High-Power Optical Burn-In for InAlGaAs Laser Screening
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Solution Overview
Problem
Conventional high-temperature thermal burn-in methods are inadequate for screening semiconductor lasers made from indium aluminum gallium arsenide (InAlGaAs), which have inherently less reliable structures despite offering improved performance at high speeds and temperatures, leading to high failure rates and reliability issues.
Innovation Solution
A high-power optical burn-in method is introduced, involving operation at relatively high drive current (three to four times the normal operating bias current) at elevated temperatures, but at room temperature, to identify and screen out weak or flawed InAlGaAs lasers effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high-temperature thermal burn-in methods are used, then InGaAsP lasers are adequately screened, but InAlGaAs lasers fail to be properly screened and exhibit high failure rates
Solution Approach 1:
The patent changes the burn-in parameters from conventional high-temperature conditions to high optical power conditions. Specifically, it uses optical powers at least 10 dB above the nominal output power, which fundamentally alters the stress mechanism from thermal to optical, enabling effective screening of InAlGaAs lasers while maintaining compatibility with other laser types.
Solution Approach 2:
The patent substitutes the thermal stress mechanism with an optical stress mechanism. Instead of relying on thermal effects to reveal defects, it uses high optical power to induce catastrophic optical damage (COD) in flawed devices, thereby replacing the thermal burn-in approach with an optical burn-in approach that is effective for InAlGaAs materials.
2Reliability
If high optical power is applied during burn-in, then InAlGaAs laser reliability is significantly improved, but the testing process requires higher power capabilities
Solution Approach 1:
The patent applies high optical power during the burn-in phase before the lasers are deployed. This preliminary stress test reveals and eliminates weak devices early in the manufacturing process, ensuring that only reliable lasers are shipped to customers, thereby extending the failure-free time in the field despite the higher power requirements during testing.
3Ease of manufacture
If conventional burn-in procedures are used, then manufacturing processes remain simple, but defective InAlGaAs lasers escape detection and cause network interruptions
Solution Approach 1:
The patent modifies the burn-in parameters by applying high optical power (at least 10 dB above nominal) during the testing phase. This change in parameters enables the detection of defective InAlGaAs lasers that would otherwise escape conventional screening, improving field performance while adding only a parameter adjustment to the manufacturing process.
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 approach significantly improves the reliability of semiconductor lasers by identifying and removing defective devices, extending failure-free times from months to several years under normal operating conditions, making them acceptable for commercialization.
Implementation Method 1
operating the laser diodes at elevated ambient temperatures for an extended period. This type of burn-in is often referred to as high-temperature thermal burn-in (TBI). The high-temperature condition makes the material of a laser diode softer by heating up the lattice
Data Source
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AI summary
Semiconductor lasers are aged to identify weak or flawed devices, resulting in improved reliability of the remaining devices. The lasers can be aged using a high-power optical burn-in that includes providing a high drive current to the lasers for a period of time, and maintaining the ambient temperature of the lasers at a low temperature. After the high-power optical burn-in, the output of the lasers can be measured to determine if the lasers are operating within specifications. Those that are not can be discarded, while those that are can be further aged using a high-temperature thermal burn-in that includes providing a drive current to the lasers while maintaining the ambient temperature of the lasers at a high-temperature.