Laser Diode Pad Positioning for High-Frequency Performance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transmitter modules with laser diodes (LDs) face performance degradation due to longer bonding wires caused by unequal pad distances from the facets, leading to suboptimal high-frequency performance.
Innovation Solution
The transmitter module design positions the second pad of the LD closer to the second facet, allowing for bonding wires of comparable length to the first pad, thereby reducing the length of the bonding wire connected to the second pad and improving high-frequency performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the second pad is positioned far from the second facet, then the LD structure is simpler and easier to manufacture, but the bonding wire length increases causing performance degradation
Solution Approach 1:
The patent applies asymmetry by positioning the second pad closer to the second facet than the first pad is to the first facet. This asymmetric arrangement creates unequal pad-to-facet distances that compensate for the driver's position, making the bonding wire lengths from both pads to the driver comparable. This resolves the contradiction by optimizing wire length for high-frequency performance while maintaining manufacturability through a straightforward pad layout modification.
2Reliability
If the bonding wire length is reduced, then high-frequency performance is improved, but the pad positioning becomes more constrained and complex
Solution Approach 1:
The patent applies local quality by differentiating the positions of the first and second pads relative to their respective facets. Specifically, the second pad is positioned closer to the second facet than the first pad is to the first facet. This localized positional adjustment optimizes the bonding wire length from the second pad to the driver, reducing parasitic effects and improving high-frequency performance without requiring complex overall restructuring.
Data Source
AI summary
A transmitter module that includes a laser diode (LD) and a driver, each mounted on a sub-mount, is disclosed. The driver directly drives the LD by supplying a modulation signal, a bias signal, and a reference. Two signals are provided to a first pad of the LD, while, the reference is provided to the second pad of the LD. The second pad in the center thereof is formed relatively closer to the second facet of the LD opposite to the first facet through which the laser light is emitted.