| Quantum coherence and interference effects,that are the fundamental phenomena of the light-matter interaction,can effectively change and control the linear and nonlinear optical responses in quantum coherent media.Simultaneously,they also lead to some interesting phenomena such as electromagnetically induced transparency,coherence population trapping,low group velocity of light pulses and enhanced high order nonlinearities.Based on these quantum coherence and interference effects,the nonlinear optical phenomena including optical bistability and multistability,optical soliton,four-wave and multi-wave mixing processes,stimulated Raman scattering,higher-order sidebands and optical combs have attracted considerable attention and have been widely studied.The further research for thesce optical phenomena not only is conducive to understand better the essence of nonlinear optics,but also is beneficial to further predict and discover the new potential applications.Generally,the optical nonlinearity in coherence medium refers to:when the coherence medium is driven by some strong laser fields,the charged particles in coherence medium experience an intersubband optical transition or redistribution,so that the electric dipole moment of coherence medium is related to the amplitude of the electric field as well as the higher-order terms of the electric field amplitude.Therefore,whether the coherence medium possesses of an observable optical nonlinearity is determined by its internal structure.How to find and provide a novel material that owns a strong optical nonlinearity has been a research hotspot.According to the recent advance of low-dimension micro-nano structure,the quantum effect and the nonlinear optical effect are significantly enhanced when the size and dimension of the coherence media decrease.Under the condition of that the crystal-growth techniques including chemical vapor deposition,molecular beam epitaxy and pulsed laser deposition become mature gradually,the low-dimension micro-nano structure that has specific nonlinear optical response has been a worthy research object.In this thesis for the Doctorate,we have studied deeply the specific optical nonlinearity in the specific low-dimension micro-nano structure.More specifically,we have studied the enhanced four-wave mixing(FWM)in semiconductor quantum wells,the competition between electromagnetically induced transparency(EIT)and hyper-Raman scattering in graphene under an external magnetic field,the tunable higher-order sideband and quadrature squeezing of higher-order sideband spectrum in cavity optomechanics.The main contents are as follows:1)We propose and analyze an efficient way to enhance four-wave mixing(FWM)signals in a four-subband semiconductor quantum well via Fano-type interference.By using Schrodinger-Maxwell formalism under the steady-state condition,we show the corresponding analytical expressions of the probe and generated FWM pulses,as well as their phase shifts,absorption coefficients,group velocities,and the related conversion efficiency,respectively.With the aid of interference between two excited subbands tunneling to the common continuum,we find that the efficiency of FWM field is found to be significantly enhanced,up to 35%.In addition,the FWM field can keep an ultraslow group velocity in the quantum well,which can be maintained for a certain propagation distance(i.e.,50?m).Then,using the similar approach,a high efficient four-wave mixing(FWM)scheme is proposed in five-subband semiconductor quantum wells(SQWs).With the aid of cross coupling between one ground state and two closely adjacent excited states,the efficiency of the generated FWM field is found to be significantly enhanced,up to 60%.More interestingly,a wide region of the maximum FWM efficiency is demonstrated as the ratio of transition dipole moments is within the values ranging from 1.1 to 1.3,which can be maintained for a certain propagation distance(i.e.100 ?m).2)Monolayer graphene under a strong magnetic field has fascinating electronic and optical properties,such as linear dispersion relation,massless Dirac low-energy electrons,chiral character of electron states and special selection rules between Landau levels.Supported by these properties of graphene,we propose and analyze an efficient way to detect the terahertz(THz)signal in a magnetized graphene system via electromagnetically induced transparency.Such a scheme for THz signal detection mainly relies on the measurement of probe transmission spectra,in which the behaviors of a weak-probe transmission spectra can be controlled by switching on/off the THz signal radiation.Taking into account the tunable optical transition frequency between the Landau levels in graphene,our analytical results demonstrate that a broad frequency bandwidth of the THz signal radiation,ranging from 0.36 to 11.4 THz,can be inspected and modulated by means of an external magnetic field.As a consequence,the proposed magnetized graphene system performs a striking potential to utilize quantum interference in the design of optical solid-state devices.3)Similar to the graphene model in above terahertz signal detection,we propose and analyze the competetion between electromagnetically induced transparency and hyper-Raman scattering.By solving the Schrodinger-Maxwell formalism,we derive explicitly analytical expressions for linear susceptibility,nonlinear susceptibility,and generated Raman electric field under the steady-state condition.Based on dressed-state theory,our results show a competition between EIT and hyper-Raman scattering,and the hyper-Raman process is totally dominant when multiphoton destructive interference is completely suppressed.4)In a quadratically coupled optomechanical system,we propose an efficient scheme for the controllable amplification of two-phonon higher-order sidebands.Beyond the conventional linearized approximation,we derive analytical expressions for the output transmission of probe pulse and the amplitude of second-order sideband by adding the nonlinear coefficients into the Heisenberg-Langevin formalism.Using experimentally achievable parameters,we identify the conditions under which the mechanical pump and the frequency detuning of control field allow us to modify the transmission of probe pulse and improve the amplitude of two-phonon higher-order sideband generation.Furthermore,we also find that the higher-order sideband generation depends sensitively on the phase of mechanical pump when the control field becomes strong.The present proposal offers a practical opportunity to design chip-scale optical communications and optical frequency combs.5)We propose an efficient scheme to generate quadrature squeezing of higher-order sideband spectrum in an optomechanical system.That is achieved by exploiting a well-established optomechanical circumstance,where a second-order nonlinearity is embedded into the optomechanical cavity driven by a strong control field and a weak probe pulse.Using experimentally achievable parameters,we demonstrate that the second-order nonlinearity intensity and the frequency detuning of control field allow us to modify the amplitude of higher-order sidebands and improve the amount of squeezing of higher-order sideband spectrum.Furthermore,when the second-order nonlinearity is nearly 'critical point',an optimizing quadrature squeezing of higher-order sideband spectrum can be achieved.In conclusion,this thesis deepens our awareness and understanding of the characteristics of nonlinear optics in low-dimension micro-nano structure.These investigations may have some reference value for the developments of nonlinear spectroscopy,terahertz science,precision measurement. |
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