Coupled Resonant Microcavity LEDs for High-Q Emission With Lower Loss
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Solution Overview
Problem
Traditional microcavities in light emitting devices face a tradeoff between optical performance and electronic efficiency, where thinner microcavities improve electronic efficiency but limit access to higher-order optical modes, while thicker microcavities enhance optical performance but increase electrical losses.
Innovation Solution
The implementation of a light emitting device with a distributed feedback structure and a periodic array of optical resonator cavities, including semitransparent mirrors and electrically driven emitter layers, allows for direct electrical stimulation and interaction of resonant modes, enabling control over light emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the microcavity thickness is increased to access higher-order optical modes, then the optical performance (Q-factor) is improved, but the electrical losses increase
Solution Approach 1:
The patent divides a single thick microcavity into multiple thinner microcavities arranged in series. Each microcavity has its own emitter layer and can be independently electrically stimulated. This segmentation allows the system to achieve the optical performance of a thick cavity (by having multiple cavities contribute to the overall optical path length) while maintaining the electrical efficiency of thin cavities (by minimizing the thickness of each individual cavity, reducing electrical resistance and Joule heating in each segment).
Solution Approach 2:
The patent combines multiple thin microcavities into a unified optical system where the resonant modes of individual cavities interact and couple together. The semitransparent mirrors allow optical fields to propagate between cavities, creating a distributed feedback structure where the combined system exhibits higher-order optical modes similar to a single thick cavity, while each component remains thin for electrical efficiency.
2Loss of energy
If the microcavity thickness is decreased to improve electronic efficiency, then the electrical losses are reduced, but access to higher-order optical modes is limited
Solution Approach 1:
By segmenting the optical path into multiple thin cavities, the system maintains the electrical efficiency of thin structures while collectively achieving the optical functionality of a thick cavity. The distributed arrangement of multiple cavities provides access to higher-order optical modes that would be unavailable in a single thin cavity, thus resolving the limitation on mode access.
Solution Approach 2:
The patent transitions from a single-dimensional (single thick cavity) approach to a multi-dimensional arrangement (multiple thin cavities stacked in series). This dimensional change allows the system to access higher-order optical modes by utilizing the cumulative optical path length of multiple cavities while maintaining the electrical advantages of thin individual structures.
3Reliability
If a single thick microcavity is used to achieve higher-order modes, then the Q-factor increases, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent segments the thick microcavity into multiple thinner, more manageable units. Each thin microcavity can be fabricated using standard thin-film deposition techniques with better process control, reducing manufacturing complexity. The modular nature of segmented cavities also allows for easier assembly and potential parallel fabrication processes, making the overall device easier to manufacture while achieving the same optical performance.
Solution Approach 2:
By changing the structural parameter from a single thick cavity to multiple thin cavities, the patent maintains the desired Q-factor and optical performance while improving manufacturability. The thinner individual cavities allow for better control of film thickness and more precise fabrication tolerances, reducing manufacturing difficulty.
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 combines the high electronic efficiency of thinner microcavities with the optical performance of thicker microcavities, reducing emission linewidth and increasing bandwidth, while allowing access to higher-order optical modes, thereby enhancing light emission characteristics.
Implementation Method 1
The microcavity effect has been utilized to control the electrically-driven emission from light emitting diodes such as the broadband organic molecules in an OLED. This effect has been well studied for decades for color tuning, improved efficiency and for the angular emission effects in regular LEDs, OLEDs and laser cavities.
Implementation Method 2
a distributed feedback structure and a periodic array of optical resonator cavities, including semitransparent mirrors and electrically driven emitter layers
Implementation Method 3
the semitransparent mirrors are designed and configured to allow interaction of the resonant modes of adjacent ones of the plurality of microcavities
Implementation Method 4
at least one electrically driven emitter layer located in each of the optical resonator cavities
Data Source
AI summary
Distributed feedback distributed gain light emitting devices that include a plurality of optical gain media including active emitter layers dispersed throughout a distributed feedback structure. In some examples, the distributed feedback structures enable direct electrical stimulation of each of the plurality of emitter layers and constitute a periodic array of high quality factor (high-Q) optical resonator cavities and/or a Bragg-type periodic variation in effective refractive index.