Ultrafast optical wide field microscopy.

We have developed a new imaging method, ultrafast optical wide field microscopy, capable of rapidly acquiring wide field images of nearly any sample in a non-contact manner with high spatial and temporal resolution. Time-resolved images of the photoinduced changes in transmission for a patterned semiconductor thin film and a single silicon nanowire after optical excitation are captured using a two-dimensional smart pixel array detector. These images represent the time-dependent carrier dynamics with high sensitivity, femtosecond time resolution and sub-micrometer spatial resolution.

Room temperature detection of sub-terahertz radiation in double-grating-gate transistors.

Room temperature photovoltaic non-resonant detection by large area double-grating-gate InGaP/InGaAs/GaAs heterostructures was investigated in sub-THz range (0.24 THz). Semi-quantitative estimation of the characteristic detection length combined with self-consistent calculations of the electric fields excited in the structure by incoming terahertz radiation allowed us to interpret quantitatively the results and conclude that this detection takes place mainly in the regions of strong oscillating electric field excited in depleted portions of the channel.