Regenerative Ring Resonator Thermal Lensing Compensation
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Solution Overview
Problem
High-power gas discharge lasers used in photolithography face challenges in maintaining consistent beam size and stability due to thermal lensing effects, leading to variations in output beam size across a range of average powers, which can result in reduced performance and potential damage to optical components.
Innovation Solution
A regenerative ring resonator design incorporating a beam modification optical system with a highly reflective convex mirror or prism set that transversely expands the laser beam profile, maintaining conditional or marginal stability by imparting negative curvature to the wavefront, ensuring the beam uniformly fills apertures and preventing excessive size increases that could exceed optical component limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high average output power is generated, then productivity and throughput are improved, but beam size variations and thermal lensing effects worsen
Solution Approach 1:
The patent changes the physical parameters of the optical system by introducing a beam modification optical system that alters the beam profile characteristics. This system adjusts parameters such as beam waist size and wavefront curvature to maintain stable beam propagation under high power conditions, directly addressing the beam size consistency issue while preserving high throughput capability
2Productivity
If high average output power is generated, then productivity is improved, but thermal lensing effects worsen
Solution Approach 1:
The patent converts the harmful thermal lensing effects into a beneficial configuration by deliberately introducing negative curvature through the beam modification optical system. This counteracts the positive thermal lensing, transforming the thermal effects from a harmful distortion into a controlled parameter that maintains beam stability under high power operation
Solution Approach 2:
The beam modification optical system applies preliminary anti-action by pre-compensating for thermal lensing effects before they can significantly degrade beam quality. The negative curvature introduced in advance counterbalances the upcoming thermal distortion, allowing the system to maintain stable operation at high average powers
3Manufacturing precision
If beam profile is transverse expanded to fill apertures uniformly, then manufacturing precision is improved, but device complexity worsens
Solution Approach 1:
The beam modification optical system is designed to perform multiple functions simultaneously: it expands the beam profile, imparts negative curvature, and ensures uniform aperture filling. By combining these functions into a single integrated system rather than separate components, the patent reduces overall device complexity while achieving the desired manufacturing precision
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 achieves stable or marginally unstable operation at high powers, maintaining consistent beam size and reducing thermal lensing effects, thereby enhancing the laser's performance and preventing damage to optical components, with average irradiance of at least 5 W/cm2 and peak irradiance less than 30 mJ/cm2.
Implementation Method 1
The optical coupler is partially reflective so that at least a portion of the laser beam impinging on the optical coupler from the amplifier discharge chamber is reflected back through the amplifier discharge chamber and at least a portion of the laser beam impinging on the optical coupler from the amplifier discharge chamber is transmitted through the optical coupler
Implementation Method 2
The beam modification optical system transversely expands a profile of the laser beam such that the near field laser beam profile uniformly fills each aperture within the laser
Implementation Method 3
The beam modification optical system can be configured to impart a negative curvature to the wavefront of the laser beam circulating within the regenerative ring resonator. The beam modification optical system can negatively alter the curvature along a transverse direction. The beam modification optical system can include a highly reflective mirror. The highly reflective mirror can be convex.
Implementation Method 4
an amplifier discharge chamber having electrodes and a gain medium between the electrodes for producing a laser beam
Implementation Method 5
a regenerative ring resonator that includes an amplifier discharge chamber having electrodes and a gain medium between the electrodes for producing a laser beam
Data Source
AI summary
A laser includes a regenerative ring resonator that includes a discharge chamber having electrodes and a gain medium between the electrodes for producing a laser beam; a partially-reflective optical coupler, and a beam modification optical system in the path of the laser beam. The beam modification optical system transversely expands a profile of the laser beam such that the near field laser beam profile uniformly fills each aperture within the laser and such that the regenerative ring resonator remains either conditionally stable or marginally unstable when operating the laser at powers that induce thermal lenses in optical elements inside the regenerative ring resonator.