Composite Semiconductor Light Source Spontaneous Pumping
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Solution Overview
Problem
Semiconductor vertical cavity devices face inefficiencies in lateral current confinement and heat management due to mechanical strain and increased drive voltage, with conventional optically pumping methods being inefficient as they generate heat and reduce laser efficiency.
Innovation Solution
The development of composite semiconductor light sources utilizing a first light source as a pump with predominantly spontaneous emission, which operates with a drive voltage less than the photon energy and eliminates heat-generating dopants, allowing for efficient optical pumping of a second light source through a depleted heterojunction current blocking region and selective diffusion techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional optically pumping methods are used, then light can be generated, but heat is generated and laser efficiency is reduced
Solution Approach 1:
The patent changes the fundamental parameter of the pump light source from stimulated emission (laser) to spontaneous emission (LED), operating below the lasing threshold. This parameter change transforms the emission mechanism to eliminate heat-generating free carrier absorption while maintaining efficient optical pumping capability, directly resolving the contradiction between pumping efficiency and heat generation
Solution Approach 2:
The patent replaces the mechanical/electrical pump system (laser requiring high current drive and complex cavity) with an optical pump system based on spontaneous emission. This substitution eliminates the need for high drive voltages and complex optical cavities in the pump, reducing heat generation while maintaining pumping effectiveness
2Ease of operation
If standard intra-cavity oxide approach is used for current confinement, then electrical current can be confined, but mechanical strain increases and drive voltage increases
Solution Approach 1:
The patent extracts and removes the problematic intra-cavity oxide layer that causes mechanical strain and high drive voltage. By eliminating this oxide confinement layer, the device achieves current confinement through alternative means (depleted heterojunction) without the harmful mechanical strain and voltage increase associated with oxide-based approaches
Solution Approach 2:
The patent changes the current confinement mechanism from oxide-based lateral confinement to depleted heterojunction-based confinement. This parameter change in the confinement mechanism eliminates the need for high drive voltages and reduces mechanical strain while maintaining effective current confinement to the active region
3Illumination intensity
If laser operates above threshold current, then laser light is generated, but heat is generated due to quasi-Fermi energy separation exceeding photon energy
Solution Approach 1:
The patent inverts the conventional approach by operating the pump light source below the lasing threshold rather than above it. This inversion changes the emission regime from stimulated emission (which generates heat when above threshold) to spontaneous emission, eliminating the heat generation mechanism while still providing sufficient optical pumping power
4Use of energy by moving object
If free carrier absorption occurs, then some laser light is absorbed, but laser light output is reduced and efficiency decreases
Solution Approach 1:
The patent changes the operational parameter of the pump light source to operate below the lasing threshold in the spontaneous emission regime. This parameter change eliminates free carrier absorption losses that occur in laser operation above threshold, as spontaneous emission does not require the high carrier densities that cause free carrier absorption, thereby improving overall system efficiency
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 enhances the efficiency of light sources by reducing heat generation, increasing the overall efficiency of the pump, and enabling high-power operation with low drive voltage, while maintaining the second light source in a spontaneous regime for improved optical pumping.
Implementation Method 1
the emission is predominantly a spontaneous emission defined herein to be at least 50.1% of the light emitted
Implementation Method 2
a first light source that optically pumps a second light source
Implementation Method 3
depleted heterojunction current blocking region
Implementation Method 4
selective diffusion techniques
Implementation Method 5
the remainder of the emitted light being light emitted by stimulated emission
Data Source
AI summary
A composite light source includes a substrate having a top surface, and a first vertical light source formed in the substrate. The first light source includes least a lower mirror, a first active region above the lower mirror, wherein the first active region has a thickness sufficient when electrically pumped to emit predominantly a spontaneous vertical emission from the first active region towards the top surface having an angular range of at least (≧) 30°. A second light source is formed in the substrate above the first active region including a second active region. The spontaneous vertical emission is at a first wavelength λ1 that optically drives said second active region to provide an emission at a second wavelength λ2, wherein λ2>λ1.