Optoelectronic materials and devices

Optoelectronics , the technology dealing with information processing with light, has been around for a long time. However, over the last fifteen years or so it has acquired a new potency, providing us products that could not have been possible without optoelectronics. The optical devices include optical sources, fibers, switches, and receivers. My research in optoelectronic area is focused on the optical detectors.

• Fabricated and studied broadband infrared detectors of YBa ₂ Cu₃O_7-x  thin films. The sensitivity and detectivity of these detectors were measured to be as high as 240 V/W and 0.8x10^-9cm-Hz^1/2/W at temperature of 90 K, respectively. This project was eventually supported by an industrial company.
  
  
• The first confirmed observation of nonthermal optical response in high temperature superconductors The discovery can in principle lead to applications in ultrafast optical switching and other photonic devices. It was demonstrated that the signal is due to the Cooper pair breaking and voltage pulses with 40 ps duration were obtained in an ultrathin YBa₂Cu₃thin film.
  
  
• Investigated the origin of the anomalous photovoltaic signal in high T_csuperconductors.
  
  
• For the first time, developed and studied a highly sensitive and fast porous silicon photodiode. It is demonstrated that close to unity quantum efficiency could be obtained in a wide wavelength range. The response time of the photodetector is as fast as 2 ns. It is also demonstrated that porous silicon film can be used as solar cells to improve the acceptance angle of the sunlight.
  
  
• Develop a three-dimensional computer model for simulating the light absorption and reflection in porous structure materials. The comparison shows that the simulation gives a good approximation of the behavior of porous silicon. It does provide the insight that the surface geometry of porous silicon is the main contributing factor to its efficiency in trapping light.