The IO-D Series "Aspirin Tablet" Isolators
are designed for applications requiring a very small Isolator. These
Isolators utilize BIG (bismuth-iron-garnet) film as the Faraday
rotating material. To retain the very small size, dichroic Very
Low Power Polarizers are used. Isolator bodies are Aluminum or Stainless Steel. Stainless steel bodies use approved zero outgassing epoxies for vacuum environment applications. VLP Polarizers absorb the unwanted
polarization vector, and are therefore limited in laser power capability.
See page IO-3 for polarizer information.
Aspirin Tablet Isolators are set at the OFR factory to the exact
laser wavelength for maximum isolation and transmission, and cannot
be readjusted thereafter. When ordering, specify the desired peak
wavelength, for example, IO-D-780.
The small body size is made possible by the extremely high Verdet
constant of the BIG film. For example, film thickness for 45°
rotation at 1310 nm is only ~330 µm. In addition, BIG films
are characterized by a low saturating magnetic field value, only
a few hundred Gauss, thus enabling performance with a small magnet.
The final result is an Isolator of small dimensions.
|At 1310 nm and 1550 nm, transmission is >96%. However,
in the NIR wavelengths, 760-850 nm, absorption is already increasing,
and transmission is around 30-50%. This is the tradeoff for the small
size, made possible because of the high Verdet constant of the BIG