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An optical pulse asymptotically reaching zero group velocity in tapered waveguides can ultimately stop at a certain position in the taper accompanied by a strong spatial compression. This phenomenon can be also observed in spatio-temporal…

Diverse applications in photonics and microwave engineering require a means of measurement of the instantaneous frequency of a signal. A photonic implementation typically applies an interferometer equipped with three or more output ports to…

Historically employed spectroscopic architectures used for large field of view mapping spectroscopy in millimetere and sub-millimetre astronomy suffer from significant drawbacks. On-chip filterbank spectrometers are a promising technology…

Instrumentation and Methods for Astrophysics · Physics 2026-04-14 Chris S. Benson , Peter S. Barry , Patrick Ashworth , Harry Gordon-Moys , Kirit S. Karkare , Izaak Morris , Gethin Robson

Diffusion pore imaging is an extension of diffusion-weighted nuclear magnetic resonance imaging enabling the direct measurement of the shape of arbitrarily formed, closed pores by probing diffusion restrictions using the motion of…

To obtain the initial pressure from the collected data on a planar sensor arrangement in Photoacoustic tomography, there exists an exact analytic frequency domain reconstruction formula. An efficient realization of this formula needs to…

Numerical Analysis · Mathematics 2015-01-14 Julian Schmid , Thomas Glatz , Behrooz Zabihian , Mengyang Liu , Wolfgang Drexler , Otmar Scherzer

Long-distance depth imaging holds great promise for applications such as autonomous driving and robotics. Direct time-of-flight (dToF) imaging offers high-precision, long-distance depth sensing, yet demands ultra-short pulse light sources…

Computer Vision and Pattern Recognition · Computer Science 2025-05-29 Manchao Bao , Shengjiang Fang , Tao Yue , Xuemei Hu

Diffraction tomography is a widely used inverse scattering technique for quantitative imaging of weakly scattering media. In its conventional formulation, diffraction tomography assumes monochromatic plane wave illumination. This…

Numerical Analysis · Mathematics 2026-03-11 Peter Elbau , Noemi Naujoks , Otmar Scherzer

We propose an all-digital telescope for 21 cm tomography, which combines key advantages of both single dishes and interferometers. The electric field is digitized by antennas on a rectangular grid, after which a series of Fast Fourier…

Astrophysics · Physics 2009-10-29 Max Tegmark , Matias Zaldarriaga

Directional wave speeds variations in anisotropic elastic solids enables material characterisation capabilities, such as determination of elastic constants and volumetric measurement of crystallographic texture. However, achieving such…

Applied Physics · Physics 2024-08-19 Melody Png , Ming Huang , Marzieh Bahreman , Christopher M. Kube , Michael J. S. Lowe , Bo Lan

Modern imaging systems typically use single-carrier short pulses for transducer excitation. Coded signals together with pulse compression are successfully used in radar and communication to increase the amount of transmitted energy.…

Information Theory · Computer Science 2016-12-07 Almog Lahav , Tanya Chernyakova , Yonina C. Eldar

The number of phase wraps in 2D wrapped phase map can be completely eliminated, or greatly reduced by frequency shifting. But the wraps usually cannot be optimally reduced using the conventional fast Fourier transform (FFT) because the…

Instrumentation and Detectors · Physics 2017-10-11 Minmin Wang , Guangliang Du , Canlin Zhou , Shuchun Si , Zhenkun Lei , XiaoLei Li , YanJie Li

We introduce the first method to enable an optical amplification of a coherent Raman spectroscopy signal called radio frequency Doppler Raman spectroscopy. Doppler Raman measurements amplify the optical signals in coherent Raman…

We consider application of the discrete Fourier transform-spread orthogonal frequency-division multiplexing (DFT-spread OFDM) technique to high-speed fiber optic communications. The DFT-spread OFDM is a form of single-carrier technique that…

Information Theory · Computer Science 2011-03-01 Fanggang Wang , Xiaodong Wang

We propose and study a method for measuring the chromatic dispersion parameter (D) of optical fibers and bulk optical elements through the use of a single-arm three-wave interferometer and a fiber femtosecond frequency comb (FFFC). The FFFC…

Recent advances in imaging sensors and digital light projection technology have facilitated a rapid progress in 3D optical sensing, enabling 3D surfaces of complex-shaped objects to be captured with improved resolution and accuracy.…

Instrumentation and Detectors · Physics 2017-11-22 Chao Zuo , Tianyang Tao , Shijie Feng , Lei Huang , Anand Asundi , Qian Chen

Imaging through a single optical fiber offers attractive possibilities in many applications such as microendoscopy or remote sensing. However, the direct transmission of an image through an optical fiber is difficult because spatial…

Optics · Physics 2015-05-29 Roman Barankov , Jerome Mertz

We present a novel, straightforward method for spatiotemporal characterization of ultra-short laser pulses. The method employs far-field interferometry and inverse Fourier transform spectroscopy, built on the theoretical basis derived in…

Diffusing-wave spectroscopy is a powerful technique which consists in measuring the temporal correlation function of the intensity of light multiply scattered by a medium. In this paper, we apply this technique to cold atoms under purely…

Despite the multitude of available methods, the characterisation of ultrafast pulses remains a challenging endeavour, especially at the single-photon level. We introduce a pulse characterisation scheme that maps the magnitude of its…

Dispersion lies at the heart of real-time signal processing systems across the entire electromagnetic spectrum from radio to optics. However, the performance and applicability of such systems have been severely plagued by distortions due to…

Optics · Physics 2016-01-08 Shulabh Gupta , Christophe Caloz