Alternating-Index Optical Waveguide for Compact Modulation
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Solution Overview
Problem
Conventional optical components, such as Mach-Zehnder modulators, are large and costly, limiting their integration in compact form factors and suffering from slow electro-optical effects, necessitating long interaction lengths for effective modulation.
Innovation Solution
An optical waveguide with alternating regions of different refractive index along its longitudinal axis, creating transmission gaps to induce a slow-wave or slow-light regime, thereby increasing modulation efficiency and reducing physical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional electro-optical effects are used for modulation, then the modulation can be achieved, but the interaction length must exceed a predetermined minimum length (millimeter to centimeter range) to accumulate sufficient relative propagation time difference
Solution Approach 1:
The patent changes the propagation speed parameter of optical waves by introducing periodic refractive index variations that create transmission gaps. This slows down the optical wave propagation speed, increasing the group refractive index and thereby enhancing the relative propagation time difference accumulated over a given interaction length, which improves modulation efficiency without requiring centimeter-scale lengths.
Solution Approach 2:
The patent introduces localized periodic modulations of the refractive index along the waveguide structure. These local modifications create specific transmission gaps at desired wavelengths while maintaining normal propagation characteristics elsewhere, enabling enhanced modulation efficiency in specific wavelength ranges without affecting the entire waveguide uniformly.
2Length of moving object
If the interaction length is reduced to decrease device size, then the physical dimensions are reduced, but the relative propagation time difference and phase difference between interferometer arms become insufficient for effective modulation
Solution Approach 1:
By changing the propagation speed parameter through periodic refractive index variations, the patent increases the effective interaction time between light and the modulating field within a shortened physical length. This maintains sufficient phase difference accumulation for effective modulation while reducing the overall device dimensions from centimeter to millimeter or sub-millimeter scale.
3Device complexity
If conventional waveguides are used, then the structure is simple, but the nominal speed of optical waves is high, resulting in insufficient relative propagation time difference for effective modulation
Solution Approach 1:
The patent modifies the propagation speed parameter by introducing periodic refractive index variations through methods such as alternating high and low refractive index layers, corrugated waveguide walls, or periodic holes. This creates transmission gaps that slow down optical wave propagation, increasing the group refractive index and enhancing the relative propagation time difference without significantly complicating the overall waveguide structure.
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 slow-wave regime enhances modulation efficiency, allowing for reduced interaction lengths and potentially smaller, more efficient electro-optic modulators.
Implementation Method 1
an optical waveguide comprising at least a first group of alternating regions of different refractive index arranged along a longitudinal axis of the waveguide effecting two transmission gaps in a transmission spectrum of the waveguide
Implementation Method 2
establish a slow-wave or slow-light regime in a wavelength range between the two transmission gaps
Implementation Method 3
these components exploit high-speed electro-optical effects to accelerate or slow down an optical wave in one of the two interferometer arms of the Mach-Zehnder modulators, which results in a relative phase difference between the two interferometer arms
Data Source
Figure 1~3
Figure 4A~4B
Figure 4C~5A
AI summary
An optical waveguide comprising at least a first group of alternating regions of different refractive index arranged along a longitudinal axis of the waveguide effecting two transmission gaps in a transmission spectrum of the waveguide.