Second Harmonic Generation Element Using SrB4O7 Crystal Resonator

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Solution Overview

Problem

Existing second harmonic generation devices face challenges in achieving high conversion efficiency of fundamental waves into ultraviolet light and are difficult to manufacture, especially when producing shorter wavelengths, due to the need for thinner nonlinear optical crystals and decreasing conversion efficiency with higher harmonic orders.

Innovation Solution

A second harmonic generation element comprising a substrate, a first multilayer film reflecting mirror, a SrB4O7 crystal second harmonic generation layer, and a second multilayer film reflecting mirror, which forms a resonator structure to enhance conversion efficiency and is easier to manufacture compared to traditional methods like Quasi Phase Matching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the wavelength of emitted light is shortened to achieve deep ultraviolet region (240 nm or less), then the sterilization effect with little impact on human body is improved, but the nonlinear optical crystal thickness must be reduced making manufacturing difficult

Engineering Contradiction:

Improvesterilization effectivenessVSAvoidmanufacturing difficulty

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter by using SrB4O7 crystal instead of conventional nonlinear optical crystals, and adjusts the resonator cavity length to specific values (0.5-2mm) to achieve deep ultraviolet generation while maintaining manufacturability through resonant enhancement

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional approach of physically thinning the crystal with a resonator-based optical field enhancement method, substituting mechanical dimension reduction with optical resonance to achieve the same effect while maintaining crystal integrity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Illumination intensity

If the harmonic wave order is increased to achieve shorter wavelengths, then the deep ultraviolet region is reached, but the conversion efficiency of fundamental wave to harmonic wave decreases resulting in lower light intensity

Engineering Contradiction:

Improvelight intensityVSAvoidconversion efficiency

Core Design Contradiction:

Illumination intensityVSProductivity

Solution Approach 1:

The patent implements optical feedback through the resonator structure where the fundamental wave is reflected back and forth between mirrors, allowing multiple passes through the nonlinear crystal to accumulate conversion efficiency while maintaining high light intensity at the output

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The resonator enables continuous interaction between the fundamental wave and nonlinear crystal by recirculating the light field, allowing the conversion process to occur continuously over multiple passes rather than in a single interaction

Inventive Principle:

Principle #20Continuity of useful action

3Manufacturing precision

If the nonlinear optical crystal thickness is reduced to enable shorter wavelength generation, then deep ultraviolet light can be produced, but the manufacturing precision requirements increase significantly

Engineering Contradiction:

Improvecrystal thickness precisionVSAvoidmanufacturing ease

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent introduces a resonator as an intermediary system that decouples the relationship between crystal thickness and conversion efficiency, allowing the crystal to maintain optimal thickness while the resonator provides the necessary field enhancement for deep ultraviolet generation

Inventive Principle:

Principle #24Intermediary (Mediator)

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 high conversion efficiency of fundamental waves into ultraviolet light with improved manufacturing ease by using a SrB4O7 crystal and a resonator structure, allowing for efficient generation of deep ultraviolet light with increased intensity and reduced manufacturing complexity.

Implementation Method 1

The second harmonic generation layer is made of a SrB4O7 crystal that receives a fundamental wave with a predetermined wavelength and emits a second harmonic wave with a wavelength in an ultraviolet region

Methodology Applied

Scientific EffectSecond harmonic generation: Second Harmonic Generation

Implementation Method 2

The second multilayer film reflecting mirror constitutes a resonator with the first multilayer film reflecting mirror

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS20240288748A1Second harmonic generation element and light source device

Publication Date: 2024.08.29 STANLEY ELECTRIC CO LTD

AI summary

A second harmonic generation element includes a substrate, a first multilayer film reflecting mirror, a second harmonic generation layer, and a second multilayer film reflecting mirror. The first multilayer film reflecting mirror is formed on the substrate. The second harmonic generation layer is disposed on the first multilayer film reflecting mirror. The second harmonic generation layer is made of a SrB4O7 crystal that receives a fundamental wave with a predetermined wavelength and emits a second harmonic wave with a wavelength in an ultraviolet region. The second multilayer film reflecting mirror is formed on the second harmonic generation layer. The second multilayer film reflecting mirror constitutes a resonator with the first multilayer film reflecting mirror.