Three Coupled Quantum Well Optical Device Voltage Absorption

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Solution Overview

Problem

Existing optical modulators face a trade-off between low driving voltage and high optical absorption strength, with increasing the thickness of quantum well layers to reduce voltage leading to degraded absorption strength due to decreased overlap of electron and hole wave functions.

Innovation Solution

The optical device employs a three coupled quantum well structure with asymmetrically arranged quantum well layers and coupling barriers, where the second quantum well layer has the largest thickness and the third quantum well layer is thinner, enhancing the overlap of electron and hole wave functions and improving absorption strength while reducing the driving voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If the thickness of quantum well layer is increased to reduce driving voltage, then the driving voltage is reduced, but the absorption strength is degraded

Engineering Contradiction:

Improvedriving voltageVSAvoidabsorption strength

Core Design Contradiction:

Use of energy by stationary objectVSStrength

Solution Approach 1:

The quantum well structure is divided into multiple discrete quantum well layers (first, second, and third quantum well layers) separated by coupling barriers. This segmentation allows each layer to contribute to absorption while the overall structure maintains a reduced effective thickness for lower driving voltage, resolving the contradiction between thickness-related voltage and absorption strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The quantum well layers are arranged asymmetrically with the second quantum well layer having the largest thickness and the third quantum well layer being thinner. This asymmetric configuration optimizes the overlap of electron and hole wave functions in the critical second layer for high absorption, while the varied thickness distribution across layers helps reduce the overall driving voltage requirement.

Inventive Principle:

Principle #4Asymmetry

2Use of energy by stationary object

If the thickness of quantum well layer is increased to reduce driving voltage, then the driving voltage is reduced, but the overlap integral of wave functions decreases

Engineering Contradiction:

Improvedriving voltageVSAvoidoverlap integral of wave functions

Core Design Contradiction:

Use of energy by stationary objectVSReliability

Solution Approach 1:

The second quantum well layer is designed with the largest thickness specifically to maximize the overlap integral of electron and hole wave functions in that local region. This localized optimization ensures high absorption strength at the critical interface where excitation occurs, while other layers have different thicknesses that contribute to the overall reduced driving voltage of the structure.

Inventive Principle:

Principle #3Local quality

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 allows for a significant reduction in driving voltage while maintaining or improving optical absorption strength, outperforming traditional single and symmetrically coupled quantum well structures by achieving low voltage and high absorption simultaneously.

Implementation Method 1

Each of the at least one coupled quantum well includes at least three quantum well layers and at least two coupling barriers interposed between the at least three quantum well layers

Methodology Applied

Scientific EffectQuantum confinement:

Implementation Method 2

the overlap integral of wave functions of holes and electrons in the quantum well. As the thickness of the quantum well layer increases, the overlap integral of the hole and electron wave functions decreases

Methodology Applied

Scientific EffectWave function overlap:

Implementation Method 3

upon application of a reverse bias voltage to both ends of the P-I-N diode, the MQW structure generates excitons in a certain wavelength region to absorb light

Methodology Applied

Scientific EffectExciton generation:

Implementation Method 4

the absorption spectrum of the MQW structure tends to move toward a longer wavelength as the reverse bias voltage increases, the degree of absorption at a certain wavelength may vary

Methodology Applied

Scientific EffectAbsorption: Absorption (EM radiation)

Implementation Method 5

The at least two coupling barriers have a potential energy which is higher than a ground level and is lower than energy levels of the at least two outer barriers

Methodology Applied

Scientific EffectPotential energy barrier:

Implementation Method 6

The first coupling barrier and the second coupling barrier may have a material thickness such that tunneling of electrons and holes occurs

Methodology Applied

Scientific EffectTunneling:

Data Source

PatentUS9082909B2Optical device including three coupled quantum well structure

Publication Date: 2015.07.14 SAMSUNG ELECTRONICS CO LTD

AI summary

Provided is an optical device which includes an active layer which includes at least two outer barriers and at least one coupled quantum well, each of the at least one coupled quantum well is sandwiched between the at least two outer barriers. Each of the at least one coupled quantum well includes at least three quantum well layers and at least two coupling barriers interposed between the at least three quantum layers. The at least two coupling barriers have a potential energy which is higher than a ground level and is lower than energy levels of the at least two outer barriers.