Optical characterisation facilities

Optical conoscope

A convergent beam polarizing optical conoscope system is available for the study of liquid crystal cells. This uses 632.8 nm radiation and has flow cell capability for exploring the director profiles in liquid crystal cells under pressure driven flow.

Angle scanned optical systems

Three computer controlled angle-scan optical systems are available for the study of the angle dependent reflectivity and transmissivity of thin film systems using single wavelength well-collimated sources.

Polarising microscope

Several polarizing microscopes are available for the optical study of liquid crystal cells as well as for the exploration of other microstructured photonic surfaces.

Micro-spectroscopy

Spectroscopy in the visible in reflection, transmission and by dark-field is available using a system based on a CCD coupled to a grating spectrometer and a Nikon inverted microscope

Scatterometer system

An optical system for imaging the angle-dependent and polarisation-dependent reflection or transmission scattering from the entire hemisphere above or behind a sample, and in this way measuring it reflection distribution function.

Magneto-optical Kerr effect magnetometer

Magnetic hysteresis loops may be acquired in either reflection or transmission geometries. Light sources include a continuous wave laser (633 nm) and a Xenon lamp with monochromator. Balanced photodiode polarizing bridge detectors are used, including qudarant photodiode detectors so that all three components of the magnetization vector may be detected simultaneously with a tightly focused optical spot.

Torque magnetometer

A cantilever torque magnetometer is used to investigate magnetic anisotropy and demagnetising fields of thin films and nanostructures. The system is based on a 7 Tesla superconducting magnet cryostat (‘MagLab - 8’, Oxford Instruments) with a variable temperature insert (1.4-300K). The temperature is maintained through a PID regulated needle valve maintaining minimum mechanical vibrations. The measurements are automated via a LabView interface and can be programmed to combine temperature-field-angle regimes. The cryostat has a capability to work with other experiments, including magneto-resistive measurements, using separate inserts and the corresponding electronic equipment.