Deep Ultraviolet Digital Holography for nanoscopic application

Digital Holographic Microscopy (DHM) has been proven to be a promising technique for 3D imaging. By improving nanotechnology, the dimension of structures and devices is decreasing in size down to the nano-scale which is smaller than the wavelength of the light in the optical range. The diffraction-limited lateral resolution is an important barrier that makes an obstacle for the conventional DHM methods to go that deep. A deep (193 nm) UV laser has been used as a source to decrease the Abbe diffraction limit. In practice, λ=193 nm is the shortest wavelength which can be conveniently used for this purpose, as a digital camera is commercially available for this wavelength which can perform direct imaging with no filter or fluorescent plate in front. And also the required optical elements are available for this range and the setup does not need to be run in vacuum. To increase the NA a new objective configuration has been designed for this wavelength (the resulting NA is 0.7) and the setup has been developed in a way to reduce the aberrations due to the non-perfect optical elements.