Chirped-Grating Waveguide Spectrometer for Compact High Resolution
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Solution Overview
Problem
Existing integrated optical spectrometers face challenges in achieving high resolution, compact size, and CMOS compatibility, particularly for free-space input applications, with limitations in spectral resolution and fabrication complexity as the number of pixels increases.
Innovation Solution
A planar waveguide spectrometer with a chirped input coupling grating and detector array, fabricated in a single lithography step, provides spectrally selective coupling and filtering, enabling high-resolution spectral analysis with CMOS compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional grating approaches are miniaturized, then device size is reduced, but spectral resolution deteriorates due to the inverse relationship between path length and resolution
Solution Approach 1:
The patent transitions from free-space propagation to waveguide-confined propagation, changing the dimensional space from 3D to 2D. This allows the light to travel through a longer effective path length within a compact footprint by confining it to a planar waveguide structure, thereby maintaining high spectral resolution while achieving miniaturization.
Solution Approach 2:
The spectrometer is segmented into distinct functional regions: a chirped grating region for wavelength-dependent coupling, a propagation region for filtering, and a detection region. This segmentation allows each region to be optimized independently, with the propagation region providing extended path length for high resolution while keeping the overall device compact.
2Measurement precision
If the number of pixels is increased, then measurement precision is improved, but fabrication complexity increases
Solution Approach 1:
The chirped grating structure serves multiple functions simultaneously: it acts as a dispersive element, a coupling interface, and a wavelength selector. This multi-functionality eliminates the need for separate components, reducing fabrication complexity while maintaining high spectral resolution through the grating's spatially varying period.
Solution Approach 2:
The patent merges the grating structure with the waveguide, creating an integrated chirped-grating waveguide. This combination eliminates the need for separate alignment and assembly steps, simplifying fabrication while enabling high-resolution spectral analysis through the integrated structure's inherent dispersive properties.
3Measurement precision
If Mach-Zehnder interferometers are used, then spectral resolution is improved, but device complexity and space requirements increase
Solution Approach 1:
The patent extracts the dispersive function from complex interferometric structures and implements it through a simpler chirped grating coupled to a waveguide. This extraction maintains the ability to achieve high spectral resolution while eliminating the need for complex interferometer architectures, reducing both device complexity and space requirements.
4Adaptability or versatility
If free-space input is implemented, then adaptability is improved, but spectral resolution deteriorates due to limited path length
Solution Approach 1:
The patent introduces a chirped grating as an intermediary element between the free-space input and the waveguide. This grating mediates the coupling by providing wavelength-dependent angular selection, allowing free-space input adaptability while the subsequent waveguide propagation provides the extended path length needed for high spectral resolution.
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 spectrometer achieves a resolution of 0.3 nm at 633 nm without signal processing deconvolution, offering a cost-effective, compact, and CMOS-compatible solution for a wide spectral range, suitable for various spectroscopic applications.
Implementation Method 1
a chirped input grating formed to couple incident light into the planar waveguide, wherein the chirped input coupling grating comprises a first transverse chirp to provide a spectrally selective coupling of incident light into the planar waveguide
Implementation Method 2
a propagation region to filter out light that is not coupled into the planar waveguide
Implementation Method 3
a detector array arranged on the opposite side of the propagation region from the chirped input coupling grating to receive light coupled out of the planar waveguide and produce output signals representative of the light
Data Source
AI summary
A spectral sensor and a method for forming the spectral sensor is disclosed. The spectral sensor includes a planar waveguide on a substrate; a restriction mechanism that restricts a range of angles of incidence of light impinging onto the chirped input coupling grating; the chirped input grating formed to couple incident light into the planar waveguide, wherein the chirped input coupling grating comprises a first transverse chirp to provide a spectrally selective coupling of incident light Into the planar waveguide; a propagation region to filter out light that is not coupled into the planar waveguide; a detector array arranged on the opposite side of the propagation region from the chirped input coupling S grating to receive light coupled out of the planar waveguide and produce output signals representative of the light; and an electrical circuit to readout output signals from the detector array.