Acousto-Optic Filtering via Folded Beam Path
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Solution Overview
Problem
Current acousto-optic filtering devices are limited in length due to crystal growth capabilities, restricting the interaction length of optical and acoustic waves, which hampers spectral resolution and efficiency, especially in birefringent materials like tellurium dioxide where beam collinearity is challenging to maintain after reflections.
Innovation Solution
The method involves using a birefringent acousto-optic crystal with a piezoelectric transducer to generate a transverse acoustic wave that propagates collinearly with the optical wave, employing multiple reflections on crystal faces perpendicular to the symmetry axes, effectively increasing the interaction length by folding the beams through strategic reflection angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the device length is extended to increase interaction length, then spectral resolution is improved, but crystal growth capabilities are exceeded and manufacturing becomes infeasible
Solution Approach 1:
The patent transforms the interaction path from a straight linear configuration to a folded multi-dimensional path using reflections. The optical and acoustic beams undergo multiple reflections between crystal faces, creating a zigzag trajectory that extends the interaction length within a compact physical device envelope, thereby achieving long interaction length without requiring proportionally long crystals
Solution Approach 2:
The interaction path is segmented into multiple reflection segments between crystal faces. Instead of a single long interaction path requiring a large crystal, the patent divides the path into multiple shorter segments that reflect between faces, allowing the total interaction length to accumulate across segments while keeping each crystal segment manufacturable
2Length of stationary object
If beams are folded by reflections on crystal faces, then interaction length is increased, but beam collinearity is lost due to anisotropic character
Solution Approach 1:
The patent selects specific crystal orientations and reflection face angles that are locally optimized to preserve collinearity. By carefully choosing which crystal faces to use for reflection and at what angles, the patent creates local conditions where the anisotropic properties of the crystal do not disrupt the collinear relationship between optical and acoustic beams, even after multiple reflections
3Device complexity
If crystal length is limited by growth capabilities, then device complexity is reduced, but interaction efficiency and spectral resolution deteriorate
Solution Approach 1:
The patent uses multiple reflections to create a folded interaction path that extends the effective interaction length without proportionally increasing the physical device dimensions. This allows high interaction efficiency to be achieved in a compact device, avoiding the need for extremely long crystals while maintaining simplicity
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 increases the interaction length by a factor of up to 3-5, enhancing spectral resolution and efficiency while adhering to economic constraints related to crystal production, and is applicable in devices like frequency extenders, spectrum analyzers, and programmable filters.
Implementation Method 1
a piezoelectric transducer intended to generate a transverse acoustic wave
Implementation Method 2
acousto-optic filtering method and device based on a long acousto-optical interaction
Implementation Method 3
employing multiple reflections on crystal faces perpendicular to the symmetry axes
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The method involves generating a transverse acoustic beam. Energy of the acoustic beam is propagated in a co-linear manner with energy of incident optical beam (Oi1) along a path of optical beam in a birefringent acousto-optical crystal (PO1) by a piezo-electric transducer (T1-T3), where the acoustic and optical beams travel a path i.e. collinear interaction zone (Z1), with reflections on one or other of reflecting faces (AB, BC, CD, DE, EA) of the crystal perpendicular to symmetric axes common to acoustic slowness curve and curves of ordinary and extraordinary optic indices of the crystal. An independent claim is also included for a device for implementing a method for acoustic-optical filtering of large acoustic and optical filtering interaction between acoustic and optical waves.