Serpentine Integrated Grating Spectrometer Cross-Dispersion
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Solution Overview
Problem
Integrated dispersive spectrometers are limited by one-dimensional dispersion, leading to restricted resolving power, spectral bin count, and increased size due to the inefficiency in using chip area, higher order free-spectral-range bandwidth limits, and the need for additional components to separate overlapping spectral bins.
Innovation Solution
A serpentine integrated grating spectrometer design incorporating a folded delay line with grating couplers, enabling two-dimensional cross-dispersion and a large optical delay path within a compact footprint, which increases resolving power and spectral bin count by mapping spectral content to a two-dimensional wavelength-beamsteered pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If one-dimensional dispersion is used in integrated spectrometers, then device simplicity is maintained, but resolving power and spectral bin count are limited
Solution Approach 1:
The patent transitions from one-dimensional dispersion to two-dimensional cross-dispersion by introducing a second dispersion dimension through additional waveguide paths and gratings. This dimensional expansion enables simultaneous achievement of high resolving power and large spectral bin count without proportionally increasing device complexity, as the second dimension operates independently to multiply the dispersion capacity.
2Measurement precision
If chip area is increased to accommodate longer delay paths, then resolving power improves, but device footprint increases
Solution Approach 1:
The patent implements nested waveguide structures where delay paths are folded within themselves and within the device footprint. The serpentine waveguide configuration nests the delay path compactly, and the second-dimensional dispersion structure nests additional functionality within the same footprint, achieving long delay paths and high resolving power without proportional area increase.
Solution Approach 2:
By introducing dispersion in a second dimension orthogonal to the first, the patent achieves additional resolving power without extending the chip area in the first dimension. The cross-dispersion geometry allows the delay path to be folded in three-dimensional space while maintaining a compact two-dimensional footprint.
3Quantity of substance
If higher order free-spectral-range bandwidth is used, then spectral coverage increases, but overlapping spectral bins occur requiring additional components
Solution Approach 1:
The patent uses two-dimensional cross-dispersion to separate overlapping spectral bins that would occur in one-dimensional systems. The second dispersion dimension creates an additional separation axis that resolves spectral order overlaps without requiring additional sequential components, thereby increasing spectral bin count while avoiding complexity increase.
Solution Approach 2:
The patent merges the functions of multiple dispersion elements and spectral separation components into a single integrated two-dimensional dispersion structure. By combining first-dimensional and second-dimensional dispersion in one device, it achieves high spectral bin count and overlap resolution without the need for separate sequential components that would increase device complexity.
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 serpentine integrated grating spectrometer achieves an order of magnitude higher resolving power and spectral bins compared to previous integrated photonic designs, with a 0.4 mm² footprint, demonstrating improved performance in compactness and spectral resolution.
Implementation Method 1
The plurality of waveguide segments is M in number and impart a total group delay time τy on light propagating therethrough
Implementation Method 2
Each of the plurality of grating couplers impart a grating coupler delay τx on light propagating therethrough that exceeds (τy/M)
Data Source
AI summary
A serpentine integrated grating spectrometer includes a serpentine delay line and a plurality of grating couplers. The serpentine delay line includes a plurality of parallel waveguide segments that are coplanar in a delay-line plane. The serpentine delay line serially connects each of the plurality of grating couplers. Each of the plurality of grating couplers (i) is located at a respective one of the plurality of parallel waveguide segments, and (ii) direct light propagating in the serpentine delay line out of the delay-line plane. The plurality of waveguide segments is M in number and impart a total group delay time ry on light propagating therethrough. Each of the plurality of grating couplers impart a grating coupler delay tx on light propagating therethrough that exceeds (ty/M), the time delay for a single segment of the M parallel segments.