Dual DBR Light Emitting Device for Pulse Width Distortion
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Solution Overview
Problem
Light emitting devices suffer from pulse width distortion due to the tailing phenomenon, which degrades transmission quality and limits high-speed data transmission rates, as the fall time of optical pulses exceeds 10 ns due to delayed light emission from deep levels in the DBR layers.
Innovation Solution
A light emitting device configuration with a first and second distributed Bragg reflector (DBR) layer, where the second DBR layer is positioned between the light emitting layer and the first DBR layer, with a center wavelength longer than the first DBR layer by 5-20 nm, reduces delayed light emission by reflecting the wavelength component around the sub-peak, thereby suppressing external emission of the delayed light emission component and minimizing pulse width distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional light emitting device structure is used, then the device can emit light, but pulse width distortion occurs due to tailing phenomenon from delayed light emission
Solution Approach 1:
The device segments the DBR structure into two distinct layers: a first DBR layer with center wavelength at the emission peak and a second DBR layer with center wavelength at the sub-peak (5-20 nm longer). This segmentation allows each layer to independently control different wavelength components, suppressing delayed light emission from the sub-peak while maintaining efficient emission at the peak wavelength, thereby reducing pulse width distortion and improving transmission quality
Solution Approach 2:
Each DBR layer is designed with specific local optical properties: the first DBR layer targets the main emission peak for efficient light extraction, while the second DBR layer specifically targets the sub-peak wavelength range for suppression. This local quality differentiation enables selective control over different wavelength components, eliminating tailing effects without compromising overall emission efficiency
2Productivity
If the fall time of optical pulse is reduced to increase transmission rate, then high-speed transmission is achieved, but the tailing phenomenon makes it difficult to reduce fall time below 10 ns
Solution Approach 1:
The invention extracts and separately manages the problematic sub-peak wavelength component through the second DBR layer. By placing a dedicated reflector specifically tuned to the sub-peak wavelength (5-20 nm longer than the main peak) between the light emitting layer and the first DBR layer, the delayed emission component is isolated and suppressed, enabling fall time reduction below 10 ns and supporting transmission rates of 100 Mbps
3Reliability
If external band reject filters are used to suppress delayed light emission, then transmission quality improves, but device complexity increases
Solution Approach 1:
The invention merges the function of delayed light emission suppression directly into the DBR mirror structure by integrating a second DBR layer with center wavelength at the sub-peak. This eliminates the need for separate external band reject filters, as the integrated structure performs both emission enhancement at the peak wavelength and suppression at the sub-peak wavelength, simplifying the overall device configuration while maintaining high transmission quality
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 reduces pulse width distortion, enabling high-speed optical transmission with improved transmission quality and increased transmission distance without the need for external band reject filters, facilitating high-speed data transmission at 100 Mbps.
Implementation Method 1
The first distributed Bragg reflector layer has a center wavelength substantially same as emission wavelength of emission light from the light emitting layer
Implementation Method 2
The second distributed Bragg reflector layer has a center wavelength longer than the center wavelength of the first distributed Bragg reflector layer in a range of 5 nm or more and 20 nm or less
Data Source
AI summary
According to one embodiment, a light emitting device includes a substrate, a light emitting layer, a first conductivity type layer, a first and a second distributed Bragg reflector layer. The first conductivity type layer is provided between the substrate and the light emitting layer. The first reflector layer is provided between the first conductivity type layer and the substrate. First and second layers are alternately stacked therein. The second layers have refractive index different from that of the first layers. The first reflector layer has a center wavelength substantially same as emission wavelength of emission light. The second reflector layer is provided between the light emitting layer and the first reflector layer. Third and fourth layers are alternately stacked therein. The fourth layers have refractive index different from that of the third layers. The second reflector layer has a center wavelength longer than the center wavelength of the first reflector layer.