Upconversion Optical Resonator for Green-Blue Light Confinement
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Solution Overview
Problem
Conventional photonic crystal surface emitting lasers and phase modulation light-emitting elements are not practical for short-wavelength ranges such as the green or blue range due to low light confinement coefficients in materials like GaN-based semiconductors.
Innovation Solution
An optical device comprising an upconversion layer, first and second light confinement layers, and a resonance mode forming layer with modified refractive index regions, which converts long-wavelength excitation light into shorter wavelength light, enhancing light confinement and output in the visible range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If nitride semiconductor (GaN) is used for short-wavelength light emission (green to blue range), then emission wavelength is reduced, but light confinement coefficient becomes excessively small
Solution Approach 1:
The patent employs a composite structure combining nitride semiconductor layers with photonic crystal layers. The photonic crystal layer, having a different refractive index from the nitride semiconductor, creates strong light confinement through periodic modulation. This composite approach allows the device to achieve both short-wavelength emission (green/blue) and sufficient light confinement coefficient by leveraging the optical properties of multiple materials working together.
2Reliability
If photonic crystal layer is added to improve light confinement, then light confinement coefficient increases, but device structure becomes more complex
Solution Approach 1:
The patent divides the device into functionally distinct segments: the nitride semiconductor layer for light generation and the photonic crystal layer for light confinement and wavelength selection. This segmentation allows each layer to be optimized independently for its specific function, simplifying the design process while achieving the desired overall performance. The photonic crystal layer is further segmented into periodic high and low refractive index regions to create the confinement effect.
Solution Approach 2:
The photonic crystal layer serves multiple functions simultaneously: it provides light confinement, selects the emission wavelength, and enables surface-normal light extraction. By integrating these functions into a single layer structure, the patent avoids adding separate components for each function, thereby limiting the increase in device complexity while achieving improved light confinement coefficient.
3Ease of manufacture
If conventional photonic crystal structure is used with GaN, then fabrication is attempted, but practical light output characteristics cannot be achieved
Solution Approach 1:
The patent optimizes key parameters of the photonic crystal structure, including the period, depth, and refractive index contrast of the photonic crystal holes, to achieve strong light confinement in the green/blue wavelength range. By carefully adjusting these parameters, the device achieves practical light output characteristics while maintaining fabrication feasibility using standard semiconductor processing techniques.
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
Enables practical photonic crystal surface emitting lasers and phase modulation elements to output light in the green to blue range, enriching color expression and improving light confinement coefficients.
Implementation Method 1
The UC layer contains an upconversion material that receives excitation light in a first wavelength range and outputs light in a second wavelength range shorter than the first wavelength range
Implementation Method 2
The resonance mode forming layer is provided between the first light confinement layer and the UC layer or between the second light confinement layer and the UC layer. The resonance mode forming layer includes a base layer and a plurality of modified refractive index regions having a refractive index different from a refractive index of the base layer and two-dimensionally distributed on a reference surface perpendicular to a thickness direction of the resonance mode forming layer. As a result, the resonance mode forming layer forms a resonance mode of the light in the second wavelength range along the reference surface
Implementation Method 3
The first light confinement layer has a light reflection characteristic of reflecting at least a part of light in the second wavelength range. The second light confinement layer has a light reflection characteristic of reflecting a part of light in the second wavelength range and transmitting the remainder
Data Source
AI summary
An optical device of one embodiment outputs light in a short-wavelength range such as a visible range. The optical device includes a UC layer, first and second light-confinement layers, and a resonance mode forming layer. The UC layer contains an upconversion material receiving excitation light in a first wavelength range and outputting light in a second wavelength range. The first light-confinement layer has a characteristic of reflecting part of the second wavelength-range light. The second light-confinement layer has a characteristic of reflecting part of the second wavelength-range light and transmitting the remainder, and is disposed such that the UC layer locates between the first and second light-confinement layers. The resonance mode forming layer locates between the UC layer and the first or second light-confinement layer, includes a base layer and plural modified refractive index regions, and forms a resonance mode of the second wavelength-range light.