Fused Silica Etalons |
Background We offer the world's finest solid and air spaced etalons, with fluid jet polishing systems allowing us to routinely provide surfaces that are better than lambda/100 peak to valley.
We have extensive expertise in the provision of all kinds of Fabry Perot etalons from 1mm square to 100mm in diameter. These devices require high quality, very flat optical surfaces and extreme parallelism to achieve high performance, making them a good match for the polishing and metrology at LightMachinery. Etalons can be made from a wide variety of materials including; Fused Silica, Silicon and even Air. Use a simple web based etalon calculator to determine the thickness and coating reflectivity to meet your requirements. Fused Silica Etalons Refer to our our standard solid fused silica etalons (we provide a lot of custom etalons so feel free to send us a request if these don't meet your needs or you require a thin film coating to enhance the finesse). Solid fused silica etalons are simple devices with a wide variety of applications in spectroscopy and lasers. We have 3 styles of fused silica etalon;
Air Spaced versus Solid Etalons Solid etalons are simple, flat, very parallel optical components. Sometimes these etalons are used uncoated using only the 4% fresnel refection to provide the etalon effect. etalon-
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Features |
Applications |
Standard
Specifications |
Technolgoy |
The Fabry Perot interferometer consists of two parallel flat semi-
The transmission spectrum of an etalon will have a series of peaks, where constructive interference occurs, spaced by the 'free spectral range' or FSR. As seen on the right in our online etalon designer. If the absorption and scattering losses are small, the reflection spectrum of the etalon is 1 -
FSR = 1/2nd cm-
FSR = lambda2 /2nd nm (wavelength)
FSR = c/2nd Hz (frequency)
You will notice that the mirror reflectivity is not part of these equations. The mirror reflectivity does not affect the FSR, it affects the number of bounces and improves the quality of the modulation (more perfect bounces = better modulation). etalon-
Bandwidth is the full width at half maximum (FWHM) of the peak
Bandwidth = FSR / F
The finesse is a dimensionless quantity and the units of the Bandwidth are the same as the FSR.
Another quantity, The Coefficient of Finesse, F, = 4R/(1-
F=PI/SQRT(4R/(1-
Actual versus Theorectical Performance
Etalons are usually described in terms of FSR and finesse. In many textbooks, the finesse is calculated using only the parameter R, reflectivity of the mirrors as in F=PI/SQRT(4R/(1-
Limits to Finesse
In reality there are other factors that 'limit' the transmission and finesse such as surface irregularity, parallelism, coating scatter. Each one makes a contribution to limiting the finesse and then all these contributions are combined to come up with the expected finesse and transmission. In our etalon calculator the graph displays both the perfect theoretical transmission and the expected transmission taking into account all the defects in a real etalon.
Surface Figure
Surface figure is the rms variation of surface away from flat. Spherical error is excluded from the rms surface figure and is treated separately. Surface figure is usually measured at the HeNe laser wavelength of 633nm and is expressed as fractions of this wavelength. The numbers that are included in the calculator are examples of practical values such as;. 633/20 = 30nm and a more difficult to achieve, 633/200 = 3nm.
Tilt or Wedge
End mirrors that are not parallel cause a change in the phase of the beam across the etalon. This results in reduced finesse since not all the beam is emerging 'in phase' creating a bright fringe or 'out of phase' creating a dark fringe. The result is a low contrast mixing of dark and bright fringes.
Spherical Error
The same is true of spherical error, the phase of the light varies over the surface of the etalon due to the curvature of the surfaces. The errors caused by both Wedge and Sphere are predictable and can be calculated in specific ways which is why they are called out specifically in our calculations for expected performance.
Scatter and Material Losses
Scatter causes light to leak out of the etalon while materials will absorb light during each pass. These losses are usually insignificant if the proper coatings and materials are used unless the finesse is very high (above ~200).
Each of the parameters that effects the finesse also limits the finesse to some value. etalon-
Specifying Etalons
Etalons are generally specified by
All of these specifications are measurable, functional specifications. The reason that mirror reflectivity is not generally specified is that the reflectivity does not guarantee performance. Scatter, surface errors and tilt can significantly reduce finesse and transmission below the finesse that would be expected from a given reflectivity.
