The FORTH’s team has recently demonstrated an extremely fast and sensitive ellipsometer, based on the amplification of the ellipsometric angle by multiple reflective passes (at least 100 and as many as a million) at the interface in question. It is able to make senstive measurements on timescales as fast as microseconds (at least), with applications including biosensing, microelectronics, and surface dyanmics. The FORTH research effort will be integrated with a larger research activity funded by an ERC Starting Grant (TRICEPS), which focuses on the development of basic scientific principles of cavity-enhanced metrology. The scientific and technological aim of the project is to investigate the commercial viabilty of the new ellipsometric techniques, and it's use to probe a range of time-dependent surface phenomena, with unprecedented time resolution and sensitivity. The proposed collaboration will be fruitful for both parties for the following reasons: a) The IESL-FORTH team has demonstrated a very promising technique (in the field where SOPRA is a world leader), but lacks experience in commercial instrument development. The research and product development is best done in conjunction with a leading company with experience with similar successful products. b) The new technique will substantially enhance the time-resolution of the classical ellipsometer by orders of magnitude (down to microseconds at least) and nonetheless remain technically simple. It will also be applicable to a new range of research, and will appeal to a wider client base, which of interest to SOPRA. c) IESL-FORTH will benefit from interaction with an industrial partner, by gaining experience in how a product should be developed, and learning about the problems that such development entails. SOPRA will benefit from contact with academic research by learning about new applications outside of its existing field of expertise.