Stark Manifold Crystal Cooling for Low-Temperature Optical Refrigeration

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Solution Overview

Problem

Optical refrigeration systems face challenges in achieving low temperatures due to limitations in absorption efficiency, particularly at lower temperatures, where resonant absorption decreases, and heat generating recombination pathways introduced by impurities reduce cooling efficiency.

Innovation Solution

Exploiting Stark manifold resonances in doped crystals, specifically by tuning an excitation laser to resonate at a predetermined wavelength corresponding to a selected Stark manifold transition, enhances cooling efficiency by increasing absorption efficiency, allowing for cooling to temperatures between 110K and 170K.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If material is cooled to lower temperatures, then cooling efficiency improves, but resonant absorption decreases exponentially following Boltzmann law

Engineering Contradiction:

Improvecooling temperatureVSAvoidresonant absorption efficiency

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The patent changes the material phase from glass to crystal, which fundamentally alters the absorption characteristics. Crystalline materials exhibit sharp Stark manifold resonances that maintain high absorption efficiency at low temperatures, unlike glass materials where absorption follows Boltzmann decay. This parameter change (material structure) resolves the contradiction between achieving low temperatures and maintaining resonant absorption efficiency.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If background absorption is reduced by purifying material, then absorption efficiency improves, but manufacturing complexity increases

Engineering Contradiction:

Improveabsorption efficiencyVSAvoidmaterial purification process

Core Design Contradiction:

Use of energy by moving objectVSEase of manufacture

Solution Approach 1:

The patent uses composite material structure - rare-earth ions (Yb3+) doped into a crystalline host (YLF - Yttrium Lithium Fluoride). This composite approach allows the crystal matrix to provide sharp resonances while the dopant ions provide the cooling transition. The crystalline host inherently provides lower background absorption than glass, reducing the need for extreme purification while maintaining high absorption efficiency.

Inventive Principle:

Principle #40Composite materials

3Use of energy by moving object

If resonant absorption is increased to enhance absorption efficiency, then cooling efficiency improves, but material purity requirements increase

Engineering Contradiction:

Improveabsorption efficiencyVSAvoidmaterial purity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes from using broad absorption bands in glass to exploiting sharp Stark manifold resonances in crystals. This parameter change (material structure) allows achieving high absorption efficiency through resonant enhancement without requiring extremely pure materials. The crystal field splitting creates discrete energy levels with sharp transitions, enabling high ηabs even with moderate material purity.

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

This approach significantly improves cooling efficiency, enabling temperatures as low as 110K to 170K, surpassing the performance of existing solid-state coolers and achieving cryogenic operation with reduced thermal load and minimal adverse heat generation.

Implementation Method 1

Following absorption, out of equilibrium excitation becomes thermalized within the ground and exited state manifolds of the rare-earth ion

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

optical refrigeration can include laser excitation of rare-earth doped glass and crystal host material systems

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 3

Exploiting Stark manifold resonances in doped crystals, specifically by tuning an excitation laser to resonate at a predetermined wavelength corresponding to a selected Stark manifold transition

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 4

This is accomplished by phonon absorption from lattice vibrations of a material host

Methodology Applied

Scientific EffectPhonon absorption:

Implementation Method 5

a cooling cycle is based on conversion of low-entropy low-energy input of an optical field (e.g. laser) into an isotropic higher-energy spontaneous emission (fluorescence)

Methodology Applied

Scientific EffectAnti-Stokes scattering:

Data Source

PatentUS9574801B1Solid state optical refrigeration using stark manifold resonances in crystals

Publication Date: 2017.02.21 STC UNM

AI summary

A method and device for cooling electronics is disclosed. The device includes a doped crystal configured to resonate at a Stark manifold resonance capable of cooling the crystal to a temperature of from about 110K to about 170K. The crystal host resonates in response to input from an excitation laser tuned to exploit the Stark manifold resonance corresponding to the cooling of the crystal.