Photonic Circuit Light Coupler Using Cavity Reflection
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Solution Overview
Problem
Existing integrated photonic devices suffer from low out-coupling efficiency of light from waveguides to photodetectors, which adversely affects the signal-to-noise ratio and requires large detector pixels, imposing constraints on commercially available imaging solutions.
Innovation Solution
A photonic integrated circuit device with a planar detector and a waveguide layer where a cavity is formed to terminate the waveguide and a reflective surface is provided within the cavity to efficiently couple light from the waveguide to a photodetector, achieving high coupling efficiency and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grating couplers are used to couple light from waveguide to photodetector, then light coupling can be achieved, but the out-coupling efficiency is low
Solution Approach 1:
Instead of using traditional grating couplers that diffract light out of the waveguide, the patent inverts the approach by using a reflective surface at the end of the waveguide to bounce light back into the waveguide and redirect it toward the photodetector. This inversion of the coupling mechanism achieves much higher out-coupling efficiency (about twice as efficient or even higher) while minimizing light signal loss.
Solution Approach 2:
The patent introduces a vertical dimension by forming a cavity in the waveguide layer and placing a reflective surface within it. This three-dimensional structure allows light to be reflected back into the waveguide from below, creating an additional optical path that significantly improves coupling efficiency compared to planar grating couplers.
2Reliability
If grating coupler length is increased to increase coupling efficiency, then coupling efficiency improves, but detector pixel size must be increased
Solution Approach 1:
The patent eliminates the need for long grating couplers by inverting the coupling approach. The reflective surface configuration achieves high coupling efficiency in a compact area, allowing detector pixels to remain small while maintaining excellent coupling performance.
Solution Approach 2:
The patent changes the fundamental parameter of the coupling mechanism from diffraction-based grating couplers to reflection-based waveguide terminations. This parameter change enables high coupling efficiency without the need for large detector pixels or long coupling structures.
3Reliability
If traditional grating couplers are used, then light can be coupled to detector, but signal to noise ratio is adversely affected
Solution Approach 1:
By inverting the coupling approach and using reflective surfaces, the patent maximizes the amount of light signal reaching the photodetector while minimizing losses. This results in a significantly improved signal-to-noise ratio compared to traditional grating couplers, enhancing detection capability.
4Reliability
If large detector pixels are used to compensate for low coupling efficiency, then more light can be detected, but constraints on commercially available imaging solutions are imposed
Solution Approach 1:
The patent resolves the contradiction by inverting the coupling approach, which enables high detection efficiency with small detector pixels. This compatibility with standard commercial imaging solutions is maintained while achieving superior light coupling performance.
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 achieves significantly higher light coupling efficiency compared to traditional grating couplers, allowing for a compact device with improved signal-to-noise ratio and enabling the integration of millions of photonic waveguide outputs on a single chip.
Implementation Method 1
A reflective surface is provided in the cavity such as to reflect the light signal guided by the integrated waveguide toward a photodetector
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
Present invention relates to a photonic integrated circuit device (1) comprising a planar detector (2) that comprises at least one photodetector (3). The device further comprises a waveguide layer (4) arranged substantially parallel to the planar detector, the waveguide layer comprising a first integrated waveguide (11) for guiding a first light signal. A cavity (5) is formed in the waveguide layer in a region spaced away from the edges of the waveguide layer such as to terminate the first integrated waveguide in that region. A first reflective surface (6) is provided in the cavity to reflect the first light signal guided by the first integrated waveguide toward a first photodetector (7) of the planar detector.