PhD Oral Exam - Vinh Son Tran, Physics
When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
The refractive indices of vanadium dioxide (VO2) abruptly change when its phase transition temperature of 68oC is reached, the point at which it goes from an insulating state to a metallic state. Modifications of complex-valued refractive indices in VO2 have been shown to produce optical phase shifts that are unequal for the s- and p-components of polarization, thereby causing a relative phase shift Δ between the two. Under certain conditions of Δ, a linearly polarized light can rotate its polarization 90 degrees or transforms between linear and circular. In this thesis, we will demonstrate all possibilities of using a VO2 thin film to change the polarized light states of reflected or transmitted light on the nanosecond and potentially shorter timescales. Possible applications for high-contrast optical modulation over a wide spectral range are discussed.