Laser Pump Module Assembly With Early Dead Diode Detection
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Solution Overview
Problem
Detecting dead laser diodes in laser pump modules during assembly is difficult, leading to labor and material waste due to late discovery of defects, which are typically identified after additional optical components are installed.
Innovation Solution
Apply a low current below the lasing threshold to induce spontaneous light emission, which is captured electronically to detect dark spots indicating defective diodes, allowing for early identification and replacement of faulty modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser pump modules are assembled without early detection testing, then assembly speed is maintained, but dead laser diodes are not detected until later testing stages causing labor and material waste
Solution Approach 1:
The patent applies preliminary action by performing spontaneous emission testing at an early stage in the assembly process, specifically after CoS modules are soldered to the laser pump module housing but before optical components are installed. This early detection allows defective laser diode chips to be identified and replaced before subsequent assembly steps, preventing waste of labor and materials that would otherwise be spent on modules with dead diodes. The testing is integrated into the assembly flow without requiring complete module assembly, thus maintaining productivity while reducing waste.
2Loss of substance
If spontaneous emission testing is performed at early assembly stage, then dead diodes are detected early reducing waste, but additional testing steps are added to the assembly process
Solution Approach 1:
The patent applies self-service by using the laser diode chips themselves to generate the test signal through spontaneous emission when a low current is applied. The laser diodes naturally emit light below their lasing threshold without requiring external test equipment or complex test setups. This self-testing capability is integrated directly into the existing assembly process, requiring only a simple current source and optical detection, thus minimizing added complexity while enabling effective early detection.
3Measurement precision
If current is applied above lasing threshold for testing, then laser output can be measured, but risk of damage to laser diodes increases and lasing behavior complicates detection
Solution Approach 1:
The patent applies parameter changes by operating the laser diodes at a low current level below the lasing threshold during testing, rather than at full operating current. This parameter change enables spontaneous emission to occur without the complex lasing behavior that would complicate detection. The spontaneous emission provides a simple, direct indication of diode functionality without risking damage from high current exposure. The testing current is specifically chosen to be sufficient to generate detectable spontaneous emission but low enough to avoid thermal damage or inducing lasing.
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
Reduces labor and material waste by enabling early detection of dead diodes, facilitating efficient mass production of laser pump modules.
Implementation Method 1
applying the current to the input conductor to generate a spontaneous light emission by each respective laser diode chip
Data Source
AI summary
A method of manufacturing a laser pump module includes mounting a plurality of chip-on-submount (CoS) modules to the laser pump module; wire bonding the plurality of CoS modules with bond wires, wherein the bond wires are provided such that the plurality of CoS modules form one or more conductive paths with one or more electrical conductors of the laser pump module; applying a current to one or more conductive paths to cause a spontaneous light emission by each CoS module; acquiring, while the current is applied to the one or more conductive paths, a spontaneous emission photo of the plurality of CoS modules; evaluating the spontaneous emission photo for the spontaneous light emission of each respective laser diode chip to obtain an evaluation result; and determining, based on the evaluation result, whether the spontaneous light emission has failed at one or more respective laser diode chips.