Air Gap Light Source Device Fluorescence Loss
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Solution Overview
Problem
In light source devices with reflective type wavelength conversion elements, there is a significant light loss due to incomplete reflectance of fluorescence on the substrate's reflecting surface, leading to increased fluorescence loss.
Innovation Solution
A light source device configuration with an air gap between the wavelength conversion section and the substrate, where the thickness of the air gap is defined by the roughness of both surfaces and is greater than the wavelength of the fluorescence, preventing evanescent wave absorption and enhancing wavelength conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the wavelength conversion section is bonded directly to the substrate with a reflecting surface, then the structure is simple and easy to manufacture, but the reflectance is not 100% causing light loss and reduced wavelength conversion efficiency
Solution Approach 1:
An air gap is introduced as an intermediary layer between the wavelength conversion section and the substrate. This air gap acts as a mediator that prevents direct contact while allowing thermal conduction, and simultaneously prevents evanescent wave absorption by the substrate, thereby reducing fluorescence loss without requiring complex bonding structures
Solution Approach 2:
The thickness of the air gap is precisely controlled to be greater than the wavelength of the fluorescence. This parameter change ensures that the evanescent waves generated by total internal reflection at the air gap interface do not extend into the substrate, preventing energy loss while maintaining a simple structural configuration
2Loss of energy
If the air gap thickness is increased to prevent evanescent wave absorption, then wavelength conversion efficiency is improved, but heat transfer from the wavelength conversion section to the substrate is reduced
Solution Approach 1:
The air gap thickness is optimized to a specific range (greater than the fluorescence wavelength but not excessively large). This parameter optimization balances two competing requirements: it is thick enough to prevent evanescent wave absorption and improve wavelength conversion efficiency, yet thin enough to maintain effective thermal conduction and prevent excessive temperature rise
Solution Approach 2:
The air gap provides localized optical isolation at the interface between the wavelength conversion section and substrate, preventing evanescent wave coupling into the substrate. However, the gap maintains sufficient proximity for thermal conduction, creating different local functions (optical isolation vs. thermal coupling) at the same interface region
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 air gap configuration reduces light loss by preventing fluorescence from entering the substrate at critical angles, maintaining wavelength conversion efficiency and allowing for effective heat transfer from the wavelength conversion section to the substrate, thus minimizing temperature rise and improving overall efficiency.
Implementation Method 1
the thickness dimension is no smaller than a wavelength of the fluorescence... preventing evanescent wave absorption
Implementation Method 2
preventing fluorescence from entering the substrate at critical angles
Implementation Method 3
a phosphor layer including a phosphor which is excited by the excitation light entering the phosphor and emits fluorescence longer in wavelength than the excitation light
Implementation Method 4
allowing for effective heat transfer from the wavelength conversion section to the substrate
Data Source
AI summary
A light source device includes a light source configured to emit excitation light, a wavelength conversion section configured to perform wavelength conversion on the excitation light to generate fluorescence having a wavelength longer than a wavelength of the excitation light, a substrate opposed to the wavelength conversion section, and an air gap disposed between the wavelength conversion section and the substrate, wherein the wavelength conversion section has a first surface opposed to the substrate, the substrate has a second surface opposed to the first surface, a thickness dimension of the air gap as a dimension in a direction from the first surface toward the second surface is defined by a sum of a roughness of the first surface and a roughness of the second surface, and the thickness dimension of the air gap is no smaller than a wavelength of the fluorescence.