Mid-IR and terahertz digital holography based on quantum cascade lasers

Year: 2015

Authors: Ravaro M., Locatelli M., Pugliese E., Siciliani De Cumis M., D’Amato F., Consolino L., Bartalini S., Vitiello M.S., De Natale P.

Autors Affiliation: INO, Istituto Nazionale di Ottica – CNR, Largo E. Fermi 6, Firenze, I-50125, Italy; LENS, European Laboratory for NonLinear Spectroscopy, Via N. Carrara 1, Sesto Fiorentino (FI), I-50019, Italy; NEST, Istituto Nanoscienze – CNR and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa, I-56127, Italy

Abstract: 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.

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KeyWords: Carbon dioxide; Coherent scattering; Computer generated holography; Holographic interferometry; Holography; Imaging techniques; Medical imaging; Nanophotonics; Nondestructive examination; Quantum cascade lasers; Semiconductor lasers; Vibrations (mechanical), Different frequency; Digital holography; Multiple wavelengths; Non destructive testing; Reduced sensitivity; Terahertz digital holographies; Transmission hologram; Transparent objects, Holograms


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