Diode Laser Current Injection Profiling for Long-Cavity Efficiency
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Solution Overview
Problem
High-power semiconductor lasers face efficiency penalties due to non-uniform current density and photon density along the cavity length, limiting further scaling of power and brightness.
Innovation Solution
Control of the longitudinal current density profile through techniques such as patterning of apertures in the dielectric or proton implantation, allowing for adjustment of current injection to optimize current flow and reduce crowding effects, thereby enhancing power conversion efficiency and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the cavity length is increased to scale brightness and power, then output power and brightness are improved, but power conversion efficiency deteriorates
Solution Approach 1:
The patent applies local quality by creating non-uniform current density distribution along the cavity length through patterned contacts or dielectric structures. Different regions of the laser cavity are provided with different current injection characteristics - high current density regions are positioned where gain is needed, while low current density regions are positioned where losses are higher. This localized optimization allows the long cavity to maintain high power conversion efficiency while delivering high output power and brightness.
2Ease of manufacture
If uniform contacts are used along the cavity length, then manufacturing is simplified, but current density uniformity deteriorates
Solution Approach 1:
Instead of uniform contacts, the patent implements patterned contacts or patterned dielectric layers that create locally optimized current density profiles. The contacts remain simple to manufacture using standard photolithography and patterning techniques, but the patterned structure ensures that current density is optimized at different positions along the cavity - with higher current density where gain is needed and lower current density where losses occur. This resolves the contradiction by achieving both manufacturability and current density control.
3Illumination intensity
If cavity length is extended beyond 5 mm, then brightness scaling is improved, but power conversion efficiency deteriorates due to asymmetry in photon density, carrier density, gain and recombination lifetime
Solution Approach 1:
The patent addresses the asymmetry issues in long cavities by implementing local quality optimization through patterned current injection. Different regions along the >5mm cavity are provided with tailored current density profiles that compensate for position-dependent variations in photon density, carrier density, gain, and recombination lifetime. This allows the extended cavity to achieve high brightness while maintaining high power conversion efficiency by matching current injection to local operational conditions.
Solution Approach 2:
The patent applies preliminary action by pre-positioning patterned contacts or dielectric structures during fabrication to anticipate and compensate for the asymmetry that will develop during laser operation. The current density profile is engineered in advance to account for expected variations in photon density, carrier density, gain, and recombination lifetime along the long cavity, ensuring optimal efficiency is achieved from the start of operation rather than requiring dynamic adjustment.
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
The described techniques enable diode lasers to operate with higher power conversion efficiency and greater output power by optimizing current densities along the cavity length, overcoming limitations in existing technologies.
Implementation Method 1
patterning of the epi-side dielectric with apertures or producing apertures through proton implantation allows control of the current density profile at the quantum wells through the adjustment of the spacing between these features due to lateral current spreading
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
The present technology can be used to control the current injection profile in the longitudinal direction of a high-power diode laser in order to optimize current densities as a function of position in the cavity to promote higher reliable output power and increase the electrical to optical conversion efficiency of the device beyond the level which can be achieved without application of this technique. This approach can be utilized, e.g., in the fabrication of semiconductor laser chips to improve the output power and wall plug efficiency for applications requiring improved performance operation.