Compact Multimode Interferometer Design
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Solution Overview
Problem
Existing photonic interferometers, such as Mach-Zehnder and ring resonators, are space-consuming and have unpredictable transmission spectra, limiting their compactness and spectral resolution in spectrometer applications.
Innovation Solution
A compact multimode interferometer design that utilizes bidirectional waveguides with integrated readout structures, eliminating the need for waveguide bends and allowing for a more compact form factor while maintaining sinusoidal transmission spectra, achieved by positioning readout structures to concentrate reflected light based on phase differences between waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If waveguide bends are used to create path length difference in interferometer, then the interferometer can achieve the required optical path difference, but the device size becomes very space consuming
Solution Approach 1:
The patent transitions from planar waveguide bends to three-dimensional resonant cavity modes. By utilizing standing wave patterns in the vertical dimension (different mode numbers m and n), the patent achieves optical path difference without requiring large lateral extensions, thus resolving the contradiction between path length and device area.
Solution Approach 2:
The patent changes the fundamental parameter from physical path length (requiring bends) to resonant mode parameters (m, n). By adjusting mode numbers and cavity dimensions, the effective optical path difference is achieved through phase relationships in standing waves rather than physical distance, dramatically reducing the required device area.
2Manufacturing precision
If Mach-Zehnder interferometer design is used to achieve sinusoidal transmission, then the transmission spectrum is predictable, but the device consumes a lot of space due to waveguide bends
Solution Approach 1:
The patent creates an optical equivalent of the Mach-Zehnder interferometer by using resonant cavity modes that replicate the sinusoidal interference pattern. The standing wave modes in the cavity copy the functional behavior of Mach-Zehnder arms without requiring the physical space of actual waveguide paths, achieving the same transmission characteristics in a compact form.
3Area of stationary object
If ring resonator is used for compact interferometer, then the device size is reduced, but the transmission spectrum becomes Lorentzian shaped and sensitive to fabrication variations
Solution Approach 1:
The patent introduces a specific resonant cavity structure with controlled boundary conditions as an intermediary between the compact ring resonator and the stable interference pattern. This cavity structure mediates the relationship between size reduction and spectral stability by providing well-defined mode patterns that are less sensitive to fabrication variations while maintaining compact dimensions.
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 design reduces the size of the interferometer, increases optical throughput, and enhances spectral resolution, enabling a higher density of interferometers on a spectrometer chip for improved Raman spectrum analysis.
Implementation Method 1
The interferometer comprises a input waveguide (110) which is coupled to a multimode waveguide (120)... distributed by the multimode waveguide (120) into a first wave (131) in a first waveguide (130) and a second wave (141) in a second waveguide (140)
Implementation Method 2
an input waveguide (110) which is coupled to a multimode waveguide (120)... first waveguide (130)... second waveguide (140)
Implementation Method 3
The first waveguide (130) is terminated by a first waveguide mirror (150)... The second waveguide (140) is terminated by a second waveguide mirror (160)... reflected by the first and second waveguide mirror (150, 160), respectively, back in the first and second waveguide (130, 140)
Implementation Method 4
positioning readout structures to concentrate reflected light based on phase differences between waveguides
Implementation Method 5
the at least one signal readout structure of the interferometer is positioned such that for a selected wavelength range of the light signal, the reflected light concentrates on the signal readout structure
Data Source
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AI summary
An interferometer (100) comprising a multimode waveguide (120) to which an input waveguide (110) is coupled at one side thereof. A first waveguide (130) is optically coupled to a second side of the multimode waveguide (120), and is terminated by a first waveguide mirror (150). A second waveguide (140) may be optically coupled to a second side of the multimode waveguide (120) and terminated by a second waveguide mirror (160), or a second waveguide mirror (160) may be directly optically coupled to a second side of the multimode waveguide (120). The multimode waveguide is adapted to distribute a light signal from the input waveguide (110) towards the first (150) and second (160) waveguide mirror via the first waveguide (130) and, if present, via the second waveguide (140). The interferometer comprises at least one signal readout structure (170) positioned for receiving reflected light from the first (150) and/or second (160) waveguide mirror with a power that depends on the phase difference between the two reflected waves.