Laser Research Institute
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Biophotonics and Imaging

White light generation, spatial light modulation and imaging

Staff members: EG Rohwer, PH Neethling

Current/recent students: D Spangenberg (Post Doc), R Viljoen (MSc)

 

The project involves the generation of a white light supercontinuum using a femtosecond laser and an all normal dispersion photonic crystal fibre. This generated supercontinuum has quite a long pulse length (~ 1ps) due to dispersion in the fibre. However, because of the fixed phase relationship between the different spectral components, it is possible to compress the pulse. The generated supercontinuum supports pulse lengths as short as < 10 fs, provided that all dispersion is compensated for. This implies that not only linear dispersion but also higher order dispersion must be addressed. This is done using a spatial light modulator (SLM) in a 4f-geometry.

 

Raman Spectroscopy

Staff members: PH Neethling

Current/recent students: C Pfukwa (MSc)

 

 

Super resolution microscopy

Staff members: GW Bosman, EG Rohwer

Current/recent students: D Ratsimandresy (MSc)

 

Super resolution microscopy is a new research activity at the Laser Research Institute, Stellenbosch University. The project entails the investigation of the diffusional mechanism in novel thin polymer films and crowded liquids like the cytosol. In this project the approach is to monitor the position to a very high accuracy of a single fluorescent molecule embedded in the polymer film and/or cytosol. To this end, the focus of the project is on the development of an epi-geometry wide-field illuminated fluorescence microscope capable of detecting the single fluorophores.

 

Entomological Remote Sensing

Staff members: PH Neethling, E Rohwer

Current/recent students: A Gebru (PhD)

 

The project on entomological LIDAR is done in collaboration with Dr Mikkel Brydegard at the University of Lund. The project entails the monitoring of atmospheric insects using either passive (sunlight and diffuse scattered surface light) or active (laser) light. Of particular interest is the observed wing-beat frequency, observable in the light reflected from the insects. This frequency seems to be specie specific which aids in the remote identification of insects. The amount of scattered light relates to the size of the insect (optical cross-section) and can further assist in identification.

The project focusses on the development of a high speed (kHz) detection system in order to perform these measurements. The passive setup is ideal for measurements during day time. Combining information such as flight direction (obtained from Si quadrant detectors) predation can also be studied. The active system is more suited to night-time measurements and can provide absolute distance measurements due to the Scheimpflug geometry employed along with a high speed line scan camera.