Fabry-Perot Optical Filter Biasing for Lower-Voltage Wavelength Tuning
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Solution Overview
Problem
Conventional wavelength-tunable optical filters using electrostrictive crystals require high drive voltages, which are difficult to implement practically due to limitations in commercial voltage sources and excessive heat generation, leading to potential cooling requirements and operational challenges.
Innovation Solution
A wavelength-tunable optical filter design incorporating a plate-like first component with electrostrictive properties, transparent electrodes, and a Fabry-Perot interferometer configuration, where electric charge is injected to reduce the drive voltage by enhancing the electrostrictive effect and warping the crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional wavelength-tunable optical filter using an electrostrictive crystal is used to achieve high-speed wavelength tuning, then the sweeping speed can reach several hundreds of kHz, but the drive voltage required becomes as high as 400 V, which is difficult to implement practically
Solution Approach 1:
The patent segments the drive voltage function into two parts: a DC bias voltage component and an AC sweep voltage component. By applying a DC bias voltage to pre-stress the electrostrictive crystal, the AC sweep voltage required for wavelength tuning is significantly reduced from 400 V to a practical level, enabling high-speed operation with commercially available voltage sources
Solution Approach 2:
The patent applies a DC bias voltage in advance to the electrostrictive crystal to establish a pre-stress state before wavelength sweeping begins. This preliminary action modifies the crystal's electrostrictive characteristics, reducing the voltage required for subsequent high-speed wavelength tuning operations
2Speed
If a high drive voltage of 400 V is applied to achieve a wavelength sweep width of 100 nm, then high-speed operation at several hundreds of kHz is possible, but heat generation becomes large, requiring sophisticated cooling mechanisms
Solution Approach 1:
By segmenting the voltage into DC bias and AC sweep components, the peak voltage requirement is reduced. Since heat generation is proportional to the square of the voltage, this segmentation dramatically reduces power consumption and heat generation while maintaining high-speed operation capability
Solution Approach 2:
The patent changes the operating parameters of the electrostrictive crystal by applying a DC bias voltage, which modifies the voltage-wavelength relationship. This parameter change allows the system to achieve the same wavelength sweep with lower AC voltage amplitude, thereby reducing heat generation
3Speed
If a high drive voltage source capable of several hundreds of kHz to MHz operation is used, then high-speed wavelength tuning is achieved, but the size of the voltage source becomes large, limiting application range
Solution Approach 1:
The voltage source is segmented into a DC voltage component and an AC voltage component. The DC bias voltage can be supplied by a simple, small voltage source, while the AC sweep voltage requires only a low-voltage amplifier, both of which are much smaller than a single high-voltage high-speed source, making the overall system more compact and applicable
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 proposed design lowers the drive voltage required for high-speed wavelength tuning, enabling practical implementation by reducing the voltage needed for wavelength sweep while maintaining effective wavelength filtering capabilities.
Implementation Method 1
a plate-like first component including a first incident surface and a first emission surface disposed on the side opposite to the first incident surface, the first component being formed with a material that has an electrostrictive effect and transmits light
Data Source
AI summary
A wavelength-tunable optical filter includes a plate-like first component, a plate-like second component, a first reflective film, and a second reflective film. The wavelength-tunable optical filter also includes a first transparent electrode and a second transparent electrode that serve as a voltage applying part that applies a voltage in the thickness direction of the first component, and as a charge injecting part that injects electric charge into the first component. The first transparent electrode is formed on a first incident surface, and is ohmically connected to the first component. The second transparent electrode is formed between a first emission surface and the first reflective film, and is ohmically connected to the first component.