Photodiode Sub-mount Wavelength Alignment for Laser Module Stability
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Solution Overview
Problem
The fluctuation of light-receiving sensitivity of photodiodes due to temperature and emission wavelength changes in light-emitting elements is not effectively addressed in existing technologies, leading to inconsistent performance in laser modules.
Innovation Solution
A sub-mount with a built-in photodiode is designed, featuring a semiconductor structure with a specific conductivity-type layer configuration, including a first conductivity-type layer and a second conductivity-type region, optimized to receive light within a specific wavelength range (790 nm to 845 nm) and maintain a depletion layer thickness of 20 μm to 45 μm, ensuring peak light-receiving wavelength alignment with the emission wavelength of the light-emitting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional photodiode structure is used, then the device complexity is low, but the light-receiving sensitivity fluctuates significantly with temperature and emission wavelength changes
Solution Approach 1:
The patent applies parameter changes by optimizing the depletion layer thickness to a specific range (20-45 μm) and configuring the conductivity-type layer structure (p-type layer depth of 1-5 μm) to reduce the fluctuation of light-receiving sensitivity. These parameter adjustments enable the photodiode to maintain stable performance across temperature and wavelength variations without adding complex external control systems.
Solution Approach 2:
The patent implements local quality by creating a specifically structured photodiode region with differentiated conductivity-type layers within the sub-mount. The p-type layer is positioned at a specific depth (1-5 μm) from the light-receiving surface, and the depletion layer is configured with controlled thickness (20-45 μm), giving different regions of the photodiode structure distinct functional properties that collectively improve sensitivity stability.
2Measurement precision
If the depletion layer thickness is increased to improve light absorption, then the light-receiving sensitivity increases, but the manufacturing precision requirements become more stringent
Solution Approach 1:
The patent specifies a depletion layer thickness range of 20-45 μm, which balances light absorption efficiency with manufacturability. This parameter range is optimized to achieve sufficient light-receiving sensitivity while remaining feasible for standard semiconductor manufacturing processes, avoiding excessively tight tolerance requirements.
Solution Approach 2:
The patent employs a depletion layer thickness that is sufficiently large (20-45 μm) to ensure adequate light absorption and sensitivity, but not excessively large to the point where manufacturing becomes prohibitively difficult. This partial action approach achieves the necessary performance threshold without over-engineering the depletion layer thickness.
3Measurement precision
If the photodiode is designed for high sensitivity at a specific wavelength, then the measurement precision at that wavelength improves, but the adaptability to wavelength variations deteriorates
Solution Approach 1:
The patent optimizes the photodiode structure parameters (depletion layer thickness of 20-45 μm, p-type layer depth of 1-5 μm) to achieve a balance between peak sensitivity and wavelength range coverage. This parameter configuration enables the photodiode to maintain acceptable detection accuracy across the emission wavelength range of 790-845 nm while preserving reasonable adaptability to wavelength variations.
Solution Approach 2:
The patent designs the photodiode with a universal structure that can effectively detect light across a wavelength range (790-845 nm) rather than being optimized for a single wavelength. The configured depletion layer and conductivity-type layer structure provide multi-functional capability, allowing the photodiode to serve as a reliable detector for various emission wavelengths within the specified range.
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 the fluctuation range of light-receiving sensitivity, maintaining consistent photocurrent generation even with temperature and emission wavelength variations, thereby enhancing the stability and accuracy of light-emitting element modules.
Implementation Method 1
a photodiode having a first conductivity-type layer arranged in a surface portion in the sub-mount of the photodiode region to form a light-receiving surface, and a second conductivity-type region arranged below the first conductivity-type layer. The photodiode is configured to receive at the light-receiving surface a light emitted from a light-emitting element and convert the light into a photocurrent.
Implementation Method 2
a depletion layer generated from the first conductivity-type layer has a thickness of 20 μm to 45 μm
Data Source
AI summary
A sub-mount having a photodiode region, includes a photodiode which has a first conductivity-type layer arranged in a surface portion of the sub-mount of the photodiode region to form a light-receiving surface and a second conductivity-type region arranged below the first conductivity-type layer and is configured to receive at the light-receiving surface a light emitted from a light-emitting element and convert the light into a photocurrent. A peak light-receiving wavelength at which the photocurrent of the photodiode becomes its maximum value is more than or equal to a minimum emission wavelength of the light-emitting element and less than or equal to a maximum emission wavelength of the light-emitting element.