Fabry-Perot Optical Modulator with Varied DBR Layers for Wide Bandwidth
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Solution Overview
Problem
Current optical modulators, such as GaAs semiconductor-based modulators, have narrow bandwidths, limiting their effectiveness in applications requiring high-speed optical modulation for distance measurement in 3D cameras, especially when the object is far from the camera, and are dependent on surface states of objects.
Innovation Solution
The optical modulator design incorporates a Fabry-Perot resonant reflection structure with alternating refractive index layers and multiple quantum well layers of different thicknesses, allowing for wide bandwidth operation and improved light absorption across a wider spectrum, reducing the dependence on surface states and enhancing distance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a GaAs semiconductor-based modulator is used, then the device is small and can operate with low voltage, but the bandwidth is very narrow (about 4 nm to 5 nm)
Solution Approach 1:
The top DBR layer is divided into multiple sections (first top DBR layer, second top DBR layer, and modified DBR layer) with different optical thickness configurations. This segmentation allows each section to contribute to different aspects of the reflection spectrum, collectively achieving a wide bandwidth while maintaining low operating voltage requirements.
Solution Approach 2:
Different sections of the DBR layer are assigned different optical thicknesses (quarter-wave, half-wave, or other multiples) to create local variations in optical properties. This local quality differentiation enables the overall structure to reflect a broader range of wavelengths while keeping the device compact and low-power.
2Speed
If an image intensifier or solid modulator device is used for optical modulation, then high optical modulation speed (tens to hundreds of MHz) is achieved, but the device occupies large volume or requires high voltage
Solution Approach 1:
The patent replaces traditional mechanical or high-voltage-based modulation mechanisms (image intensifier, MCP, thick EO modulator) with a semiconductor-based Fabry-Perot resonant reflection structure. This substitution achieves high-speed modulation through optical resonance and quantum well effects, eliminating the need for large device volume or high voltage operation.
3Device complexity
If the optical thickness of DBR layers is uniformly set to quarter-wave, then the structure is simple, but the bandwidth is limited
Solution Approach 1:
The patent changes the optical thickness parameter of the DBR layers from a uniform quarter-wave configuration to a varied configuration including quarter-wave, half-wave, and other multiples. This parameter change broadens the reflection spectrum bandwidth while maintaining reasonable structural complexity through systematic design.
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 optical modulator achieves a wide bandwidth of about 13 nm, enabling stable and accurate distance measurement in 3D cameras, independent of object distance and surface state, with reduced voltage requirements and increased absorption efficiency.
Implementation Method 1
optical modulators having a wide bandwidth based on Fabry-Perot resonant reflection
Implementation Method 2
Fabry-Perot resonant reflection structure
Implementation Method 3
uses a phenomenon of the MQW layer absorbing light when a reverse bias voltage is applied to the P- and N-electrodes
Data Source
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AI summary
Optical modulator having wide bandwidth based on Fabry-Perot resonant reflection is disclosed. The optical modulator includes: a bottom Distributed Bragg Reflector (DBR) layer (110); a top DBR layer (130) including at least one layer and a modified layer; and an active layer (120) disposed between bottom and top DBR layers, wherein the at least one layer includes at least one pair of a first refractive index sub-layer having a first refractive index and a second refractive index sub-layer having a second refractive index, the modified layer includes at least one pair of a third refractive index sub-layer having a third refractive index and a fourth refractive index sub-layer having a fourth refractive index, the third and the fourth refractive indexes being different, and at least one of the third and the fourth refractive index sub-layers have a second optical thickness that is not λ/4 or that is not an odd multiple thereof.