Nano-layer Optical Field Concentrator for CMOS Laser Confinement
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Solution Overview
Problem
Conventional optical field concentrators face challenges in confining and guiding light in nanometer-sized low-index media with high optical confinement and power density, particularly due to limitations in carrier injection and optical confinement in silicon-based photonic integration, and existing waveguide structures are sensitive to physical parameters and wavelength.
Innovation Solution
A multiple nano-layer optical field concentrator structure is proposed, featuring high-index waveguide layers with low-index nano-layers and cladding layers, allowing precise control of layer thickness and refractive indices to enhance optical confinement and power density, using a vertically stacked horizontal nano-layer configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional waveguide structures are used to confine light in low-index media, then the structure is simple to manufacture, but the optical confinement factor is low and the device size cannot be reduced to nanometer range
Solution Approach 1:
The patent divides a single thick low-index layer into multiple thin nano-layers (e.g., five 10 nm layers instead of one 50 nm layer). This segmentation creates multiple high-index contrast interfaces that enhance optical field confinement in each layer while maintaining overall structural simplicity compatible with standard CMOS fabrication processes.
Solution Approach 2:
The patent transitions from a single thick layer configuration to a multi-layer stacked configuration in the vertical dimension. By stacking multiple thin low-index layers between high-index silicon layers, the structure achieves enhanced optical confinement through cumulative interface effects without increasing lateral device dimensions.
2Reliability
If the slot width is increased to maintain confinement factor, then the field concentration is improved, but the normalized power density decreases
Solution Approach 1:
By segmenting a single thick low-index layer into multiple thin layers, the patent achieves high field concentration in each thin layer while maintaining adequate total confinement. The multiple interfaces create localized field enhancement regions that increase normalized power density without requiring a large overall slot width.
Solution Approach 2:
The patent changes the thickness parameter of low-index layers from tens of nanometers to single-digit nanometers (e.g., 10 nm per layer). This parameter change, combined with increasing the number of layers, optimizes the balance between confinement factor and normalized power density by creating stronger field confinement at each interface.
3Use of energy by moving object
If the slot width is decreased to increase field concentration, then the normalized power density is improved, but the confinement factor is lost
Solution Approach 1:
The patent compensates for the reduced width of individual nano-layers by increasing the number of stacked layers. Each thin layer provides localized field confinement, and the cumulative effect of multiple layers maintains the overall confinement factor while achieving high normalized power density in each layer.
Solution Approach 2:
The patent shifts the confinement mechanism from lateral expansion (width) to vertical stacking (height). By arranging multiple thin layers vertically between high-index silicon layers, the structure achieves both high field concentration and adequate total confinement through the vertical dimension.
4Manufacturing precision
If PBG or ARROW-type waveguides are used to confine light in low-index core, then the optical confinement is improved, but the structure becomes sensitive to physical parameters and wavelength
Solution Approach 1:
The patent uses standard CMOS-compatible materials (silicon and silicon dioxide) with fixed, well-known refractive indices, eliminating the need to precisely control layer thicknesses or periods for resonant conditions. The optical confinement arises from high-index contrast at interfaces rather than from wavelength-specific resonant effects, making the structure insensitive to parameter variations.
Solution Approach 2:
The patent employs standard silicon-on-insulator (SOI) wafer structures that are already widely used in the semiconductor industry. This approach leverages existing, well-controlled fabrication processes rather than requiring specialized photonic crystal or resonant cavity structures, thereby reducing sensitivity to manufacturing parameters and enabling scalable production.
5Manufacturing precision
If nanometer-sized low-index guiding is attempted with ARROW-type waveguides, then the optical confinement is improved, but the core layer thickness must be in the order of half wavelength making nanometer size guiding impossible
Solution Approach 1:
The patent divides a half-wavelength-thick low-index layer into multiple thin nano-layers (e.g., five 10 nm layers). Each thin layer is much thinner than half a wavelength, yet the stack collectively provides strong optical confinement through multiple high-index contrast interfaces, enabling nanometer-scale guiding.
Solution Approach 2:
The patent achieves nanometer-scale thickness in the vertical dimension by stacking multiple thin layers, while the lateral dimensions remain in the micrometer range for single-mode operation. This separation of scales in different dimensions enables true nanometer-sized optical guiding.
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 configuration achieves a confinement factor of up to 42% and normalized power density of 80 μm−2, significantly surpassing conventional silicon-on-insulator waveguides, with improved fabrication tolerances and bending characteristics, enabling efficient light confinement and guidance in nanometer-sized low-index media.
Implementation Method 1
Conventional optical field confining and concentrating are based on optical waveguides made of a high-index core surrounded by low-index claddings. For the guided modes with steady spatial pattern to exist in the waveguide, it requires total internal reflections (TIR) at the boundaries to ensure that the optical field mainly concentrates and propagates in the core region.
Implementation Method 2
In some other circumstances, such as in the photonic bandgap (PBG) structures and antiresonant reflecting optical waveguides (ARROWs), by utilizing the external reflection induced by the multiple-dielectric-layer interferences, light can be confined and guided in the low-index core.
Data Source
AI summary
An optical field concentrator includes a plurality of waveguide layers comprising high index materials having a first defined thickness. At least one nano-layer structure is positioned between said waveguide layers. The at least one nano-layer structure comprises low index materials having a second defined thickness that is smaller than the first defined thickness. A plurality of cladding layers are positioned between the waveguide layers and the at least one nano-layer structure. The cladding layers have a third defined thickness that is larger than the first defined thickness.