Optical Coupler for LED Light Source with Enhanced Output Brightness
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Solution Overview
Problem
Solid state light sources, such as LEDs, face limitations in brightness and power output due to low light coupling efficiency when coupling light into waveguides or optical fibers, as light emitted at angles outside the numerical aperture is lost.
Innovation Solution
A light source design incorporating a waveguide with a reflector and optical media, where the waveguide has a higher refractive index than the optical media, and a reflective layer or surface to recycle light outside the numerical aperture back into the waveguide, enhancing coupling efficiency and output brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If light is coupled directly from LED to waveguide by placing fiber end surface on top of LED, then device structure is simple, but light coupling efficiency is low (about 25% for NA=0.5) due to loss of light emitted at angles outside numerical aperture
Solution Approach 1:
The patent transitions from direct top-down coupling to side-coupling by positioning the waveguide adjacent to the LED and using a reflector to redirect light at angles into the waveguide, effectively utilizing a different spatial dimension for light collection
Solution Approach 2:
The patent converts the harmful loss of light emitted at large angles into a beneficial resource by using a reflector to capture and redirect this previously wasted light into the waveguide, thereby improving coupling efficiency
2Loss of energy
If reflector is added to recycle light outside numerical aperture back into waveguide, then light coupling efficiency increases, but device complexity increases
Solution Approach 1:
The patent introduces an optical medium with refractive index between the waveguide and reflector as an intermediary to facilitate light redirection, using refraction to bend light at controlled angles into the waveguide
Solution Approach 2:
The patent optimizes the refractive index of the optical medium as a key parameter to achieve optimal light redirection efficiency, balancing coupling performance with device simplicity
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 solution significantly increases light coupling efficiency by recycling light that would otherwise be lost, resulting in enhanced output brightness and power delivery.
Implementation Method 1
a waveguide disposed above and adjacent the light emitting device for collecting the light emitted by the light emitting device
Implementation Method 2
a reflector disposed around a segment of the waveguide adjacent the light emitting device; providing a reflector around a segment of the waveguide adjacent the light emitting device to reflect light leaking out of the segment of the waveguide back to the waveguide
Implementation Method 3
one or more optical media disposed in a space between the substrate, the waveguide and the reflector, wherein the waveguide has a refractive index higher than a refractive index of the one or more optical media
Data Source
AI summary
A light source is described where the light emitted by a solid-state light emitting device such as an LED is coupled into an optical waveguide such as an optical fiber. A highly reflective coupler (reflector) is disposed around the LED and a segment of the waveguide adjacent the LED. Light emitted from the LED that falls outside of the numerical aperture of the waveguide leaks out of the waveguide, but is reflected back to the waveguide by the reflector. The reflected light is re-reflected or scattered by the LED or the substrate the LED is mounted on, and the re-reflected or scattered light that falls within the numerical aperture of the waveguide is coupled into the waveguide. As a result, light coupling efficiency is increased and the output brightness of the light at the other end of the fiber is enhanced.