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Etalon
An etalon is an optical interferometer in which a beam of light undergoes multiple reflections between two
reflecting surfaces, and whose resulting optical transmission (or reflection) is periodic in wavelength. Actually
it is narrowband wavelength filters. Etalons can be used as precise wavelength references in
telecommunication applications where the periodicity of the signal provides an array of reference frequencies
for the telecommunication frequency grid. When used with active feedback electronics, etalons form the basis
of wavelength locking systems that can be used to stabilize the wavelength of a laser.
The typical Etalon types Photop can offer are Air-space and Solid.
Air-Spaced Etalons are two extremely parallel plates polished to very tight specification with an air gap
between them. Using a ULE or fused silica as a space that is optically contacted between the two plates
creates the air gap. Designed with special partial reflecting etalon coatings and AR coatings results in
improved transmission. The mechanical design is robust and our etalon has great thermal stability. Photop's
Air-spaced Etalons are available in a wide range of FSR values from 1500 GHz to 10 GHz.
Air-Spaced Etalons
Solid Etalons
Partial reflection etalon coating on both sides of very good polished substrate, its high quality cavities result in
higher transmission a compact size and lower cost. These etalons have the potential for a high damage
threshold and are particularly good for intercavity use. Our Solid Etalons are also available in a wide range of
FSR values from 1500 Ghz to 10 Ghz.
Teleco
m O
ptics
Teleco
m O
ptics
Features:
High Precision FSR Tolerance
Optical Contact Available upon Request
High Damage Threshold
Great Thermal Stability
Telcordia Compliant
High Transmission
Easy Tenability
Applications:
WDM Networks
Tunable Filter
Wavelength Locker
Dispersion Compensation
Laser Cavity
Interleavers
2008Rev.A
253 Fuxin East Road, Fuzhou, Fujian 350014 P.R. China Tel: +86-591-83610157/ 83610592
Fax: +86-591-83610136 E-mail: [email protected] www.photoptech.com/optics
Type 1: Principle of Air-Space Etalon
Wavelength (nm)
1500 1520 1540 1560 1580
-5
T
ra
n
sm
issio
n
(dB
)
-4
-3
-2
-1
1600
Incident angle 0deg
5deg
1
0
Type 2: Transmission curve
Light Entering
and Exiting an
Air-Spaced
Etalon
R1 R2
Out 2Out 1
Air
Input
The frequency separation between adjacent peaks is termed the Free Spectral Range(FSR).
The full width at half maxmum of peaks is termed FWHM. It is given by the following formula:
Principle of Etalon:
The Finesse (F) is given by:
The Finesse (F) indicates sharp extent of interference stripe. The factor that affects finesse is the
reflectivity of the mirrors, surface figure and parallelism.
FWHM= inHz
FSR
Finesse
F=Finesse= =
p.
(R1
.
R2)
1/ 4
1- R1
.
R2
FSR
FWHM
T
eleco
m O
ptics
T
eleco
m O
ptics
2008Rev.A
253 Fuxin East Road, Fuzhou, Fujian 350014 P.R. China Tel: +86-591-83610157/ 83610592
Fax: +86-591-83610136 E-mail: [email protected] www.photoptech.com/optics
Teleco
m O
ptics
Teleco
m O
ptics
Etalon
Material: Schott Zerodur, Corning ULE or Fused Silica
Typical Type: Air-space, Solid Etalon
Standard Size: 4 x 3 x 6mm
Parallelism: 1 arc second
Dimension Tolerance: +0/-0.2mm
Flatness: /20 @632.8nm
Typical FSR: 25, 50, 100, 200G
Typical FSR Tolerance: +/- 0.02G for 50-100G
+/- 0.04G for 100-200G
Surface Quality (scratch/dig): 10-5
l
better than
better than
Other sizes, FSR and coatings are also available upon request.
2008Rev.A
253 Fuxin East Road, Fuzhou, Fujian 350014 P.R. China Tel: +86-591-83610157/ 83610592
Fax: +86-591-83610136 E-mail: [email protected] www.photoptech.com/optics
