Theoretical Research On The Improvement Of Solid Harmonic Generation Efficiency And Multichannel Discrimination

The high-order harmonic emitted by the interaction between strong laser and matter are concerned for their wide application prospect.However,the physical mechanism of solid harmonic radiation is still controversial.The sources of solid harmonic radiation are the Bloch oscillations of the electron on each energy band.Therefore,by adjusting the Bloch oscillations at each energy band and the transition population between energy bands,the electron movement at each energy band can be controlled.It points out a new direction for controlling the high-order harmonic radiation and provides a new idea for controlling the quantum path interference.Based on the one-dimensional(Mathieu Type Potential)periodic model Potential,the high-order harmonic radiation mechanism of solid system by solving the single electron time-dependent sch?dinger equation.The main research contents include the following two aspects:(1)The effect of semiconductor carriers on harmonic emission efficiency is studied theoretically.For the electron in semiconductor materials have a certain population of being in the conduction band,that is,forming holes in the valence band,which has a certain conductivity.However,there are few researches on semiconductor harmonic radiation with carrier in the initial state.The superposition of the conduction band minimum(CBM)and valence band maximum(VBM)states are simulate the high-order harmonic radiation of this situation,and it is find that the population of carriers in the conduction band in the initial state will enhance the high-order harmonic intensity.The physical mechanism is discussed by the picture of time-dependent population imaging(TDPI).In addition,the influence of carrier envelope phase(CEP)on harmonic spectrum under the condition of the few periods are also investigated.(2)The multichannel effect caused by interband transitions on solid high-order harmonic radiation is studied theoretically.In solid system,The quantum path of HHG is complex in solid system,multichannel paths contributing the High-order harmonic are identified.Our simulations show that the HHG contributed from the transitions between the conduction bands(CBs)cannot be ignored when the population in high CBs is considerable.The interference of different channels makes the structure of harmonic spectrum more complicated in the second plateau.A scheme is provided to increase the yield of high-order harmonics by adding weak pulses in the fundamental frequency field to strengthen the transition between conduction bands.The physical mechanism is discussed by the time–frequency and quasi-classical analysis.The strength of the quantum path is explained by the population that each band changes over time.It provides a theoretical basis for experimental manipulation of electron dynamics.