Temperature Independent Lasers Using Volumetric Bragg Gratings

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Solution Overview

Problem

Solid state lasers operating in varying temperature conditions experience significant performance variations due to temperature-dependent stimulated emission cross sections, making them unsuitable for applications in different climatic environments.

Innovation Solution

Constraining the lasing wavelength of broad spectrum lasers, such as Er3+ doped glass lasers, using volumetric Bragg gratings in photo-thermal refractive glass to minimize temperature dependence, and selecting operational wavelengths that compensate for temperature variations in other laser components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If broad spectrum lasers are operated at the peak of the emission spectrum where the stimulated emission cross section is largest, then the laser output power is maximized, but the laser performance varies dramatically with temperature changes

Engineering Contradiction:

Improvelaser output powerVSAvoidtemperature stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the operational wavelength parameter from the peak emission wavelength to a wavelength where the stimulated emission cross section has minimal temperature dependence. This parameter change resolves the contradiction by sacrificing some peak power output for significantly improved temperature stability and reliability in varying environmental conditions.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the lasing wavelength is selected for maximum stimulated emission cross section, then the laser efficiency is improved, but the laser becomes sensitive to temperature variations

Engineering Contradiction:

Improvelaser efficiencyVSAvoidenvironmental adaptability

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent modifies the operational wavelength parameter from the peak emission wavelength to a wavelength with minimal temperature dependence in the stimulated emission cross section. This resolves the contradiction by maintaining acceptable efficiency while dramatically improving environmental adaptability for field applications.

Inventive Principle:

Principle #35Parameter changes

3Power

If standard dielectric mirror coatings are used in laser resonators, then the mirror reflectivity is high, but the overall laser system remains temperature dependent due to the stimulated emission cross section

Engineering Contradiction:

Improvemirror reflectivityVSAvoidtemperature independence

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the operational wavelength parameter to compensate for the temperature dependence of the stimulated emission cross section. This resolves the contradiction by maintaining high mirror reflectivity with standard dielectric coatings while achieving temperature independence through wavelength selection that offsets the gain medium's temperature sensitivity.

Inventive Principle:

Principle #35Parameter changes

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

Enables broad spectrum lasers to operate with little to no performance variation across a wide temperature range, making them suitable for use in diverse environmental conditions, including military and commercial applications like range finders and laser radars.

Implementation Method 1

volumetric Bragg grating in photo-thermal refractive glass is used as a laser cavity mirror for constraining the laser emission at the selected wavelength

Methodology Applied

Scientific EffectBragg diffraction: Bragg Diffraction

Implementation Method 2

volumetric Bragg grating in photo-thermal refractive glass

Methodology Applied

Scientific EffectPhoto-thermal refractive effect: Thermal Expansion

Data Source

PatentUS7450626B1Lasers that operate independently of temperature

Publication Date: 2008.11.11 NORTHROP GRUMMAN SYSTEMS CORP

AI summary

Apparatus, methods, systems and devices for providing a temperature independent laser by determining a temperature dependence of a lasing wavelength, selecting the lasing wavelength having minimal temperature dependence and constraining the lasing wavelength of the laser device to the selected lasing wavelength. In an embodiment, a volumetric Bragg grating in photo-thermal refractive glass is used as a laser cavity mirror for constraining the laser emission at the selected wavelength. The laser device may be a broad spectrum laser such as an Er3+ doped glass broad spectrum laser. In an embodiment, the lasers are operated where the temperature dependence of the stimulated emission cross section is used to compensate for temperature dependent changes of other laser components.