Tapered Optical Fiber Supercontinuum Generation

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Solution Overview

Problem

Existing optical measurement systems for lithography face challenges in obtaining bright, spatially coherent radiation with a broad spectral width and short coherence length, which is essential for precise alignment and measurement, but current solutions are complex and unreliable.

Innovation Solution

A tapered optical fiber is used to spectrally broaden radiation, generating output with a spectral width between 500 nm and 900 nm, providing a compact, reliable, and bright radiation source for optical measurement systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional radiation sources (lasers, LEDs) are used, then spatial coherence and brightness can be achieved, but spectral width remains narrow and coherence length is too long

Engineering Contradiction:

ImprovebrightnessVSAvoidsystem complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

A tapered optical fiber is introduced as an intermediary component between the laser source and the measurement system. The fiber's tapered geometry creates nonlinear optical effects that broaden the spectral width while maintaining spatial coherence, eliminating the need for complex multi-component radiation sources

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The optical parameters of the radiation are transformed by passing through the tapered fiber region. The intense laser field interacting with the tapered fiber structure generates supercontinuum radiation, changing the spectral width parameter from narrow to broad (500-900 nm) while maintaining other desirable properties

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If spectral width is broadened to reduce coherence length, then coherence interference effects are reduced, but system complexity and reliability deteriorate

Engineering Contradiction:

Improvecoherence interference effectsVSAvoidsystem reliability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The potentially harmful coherence interference effects are converted into a beneficial measurement mechanism. The known coherence properties of laser radiation are preserved and utilized for precise alignment measurements, while the tapered fiber provides sufficient spectral broadening to reduce unwanted interference without compromising reliability

Inventive Principle:

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

3Adaptability or versatility

If multiple radiation sources with different wavelengths are combined, then broad spectral coverage is achieved, but device complexity increases

Engineering Contradiction:

Improvespectral coverageVSAvoidnumber of radiation sources

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The broad spectrum is generated by segmenting a single laser wavelength through nonlinear optical processes in the tapered fiber. Instead of combining multiple independent radiation sources, the system segments the spectral content from one coherent source, achieving 500-900 nm coverage with a single laser and tapered fiber combination

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The tapered optical fiber serves multiple functions simultaneously: it acts as a waveguide, a nonlinear optical medium for spectral broadening, and a spatial coherence maintainer. This multi-functionality eliminates the need for multiple specialized components to achieve broad spectral coverage

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution enables the production of a bright, spectrally broadened radiation with a short coherence length, improving the reliability and simplicity of optical measurement systems while reducing coherence interference effects, thus enhancing alignment and measurement precision.

Implementation Method 1

Broad spectrum radiation by supercontinuum generation using a tapered optical fiber

Methodology Applied

Scientific EffectSupercontinuum generation:

Implementation Method 2

radiation from a laser with a nominal wavelength in the visible or near-infrared region is coupled to a tapered optical fiber and spectrally broadened in a nonlinear optical process

Methodology Applied

Scientific EffectNonlinear optical process:

Data Source

PatentUS11835752B2Broad spectrum radiation by supercontinuum generation using a tapered optical fiber

Publication Date: 2023.12.05 ASML HLDG NV

AI summary

A measurement apparatus, including: a tapered optical fiber, the tapered optical fiber having an input to receive radiation and having an output to provide spectrally broadened output radiation toward a measurement target, the tapered optical fiber configured to spectrally broaden the radiation received at the input; and a detector system configured to receive a redirected portion of the output radiation from the measurement target.