Extremely low loss laser optics
So-called supermirrors in ring laser gyroscope assemblies or certain scientific applications require coated optics with extremely low losses (i.e. absorption and scattering). These mirrors also have a maximum reflectivity with R > 99.998% and total losses < 10 ppm.
LASEROPTIK uses modified IBS machines that are capable to produce coatings on super-polished substrates. The cleanliness of the machines and environment is maintained in dedicated cleanrooms, where also the extensive substrate pre- and aftertreatment takes place.
Measurement devices such as white light profilometers and high resolution microscopes (up to x 1000) for the inspection procedures are in place. A custom built cavity ring-down setup allows to determine the reflection with a precision of up to four decimal places and and to quantify the losses.
The total back scattering (TSB, as referred to in ISO 13696) of a supermirror at 633 nm taken from LASEROPTIK’s current production has been measured at the Fraunhofer Institute for Applied Optics and Precision Engineering in Jena and achieved a value of TSB = 1.1 ppm. The typical absorption and residual transmission of together < 15 ppm is equivalent to a reflectivity of at least 99.998%. For longer wavelengths even 99.999% has been achieved which is very close to the perfect laser mirror with R = 100%.
The results have been confirmed by LASEROPTIK’s in-house cavity ring-down setup and scatter measurement. The use of super-polished substrates with a surface roughness RMS < 0.1 nm is essential for the values mentioned above. Their quality is inspected with a white light profilometer. Below some measured values:
| Scatter TSB | Absorption | Reflection CRD | |
|---|---|---|---|
| HR 532 nm / 0° | 4.9 ppm1) (int. ARS) | 10.2 ppm 2) | > 99.997% 2) (T~5 ppm) |
| HR 633 nm / 0° | 1.1 ppm 1) | > 99.998% (T~5 ppm) | |
| HR 1064 nm / 0° | (< 1 ppm) 3) | < 2 ppm 4) | > 99.999% (T~5 ppm) |
| HR 2940 nm / 0° | 24 ±12 ppm6) | 99.994% 5) (T=36 ppm) | |
1) Measured at IOF Jena; 2) Measured at LZH; 3) Calculated from surface roughness; 4) Measured at ILT Aachen; 5) measured by customer; 6) 1-R-T
Every coating type can be optimized
for every
• substrate material
• wavelength
• reflection/transmis-
sion value
• angle of incidence
• polarization
• GDD value
• ...
Alternatively we can create
a totally new design for you.
