The Emulated Spacetime With Central Gravitational Potential And Light Manipulation On Transformation Optics Chip

Information technology has deeply impacted human daily life. As well known, electrons and photons play a very important role as information carriers. Since the invention of first electronic computer, electronics integration technology has achieved great success, such as labtops and cellphones in daily lives. Furthermore, the rapid development of information technology needs information carrier with higher speed and larger information capacity. As well known, photon is the fastest information carrier in nature. Therefore, photonics integration technology has an important application value to the future information technology. However, compared with electronics integration technology, the development of photonics integration technology is very slow. That is because the wavelength of photon is very larger than electron, and there are many challenge works to be overcomed to realize photonics integration devices. According to Huygens’ Principle, the light propagation in space can be described as wavefront of light. Therefore, if we can shape wavefront of light, we can manipulate light propagation on chip, and even realize some kind of integration photonics devices. Furthermore, scientists provide many different artificial materials to achieve integration photonics chips, such as photonic crystals, surface plasmon, metamaterials and so on.On the other hand, the successes of Einstein’s general relativity uncover cosmogenic origin and the movement of celestial body. According to this theory, the propagation of light in gravitational field follows geodesic line, not a straight line. Therefore, if we can control curvature of cosmic spacetime, the propagation of light can be manipulated as wills. However, how to control curvature of cosmic spacetime goes far beyond the current level of human science and technology. But scientists had found the good correspondence between macroscopic Maxwell’s equations in complex inhomogeneous media and the macroscopic Maxwell’s equations for the background of an arbitrary spacetime metric. So instead of controlling curvature of cosmic spacetime, we can use inhomogeneous and anisotropic medium to emulate gravitational field in curved spacetime. In recent years, transformation optics is proposed along with the development of micro/nano technology, and the basic core idea is equivalence relation between material electromagnetic parameters and metric of spacetime from the point of electromagnetic material constitutive equation. Therefore, we can fabricate an inhomogeneous refractive index distribution to emulate optical analogy of general relativity phenomena in laboratory environment. Especially, some general relativity phenomena has been theoretically predicted but cannot be directly detected by experimental astronomical apparatus at the moment. Furthermore, transformation optics can also design photonics integration chips, which provides an alternative way to achieve next generation integration chips with higher speed and larger capacity.Although transformation optics is very concise and provides a strong method to design kinds of optical integration devices, there is a huge challenge to fabricate these devices in practice. In conventional transformation optics devices, the variation of spatial refractive index is obtained by varying the structural parameter of metal resonant unit. For large operating wavelength, the fabrication is feasible. However, how to fabricate the metal resonant unit with nanometer precision at short wavelength is very challenging. Furthermore, the metal loss in conventional transformation optics devices at high frequency is very heavy. These hinder the progress of experimental work in transformation optics. Even if the reported experimental work, the working frequency is in microwave and infrared wavelength. And for the visible frequency, the theoretical works take the most proportion. During the period of pursuing doctorate degree, I have tried many kinds of fabrication process to find an efficient transformation optics device at the visible frequency. Instead of metal resonant structure, the slab waveguide is used on the basis of previous research in our group. Given that effective refractive index of waveguide mode is varying as the width, we use photoresist spin coating technology to fabricate variant thickness in polymer waveguide. Through this technology, we realize effective refractive index distribution as analogy of central symmetrical gravitational field, and mimic some general relativity phenomena. On the other hand, the conventional transformation optics measurement is used by near-field scanning technique. This technique has good detection effect for operating large wavelength, but image resolution gets obscure as decreasing the working wavelength. Therefore, we use quantum dot fluorescence microscopic imaging technology to measure transformation optics waveguide on the basis of accumulation technology in our group, and succeed in characterization of light propagation in various kind of emulated curved spacetime. The thesis can be divided into the following parts:1. We investigate transformation optics waveguide to realize a central symmetric effective index potential as analogy of black hole through changing thickness of waveguide. In our experiment, we observe light deflection and light trapping caused by strong gravitational lensing of black hole, and study light propagation around the event horizon of black hole.2. We investigate transformation optics waveguide to introduce the concept of curved space into wavefront shaping in waveguide settings. We experimentally demonstrate light focusing through Einstein’s Rings, and obtain collimated narrow non-diffractive beam using the tidal force of gravitational field, and theoretically propose shape-invariant beams accelerating on arbitrary trajectories through emulated curved space.3. We investigate the dynamic beam control in transformation optics waveguide. The central symmetric effective index potential is generated with aid of thermal-optical effect of polymer in the pumping of outside controlling laser. The trajectory of a second probe laser beam propagating in the waveguide is then continuously tuned by the controlling laser. The reported method can provide a new approach to achieve active all-optical control transformation optics devices.4. We investigate structured surface plasmon polaritons (SPPs) waveguide to realize SPPs black hole. The structured SPPs waveguide comprises of a sliver microsphere embedded within sliver/dielectric/sliver multilayer structure, and allows for adiabatic, deep sub-wavelength focusing of SPPs. We also study microsphere size and working frequency on the influence of nano-focusing by full-wave numerical simulations.