Publication

Backpropagation Imaging in Nonlinear Harmonic Holography in the Presence of Measurement and Medium Noises

2014
Journal Articles

Abstract

In this paper, the detection of a small reflector in a randomly heterogeneous medium using secondharmonic generation is investigated. The medium is illuminated by a time-harmonic plane wave at frequency ω. It is assumed that the reflector has a nonzero second-order nonlinear susceptibility, and thus emits a wave at frequency 2ω in addition to the fundamental frequency linear scattering. It is shown how the fundamental frequency signal and the second-harmonic signal propagate in the medium. A statistical study of the images obtained by migrating the boundary data is performed. It is proved that the second-harmonic image is more stable with respect to medium noise than the one obtained with the fundamental signal. Moreover, the signal-to-noise ratio for the second-harmonic image does not depend either on the second-order susceptibility tensor or on the volume of the particle. © 2014 Society for Industrial and Applied Mathematics.

Official source

https://infoscience.epfl.ch/entities/publication/6d3aac35-b918-4531-a576-478ab1c91b4c

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2014
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/6d3aac35-b918-4531-a576-478ab1c91b4c

About this result

Related concepts (32)

Noise (electronics)

In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics and central to thermodynamics. Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically, and even then quantum noise would remain inherent. Electronic noise is a common component of noise in signal processing.

Second-harmonic generation

Second-harmonic generation (SHG, also called frequency doubling) is a nonlinear optical process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons (equivalently, twice the frequency and half the wavelength), that conserves the coherence of the excitation. It is a special case of sum-frequency generation (2 photons), and more generally of harmonic generation.

Signal-to-noise ratio

Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. SNR is an important parameter that affects the performance and quality of systems that process or transmit signals, such as communication systems, audio systems, radar systems, imaging systems, and data acquisition systems.

Related publications (32)

Backpropagation Imaging in Nonlinear Harmonic Holography in the Presence of Measurement and Medium Noises

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