Series-Connected Laser Diode Bar for Lower Joule Heating
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Solution Overview
Problem
High-power laser diode bars face significant heat dissipation issues due to high drive currents, leading to degraded performance and efficiency, primarily because individual diodes are connected in parallel, increasing overall current requirements.
Innovation Solution
The laser diodes are connected in series, with a highly doped semiconductor layer providing a low resistance path and shunt electrodes reducing series resistance, limiting maximum current and minimizing Joule heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If laser diodes are connected in parallel to achieve high power output, then power output increases, but drive current increases quadratically leading to excessive Joule heating
Solution Approach 1:
The patent inverts the conventional parallel connection approach by connecting laser diodes in series. This inversion allows high power output to be achieved without the quadratic increase in drive current that causes Joule heating in parallel configurations. The series connection maintains current at manageable levels while still achieving the desired power output through voltage multiplication.
Solution Approach 2:
The patent changes the electrical connection parameter from parallel to series, fundamentally altering how power is delivered to the laser diode array. This parameter change transforms the current-scaling behavior from quadratic (parallel) to linear (series), thereby reducing Joule heating while maintaining high power output capability.
2Power
If drive current is increased to achieve high power output, then power output increases, but device performance degrades due to heat dissipation
Solution Approach 1:
By inverting the connection topology from parallel to series, the patent achieves high power output without requiring high drive currents. This preserves device performance and reliability by keeping operating conditions within safe thermal limits while still delivering the required power output.
3Loss of energy
If series connection is used to reduce current, then Joule heating decreases, but electrical conductivity requirements increase
Solution Approach 1:
The patent applies local quality by creating a highly doped semiconductor layer specifically at the contact region between laser diodes. This localized high-conductivity region ensures low series resistance at the critical interface without requiring the entire semiconductor structure to have uniformly high conductivity, thereby simplifying manufacturing while achieving the desired electrical performance.
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 maximum current required and decreases Joule heating, enhancing the performance and efficiency of high-power laser diode bars by limiting current to the lowest drive current of individual diodes and reducing series resistance.
Implementation Method 1
a highly doped semiconductor layer providing a low resistance path and shunt electrodes reducing series resistance
Implementation Method 2
Given that Joule heating scales quadratically with diode current, laser diodes experience significant heat dissipation
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 2D~2F
AI summary
A laser diode bar: includes a semiconductor substrate comprising a first semiconductor layer of a first conductivity type; a first laser diode stack on an upper side of the semiconductor layer; a second laser diode stack on the upper side of the semiconductor layer, the second laser diode stack being electrically connected in series with the first laser diode stack, in which an electrical conductivity of the first semiconductor layer of the first conductivity type is higher than an electrical conductivity of each semiconductor layer of the first and second laser diode stacks; and a first electrode layer on the first laser diode stack, in which the first electrode layer electrically connects the first laser diode stack to a portion of the first semiconductor layer of the first conductivity type that is between the first laser diode stack and the second laser diode stack.