Terahertz Wave Generator Rotation Axis Layout for Wider Tuning

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Solution Overview

Problem

Existing terahertz wave generating devices face challenges in achieving a large rotation angle range for nonlinear optical elements without causing damage due to edge contact with pump light, leading to limitations in wavelength adjustment.

Innovation Solution

A terahertz wave generating device design that positions the rotation axis of the nonlinear optical element closer to the incident end face than the output end face, allowing for a larger rotation angle without edge contact and damage, while using a wavelength filter to align optical paths and a dichroic mirror to extract signal light without attenuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the nonlinear optical element is rotated to adjust the wavelength of signal light, then the wavelength tunability is improved, but the risk of damage to the nonlinear optical element increases due to pump light reaching the edge

Engineering Contradiction:

Improvewavelength tunabilityVSAvoidelement damage risk

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies asymmetry by positioning the rotation axis asymmetrically within the nonlinear optical element, specifically closer to the incident end face than to the output end face. This asymmetric positioning ensures that during rotation, the pump light beam remains safely within the element boundaries and does not reach the edges, thereby preventing damage while enabling wavelength adjustment through rotation.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent introduces an optical path adjustment mechanism as an intermediary between the pump light source and the nonlinear optical element. By adjusting the optical path (e.g., using mirrors or lenses), the pump light beam can be precisely directed to enter the element at the correct position and angle, ensuring that rotation for wavelength tuning does not cause the beam to reach damaging edge positions.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the rotation axis is positioned centrally in the nonlinear optical element, then the structural symmetry is maintained, but the allowable rotation angle range is limited due to edge contact

Engineering Contradiction:

Improvestructural symmetryVSAvoidrotation angle range

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent deliberately breaks structural symmetry by positioning the rotation axis asymmetrically within the nonlinear optical element. Specifically, the rotation axis is placed closer to the incident end face than to the output end face. This asymmetric positioning expands the allowable rotation angle range in the direction that moves the pump light beam away from the edges, thereby increasing the tunable wavelength range without causing damage.

Inventive Principle:

Principle #4Asymmetry

3Power

If the pump light beam diameter is increased to improve signal strength, then the signal light intensity is improved, but the margin for rotation angle before edge contact decreases

Engineering Contradiction:

Improvesignal light intensityVSAvoidrotation angle margin

Core Design Contradiction:

PowerVSAdaptability or versatility

Solution Approach 1:

The patent uses optical copying or imaging techniques (e.g., through lens systems) to precisely control the position and size of the pump light beam at the input face of the nonlinear optical element. This allows optimization of the beam diameter for signal strength while maintaining precise positional control that ensures the beam remains within safe margins from the edges during rotation.

Inventive Principle:

Principle #26Copying

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 a significant rotation angle range for the nonlinear optical element, facilitating wide tunable frequency of terahertz waves without damage, and achieves a compact device design with efficient light management.

Implementation Method 1

a nonlinear optical element having a periodic structure in which a polarization or a crystal orientation is inverted at a certain inversion period... causing the pump light to enter the nonlinear optical element to generate signal light that is a terahertz wave

Methodology Applied

Scientific EffectParametric down-conversion:

Implementation Method 2

a wavelength filter that transmits the seed light and reflects the pump light

Methodology Applied

Scientific EffectWavelength selective transmission and reflection: Filter (optical)

Implementation Method 3

a dichroic mirror that reflects the signal light toward a signal light output

Methodology Applied

Scientific EffectDichroic reflection: Dichroic Filter

Data Source

PatentUS20260036870A1Terahertz wave generating device

Publication Date: 2026.02.05 RIKEN CO LTD

AI summary

A terahertz wave generating device includes: a pump light source configured to generate pump light; a periodically poled element as a nonlinear optical element having a periodic structure in which a polarization or a crystal orientation is inverted at a certain inversion period; and a rotation stage configured to rotatably support the periodically poled element. The terahertz wave generating device causes the pump light to enter the periodically poled element to generate signal light that is a terahertz wave, and rotates the periodically poled element to change a wavelength of the signal light. The periodically poled element has an incident end face through which the pump light enters and an output end face through which the pump light exits. A rotation axis of the periodically poled element is closer to the incident end face than to the output end face.