In this paper we present a scheme for ghost imaging based on partially coherent light produced when coherent light
passes through a turbid medium. The light is described by a transport model incorporating Mie scattering theory.
Using this model it is possible to predict the second order correlation function of the pseudo thermal source and to
estimate key parameters for its application in ghost imaging experiments. Analytical and numerical simulations
of the second order coherence function are performed in terms of scattered and un-scattered components of the
light. The coherence length of the scattered component, responsible for ghost images formation, is determined in
terms of concentration and diameters of the scattering elements. The advantage of using this type of source with
respect to previous experiments is a better understanding of its coherence properties responsible for resolution
and visibility of ghost imaging with thermal light.
Micro Optics frequently require the fabrication of complex 3D structures with surface qualities and metrological tolerances that challenge many manufacturing techniques. In this paper we describe two excimer laser abalation techniques for creating spiral phase modulation structures and a technique for fabricating a diffractive optical structure. The spiral phase structures are intended to be used to convert a 780nm TEM<SUB>00</SUB> laser beam into the doughnut mose TEM*<SUB>01</SUB> field and the diffractive structure is used to create the double-D TEM<SUB>01</SUB> mode in the transmitted first order diffraction. Each of the techniques involve the use of mask projection excimer laser abalation. One of the techniques used to create the smoothly varying ramp of the spiral phase structure involes the use of a single mask that rotates about one of its vertices while the matching laser is pulsed. The second process uses a set of 15 separate patterns that are prepared on a chrome-on-quartz mask. The fabrication of the diffractive optical element is performed in a similar way. We have used 248nm radiation from a KrF laser source to demonstrate the fabrication in polycarbonate of the spiral phase modulation structure and have been able to produce the diffractive optical element in both polycarbonate and glass microscope slides.
Slow neutral beams of metal atoms can be manipulated using the intensity gradient of near-resonant light-fields enabling the deposition of atoms onto a substrate in a processes often referred to an atom lithography. A suitably shaped light-field gradient is used to control the path of metal atoms using the dipole force created by the interaction between atoms and the strong, near-resonant optical intensity gradient. Relatively simple patterns such as lines and dots have been created using optical standing waves while more complex light-fields might be created using computer generated optical elements to manipulate the laser beam.