Transient Thermal Lens Formation for Sub-Diffraction Light Focusing

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Solution Overview

Problem

Current imaging techniques face limitations in achieving sub-diffraction resolution due to the diffraction limit, and existing methods requiring precise placement of external optical elements can be challenging, especially for certain sample types.

Innovation Solution

A transient converging thermal lens is formed in a thermo-optic material by absorbing a radially-varying light pattern, creating a semi-parabolic refractive index profile that acts as a converging lens, allowing for focusing beyond the diffraction limit, either within the sample or in a separate thermo-optic material placed before the sample.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If external optical elements are placed in close proximity to the sample to achieve sub-wavelength resolution, then resolution is improved, but device complexity and ease of operation deteriorate due to precise placement requirements

Engineering Contradiction:

ImproveresolutionVSAvoidease of placement

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

A beam-shaping optical assembly acts as an intermediary component that transforms the light beam into a radially-varying pattern before it reaches the sample. This intermediary element enables the formation of a thermal lens within the sample or a nearby thermo-optic material, achieving sub-diffraction focusing without requiring direct placement of complex optical elements at the sample location.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a radially-varying light pattern is absorbed by a thermo-optic material to form a thermal lens, then focusing capability beyond the diffraction limit is achieved, but temperature increases causing potential sample damage

Engineering Contradiction:

Improvefocusing precisionVSAvoidtemperature increase

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The light beam is shaped to have a radially-varying pattern with specific intensity distribution, creating localized heating regions within the thermo-optic material. This local quality approach concentrates the thermal effect precisely where needed to form the lens, while the surrounding areas remain cooler, thereby achieving the desired refractive index profile with controlled temperature distribution.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes the temperature dependence of the refractive index of the thermo-optic material to convert thermal energy into optical focusing capability. By controlling the temperature distribution through the radially-varying light pattern, the refractive index is modulated spatially to create a converging lens effect, transforming thermal parameters into optical function.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If a thermal lens is formed within the sample to achieve super-resolution imaging, then resolution is improved, but the sample must withstand localized heating

Engineering Contradiction:

Improveimaging resolutionVSAvoidsample tolerance to heating

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The patent introduces a separate thermo-optic material as an intermediary that can be positioned near the sample without direct contact. This mediator absorbs the radially-varying light pattern and forms the thermal lens in its own structure, allowing the sample to remain free from direct thermal exposure while still benefiting from the super-resolution focusing capability.

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

This approach enables super-resolution imaging by physically focusing light to a spot size below the diffraction limit of the optical system, improving resolution and flexibility in imaging applications without requiring external optical elements close to the sample.

Implementation Method 1

The thermo-optic material can absorb light at the first wavelength

Methodology Applied

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

Implementation Method 2

The transient converging thermal lens can be formed in the thermo-optic material by a heating-induced refractive index profile generated by the absorption of the shaped first beam

Methodology Applied

Scientific EffectThermo-optic effect:

Data Source

PatentUS12199396B2Converging thermal lenses, and optical systems, kits, and methods for formation and use thereof

Publication Date: 2025.01.14 UNIV OF MARYLAND

AI summary

A converging thermal lens is transiently formed by directing a shaped pulsed light beam having at least a first wavelength to a thermo-optic material, whereby the thermo-optic material absorbs the light beam and experiences local heating in response thereto. The heating induces a refractive index profile in the thermo-optic material that temporarily forms the converging thermal lens. In some embodiments, the refractive index of the thermo-optic material has a negative temperature dependence, and the pulsed light beam is shaped to have an inverted light pattern with a maximum intensity in an outer region of the beam cross-section. Alternatively, in some embodiments, the refractive index of the thermo-optic material has a positive temperature dependence, and the pulsed light beam is shaped to have a radially-varying light pattern with a maximum intensity in a central region of the beam cross-section.