Optical Modulation Of Nuclear Spin Polarization And Fluctuation

This thesis focuses on the theoretical study of the modulation and applica-tion of coherent optical properties in semiconductor quantum dot and NV center,which the nuclear spin cooling and polarization by dark state is mainly studied.The research background,the essential conception and the potential application are outlined first.And our work mainly includes two parts:the nuclear spin polarization and fluctuation suppression in quantum dot and NV center through nonlinear quantum optical effects;and the nonlinear optical properties of quan-tum dot induced by intense fields.Nuclear spin fluctuation suppression is a key issue in preserving electron coherence for quantum information/computation.Due to that the hyperfine interaction between electron and nuclear spins is a main reason for electron spin decoherence.In the first part,we propose an efficient way of nuclear spin cooling in semiconductor quantum dots by the coherent population trapping and the electric dipole spin resonance induced by optical fields and ac electric field.The electric dipole spin resonance can enhance the spin flip-flop rate and may bring out bistability under certain conditions.By tuning the optical fields,we can avoid the electric dipole spin resonance induced bistability and obtain highly polarized nuclear spin state,which results in long electron coherence time.With the help of coherent population trapping and electric dipole spin resonance,an enhancement of 1500 times of the electron coherence time can been obtained after a preparation time of 500 ns.In addition,the condition of dark state can be met by changing the direction of the magnetic field.By rotating the direction of the static magnetic field,we can have the electron dark state and highly polarized nuclear spins state with ultra narrow distribution width.Besides the electron spin,the single nuclear spin in NV center is a prepon-derant candidate for quantum bit too.We find a possible reason may destroy the formation of dark state of nuclear spin,and solving this problem by“double dark states ".And then we study the manipulation of emission spectra of strongly driv-en semiconductor quantum dot due to its fundamental importance and various applications.By mapping the optical process in semiconductor quantum dot to a quantum transport process,we have established the connection between the emission intensity in optics and the bandwidth in quantum transport.Moreover,we are able to use dynamic and symmetry methods to tune the nonlinear emis-sion spectra of the semiconductor quantum dot,including high-order harmonics and hyper-Raman lines.In particular,we may obtain unusual emission spectra,with hyper-Raman line component alone,or with "odd high-order harmonic"/"even high-order harmonic" component alone.