Voigt & Faraday Geometry
attoCFM I configurations
For many samples studied with confocal microscopy under magnetic
fields, switching between the out-of-plane (Faraday) and in-plane
(Voigt) geometry reveals inter-esting differences in behavior. Our new
ASH/QE/4CX/CFM sample holder in conjunction with the LT-APO and
Voigt objectives respectively allows to study both configurations for
one sample within only a few minutes for switching between both set-
ups ex-situ (i.e. after warming up the microscope insert). The ASH/QE/4CX/CFM sample holder consists of a base plate including
a calibrated temperature sensor and a heater, and a quick exchange
slider for the sample PCB in two alternative configurations. In addi-
tion, it features 8 electrical contacts on the PCB, which is identical for
both configurations. Hence, upon switching from Faraday to Voigt, no
rebonding of the sample wires is required – only the PCB is unmounted
from the Faraday holder, and remounted on the Voigt holder plate.
In Faraday geometry, the sample is aligned horizontally, such that
the vertical magnetic field of a typical single solenoid (such as in the
attoDRY1000/1100/2100) is out-of-plane. In this configuration, any
of the LT-APO objectives can be used. In Voigt geometry on the other
hand, the PCB that hosts the sample is mounted vertically parallel to
the magnetic field onto the quick exchange slider, and the LT-APO is
exchanged by the Voigt-IWDO objective. The latter takes care that the
optical beam is deflected by 90° into the horizontal direction, and
focused onto the sample by the IWDO lens. Only the 8 pin connectors for the wiring need to be unplugged and re-
connected. Typically, the 8 pins are connected to 4 coaxial wires in our
microscope insert, that terminate in a vacuum feedthrough with SMA
connectors on the outside.Both configurations are compatible with
the closed loop scanning option (attoFPS based interferometer with 1
nm resolution). In case a scanner is required, the large range scanners
ANSxy100/lr and ANSz100/lr yield a combined scan range of 50 µm
x 50 µm x 50 µm @ 300 K or 30 µm x 30 µm x 30 µm @ 4 K, and hence
allow for horizontal or vertical scans with the same full range of 50 µm
in either configuration.