Slanted Periodically Poled Device for Terahertz Detection
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Solution Overview
Problem
Conventional terahertz wave detection devices using nonlinear optical effects suffer from low conversion efficiency due to small interaction regions and significant terahertz wave introduction losses, making it difficult to detect weak terahertz waves effectively.
Innovation Solution
A terahertz wave detection device employing a slanted periodically poled device with parallel light input and output surfaces and a perpendicularly incident terahertz wave input surface, utilizing quasi phase matching for efficient generation of up-conversion signals in the same direction as the pump beam, thereby reducing introduction losses and increasing the interaction region between the pump and up-conversion signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a bulk crystal is used for terahertz wave detection, then the device structure is simple, but the interaction region is small and conversion efficiency is low
Solution Approach 1:
The patent changes the geometric parameters of the crystal by creating a slanted waveguide structure with specific inclination angles and periodic poling patterns. This transforms the bulk crystal into a structured waveguide that increases the interaction region between pump beam and terahertz wave, thereby improving conversion efficiency without significantly complicating the device structure
Solution Approach 2:
The patent introduces a spatial dimension by creating a slanted waveguide structure that extends the interaction region along the propagation direction. The periodic poling structure adds another dimensional aspect by creating alternating regions that enhance the nonlinear optical interaction, effectively increasing the conversion efficiency through dimensional expansion
2Ease of operation
If an input coupling element is used to introduce terahertz wave, then the terahertz wave can be coupled into the crystal, but introduction losses are significant
Solution Approach 1:
The patent removes the input coupling element from the system by designing the slanted waveguide structure to accept terahertz waves directly at its input surface. The waveguide geometry is optimized so that terahertz waves can be coupled in without additional components, eliminating the source of introduction losses while maintaining effective coupling
Solution Approach 2:
The slanted waveguide structure itself acts as an intermediary that facilitates direct coupling of terahertz waves into the crystal. The waveguide structure provides a transition zone that matches the impedance between free space and the crystal, enabling efficient coupling without separate coupling elements
3Measurement precision
If the up-conversion signal beam is generated at an angle to the pump beam, then phase matching is achieved, but the interaction region is reduced
Solution Approach 1:
The patent introduces asymmetry through the slanted waveguide structure with a specific inclination angle. This asymmetric geometry allows the pump beam and up-conversion signal beam to propagate in the same direction while maintaining phase matching conditions through the periodic poling structure, thereby preserving both phase matching precision and interaction region
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 configuration enhances the conversion efficiency of terahertz waves into detectable up-conversion signals, allowing for high-efficiency detection of weak terahertz waves by eliminating the need for input coupling elements and increasing the interaction area through optical parametric amplification.
Implementation Method 1
converting a terahertz wave into an up-conversion signal beam easy to detect with high efficiency by optical parametric amplification
Implementation Method 2
The up-conversion signal beam propagating in the same direction as the pump beam in the inside of the slanted periodically poled device (in the optical waveguide) satisfies the phase matching condition and therefore is amplified by the pump beam through optical parametric amplification
Implementation Method 3
The pump beam and the up-conversion signal beam are confined inside the waveguide structure by the total internal reflection
Data Source
AI summary
The present invention includes a slanted periodically poled device 12 including a light input surface 12a and a light output surface 12b parallel to each other and a terahertz wave input surface 12c orthogonal to the light input surface 12a and the light output surface 12b, a pump beam source 14 which emits pump beam 1 perpendicularly to the light input surface 12a, and a photodetector 16 which detects an up-conversion signal beam A converted from a terahertz wave 3 emitted perpendicularly from the light output surface 12b. The slanted periodically poled device 12 is configured to generate the up-conversion signal beam A in the same direction as and in parallel with the pump beam 1 by quasi phase matching between the terahertz wave 3 perpendicularly incident from the terahertz wave input surface 12c and the pump beam 1.