Methods and systems for stabilization of wavelength-selective optical elements during transient laser operations

Solution Overview

Problem

High-power laser systems face challenges in maintaining stable spectral and pointing characteristics due to thermal changes in optical components caused by residual optical absorption during transient operations, leading to unacceptable wavelength shifts and long response times, which are difficult to mitigate with aggressive heat sinking or convective gas cooling.

Innovation Solution

Implementing a combination of time-varying heat sources and thermal resistance/heat sink temperatures to minimize transient variations in optical components, using external heating and reduced thermal resistance to maintain temperature stability without requiring low thermal resistance or low optical absorption, and employing convective cooling with variable gas flow rates to achieve rapid and precise temperature control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If aggressive heat sinking or convective gas cooling is used to mitigate thermal changes, then temperature stability is improved, but device complexity and system size increase

Engineering Contradiction:

Improvetemperature stabilityVSAvoidsystem complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-heating the optical component using a heating element before the laser is activated. This anticipates the thermal effects that will occur during laser operation, bringing the component closer to its optimal operating temperature in advance. The system includes a controller that activates the heating element prior to laser operation, and a transparent barrier that directs heated gas to the optical component, thereby reducing transient thermal effects when the laser starts without requiring complex active cooling systems.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary substance (gas) that serves as a heat transfer medium between the heating element and the optical component. The gas is heated by the heating element and then directed through a flow channel formed by a transparent barrier to the optical component, acting as a mediator to transfer thermal energy efficiently. This intermediary approach allows for controlled thermal management without direct contact between the heating element and the optical component, simplifying the overall system design.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of time

If the optical component is designed with low thermal resistance to rapidly dissipate heat, then response time is improved, but manufacturing precision and material selection become more difficult

Engineering Contradiction:

Improveresponse timeVSAvoidmanufacturing difficulty

Core Design Contradiction:

Loss of timeVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by pre-heating the optical component using a heating element before the laser is activated. This anticipates the thermal effects that will occur during laser operation, bringing the component closer to its optimal operating temperature in advance. The system includes a controller that activates the heating element prior to laser operation, and a transparent barrier that directs heated gas to the optical component, thereby reducing transient thermal effects when the laser starts without requiring complex active cooling systems.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies parameter changes by dynamically adjusting the thermal environment of the optical component. A controller monitors laser operation and adjusts the heating element power and gas flow rate to maintain optimal temperature. This dynamic parameter adjustment allows the system to adapt to varying laser power levels and operational conditions, achieving rapid thermal response without requiring the optical component itself to have specialized low thermal resistance materials or structures.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the laser power is rapidly increased from cold start, then productivity is improved, but wavelength stability deteriorates due to thermal expansion and refractive index changes

Engineering Contradiction:

Improvelaser ramp-up speedVSAvoidwavelength stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary action by pre-heating the optical component using a heating element before the laser is activated. This anticipates the thermal effects that will occur during laser operation, bringing the component closer to its optimal operating temperature in advance. The system includes a controller that activates the heating element prior to laser operation, and a transparent barrier that directs heated gas to the optical component, thereby reducing transient thermal effects when the laser starts without requiring complex active cooling systems.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback control by using a controller to monitor laser operation and adjust heating element power and gas flow rate accordingly. The controller receives information about laser power levels and adjusts the thermal management system to maintain optimal optical component temperature. This feedback mechanism allows the system to compensate for thermal effects in real-time, maintaining wavelength stability during rapid power changes without sacrificing productivity.

Inventive Principle:

Principle #23Feedback

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 rapid stabilization of optical components during power changes, reducing temperature variations and wavelength shifts, enabling high-power laser systems to maintain precise performance during transients without the need for low thermal resistance or low absorption materials.

Implementation Method 1

heating the optical component using a heating element

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

changing the gas flow rate of the convective gas flow

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

residual optical absorption in such elements can cause shifts in their spectral characteristics

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Data Source

PatentUS20240364068A1Methods and systems for stabilization of wavelength-selective optical elements during transient laser operations

Publication Date: 2024.10.31 LAWRENCE LIVERMORE NAT SECURITY LLC

AI summary

Methods, devices and systems are described that enable maintaining the temperature of an optical component at a target temperature despite transient fluctuations in the laser beam that illuminates the component. One example method includes preheating the optical component to a target temperature value by applying an external heat source to the optical component. The optical component has an initial thermal resistance and heat sink temperature while being preheated. Next, the laser is turned on, and the external heat source is removed or reduced, while changing one or both the thermal resistance or heat sink temperature from their initial values to lower values to maintain a temperature of the optical component at the target temperature value while the laser source is illuminating the optical component.