Gas Laser Frequency Stabilization via Ambient-Adaptive Thermal Control

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Solution Overview

Problem

Existing frequency stabilization methods for gas lasers consume high energy and have long start-up times, as well as impose significant thermal loads on the laser and its mount, due to maintaining a constant temperature that is often higher than ambient conditions.

Innovation Solution

A method and system for frequency stabilization of gas lasers that adjusts the laser tube temperature to match ambient conditions during start-up, using continuous operation control to minimize energy consumption and thermal loads, by measuring ambient and tube temperatures and iteratively adjusting the heating or cooling power based on the number of modes passed through, allowing the system to reach a stable state where it is only heated by its own power loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the laser tube temperature is maintained at a constant value significantly higher than ambient temperature, then the frequency stability is improved, but the energy consumption increases and thermal loads are intensified

Engineering Contradiction:
Improvefrequency stabilityVSAvoidenergy consumption
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies dynamics by transitioning from a static temperature control approach (maintaining constant high temperature) to a dynamic approach where the target temperature varies with ambient conditions. The control system adapts the target temperature based on ambient temperature measurements, allowing the laser tube temperature to be maintained at a constant offset above ambient rather than at a fixed high value, thereby reducing energy consumption while preserving frequency stability.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the temperature parameter dynamically based on ambient conditions. Instead of maintaining a fixed temperature setpoint, the system adjusts the target temperature parameter as a function of ambient temperature, ensuring the laser tube operates at a temperature that is constantly adapted to environmental conditions, thus reducing the temperature differential and associated energy consumption.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If the laser tube temperature is maintained at a constant value significantly higher than ambient temperature, then the frequency stability is improved, but the thermal loads on the laser and its mount increase

Engineering Contradiction:
Improvefrequency stabilityVSAvoidthermal loads
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system dynamically adjusts the operating temperature based on ambient conditions, reducing the temperature differential between the laser tube and its environment. This dynamic adaptation minimizes thermal gradients and associated thermal loads on the laser tube and mounting structure, while still maintaining sufficient temperature elevation to ensure frequency stability.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent converts the previously harmful effect of large thermal gradients into a benefit by using ambient temperature as the reference point. By maintaining the laser tube at a constant offset above ambient rather than at a fixed high temperature, the system reduces thermal stress and loading on the mount while preserving the necessary temperature elevation for stable operation.

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

3Reliability

If the laser tube is continuously heated to maintain constant temperature, then the frequency stability is improved, but the start-up time increases

Engineering Contradiction:
Improvefrequency stabilityVSAvoidstart-up time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-heating the laser tube during the start-up phase to reach the ambient-adapted target temperature before normal operation begins. This preliminary heating action reduces the time required to reach operational temperature compared to waiting for natural heating, while the adapted target temperature (based on ambient conditions) ensures faster reach than would be required for a fixed high temperature setpoint.

Inventive Principle:
Principle #10Preliminary action

4Device complexity

If the laser tube temperature is set to a fixed predetermined value, then the control is simplified, but the energy consumption increases

Engineering Contradiction:
Improvecontrol simplicityVSAvoidenergy consumption
Core Design Contradiction:
Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent changes the temperature parameter from a fixed predetermined value to a dynamically adjusted value based on ambient temperature. The control system measures ambient temperature and uses this information to determine the appropriate target temperature for the laser tube, maintaining a constant offset above ambient. This parameter change reduces energy consumption by minimizing the temperature differential, while the control logic remains relatively simple.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The system implements feedback by continuously monitoring ambient temperature and using this information to adjust the target temperature for the laser tube. This feedback mechanism allows the system to adapt to changing environmental conditions automatically, reducing energy consumption when ambient temperature is high while maintaining appropriate temperature elevation when ambient temperature is low.

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 reduces energy consumption and thermal loads by aligning the laser tube temperature with ambient conditions, allowing for quicker stabilization and minimizing continuous heating power, thus reducing the overall energy usage and thermal stress on the system.

Implementation Method 1

a laser tube (1) for emitting laser light

Methodology Applied
Scientific EffectStimulated emission: Laser

Implementation Method 2

heat transfer from the laser tube (1) to a heat sink (5) taking place by means of Peltier elements (4)

Methodology Applied
Scientific EffectPeltier effect: Peltier Effect

Implementation Method 3

a controlled heater (32) for heating the laser tube (1)

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP1775805B1Frequency Stabilised Gaslaser
Publication Date: 2011.04.20 LEICA GEOSYSTEMS AG
  • EP1775805B1 patent drawingFigure 1
  • EP1775805B1 patent drawingFigure 2~5
  • EP1775805B1 patent drawingFigure 3~4

AI summary

A gas laser radiates laser light. A first detecting diode (8) measures intensity of radiated laser light in a component. A laser tube's (1) temperature is adjusted by means of a control device (7) so that measured intensity is controlled at a target value. During operation, surrounding temperature is measured. The control device keeps the laser tube's condition at a desired condition. An independent claim is also included for a gas laser with stabilized frequency, especially for use in a laser interferometer.