Dr. Roohollah Ghobadi, Ms Samira Gholizadeh, Dr. Mojtaba Mazaheri,
Volume 9, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol 9, No 1, Winter-Spring 2015)
Abstract
One of the main milestones in the study of opto-mechanical system is to increase the sensitivity of weak forces measurement up to the standard quantum limit. We have studied the detection of weak force under a bistable condition in red detuned regime. In this case, dynamics of the system behaves asymptotically similar to stationary state and applying external force affects phase and fluctuation of the cavity field. Using the signal to noise ratio, we have found the sensitivity of the system to external force. The system show the maximum sensitivity in the region where bistability approaches zero. We also studied the destructive effects of thermal noise on the sensitivity. Our approach is based on the covariance matrix formalism which can be solved by first Lyapunov theorem.
Ahmadzia Sherzad, Hakimeh Zare, Zahra Shahedi, Fatemeh Ostovari, Yousef Fazaeli, Zeinab Pourghobadi,
Volume 14, Issue 2 (Summer-Fall 2020)
Abstract
Luminescent graphene oxide quantum dots (GOQDs) have attracted tremendous attention from scientists in chemistry, materials, biology, and physics science. They have specific properties such as low cytotoxicity, excellent electrochemical and optical properties, resistance to photo-bleaching, and good stability. In this study, GOQDs were synthesized using a simple and straightforward methodology. The synthesized GOQDs were characterized by Fourier Transform Infrared (FTIR) analyzer, ultraviolet–visible spectrophotometry (UV–VIS) absorption, Photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM) analyses. Then, optical properties of GOQDs such as absorption and luminescence with various pH values were investigated. GOQDs show absorption in the ultraviolet (UV) region and their position of photoluminescence peak is independent of pH value. The average size of QDs is less than 5 nm, as revealed by TEM. The GOQDs show green luminescence under UV irradiation (360 nm).
