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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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Presentation on theme: "Wavelength Selection Devices 1. Absorption Filters 2. Interference Filters 3. Prism Monochromators 4. Grating Monochromators 5. Interferometers."— Presentation transcript:

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

2 1. Absorption Filters Optical material containing an absorber that permits transmission only at certain wavelengths

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8 2. Interference Filter A “sandwich” of at least two parallel optical flats that transmit only rays that undergo constructive interference.

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12 3. Prism Monochromator Wavelength selection device containing a movable prism.

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14 Snell’s Law of Refraction n 1 sin Θ 1 = n 2 sin Θ 2

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18 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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21 Reflection Grating:

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25 Linear Dispersion D l D l = f × D a = dx/dλ where: f = focal length (of monochromator) x = distance (along focal plane)

26 Spectral Bandpass (s or Δλ) s = RLD × w where: w = slit width (mm) s in nm Reciprocal Linear Dispersion (RLD) RLD = D l -1 =dλ/dx nm/mm

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31 Echelle prism ICP Camera

32 Rowland Circle

33 Limitations??

34 5. Interferometer Allows multiple wavelengths to fall on the detector simultaneously. Corrects for interference patterns to calculate the signal at different wavelengths.

35 Fabrey-Perot Interferometer

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37 Michelson Interferometer

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39 Interferometer Advantages 1. Fellget’s Advantage (multiplex) 2. Jacquinot’s Advantage (throughput) 3. Wavelength Accuracy

40 Interferometer Disadvantages 1. Fellget’s Disadvantage (multiplex) 2. Low wavelengths 3. $$$ for high resolution


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