Gas Refraction Compensation in Laser-Sustained Plasma Bulbs

Solution Overview

Problem

Laser-sustained plasma illuminator systems face significant optical aberrations due to enclosure shapes and gas refractive index, leading to irregular plasma shapes and uncontrollable plasma sizes, especially with high numerical aperture systems.

Innovation Solution

The enclosure walls are varied in thickness to compensate for optical aberrations, allowing a single uncompensated reflector to be used across different enclosure shapes and fill pressures, optimizing plasma performance and UV light collection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a high NA reflector is used to pump the plasma, then the plasma illumination intensity is improved, but optical aberrations increase significantly

Engineering Contradiction:

Improveplasma illumination intensityVSAvoidoptical aberration control

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The enclosure wall thickness is varied locally to compensate for optical aberrations. Specifically, the wall thickness changes in different regions of the enclosure to correct the path of laser light at different angles, maintaining focus quality while using high NA reflectors for intense plasma illumination.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the enclosure wall thickness is uniform, then the manufacturing is simplified, but optical aberrations from the enclosure become significant

Engineering Contradiction:

Improveenclosure manufacturing simplicityVSAvoidoptical aberration control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The enclosure wall thickness is varied locally to compensate for optical aberrations. Specifically, the wall thickness changes in different regions of the enclosure to correct the path of laser light at different angles, maintaining focus quality while using high NA reflectors for intense plasma illumination.

Inventive Principle:

Principle #3Local quality

3Illumination intensity

If the gas pressure is increased to improve plasma density, then the plasma brightness is improved, but gas-related optical aberrations increase

Engineering Contradiction:

Improveplasma brightnessVSAvoidoptical aberration control

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The enclosure wall thickness is varied locally to compensate for optical aberrations. Specifically, the wall thickness changes in different regions of the enclosure to correct the path of laser light at different angles, maintaining focus quality while using high NA reflectors for intense plasma illumination.

Inventive Principle:

Principle #3Local quality

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 improves plasma shape control and UV light focus, enhancing the performance and cost efficiency of laser-sustained plasma illuminator systems by adjusting enclosure wall thickness to correct aberrations, resulting in more reproducible and controlled plasma shapes and light collection.

Implementation Method 1

the refractive index of the gas inside the enclosure is another source of aberrations in the system

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS8853655B2Gas refraction compensation for laser-sustained plasma bulbs

Publication Date: 2014.10.07 KLA CORP

AI summary

A laser-sustained plasma illuminator system includes at least one laser light source to provide light. At least one reflector focuses the light from the laser light source at a focal point of the reflector. An enclosure substantially filled with a gas is positioned at or near the focal point of the reflector. The light from the laser light source at least partially sustains a plasma contained in the enclosure. The enclosure has at least one wall with a thickness that is varied to compensate for optical aberrations in the system.