Item |
Solid Fused Silica Etalons |
Part No |
Description |
1 |
2x4mm 25um thick |
2mm x 4mm, 25um thick, FSR 4023GHz, uncoated, finesse = 0.6 |
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2 |
2x4mm 50um thick |
2mm x 4mm, 50um thick, FSR 2011GHz, uncoated, finesse = 0.6 |
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3 |
2x4mm 88um thick |
2mm x 4mm, 88um thick, FSR 1143GHz, uncoated, finesse = 0.6 |
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4 |
2x4mm 100um thick |
2mm x 4mm, 100um thick, FSR 1005GHz, uncoated, finesse = 0.6 |
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5 |
2x4mm 200um thick |
2mm x 4mm, 200um thick, FSR 502GHz, uncoated, finesse = 0.6 |
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6 |
2x4mm 300um thick |
2mm x 4mm, 300um thick, FSR 335GHz, uncoated, finesse = 0.6 |
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7 |
1/2" diameter mount for 2 x 4mm etalons |
A 1/2" diameter aluminum mount designed to hold 2x4 mm etalons. |
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8 |
5x5mm 25um thick |
5mmx5mm, 25um thick, FSR 4023GHz, uncoated, finesse = 0.6 |
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9 |
5x5mm 50um thick |
5mmx5mm, 50um thick, FSR 2011GHz, uncoated, finesse = 0.6 |
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10 |
5x5mm 88um thick |
5mmx5mm, 88um thick, FSR 1143GHz, uncoated, finesse = 0.6 |
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11 |
5x5mm 100um thick |
5mmx5mm, 100um thick, FSR 1005GHz, uncoated fused silica etalon |
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12 |
5x5mm 107um thick |
5mmx5mm, 107um thick, FSR 940GHz, uncoated, finesse = 0.6 |
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13 |
5x5mm 200um thick |
5mmx5mm, 200um thick, FSR 502GHz, uncoated, finesse = 0.6 |
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14 |
5x5mm 300um thick |
5mmx5mm, 300um thick, FSR 335GHz, uncoated, finesse = 0.6 |
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15 |
5x5mm 1000um thick |
5mmx5mm, 1mm thick, FSR ~100GHz, uncoated, finesse = 0.6 |
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16 |
5x5mm 2000um thick |
5mmx5mm, 2mm thick, FSR ~50GHz, uncoated, finesse = 0.6 |
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17 |
5x5mm 3000um thick |
5mmx5mm, 3mm thick, FSR ~33GHz, uncoated, finesse = 0.6 |
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18 |
5x5mm 5000um thick |
5mmx5mm, 5mm thick, FSR ~20GHz, uncoated, finesse = 0.6 |
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19 |
5x5mm Etalon Mount |
OP- |
1" diameter mount designed to hold 5mm x 5mm etalon |
20 |
FSR= 2/cm, finesse =6 |
1.68mm thick, 1" diameter, nominal finesse = 6, 450 to 650nm, clear aperture 85%, |
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21 |
FSR= 1/cm, finesse = 6 |
3.37mm thick, 1" diameter, nominal finesse = 6, 450 to 650nm, clear aperture 85% |
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22 |
FSR= 0.5/cm, finesse = 6 |
6.74mm thick, 1" diameter, nominal finesse = 6, 450 to 650nm, clear aperture 85% |
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23 |
FSR = 2/cm, Finesse >30, 530nm to 660nm |
1" diameter, clear aperture 20mm, FSR = 2/cm (thickness 1.686mm), Finesse 30 min. (35 typical) |
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24 |
FSR = 1/cm, Finesse >30, 530 to 660nm |
1" diameter, clear aperture 20mm, FSR = 1/cm (thickness 3.371mm), Finesse 30 (35 typical) |
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25 |
FSR=0.5/cm, Finesse >30, 530nm to 660nm |
1" diameter, clear aperture 20mm, FSR = 0.5/cm (thickness 6.743mm), Finesse 30 min. (35 typical) |
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26 |
FSR = 2/cm, Finesse 30, 700nm to 850nm |
1" diameter, clear aperture 20mm, FSR = 2/cm (thickness 1.686mm), Finesse 30 min. (40 typical) |
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27 |
FSR = 1/cm, Finesse 30, 700nm to 850nm |
1" diameter, clear aperture 20mm, FSR = 1/cm (thickness 3.371mm), Finesse 30 min. (40 typical) |
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28 |
FSR = 0.5/cm, Finesse 30 700nm to 850nm |
1" diameter, clear aperture 20mm, FSR = 0.5/cm (thickness 6.743mm), Finesse 30 min. (40 typical) |
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29 |
FSR = 2/cm, Finesse 30, 850nm to 1100nm |
1" diameter, clear aperture 20mm, FSR = 2/cm (thickness 1.686mm), Finesse 30 min. (43 typical) |
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30 |
FSR = 1/cm, Finesse 30, 850nm to 1100nm |
1" diameter, clear aperture 20mm, FSR = 1/cm (thickness 3.371mm), Finesse 30 min. (43 typical) |
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31 |
FSR = 0.5/cm, Finesse 30, 850nm to 1100nm |
1" diameter, clear aperture 20mm, FSR = 0.5/cm (thickness 6.743mm), Finesse 30 min. (43 typical) |
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32 |
FSR = 2/cm, Finesse 30, 1450nm to 1700nm |
1" diameter, clear aperture 20mm, FSR = 2/cm (thickness 1.686mm), Finesse 30 min. (47 typical) |
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33 |
FSR = 1/cm, Finesse 30, 1450nm to 1700nm |
1" diameter, clear aperture 20mm, FSR = 1/cm (thickness 3.371mm), Finesse 30 min. (47 typical) |
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34 |
FSR = 0.5/cm, Finesse 30 1450nm to 1700nm |
1" diameter, clear aperture 20mm, FSR = 0.5/cm (thickness 6.743mm), Finesse 30 min. (47 typical) |
Stock Parts |