Surface Emitting Laser Composition Gradient Layers
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Solution Overview
Problem
Conventional surface emitting lasers experience increased power consumption when a bias current equal to or larger than the threshold current is applied, due to rising element resistance with ambient temperature changes, which is not effectively managed by existing technologies.
Innovation Solution
A surface emitting laser design featuring a substrate with lower and upper multilayer mirrors, conductivity-type contact layers, an active layer, and composition gradient layers that reduce bandgap energy and carrier concentration, along with a current confinement layer and electrodes, to minimize differential resistance and power consumption by applying modulation voltages with equal positive and negative amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias current equal to or larger than threshold current is applied to conventional surface emitting lasers, then laser oscillation is achieved, but power consumption increases due to rising element resistance with temperature
Solution Approach 1:
The patent changes the doping concentration parameter in the cladding layers, specifically setting the carrier concentration of the second composition gradient layer to be equal to or more than that of the current injection portion. This parameter change optimizes the differential resistance characteristics to remain flat near the threshold current, enabling low-power operation while maintaining reliable laser oscillation.
2Use of energy by moving object
If the oscillation wavelength is extended beyond 850 nm to reduce bias voltage, then power consumption can be reduced, but differential resistance becomes more sensitive to temperature changes
Solution Approach 1:
The patent employs composition gradient layers with monotonically decreasing bandgap energy from the current confinement layer toward adjacent layers. This compositional parameter change creates a structured variation in carrier concentration that stabilizes differential resistance against temperature fluctuations, even when operating at extended wavelengths with lower bias voltages.
Solution Approach 2:
The patent uses composite material structures including strained InGaAs quantum wells combined with specific cladding layer compositions. The composite structure of multiple layers with graded compositions works synergistically to maintain stable differential resistance characteristics while enabling operation at reduced bias voltages for wavelengths beyond 850 nm.
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 design significantly reduces power consumption by maintaining stable differential resistance even at low bias currents near the threshold, enabling efficient operation with lower power consumption and reduced temperature dependence, suitable for high-speed optical interconnections.
Implementation Method 1
The first composition gradient layer and the second composition gradient layer are formed such that bandgap energy of each of the layers is monotonically decreased from the current confinement layer to an adjacent layer and approach bandgap energy of the adjacent layer in a growth direction
Implementation Method 2
The second-conductivity-type cladding layer includes material for reducing mobility of carrier
Implementation Method 3
distributed Bragg reflector (DBR) mirrors that are multilayer reflection mirrors formed of a periodic structure of a high refractive index layer and a low refractive index layer are used as an optical resonator
Implementation Method 4
By using a strained InGaAs quantum well for the active layer in order to increase the oscillation wavelength, a differential gain is increased and the power consumption can be further reduced
Data Source
AI summary
A surface emitting laser includes lower and upper multilayer mirrors, first-conductivity-type and second-conductivity-type contact layers formed between the lower and the upper multilayer mirrors, an active layer formed between the first-conductivity-type and the second-conductivity-type contact layers, a current confinement layer formed between the second-conductivity-type contact layer and the active layer, and first and second composition gradient layers formed facing each other across the current confinement layer. The first composition gradient layer and the second composition gradient layer are formed such that bandgap energy of each of the layers is monotonically decreased from the current confinement layer to an adjacent layer and approach bandgap energy of the adjacent layer in a growth direction.