Figure 2.1: Quantum coherent control influencing the evolution of a wavefunction. The system‘s initial wavefunction ψi evolves to a coherent superposition of the all possible final states ψf(n) under the influence of the control-free Hamiltonian Ho....(이미지참조) 16

Figure 2.2: Schematic of femtosecond pulse shaping in frequency domain with spatial light modulator. Gratings and lenses are arranged in a 4f configuration. The pulse shaping procedure is described in the text. 18

Figure 2.3: (a) AOPDF top view. The output beam is diffracted by 1 degree from the input beam, in the 90-degree-rotated linear polarization. (b) Schematic of AOPDF. Mode 1 in fast ordinary axis and mode 2 in slow extraordinary axis, are coupled by acousto-optic interaction when the phase matching... 20

Figure 2.4: Synthesis of the pulse shaping function parameters of the acoustic wave. Acoustic wave parameters are categorized into amplitude shaping and phase shaping parts. The frequency domain acoustic wave is Fourier transformed to the time domain signal and applied to the acousto-optic medium... 21

Figure 2.5: Experimental setup of adaptive coherent control. A SLM or femtosecond pulse shaper is used to shape the pulse with a help of feedback signal and closed-loop learning algorithm. The learning algorithm iteratively finds optimum pulses for different types of experiments. 23

Figure 2.6: (a) Drawing of the MLCT chromophore [Ru(dpb)₃]2+. (b) Normalized absorption (dashed line) and emission spectra (solid line) collected for the molecule dissolved in methanol at 298 K. (c) The schematic of the control methodology where multiphoton absorption of a shaped 800 nm laser pulse...(이미지참조) 24

Figure 2.7: Experimental results of adaptive control on [Ru(dpb)₃](PF6)₂. Solid circles are for maximization and open circles are for minimization of the ratio excitation/SHG.(이미지참조) 24

Figure 2.8: Energy level diagram of a resonant TPA in Rb. The frequencies of the 5S-5P (ωig) and 5P- 5D (ωfi) resonant transitions correspond to 780.2 nm and 776.0 nm, respectively. The pulse spectrum is centered on the two-photon transition frequency (ωfg/2) at 778.1 nm, with a bandwidth of Δω=...(이미지참조) 26

Figure 2.9: Experimental and calculated results performed on resonant two-photon transition in Rb atom. (a) Schematic expression of tested scheme. spectral components of the pulse was blocked symmetrically around ωfg /2 by an adjustable slit....(이미지참조) 27

Figure 2.10: Excitation scheme of rubidium. т is the pump-probe delay. 29

Figure 2.11: (a) Calculation results of excited transient population with unshaped (in amplitude) chirped pump pulse (black line) and with hole-shaped (in amplitude) in time domain chirped pulse (solid gray line) as the inset. The amount of chirp is same for both pulses.... 30

Figure 3.1: (a) Energy diagram of a V-type three-level system with one ground state |g〉 and two excited states |a〉 and |b〉. The transition energies of |a〉 and |b〉 from |g〉 are hωa and hωb respectively. The transition between |a〉 and |b〉 via |g〉 is presented by a red line and transition between |b〉 and |g〉 by...(이미지참조) 32

Figure 3.2: Peaks of 2D Fourier transform plane of |〈b|ψ〉|² state population coefficients (left part). Row and column are Fourier transform of т₁and т₂ respectively, and categorized with the coefficients of т₁and т₂.... 40

Figure 3.3: Peaks of 2D Fourier transform plane of |〈b|ψ〉|² state population coefficients (right part). Row and column are Fourier transform of т₁and т₂ respectively, and categorized with the coefficients of т₁and т₂.... 41

Figure 4.1: (a) Schematic representation of the experimental setup. (b) Pulse shaping scheme. The first pulse had a spectral hole around D₂ transition and the second pulse was pulse-shaped in various methods correspond to experimental purposes.... 44

Figure 4.2: (a) Experimental fluorescence data of 2D-FTOS measurement given as a function of two time delays, т₁and т₂. (b) 2D Fourier-transformed spectrum S(ω₁, ω₂) obtained from the time domain data (a).... 46

Figure 4.3: (a) Schematic diagram of the pulse shaping scenario. The first pulse has a spectral hole around D₂ transition and the second pulse is pulse-shaped to control the inter-excited state transition. The third pulse is unshaped.... 48

