Multi-Resolution Spectrometer Using VIPA and Grating
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Solution Overview
Problem
High-resolution optical spectrometers typically have a limited free spectral range, restricting their ability to distinguish between overlapping wavelengths and requiring additional dispersive elements to broaden their operating range, which often results in a trade-off between spectral resolution and measurement spectral window.
Innovation Solution
A spectrometer design incorporating two dispersive elements, including a VIPA and a second element like a diffraction grating, with one element having a smaller free spectral range than the operating wavelength range, and two lenses of different focus lengths to separately focus dispersed light onto 2D detector arrays, allowing for higher spectral resolution in a narrower wavelength band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a VIPA with high angular dispersion is used to achieve high spectral resolution, then the spectral resolution is improved, but the free spectral range becomes limited and overlapping wavelengths cannot be distinguished
Solution Approach 1:
The patent introduces a second dispersive element (diffraction grating or prism) oriented perpendicular to the VIPA dispersion direction, adding a second dimensional separation of wavelengths. This cross-orientation dispersion allows wavelengths separated by one VIPA FSR to be spatially separated in the orthogonal direction, effectively extending the operational range beyond the single VIPA FSR limitation while maintaining high spectral resolution from the VIPA.
2Measurement precision
If the spectral resolution is increased by adjusting the VIPA and detector configuration, then the measurement precision is improved, but the measurement spectral window becomes narrower
Solution Approach 1:
By adding the second dispersive element in cross-orientation, the system maps the spectral information onto a two-dimensional detector plane. The VIPA provides high resolution in one dimension while the second element expands the wavelength range in the orthogonal dimension, allowing both high spectral resolution and broader measurement spectral window to be achieved simultaneously through the 2D spatial encoding of spectral data.
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
This configuration enables a broader operating wavelength range while maintaining high spectral resolution, allowing for more effective separation of wavelengths and improved spectral analysis without the traditional trade-offs between resolution and window size.
Implementation Method 1
a virtually imaged phase array (VIPA), which is an optical component that has a very high angular dispersion D=dθ/dλ, where θ is a dispersion angle at which light of wavelength λ is dispersed by the VIPA
Implementation Method 2
the output beams have a well-defined phase relationship, which interference in a focal plane of a lens results in a strong angular dispersion
Implementation Method 3
a second dispersive element in a cross-orientation with the VIPA may be added after the VIPA to allow separation of these otherwise overlapping wavelengths
Implementation Method 4
the focal length of a lens that focuses the dispersed light upon the camera
Data Source
AI summary
The invention relates to a multi-resolution optical spectrometer that employs two output lenses of different focal length to provide a broad wavelength range, coarse resolution spectral measurement and a high resolution, lower range spectral measurement. Light dispersed by a virtual image phase array followed by a diffraction grating in two different dispersion orders may be separately focused by the two lenses upon to 2D detector array to provide the two measurements.