When an optical parametric amplifier (OPA) operated as a phase-sensitive amplifier (PSA) is used for point source imaging, the angular resolution improvement can defeat the classical Rayleigh limit, and approach the de Broglie resolution.
Classical information theory can be used to quantify the resolution performance of optical imaging systems. When an optical parametric amplifier (OPA) operated as a phase-sensitive amplifier (PSA) in the transverse spatial domain is used for point source imaging, the angular resolution improvement can approach the de Broglie resolution (i.e. Heisenberg limit). In this paper, classical information theory is employed to quantify the signal-to-noise ratio (SNR) improvement for both an ideal and a realistic multimode PSA applied to the problem of sub-Rayleigh imaging. When only considering the noise originating from the detector, the SNR improvement is found to scale quadratically as a function of the PSA gain, in the limit of noise power comparable to signal power. Differences in performance of an ideal PSA and a realistic PSA are discussed.
The Rayleigh criterion sets a classical limit on the resolution of optical imaging systems, which brings challenges in remote sensing of spatial information. According to the Rayleigh criterion, only a limited control of resolution can be accomplished by adjusting the optical wavelength or aperture diameter. The resolvability of optical imaging systems can also be represented in terms of the signal-to-noise ratio (SNR). The optical parametric amplier (OPA) is a common nonlinear device used in a variety of applications, such as imaging, quantum information, and ultrafast laser science. It has been shown that when the OPA is operated as a phase-sensitive amplifier (PSA), no quantum noise is added thus preserving the SNR. In this thesis, the hypothesis testing from the classical information theory has been applied to the problem of distinguishing distant point sources. It is numerically demonstrated that an improvement of resolution beyond the classical limit and SNR enhancement could be achieved by utilizing the PSA operated in spatial domain. Plasma diagnostics deducts information of important parameters (such as temperature, plasma density and confinement) in magnetic confinement fusion (MCF) reactions. Interferometer can be used to measure the refractive index of plasma which is correlated with the plasma density. A Mach-Zehnder type interferometer enhanced by the PSA is studied. It has been found that the effect of the PSA is to increase the minimum resolvable interference fringe shift caused by plasma density perturbation so that a better resolution of the interferogram can be obtained. This method may enable significant improvement in plasma density measurement.
High-angular-resolution imaging is crucial for many applications in modern astronomy and astrophysics. The fundamental diffraction limit constrains the resolving power of both ground-based and spaceborne telescopes. The recent idea of a quantum telescope based on the optical parametric amplification (OPA) of light aims to bypass this limit for the imaging of extended sources by an order of magnitude or more. We present an updated scheme of an OPA-based device and a more accurate model of the signal amplification by such a device. The semiclassical model that we present predicts that the noise in such a system will form so-called light speckles as a result of light interference in the optical path. Based on this model, we analysed the efficiency of OPA in increasing the angular resolution of the imaging of extended targets and the precise localization of a distant point source. According to our new model, OPA offers a gain in resolved imaging in comparison to classical optics. For a given time-span, we found that OPA can be more efficient in localizing a single distant point source than classical telescopes.