Enhanced Imaging with use of a Phase-Sensitive Fiber-Optic Parametric Amplifier.

摘要

Fiber-optic parametric amplifiers (FOPAs) have been extensively studied since the 1980s, primarily for purposes of fiber-optic communication. FOPAs' low noise figure and broad gain spectrum render them particularly attractive for communication purposes. While these features have the potential of extending optical fiber links, they could also be exploited in imaging applications. One such application is the enhancement of low-light images such as those produced by near-field scanning optical microscopes (NSOMs). While NSOMs are able to image beyond the diffraction limit of conventional optics, they do so at the cost of low optical transmission. The unique features of FOPAs could improve the optical performance of such devices.;This work provides the design for a new fiber-optic amplifier that can be interfaced to an imaging system in order to enhance its capability. The optical amplifier acts as an ideal preamplifier: it increases the optical signal to a detectable power level while preserving the signal-to-noise ratio. This document presents the theoretical constructs necessary to analyze the experiments described herein, along with detail of the prototypical research. Three iterations of the optical amplifier design are presented. First, a proof-of-concept experiment successfully demonstrates the ability of a phase-sensitive FOPA to amplify a low-light image. The second design optimizes the gain of the optical amplifier and in the process introduces a new technique which permits dynamic control of the gain up to two orders of magnitude faster than previous designs. The third design creates an entirely new fiber-optic amplifier along with a numerical model to both characterize its performance and provide a tool for the creation of custom amplifiers. The design utilizes a pulsed laser to create a dual-pump phase-sensitive FOPA. A FOPA amplifies according to a parametric process, allowing the ability to design a fiber-optic amplifier tailored to a specific signal wavelength. Additionally, by using two pumps, the entirety of the signal information can be contained in one optical wavelength. Finally, a phase-sensitive FOPA is capable of operating at a theoretical 0-dB noise figure. Taken together, these qualities demonstrate that this design is an ideal amplifier for image enhancement.