Infrared (IR) digital holography (DH) based on CO2 lasers has proven to be a powerful coherent imaging technique due
to the reduced sensitivity to mechanical vibrations, to the increased field of view, to the high optical power and to
possible vision through scattering media, such as smoke. In this contribution we report IR DH based on the combination
of quantum cascade laser (QCL) sources and a high resolution microbolometric camera. QCLs combine highly desirable
features for coherent imaging, such as compactness, high optical power, and spectral purity. The present availability of
external cavity mounted QCLs having a broad tuning range, makes them suitable sources for multiple wavelength
holographic interferometry. In addition, QCL emission covers several windows throughout a large portion of the IR
spectrum, from the mid-IR to the terahertz region. This allows taking advantage of the different optical response of the
imaged objects at different frequencies, which is crucial for applications such as non-destructive testing and biomedical
imaging. Our holographic system is suitable for the acquisition of both transmission holograms of transparent objects
and speckle holograms of scattering objects, which can be processed in real time to retrieve both amplitude and phase.
We show that imaging alive people through smoke and flames is possible by Digital Holography at far infrared. This
capability is of crucial importance in the security field to provide a new tool for firefighters and first responders in fire
accidents. So far, the existing thermographic infrared cameras allows to see people through dense smoke, sensing the
radiation emitted by human body. However, these devices are often blinded due to the flame emission, which is collected by the zoom lenses employed for the scope, and the information of the targets beyond the flames is unavoidably lost. On the contrary, lensless Digital Holography at far infrared avoids the typical saturation of the camera detectors returning clear images of targets seen behind veils of smoke and curtains of flames. Moreover, we demonstrate that human-size holograms can be recorded, allowing to move this promising technology outside the lab for safety applications.
We report on Infrared Digital Holography (IRDH) and discuss the advantages offered by this technique. Efficient
recording-reconstructions of IR holograms of various objects, which differ in composition and dimensions, are shown.
We demonstrate optical holographic display by means of a liquid crystal based Spatial Light Modulator (SLM), which
gives the chance to get direct 3D imaging and display of the IR holograms. Finally, 3D dynamical scenes can be
numerically synthesized and displayed in the visible region, using holograms of different objects.
Infrared digital holograms of different statuettes are acquired. For each object, a sequence of holograms is recorded
rotating the statuette with an angular step of few degrees. The holograms of the moving objects are used to compose
dynamic 3D scenes that, then, are optically reconstructed by means of spatial light modulators (SLMs) using an
illumination wavelength of 532 nm. This kind of reconstruction allows to obtain a 3D imaging of the statuettes that could
be exploited for virtual museums.
We report on the fabrication of optical Bragg type phase gratings in polymethyl methacrylate substrates irradiated by a
femtosecond Ti: Sapphire laser. In order to investigate the distribution of the refractive index change produced by the
femtosecond laser irradiation, we performed a two-dimensional visualization and spatially resolved optical analysis of
the induced refractive index profile by using a digital holographic technique and an adaptive-iterative algorithm for
wavefront reconstruction. The technique gives a direct and quantitative two-dimensional profile of the index of
refraction in irradiated samples, providing information how the fabrication process depends on the laser irradiation.
In this work we show several acquisition setups and techniques which make it possible to obtain holographic recording
and reconstruction of large objects by means of Infrared Digital Holography (IDH). In previous works it was
demonstrated that, using the long wavelength coherent radiation produced by a CO2 laser instead of visible radiation, it is
possible to obtain advantages in terms of larger field of view and lower seismic noise sensitivity. The only drawback
using this wavelength is represented by the low resolution of current recording devices in this spectral region. The
reported methods may have industrial applications where investigation of large dimension samples is needed.
A major issue so far for digital holography has been the limited number of pixels of currently available detectors, such as
CCD sensors, which allows a spatial resolution significantly lower than that of a holographic plate. This is an even more
sever limitation when IR sensors such as microbolometers are taken into consideration. In order to increase the numerical
aperture of such systems, we developed an automatic technique which is capable to record several holograms and stitch
them together before reconstruction. This method can cope with some of the inherent differences of the image structures
and tone dynamics of recorded holograms. The joint holograms have been applied for reconstruction of an image by
means of numerical and optoelectronic reconstruction processes and they show significant increase of quality.
Fundamental laws of quantum mechanics impose that arbitrary quantum states cannot be perfectly cloned
or amplified without introducing some unavoidable noise in the process. The quantum noise intrinsic to the
functioning of a linear phase-insensitive amplifier can however be avoided by relaxing the requirement of a deterministic
operation. Non-deterministic noiseless linear amplifiers that do not violate any fundamental quantum
law are therefore possible and here we present the first experimental realization of a scheme that allows noiseless
amplification of coherent states at the best level of effective gain and final state fidelity ever reached. This
scheme, based on a sequence of photon addition and subtraction, and characterized by a significant amplification
and low distortions, may become a useful tool for quantum communications and metrology, by enhancing the
discrimination between partially overlapping quantum states or by recovering the information transmitted over lossy channels.
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