Curved Interdigitated Photoconductive Switch for Polarization Stability
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Solution Overview
Problem
Standard photoconductive switches experience variations in ON resistance due to changes in polarization direction caused by movement or bending of single-mode fibre optics, leading to inconsistent output voltages in environments with vibrations, shocks, or accelerations.
Innovation Solution
A photoconductive switch design featuring interdigitated tracks with a circular or high-symmetry shape, maintaining a consistent minimum photoconductive gap regardless of orientation, which stabilizes ON resistance and output voltage despite polarisation changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standard linear photoconductive switch design is used, then device structure is simple, but ON resistance varies with polarisation direction changes
Solution Approach 1:
The patent replaces the standard linear interdigitated finger design with a circular interdigitated track configuration. The circular geometry ensures that the photoconductive gap distance remains constant regardless of the polarisation direction of incident light, thereby stabilizing the ON resistance. This curvature-based design resolves the contradiction by maintaining reliability (stable ON resistance) without significantly increasing device complexity.
2Use of energy by moving object
If single-mode fibre is used to deliver light, then light delivery is efficient, but fibre movement causes polarisation rotation affecting device performance
Solution Approach 1:
The circular interdigitated track design makes the photoconductive switch insensitive to polarisation direction changes. Whether the fibre is stationary or moving, the constant gap distance in all radial directions ensures consistent ON resistance and output voltage, thereby maintaining reliability while preserving the efficient light delivery capability of single-mode fibres.
3Adaptability or versatility
If photoconductive switch is used in vibrating environment, then application versatility is increased, but output voltage becomes inconsistent due to fibre movement
Solution Approach 1:
The circular geometry provides rotational symmetry that eliminates dependence on polarisation direction. This allows the device to maintain accurate and consistent sampling performance in vibrating environments (such as on ships, vehicles, or aircraft) where fibre movement would otherwise cause output voltage variations, thereby enabling versatile deployment while preserving sampling accuracy.
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 design ensures constant output voltage and improved reliability in sampling microwave signals up to 40 GHz, even in environments with mechanical stress, by maintaining consistent ON resistance across varying polarisation directions.
Implementation Method 1
a photoconductive switch which allows photoconductive switches to be used to directly sample a microwave signal
Implementation Method 2
The photoconductive switch is generally actuated using light delivered to the photoconductive switches via a single-mode fibre from a laser
Data Source
AI summary
A photoconductive switch comprising a photoconductive material and first and second contacts provided on said photoconductive material, wherein said first and second contacts comprise a plurality of interdigitated tracks, the tracks of each contact being separated from the tracks of the other contact by a photoconductive gap, the tracks being curved such that the minimum photoconductive gap measured in a first direction remains substantially similar regardless of the orientation of the first direction.