Wavelength Selection Devices 1. Absorption Filters 2. Interference Filters 3. Prism Monochromators...

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Wavelength Selection Devices 1. Absorption Filters 2. Interference Filters 3. Prism Monochromators 4. Grating Monochromators 5. Interferometers

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  • Wavelength Selection Devices 1. Absorption Filters 2. Interference Filters 3. Prism Monochromators 4. Grating Monochromators 5. Interferometers
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  • 1. Absorption Filters Optical material containing an absorber that permits transmission only at certain wavelengths
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  • 2. Interference Filter A sandwich of at least two parallel optical flats that transmit only rays that undergo constructive interference.
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  • 3. Prism Monochromator Wavelength selection device containing a movable prism.
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  • Snells Law of Refraction n 1 sin 1 = n 2 sin 2
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  • 4. Grating Monochromator Wavelength selection device based on the constructive interference of light rays that have traveled different differences to reach the same point. Work via: (1) transmission, or (2) reflection
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  • Reflection Grating:
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  • Linear Dispersion D l D l = f D a = dx/d where: f = focal length (of monochromator) x = distance (along focal plane)
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  • Spectral Bandpass (s or ) s = RLD w where: w = slit width (mm) s in nm Reciprocal Linear Dispersion (RLD) RLD = D l -1 =d/dx nm/mm
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  • Echelle prism ICP Camera
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  • Rowland Circle
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  • Limitations??
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  • 5. Interferometer Allows multiple wavelengths to fall on the detector simultaneously. Corrects for interference patterns to calculate the signal at different wavelengths.
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  • Fabrey-Perot Interferometer
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  • Michelson Interferometer
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  • Interferometer Advantages 1. Fellgets Advantage (multiplex) 2. Jacquinots Advantage (throughput) 3. Wavelength Accuracy
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  • Interferometer Disadvantages 1. Fellgets Disadvantage (multiplex) 2. Low wavelengths 3. $$$ for high resolution