Studies of adsorption at interfaces by optical techniques: ellipsometry, second harmonic generation and sum-frequency generation

Optical techniques play an increasingly important role in the characterisation of thin films and liquid interfaces. The classical technique of ellipsometry continues to evolve through improvements in instrumentation (particularly in IR) and interpretation. Techniques based on the quadratic nonlinear optical effects of second harmonic generation and sum-frequency generation have reached a stage of development where they can now be applied outside of specialist research laboratories. These effects are forbidden in isotropic media but permitted at interfaces, providing unique surface selectivity where other techniques are swamped by bulk signals. New applications have appeared in the field of colloids and polymers.