Grating Coupler
Grating Coupler - Related Videos
08:48
Writing Bragg Gratings in Multicore Fibers
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Cited by 3 •
2016
We describe a technique for inscribing identical fiber Bragg gratings into each core of a multicore fiber. This is achieved by introducing an additional surface into the optical path to mitigate lensing by the curved surface of the fiber cladding.
10:39
Measurement of X-ray Beam Coherence along Multiple Directions Using 2-D Checkerboard Phase Grating
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Cited by 10 •
2016
The measurement protocol and data analysis procedure are given for obtaining transverse coherence of a synchrotron radiation X-ray source along four directions simultaneously using a single 2-D checkerboard phase grating. This simple technique can be applied for complete transverse coherence characterization of X-ray sources and X-ray optics.
12:08
Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System
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2015
The fabrication of high contrast gratings as the parallel spectrum splitting dispersive element in a concentrated photovoltaic system is demonstrated. Fabrication processes including nanoimprint lithography, TiO2 sputtering and reactive ion etching are described. Reflectance measurement results are used to characterize the optical performance.
06:00
Assessment of Spatial Lingual Tactile Sensitivity using a Gratings Orientation Test
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Cited by 2 •
2021
This work illustrates a standard procedure and threshold determination by the R-index to assess spatial lingual tactile sensitivity using a gratings orientation test.
00:08
A Random-displacement Measurement by Combining a Magnetic Scale and Two Fiber Bragg Gratings
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Cited by 2 •
2019
A protocol to create a full-range linear displacement sensor, combining two packaged fiber Bragg grating detectors with a magnetic scale, is presented.
FAQs
Efficient coupling requires the grating-generated optical field to match the propagation conditions of the planar waveguide mode. The grating period and coupling angle establish this phase relationship, while the periodic surface structure supplies the required diffraction. When the conditions are mismatched, less light enters the guided mode or less guided light is scattered into the external beam, reducing coupling efficiency.
Grating period, etch depth, fill factor, and coupling angle jointly determine how effectively light is transferred. These parameters affect phase matching and the strength of the diffracted field, so changing one can alter efficiency and the usable optical bandwidth. Engineering designs must therefore balance efficient transfer with the bandwidth requirements of the photonic integrated circuit.
The coupling angle participates directly in phase matching, so small changes can affect the amount of light transferred between the external beam and the waveguide. Polarization dependence is another important limitation because the grating may not couple all polarization states equally. These factors influence alignment requirements, insertion loss, and the consistency of measurements made on integrated photonic circuits.
A grating coupler can operate in either direction. Light arriving from an optical fiber or free-space beam is diffracted toward a guided mode, while light traveling in the planar waveguide can be scattered outward for collection. This bidirectional behavior makes the same type of device useful for both injecting optical signals into a circuit and observing signals produced by it.
Characterization should consider coupling efficiency, insertion loss, usable bandwidth, polarization dependence, and sensitivity to the coupling angle. Together, these measurements show how much optical power enters or leaves the circuit, how performance changes across operating wavelengths, and how strongly alignment or polarization affects results. The resulting data help assess whether the coupler meets photonic circuit testing requirements.
Their lithographically fabricated, compact structure provides an optical access point to planar waveguides without requiring every circuit to be connected through permanently aligned fiber interfaces. This can simplify alignment during wafer-level testing and support characterization across multiple devices on a wafer. Engineers can use the couplers to evaluate integrated photonic circuits before packaging or further system integration.
Grating couplers support fiber-to-chip communication, optical sensing, and photonic integrated circuit characterization. In communication systems, they provide an interface between external optical signals and on-chip waveguides. In sensing, they enable optical access to integrated structures, while characterization uses them to examine device behavior through measurable coupling, bandwidth, polarization, and insertion-loss performance.