Light Propagation And Applications In Generalized Nano-optomechanical Systems

Nanomechanical system (NMS) is a nanoscale system. Usually, it has high Q factor,high vibration frequency, small size, high sensitivity and other excellent characteristics.Due to these advantages, nanomechanical system is widely employed in force detectonand mass measurement. Some ultraminiature sensors can provide spatial resolutions atthe atomic scale and vibrate at frequencies in the gigahertz range. Another excitingpossibility is physically couple nanomechanical resonator to some small quantumsystems such as atoms, electrons, quantum dots, and single electron transistors. Thesecoupled nanomechanical systems can be used to study some specific quantum effectsand fundamental quantum principles. Particulary, a nanomechanical resonator coupledwith an optical cavity can serve as nano-optomechanical system, which is a hot researchtopic recently. Meanwhile, slow and fast light, and nonlinear effect baed onnano-optomechanical system have many potential applications in the areas of quantumcommunication, all-optical switch, information transmission and so on. It can bepredicted that the quantum mechanics will penetrate into other interdiscipline subjectsgradually in the future, along with the wide application of nano-optomechanical system.Based on the quantum mechanics and optics, this thesis introduce five representativenano-optomechanical systems, i.e.,(1) the smallest nano-optomechanical system—quantum dot;(2) a single quantum dot coupled to nanomechanical resonator;(3) asingle quantum dot coupled to photonic crystal nanocavity;(4) a carbon nanotubesystem;(5) quantum dots coupled to DNA molecules. Using quantum mechanics, suchas Heisenberg-Langevin approach and Born-Markovian approximation, we study thelight propagation properties of these five nano-optomechanical systems via computersimulation. We theoretically overcome some problems and defects exsiting in current nanomechanical nanotechnology and put forward some new optical devices to explorethe basic quantum properties of nano-optomechanical system, which enables thedevelopment of interdiscipline subjects, such as biophysics and physical chemistry. Themain structures of this thesis are as follows.The first chapter is the introduction, where the basic concept of nano-optomechanicalsystem is introduced, including the preparation methods, applications, developmenthistory and the current status of nanomechanical system.The second chapter introduces three theoretical methods to solve the Hamiltonianequantion of motion in generalized optomechanical system. They are Heisenbergequation of motion, density matrix approach and quantum Heisenberg-Langevin theory.We prove that these three treatments can get the same results in light propagationproperties of generalized optomechanical system. Therefore, we can solve theHamiltonian equantion of motion in generalized optomechanical system quickly andconveniently if handing the three treatments proficiently, which offers a platform topredict new materials and new effects in the future.The third chapter introduces the light propagation properties of the smallestnano-optomechanical system-quantum dot, under the radiation of two optical fields. Asa solid state material, quantum dot has been investigated since several years ago bymany researchers. The present thesis is the first time to point out that a single quantumdot can be a nano-optomechanical system, which has some advantages, such as the lowcost, the mature technology and the miniaturization.The fourth chapter investigates the light propagation properties of a single quantum dotcoupled to a nanomechanical resonator system. We theoretically design four usefuldevices, i.e., the optical knob from slow light to fast light, the nano-optical Kerr switch,the mass spectrometry with high sensitivity, and the quantum memory device.Furthermore, we first propose an optical method to measure the vibrational frequency ofnanomechanical resonator and the coupling strength between quantum dot andnanomechanical resonator, while using the pump-probe technique. The fifth chapter is the investigation of light propagation properties of a single quantumdot coupled to photonic crystal nanocavity system. We theoretically put forward aquantum optical transistor while using pump-probe technique. Compared withtraditional electronic transistor, the quantum optical transistor has higher sensitivity,lower energy consumption and less cost.The sixth chapter studies the light propagation properties in a carbon nanotube system.Theoretical analysis shows that in the presence of two optical fields, the interactionbetween the resonance of nanotube and the localized exciton in nanotube make thenanotube serve as nano-optomechanical system. In linear regime, the carbon nanotubecan be used to weigh the mass of nanoscale particles, which has a higher sensitivity dueto its light weight, small size and high quality factor. Otherwise, in nonlinear domain,we propose quantum optical Kerr modulator based on a carbon nanotube. In the last part,we propose some quantum optical devices based on spin-carbon nanotube system, i.e., asingle photon router and a quantum microwave transistor.The seventh chapter puts forward a coupled quantum dot and DNA molecule system,where the DNA molecule is treated as classical oscillator model. We point out that, inthe present of a pump field, the output probe field can be amplified while it's passingthrough the coupled system, which maybe make a contribution to the development ofthe clinical medicine theory, for example, the biomedical imaging, the DNA moleculebiomarker, and the cancer detection technology.This work was supported by the National Natural Science Foundation of China(No.10774101and No.10974133), the National Ministry of Education Program forPh.D, the Scholarship Award for Excellent Doctoral Student granted by Ministry ofEducation, and the Academic Award for Distinguished Doctoral Candidates granted bySJTU.