SP-MQW Optical Modulator for Low Voltage High Extinction Ratio

Solution Overview

Problem

Conventional surface-incident electro-absorption modulators suffer from high driving voltage and limited extinction ratio, making them unsuitable for modern high-performance processor integrated circuits due to high power consumption and limited contrast ratio.

Innovation Solution

A surface-incident, plasmon-enhanced multiple quantum well (SP-MQW) optical modulator is developed, utilizing both refractive index and absorption coefficient changes via surface plasmon coupling to achieve high extinction ratio and low driving voltage, with a structure comprising multiple quantum well layers, metallic, and dielectric layers that allow light to be coupled into a surface plasmon mode when an electric field is applied.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional surface-incident electro-absorption modulators are used, then the device structure is simple, but the driving voltage is high and extinction ratio is limited

Engineering Contradiction:

Improvemodulator structureVSAvoiddriving voltage

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent employs a composite structure combining multiple quantum well layers with metallic layers to create surface plasmon modes. This composite material approach enables simultaneous achievement of low driving voltage (0.7 V) and high extinction ratio (>16 dB) by leveraging the unique optical properties of the metal-semiconductor interface, resolving the contradiction between device simplicity and energy efficiency.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention utilizes electric field-induced changes in refractive index and absorption coefficient of the multiple quantum well structure to modulate surface plasmon modes. By changing the electrical parameter (voltage) to control optical properties, the modulator achieves low driving voltage operation while maintaining high extinction ratio, addressing the energy consumption issue.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional surface-incident electro-absorption modulators are used, then the device structure is simple, but the extinction ratio is limited

Engineering Contradiction:

Improvemodulator structureVSAvoidextinction ratio

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent employs a composite structure combining multiple quantum well layers with metallic layers to create surface plasmon modes. This composite material approach enables simultaneous achievement of low driving voltage (0.7 V) and high extinction ratio (>16 dB) by leveraging the unique optical properties of the metal-semiconductor interface, resolving the contradiction between device simplicity and energy efficiency.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention utilizes electric field-induced changes in refractive index and absorption coefficient of the multiple quantum well structure to modulate surface plasmon modes. By changing the electrical parameter (voltage) to control optical properties, the modulator achieves low driving voltage operation while maintaining high extinction ratio, addressing the energy consumption issue.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If direct modulation of VCSELs is used, then the interconnect configuration is simple, but power consumption increases with data rate

Engineering Contradiction:

Improveinterconnect configurationVSAvoidpower consumption

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent introduces an external modulator as an intermediary component between the VCSEL and waveguide. This separation allows the VCSEL to operate continuously at optimal power levels while the external modulator handles the data encoding, eliminating the need for high-current switching and thereby reducing overall power consumption at high data rates while maintaining configuration simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Use of energy by moving object

If optical photonic modulators are used, then power consumption is reduced, but the device structure becomes complex

Engineering Contradiction:

Improvepower consumptionVSAvoidmodulator structure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent employs a composite structure combining multiple quantum well layers with metallic layers to create surface plasmon modes. This composite material approach enables simultaneous achievement of low driving voltage (0.7 V) and high extinction ratio (>16 dB) by leveraging the unique optical properties of the metal-semiconductor interface, resolving the contradiction between device simplicity and energy efficiency.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention utilizes electric field-induced changes in refractive index and absorption coefficient of the multiple quantum well structure to modulate surface plasmon modes. By changing the electrical parameter (voltage) to control optical properties, the modulator achieves low driving voltage operation while maintaining high extinction ratio, addressing the energy consumption issue.

Inventive Principle:

Principle #35Parameter changes

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 SP-MQW modulator achieves a high extinction ratio exceeding 16 dB and low driving voltage of 0.7 V, significantly reducing power consumption and insertion loss, with energy efficiency improved by over 100 times compared to existing technologies, enabling efficient optical interconnects in data centers and computing systems.

Implementation Method 1

applying a voltage on said modulator structure changes the refractive index and absorption coefficient of said multiple quantum wells and couples the incident light into a surface plasmon (SP) mode propagating on the surface of said metal layer

Methodology Applied

Scientific EffectSurface plasmon coupling:

Implementation Method 2

changes the refractive index and absorption coefficient of said multiple quantum wells

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

the incidence angle being large enough to allow total internal reflection at a second surface of said multiple quantum well when no voltage is applied on said modulator structure

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS10656443B2Method and apparatus of surface-incident, plasmon-enhanced multiple quantum well modulators and optical coupling thereon

Publication Date: 2020.05.19 LAXENSE

AI summary

An optical interconnect system has first and second waveguides each with wedge-shaped cross-section at a first end, disposed over an optical modulator. The optical modulator is a surface-plasmon multi quantum well (SP-MQW) modulator, the first waveguide an input waveguide and the second waveguide configured an output waveguide. In embodiments the SP-MQW modulator has multiple semiconductor layers disposed atop a lower metal layer between 10 and 300 nanometers thick and configured such that incident light is reflected at the lower metal layer unless a voltage is applied to the semiconductor layers, when incident light is coupled into a surface plasmon mode in the lower metal layer.