a) Second harmonic optical scan over mono-layers of In2Se3 accompany with optical microscope image
b) Bitumen ?bee? microstructure observed with b-1) optical microscope b-2) Atomic Force Microscope (AFM) and c) optical dark field setup showing scattering from large number of microstructures
c) 1PA and 2PA-excited confocal microscopy image of the PL emitted by ncSi and DAPI dye
d) Nonlinear optical localization of light at dislocation defect area at GaAs-Si interface collected by fiber Nearfield Scanning Optical Microscope (NSOM)
e) Optical microscope image of In2Se3 showing growth of mono-layers on Mica

Lab Focus:

Nonlinear/linear optical studies of surface, subsurface, interfaces and thin films in farfield/nearfield regime to understand structure and electrical properties.

Laser and Light Sources:

1) Coherent Mira 900 Ti-Sappire unamplified pulse laser 76MHz repetition, 150 fs pulse width, +1W variable wavelength output in visible range

2) Spitfire Ti-Sappire amplified pulse laser system (in combination with NOPA system) with variable repetition output (usually used at 1KHz)

3) Monochromator (visible-near infrared red)

Lab Made Setups and Experiment:

1) Optical nonlinear scanning microscope setup with rotational ability, temperature controller and mechanical stress manipulator

Optical 2HG technique on this setup is used to study a) optical domains and curie temperature of ferroelectic materials such as CaMnTi2O6 b) Strain study in TSV(Through Silicon Vias) c) Ferroelectric materials with memory application such as BTO/Ge and BTO/PMN-PT thin films d)Study of In2Se3 thin film and flakes in 2HG nonlinear regime

2) Nonlinear nearfield scanning optical microscope (NSOM) with 50 nm fiber probe aperture

The nearfield system is used to study III-V thin film such as GaAs-Si , InP-Si, InGaAs-GaAs or InGaAs-InP-GaAs-Si to optically detect defects (like dislocations) created at mis-match interfaces of these films and other optical domains. The fiber probe collecting propagating waves in this experiment. It has been used in combination of spectromter to map the spectrum plot of these thin film through fiber.

3) Dark-field and bright-field scattering setup with near-infrared and white light source and temperature controller

This setup is used to optically study micro- and sub-micro structures in samples such as bulk bitumen (asphalt binder) in the linear regime as a function of temperature. Measurements are compared to macroscopic measurement techniques, such as dynamic shear rheometry. “Bee” microstructures are one example of the scattering structures currently being studied.

4) Nonlinear photoluminescence (PL) setup

The setup is used to indirectly study Si nanocrystals 2 photon absorption by measuring 2photon absorption photoluminescence.

5) Darkfield scattering microscopy with spectrometer

The setup is used to optically study miacro/nanostructures darkfield scattering. Spectrometer helps to isolate individual structure signal. It is also used for PL study sometimes.

6) Reflectance anisotropy spectroscopy (RAS) in combination to ultra-high vacuum (UHV) chamber to study intrinsic surface anisotropy

This optical technique is used to study broken symmetry in dangling bond of Si surface or other samples.