Twisted Photonic Crystal Fiber Supercontinuum Source

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Solution Overview

Problem

Existing systems for generating stable, linearly polarized supercontinuum light suffer from a 50% loss of light due to the need for a polarization filter, which also limits the lifetime of photonic crystal fibers (PCFs) due to photoinduced photodarkening.

Innovation Solution

A supercontinuum light generation apparatus using a twisted photonic crystal fiber and a wideband quarter-wave retarder to convert circularly polarized pump light into linearly polarized supercontinuum light, thereby eliminating the need for a polarization filter and reducing the optical power required.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a polarisation filter is used to generate linearly polarised supercontinuum light, then the desired polarisation state is achieved, but approximately 50% of the generated light is lost

Engineering Contradiction:

Improvepolarisation stabilityVSAvoidlight loss

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

Instead of using a polarisation filter to select the desired linear polarisation state from unpolarised supercontinuum light (which discards 50% of the light), the invention inverts the approach by generating circularly polarised supercontinuum light and then using a quarter-wave retarder to convert it to the desired linear polarisation state. This inversion of the polarisation generation sequence eliminates the need for a polarisation filter and preserves all generated light.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the polarisation parameter of the supercontinuum light from linear (requiring filtering) to circular (enabling efficient conversion). By generating circularly polarised light in the photonic crystal fibre and then using a quarter-wave retarder to convert it to linear polarisation, the system achieves the desired polarisation stability without the 50% light loss associated with polarisation filtering.

Inventive Principle:

Principle #35Parameter changes

2Power

If high optical power is used in the photonic crystal fibre to compensate for light loss, then the desired output power is achieved, but photoinduced photodarkening develops at an increased rate, limiting component lifetime

Engineering Contradiction:

Improveoutput powerVSAvoidcomponent lifetime

Core Design Contradiction:

PowerVSDuration of action of stationary object

Solution Approach 1:

The invention converts the harmful effect of requiring high optical power (which accelerates photodarkening) into a benefit by changing the polarisation state sequence. By generating circularly polarised light and converting it to linear polarisation after the photonic crystal fibre, the system achieves the desired output power without increasing the optical power inside the fibre, thereby extending component lifetime.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Stability of the object's composition

If linearly polarised pump light is used in the photonic crystal fibre, then polarisation maintaining properties are improved, but the polarisation stability remains challenging due to PCF instability

Engineering Contradiction:

Improvepolarisation stabilityVSAvoidpolarisation maintaining reliability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The invention inverts the conventional approach by using circularly polarised pump light instead of linearly polarised light. Circularly polarised light is less sensitive to polarisation mode dispersion and birefringence in the photonic crystal fibre, resulting in more stable circularly polarised supercontinuum light generation. The quarter-wave retarder then efficiently converts this stable circular polarisation to the desired linear polarisation state.

Inventive Principle:

Principle #13The other way round (Inversion)

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 allows for the generation of linearly polarized supercontinuum light with reduced optical power, extending the lifetime of the optical source components and preserving the full optical power of the generated light.

Implementation Method 1

The twisted PCF is arranged to receive the pump light from the pump light source and to convert the pump light into circularly polarised supercontinuum light

Methodology Applied

Scientific EffectSupercontinuum generation:

Implementation Method 2

The wideband quarter-wave retarder is arranged to convert the circularly polarised supercontinuum light into linearly polarised supercontinuum light

Methodology Applied

Scientific EffectQuarter-wave retardation:

Data Source

PatentUS12210266B2Optical source and supercontinuum light generation apparatus

Publication Date: 2025.01.28 NKT PHOTONICS AS

AI summary

An optical source (100) comprising a supercontinuum generation apparatus comprising a pump light source (102), a twisted photonic crystal fibre, PCF, (104) and a wideband quarter-wave retarder (106). The pump light source is arranged to provide circularly polarised pump light. The twisted PCF is arranged to receive the pump light and to convert the pump light into circularly polarised supercontinuum light. The wideband quarter-wave retarder is arranged to convert the circularly polarised supercontinuum light into linearly polarised supercontinuum light. The optical source may additionally comprise a wavelength tunable bandpass optical filter arranged to transmit the linearly polarised supercontinuum light at wavelengths within a selected range.