No abstract

A refractive lens is one of the simplest, most cost-effective and easily available imaging elements. Given a spatially incoherent illumination, a refractive lens can faithfully map every object point to an image point in the sensor plane, when the object and image distances satisfy the imaging conditions. However, static imaging is limited to the depth of focus, beyond which the point-to-point mapping can only be obtained by changing either the location of the lens, object or the imaging sensor. In this study, the depth of focus of a refractive lens in static mode has been expanded using a recently developed computational reconstruction method, Lucy-Richardson-Rosen algorithm (LRRA). The imaging process consists of three steps. In the first step, point spread functions (PSFs) were recorded along different depths and stored in the computer as PSF library. In the next step, the object intensity distribution was recorded. The LRRA was then applied to deconvolve the object information from the recorded intensity distributions during the final step. The results of LRRA were compared with two well-known reconstruction methods, namely the Lucy-Richardson algorithm and non-linear reconstruction.

New measurements of the angular distributions of effusive gas beams emanating from two collimating tube sources are presented. These sources are a single tube of aspect ratio 25 and a multi-capillary array of aspect ratio 100. The data were collected for a wide variety of gases (He, Ne, Ar, Kr, Xe, H2, N2, CO2 and C2H2) over a broad range of driving pressures. The profiles were obtained by rotating the ionization gauge gas detector about the centre of the exit of the tube. The data were acquired as a function of the gas flow rate and pressure in the source line. Comparisons of the present measurements with other experimental work and models are made.

High average power, diode pumped petawatt laser systems: a new generation of lasers enabling precision science and commercial applications,"

Fabrication of large area (sub-1 cm cross-section) micro-optical components in a short period of time (~10 min) and with lesser number of processing steps is highly desirable and cost-effective. In the recent years, femtosecond laser fabrication technology has revolutionized the field of manufacturing by offering the above capabilities. In this study, a fundamental diffractive optical element, binary axicon -axicon with two phase or amplitude levels, has been designed in three configurations namely conventional axicon, photon sieve axicon (PSA) and sparse PSA and directly milled onto a Sapphire substrate. The fabrication results revealed that a single pulse burst fabrication can produce a flatter and smoother profile than pulse overlapped fabrication which gives rise to surface damage and increased roughness.The fabricated elements were processed in IsoPropyl Alcohol and Potassium Hydroxide to remove debris and redeposited amorphous Sapphire. An incoherent illumination was used for optical testing of the components and a non-linear optical filter was used for cleaning the noisy images generated by the diffractive optical elements.