Optical Resonant Cavity and Demultiplexer for High-Resolution Spectrometry
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Solution Overview
Problem
Current spectrometer designs face challenges in achieving high resolution, wide spectral range, and small footprint, with existing technologies like etched diffraction gratings and arrayed waveguide gratings limited by the number of grooves/waveguides, leading to increased device size and complexity, and optical attenuation issues in serial cascading of ring resonators.
Innovation Solution
An optical spectrometer apparatus combining an optical resonant cavity with a wavelength demultiplexer, generating a wavelength comb of sharp resonances that are spatially separated, achieving higher resolution than the demultiplexer alone, with the cavity and demultiplexer having a free spectral range matched for enhanced channel spacing and spectral range, and the apparatus being tunable and integrally disposed on a planar photonic circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If etched diffraction gratings or arrayed waveguide gratings are used to improve resolution, then the number of grooves/waveguides must increase, but the device area increases with the square of the resolution improvement
Solution Approach 1:
The invention segments the spectral analysis function into two independent parts: (1) an optical resonant cavity that generates a wavelength comb with sharp resonances at specific wavelengths, and (2) a wavelength demultiplexer that spatially separates these wavelengths. This segmentation allows the cavity to provide high resolution through its narrow resonance linewidths while the demultiplexer provides wavelength separation, decoupling the resolution from the device area.
Solution Approach 2:
The invention introduces an optical resonant cavity as an intermediary component between the light source and the demultiplexer. The cavity generates a wavelength comb of sharp resonances that act as a high-resolution spectral reference, which is then fed into the demultiplexer. This intermediary enables the system to achieve resolution determined by the cavity's quality factor rather than by the number of demultiplexer channels.
2Measurement precision
If arrayed waveguide gratings employ high order diffraction to improve resolution, then the free spectral range decreases, but the spectral range available is reduced
Solution Approach 1:
The invention makes the spectral analysis system tunable by using a tunable optical resonant cavity whose resonance wavelengths can be adjusted. This allows the wavelength comb generated by the cavity to be tuned across different spectral ranges, enabling the same device to operate at different wavelengths and spectral regions, thereby providing adaptability and versatility without sacrificing resolution.
3Measurement precision
If ring resonators are used to achieve high resolution with small device area, then individual tuning is required for each resonator, but the system complexity increases
Solution Approach 1:
The invention merges multiple ring resonators into a single integrated optical resonant cavity structure that generates a wavelength comb with multiple sharp resonances. Instead of requiring individual tuning of separate resonators, the combined cavity structure produces a comb of resonances at regularly spaced wavelengths, all of which can be simultaneously utilized. This merging reduces the number of independently tunable elements and simplifies the overall system.
4Quantity of substance
If a very large number of ring resonators are serially cascaded to increase channel density, then optical attenuation increases, but the insertion loss accumulates
Solution Approach 1:
The invention transitions from increasing channel density by adding more resonators in series (one-dimensional scaling) to generating a wavelength comb with multiple channels simultaneously from a single cavity (dimensional transformation). The cavity generates N sharp resonances at different wavelengths that are then spatially separated by the demultiplexer, achieving high channel density without serial cascading and thus avoiding cumulative insertion losses.
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 enables a high-resolution, wide spectral range spectrometer with a small footprint, achieving channel spacing of 0.1 nm and over 100 channels, with a footprint of 2 mm^2, and allows for increased channel density through serialization techniques, significantly reducing device size compared to traditional demultiplexers.
Implementation Method 1
an optical resonant cavity having an input, an output, wherein multiple wavelengths that are matched to the cavity resonances and separated by a free spectral range (FSR) can be transmitted from the input to the output
Implementation Method 2
a wavelength demultiplexer having an input and a plurality of outputs, wherein the optical resonant cavity output is coupled to the demultiplexer input, further wherein the demultiplexer outputs are characterized by a channel spacing that is closely matched to the free spectral range of the optical resonant cavity
Data Source
AI summary
A high resolution, wide spectral range, optical apparatus that includes an optical resonator cavity and a wavelength demultiplexer, arrangeable in multiple configurations. A method for increasing the resolution of a wavelength demultiplexer involves inputting light into an optical resonant cavity; inputting a plurality of different resonant output wavelengths to a wavelength demultiplexer; and routing each different resonant wavelength to a different output waveguide of the demultiplexer to generate a demultiplexer output spectrum. The method further involves performing either a time serialization or a space serialization procedure to increase the channel density and fully cover the spectrum of interest.