The Quantum Properties Of Light:Several Investigations

This thesis introduces several investigations on the quantum properties of light, including entangled photon states, optical angular momentum and its applications and quantum states of surface plasmon polariton. We investigate entangled photon states based on integratal lithium niobate waveguide systems. Through domain-engineering, the schemes of generating nonmaximally mode-entangled photon state and electro-optically tunable polarization-entangled photon state are proposed. For the researches on the angular momentum of photon, we discuss to impress it onto the NOON state for the generation of two-photon NOON state with orbital angular momentum. The applications of such a state are also involved. Moreover, we investigate the optical analogue of intrinsic spin Hall effect based on the spin-orbit coupling. In the last part, we study the entangled states and squeezed states of surface plasmon polariton. The contents could be divided into four parts as follows.1. The generation of electro-optically tunable entangled photon statesWe first discuss the quantization of electro-optic effect in lithium niobate systems. It is shown to be a two-photon interaction process at the quantum level. Lithium niobate could be used to prepare high quality optical waveguides, so it provides a potential platform for the integration of quantum circuits. Moreover, it is flexible to design the domain structures for controlling the processes of spontaneous parametric down conversion and electro-optic interaction, which provides an effective approach to generating and modulating the entangled photon states. We do two works based on this system. For the first one, we propose the generation of nonmaximally mode-entangled photon state. The waveguide is divided into two regions according different functions. In Region Ⅰ, the polarization of pump light is tuned through electro-optic modulation. The degree of entanglement could be controlled by changing the value of the applied voltage. In Region Ⅱ, the two eigenvectors of the entangled state are generated by photons with different polarization states correspondingly through three interaction processes. For the second work, we have demonstrated an electro-optically tunable polarization entangled photon pair source, which is based on the domain-engineered lithium niobate waveguide substrates. If there is no applied voltage, we can obtain type-Ⅱ polarization-entangled photon state. While a proper voltage is applied, the generated state is type-Ⅰ polarization-entangled photon state.2. Generating two-photon NOON state with orbital angular momentumWe discuss to introduce the orbital angular momentum into a special entangled state—the NOON state. Such a state could be generated with a lithium niobate crystal possessing a poled pattern of forked-grating-like shape. The spontaneous parametric down conversion process in this system could be described based on the nonlinear Huygens-Fresnel principle, the state vector is also derived. In addition, we propose the approach to detecting the coherence of the state using an orbital angular momentum compensator and a HOM interferometer together with other optical components. The NOON state with orbital angular momentum could work like a multi-photon NOON state in angular displacement measurement, remote sensing and other applications, so it is of great practical value.3. The optical analogue of intrinsic spin Hall effect based on the spin-orbit couplingWe consider one of the recent research hotspots-the spin Hall effect of light (SHEL). The investigation is based on the liquid-crystal-based twisting structures. The spin-orbit coupling in such structures could provide an effective magnetic field, which acts on a pseudospin vector to bring an optical analogue of intrinsic spin Hall effect. Several samples are prepared through the DMD based micro-lithography technology, and the SHEL patterns are experimentally observed. Theoretical simulations are consistent with experimental results. Through designing the distribution of optical axis, tunable SHEL with any desired splitting pattern could be realized.4. The quantum properties of surface plasmon polaritonWe study the quantum properties of a special interface electromagnetic propagation mode-the surface plasmon polariton (SPP). We mainly focus on the entangled states and squeezed states of SPP. Based on a "survival" system, the two-SPP state is shown to be entangled, for which the entanglement is passed on from the incident entangled photon state. Its spectral properties are studied, and we apply it in energy-time entanglement. In the latter part, we consider the nonlinear interaction between the single SPP quanta. The direct generation of SPP squeezing state in the parametric down conversion process is studied, and actual squeezing results in a hybrid plasmonic waveguide system are calculated. Our results indicate that the SPP-based quantum system is a possible candidate for the integration of quantum circuits.