Hollow Core Waveguide Optimized Contour Reduces Transmission Losses

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Solution Overview

Problem

Hollow-core photonic crystal fibers guided by Photonic Band Gap suffer from high transmission losses at shorter wavelengths, narrow bandwidth, structured dispersion, and low laser damage threshold, while inhibited coupling guided fibers have high transmission losses and limited applications due to these issues.

Innovation Solution

A hollow-core waveguide with an optimized contour, featuring a Kagome-type sheath structure and a contour comprising alternating small and large arcs with specific curvature ratios, reduces transmission losses and increases the laser damage threshold by minimizing field overlap and enhancing mode inhibition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hollow-core photonic crystal fibers are guided by Photonic Band Gap, then guidance is achieved for certain wavelengths, but transmission losses increase very quickly for shorter wavelengths

Engineering Contradiction:

Improveguidance capabilityVSAvoidtransmission losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the geometric parameters of the hollow core contour, specifically using a hypocycloidal shape with optimized curvature radii ratios. This parameter optimization reduces field overlap with the cladding structure, thereby reducing transmission losses across a broader wavelength range including shorter wavelengths.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a hypocycloidal contour with specifically optimized curvature radii (R1 and R2) for the arcs forming the hollow core. The optimized curvature reduces the overlap between the guided mode field and the cladding material, minimizing transmission losses while maintaining guidance capability.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If hollow-core photonic crystal fibers are guided by Photonic Band Gap, then guidance is achieved, but bandwidth is narrow (order of 70 THz)

Engineering Contradiction:

Improveguidance capabilityVSAvoidbandwidth

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent optimizes the geometric parameters of the hypocycloidal contour, specifically the curvature radii R1 and R2 and their ratio. This parameter optimization broadens the photonic band gap, enabling guidance across a wider bandwidth including visible, infrared, and terahertz ranges, thus improving adaptability for various applications.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If hollow-core photonic crystal fibers are guided by Photonic Band Gap, then guidance is achieved, but dispersion is high and structured

Engineering Contradiction:

Improveguidance capabilityVSAvoiddispersion characteristics

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses a hypocycloidal contour with optimized curvature radii that smooths the field distribution at the core-cladding interface. This optimized curvature reduces structured dispersion effects and provides more uniform dispersion characteristics across the bandwidth, improving suitability for high-resolution spectroscopy and ultrafast laser applications.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Reliability

If hollow-core photonic crystal fibers are guided by Photonic Band Gap, then guidance is achieved, but power overlap between guided mode and contour is high

Engineering Contradiction:

Improveguidance capabilityVSAvoidlaser damage threshold

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs a hypocycloidal contour with optimized curvature radii R1 and R2 that increases the distance between the guided mode field and the cladding material. This optimized geometry reduces the power overlap between the guided mode and the contour, thereby increasing the laser damage threshold and enabling higher power transmission.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 optimized contour design achieves low transmission losses across a wide spectral range, including UV to IR, and high laser damage threshold, making it suitable for applications like laser power transfer and terahertz imaging.

Implementation Method 1

Fibers guided by Photonic Band Gap (BIP fiber or PBG fiber in English for 'Photonic Band Gap fiber')

Methodology Applied

Scientific EffectPhotonic band gap:

Implementation Method 2

Thanks to their structures, these fibers ensure the confinement of electromagnetic waves in the core of the fiber

Methodology Applied

Scientific EffectElectromagnetic wave confinement:

Implementation Method 3

a very low overlap of the field of the guided mode with the material. constituting the outline of the hollow heart

Methodology Applied

Scientific EffectField overlap minimization:

Implementation Method 4

fibers guided by inhibited coupling (in English Inhibited coupling guiding HC-PCF) also called wide-pitch fibers (in English large-pitch HC-PCF) or kagome type

Methodology Applied

Scientific EffectInhibited coupling guidance:

Data Source

PatentEP3008021B1Hollow core waveguide with optimized contour

Publication Date: 2019.11.13 GLOPHOTONICS

Figure 1~3
Figure 4~5B

AI summary

A waveguide with a hollow core (16) delimited by a closed contour includes a succession of arcs (20) of negative curvature, each arc including a chord (24), characterized in that the contour of the hollow core (16) includes small arcs (PA) and large arcs (GA) arranged alternately, each arc (20) being symmetric with respect to a straight line passing through the center (18) of the hollow core (16) and the middle of the chord (24) thereof, the ratio b=2Ra/C of the large arcs being greater than 0.9 for the large arcs (GA), Ra corresponding to the maximum distance between the chord (24) and the arc (20), C corresponding to the length of the chord (24).