective/highly reflective coating to an exit face of the SAW modulator can suppress transmission of undesired diffractive order(s).