Photonic Crystal Waveguide Wavelength Dependency
Solution Overview
Problem
Optical waveguides utilizing two-dimensional photonic crystals face challenges in maintaining consistent properties across a wide wavelength range due to significant dependency on frequency, leading to defects in device characteristics when used over a broad spectrum.
Innovation Solution
The optical waveguide structure incorporates dielectric pillars with varying sizes and shapes within the lattice columns, specifically using equilateral polygons or circles, to control light confinement and reduce wavelength dependency by adjusting the size of voids near the core portion, thereby modifying the propagation constant and refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional two-dimensional photonic crystal waveguide is used, then the device achieves compact size and high functionality through multiple reflection, but the device characteristics show strong dependency on frequency and wavelength
Solution Approach 1:
The patent applies local quality by introducing lattice columns with different sizes (first size and second size different from fundamental size) at specific positions (first and second regions) relative to the optical waveguide. This non-uniform local modification of the photonic crystal structure allows control over light propagation characteristics while reducing wavelength dependency, thereby expanding the operational wavelength range without sacrificing device reliability
Solution Approach 2:
The patent changes the structural parameters of the photonic crystal by defining lattice columns with varying sizes (rn ≠ ro) at different orders and regions. By adjusting the size parameter of lattice columns relative to the fundamental size, the invention modifies the photonic band structure and dispersion characteristics, reducing the strong frequency dependency inherent in conventional uniform photonic crystal waveguides
2Adaptability or versatility
If the size of lattice columns is varied to reduce wavelength dependency, then the operational bandwidth is expanded, but the structural complexity increases
Solution Approach 1:
The patent segments the photonic crystal structure into distinct regions (first region and second region) with different lattice column size characteristics. The first region contains lattice columns of a first size, while the second region contains lattice columns of a second size, both different from the fundamental size. This segmentation allows systematic control of light propagation while managing structural complexity through organized regional differentiation
Solution Approach 2:
The patent introduces asymmetry by using lattice columns with different sizes at different positions and orders relative to the optical waveguide. The first and second lattice columns have sizes different from the fundamental size, creating an asymmetric structure that breaks the uniformity of conventional photonic crystals. This controlled asymmetry enables reduced wavelength dependency while maintaining manufacturability through defined geometric relationships
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
This approach effectively reduces the wavelength dependency of the group refractive index and effective electro-optic constant, allowing the optical waveguide to maintain superior properties across a wider frequency band.
Implementation Method 1
the internal multiple reflection phenomenon is utilized to provide various kinds of devices having superior functions and of very small sizes
Implementation Method 2
An optical waveguide structure of a two-dimensional and triangular lattice photonic crystal
Data Source
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AI summary
An optical waveguide structure has a slab type photonic crystal and an optical waveguide provided in the photonic crystal. The photonic crystal has a slab of a dielectric film and a plurality of lattice columns (T1-T5) each having dielectric pillars (H1-H7). The dielectric pillars included in the lattice columns at least in n'th order (n represents 1,2,3,4 and 5) in distance with respect to said optical waveguide, respectively, has a planar shape of an equilateral polygon or exact circle. At least one of the dielectric pillars included in the lattice columns at least in n'th order (n represents 2,3,4 and 5) with respect to the optical waveguide has a size rn different from a fundamental size ro.