Figure 4.4: Numerical calculation results of 2D Fourier transform spectra, S(ω₁, ω₂), for the linearly chirped second pulses of the two different chirp coefficients: (a) -1 x 10³ fs², and (b) 1 x 10³ fs². The peak at (ωag - ω0, ωbg - ω0) denotes the the controlled transition |a〉 → |b〉.(이미지참조) 49

Figure 4.5: Experimental results of 2D FT spectra S(ω₁,ω₂) for shaped pulses with the five different chirp coefficients: (a) -1 x 10³ fs², (b) -5 x 10² fs², (c) zero, (d)5 x 10² fs², and (e) 1 x 10³ fs². The peaks at (ωag - ω0, ωbg - ω0) are marked by white arrows which represent the target two-photon process, 5P1/2 →...(이미지참조) 51

Figure 4.6: (a)-(c) Experimental results of 2D Fourier transformed spectra S(ω₁,ω₂) in contour map representation for linear chirp values of (a) -1000 fs², (b) zero, and (c) 1000 fs². The peaks (ωag - ω0, ωbg - ω0) are marked by black arrows....(이미지참조) 53

Figure 4.7: (a) Experimental and theoretical results for the quantum interference engineering. Dots: measured transition amplitude absolutes, dashed line: numerical calculation based on Eq. (4.6), solid line: numerical calculation considering the spectrally smeared phase (see the text).... 54

Figure 4.8: Coherent enhancement experiment of the 5P1/2 → 5P3/2 transition of Rb by spectral amplitude shaping. The measured transition probability amplitudes, normalized to the full spectrum limit (dots), are plotted along with the calculated data (dark line) as a function of the cutoff wavelength....(이미지참조) 55

Figure 5.1: Calculated transition probability amplitude from |a〉 to |b〉 via an intermediate state |g〉 using the Eq. (5.23): (a) is the resonant part (the first term), and (b) the nonresonant part (the second term). 62

Figure 5.2: (a) Numerical calculation of |cba(2)| plotted as a function of linear and quadratic chirps. (b) Extracted amplitudes of (ωag - ω0, ωbg - ω0) peaks of 2D Fourier transformed spectra (experimented for the white rectangular area in (a); interpolated twice from 13 x 7 measurements....(이미지참조) 63

Figure 5.3: (a) Extracted transition probabilities from the experimental 2D-spectra at (ωag-ω0, ωbg-ω0) peaks (circles) together with the numerical calculations of 5P1/2-5P3/2 transition (lines) as a function of linear chirp for quadratic chirp of the second pulse, (a) -5x10⁴fs³, (b) -3x10⁴fs³, (c) -1x10⁴fs³, (d)...(이미지참조) 65

Figure 6.1: Schematic exciton energy diagram of a localized state and a Wannier-Stark mini-band in a quantum-well superlattice under an external electric Stark field. As the field varies, the mini-band becomes lifted in energy, then, the localized state couples to lower-energy states of the band.... 67

Figure 6.2: Excitonic spectra of a 97/17 Å superlattice for different bias Stark fields, measured in reflection. 69

Figure 6.3: (a) The conventional Fano coupling parameter Г (asterisks) and the “bare" coupling parameter Гo (circles) which compensates the effects of the density of continuum states, depicted as a function of the Stark field for the hh-1 transition....(이미지참조) 71

Figure 6.4: Fano resonance of an exciton state with neighboring extended Wannier-Stark states. Between the resonant couplings with the next nearest neighboring WS state in (I) and with the nearest neighboring WS state in (III), the exciton state resonantly sweeps through the energy interval, having the minimal... 73

Figure 6.5: Bandgap energy and lattice constant of various III-V compounds at room temperature (adopted from Tien 1988). 74

Figure 6.6: (a) Band diagram of the double-quantum well structure and the energies of the bound states. Band diagrams are shown in black (valence band) and gray (conduction band) lines, and the excited states energies in pink (narrower well) and orange (wider well).... 75

Figure 6.7: Band diagram of the newly designed double-quantum well structure forming a V-type quantum system and the wavefunctions of one ground state and two excited states. 76

Figure 6.8: Band edges as a function of lattice constant of various III- V compounds at room temperature, relative to Fermi level of gold Schottky contact (after Tiwari and Frank, 1992). 76