Semiconductor Light Emitting Device Multilayer Filter Spontaneous Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor light emitting devices face challenges in achieving high-precision light detection due to the interference of spontaneous emission light with stimulated emission light, leading to inaccurate light output level measurements.
Innovation Solution
A semiconductor light emitting device is designed with a multilayer filter that selectively reflects spontaneous emission light, featuring a stack structure of low-refractive-index and high-refractive-index layers, which effectively suppresses the incidence of spontaneous emission light to the photodetector, allowing only stimulated emission light to be detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the semiconductor light emitting element and the semiconductor photodetector are formed integrally, then the number of parts is reduced and alignment precision is improved, but the photodetector detects both stimulated emission light and spontaneous emission light, resulting in measurement errors
Solution Approach 1:
The patent segments the light detection function by introducing a multilayer filter structure that separates stimulated emission light from spontaneous emission light. The filter divides the optical path into transmitted light (stimulated emission) and reflected light (spontaneous emission), allowing the photodetector to selectively detect only stimulated emission light while blocking spontaneous emission light, thus resolving the measurement accuracy issue while maintaining integral device structure
Solution Approach 2:
The multilayer filter acts as an intermediary component between the light emitting element and the photodetector. This filter mediates the light detection process by selectively transmitting stimulated emission light and reflecting spontaneous emission light, enabling the photodetector to accurately measure only the stimulated emission light output without interference from spontaneous emission light
2Measurement precision
If a control layer is formed by oxidizing semiconductor material to interrupt spontaneous emission light, then some spontaneous emission light is blocked, but the oxidized layer does not selectively reflect spontaneous emission light and transmits some of it, so the spontaneous emission light detection level is not sufficiently lowered
Solution Approach 1:
The patent changes the optical parameters of the filter by carefully designing the thickness of each layer in the multilayer structure. The low-refractive-index layer thickness is set to λ1/(4×na) and the high-refractive-index layer thickness to λ1/(4×nb), where λ1 is the wavelength of spontaneous emission light. This parameter optimization enables the filter to achieve high reflectivity for spontaneous emission light while maintaining transmission for stimulated emission light, effectively lowering the spontaneous emission detection level to enhance measurement precision
3Measurement precision
If a multilayer filter with specific thickness layers is used to reflect spontaneous emission light, then light detection precision is improved, but the device structure becomes more complex
Solution Approach 1:
The patent merges the multilayer filter structure directly with the semiconductor light emitting device by forming the filter layers on the same substrate as the light emitting element and photodetector. This integration approach combines multiple functions (light emission, light detection, and wavelength-selective filtering) into a single unified device structure, reducing the need for separate external filter components and simplifying the overall system architecture while maintaining high light detection precision
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 significantly improves light detection precision by reducing the detection level of spontaneous emission light, ensuring accurate measurement of the light output level and enhancing the reliability of the semiconductor light emitting device.
Implementation Method 1
The multilayer filter has a stack structure in which a low-refractive-index layer having a thickness of λ1/(4×na) and a high-refractive-index layer having a thickness of λ1/(4×nb) are alternately stacked. The multilayer filter selectively reflects spontaneous emission light and transmits stimulated emission light based on wavelength.
Implementation Method 2
Since the multilayer filter has a stack structure in which a low-refractive-index layer having a thickness of λ1/(4×na) and a high-refractive-index layer having a thickness of λ1/(4×nb) are stacked alternately, light having a wavelength band shorter than the wavelength λo in the spontaneous emission light is reflected by the multilayer filter.
Implementation Method 3
The semiconductor photodetector has a light absorption layer that absorbs part of the light passed through the multilayer filter.
Data Source
AI summary
The present invention provides a semiconductor light emitting device realizing a lower detection level of spontaneous emission light by a semiconductor photodetector and an improvement in light detection precision by selectively reflecting spontaneous emission light. The semiconductor light emitting device includes a semiconductor light emitting element for generating light including stimulated emission light having a wavelength lambdao and spontaneous emission light having a wavelength band including the wavelength lambdao, a multilayer filter having a stack structure in which a low-refractive-index layer having a thickness of lambda1/(4xna) (lambda1<lambdao and na denote refractive index) and a high-refractive-index layer having a thickness of lambda1/(4xnb) (nb>na and nb denote refractive index) are alternately stacked, and a semiconductor photodetector having a light absorption layer that absorbs part of the light passed through the multilayer filter.