Selective Population Of Dressed States Research Articles

Quantum control of K2 molecule in an intense laser field：Selective population of dressed states

Control of molecular dynamics in an intense laser field has been studied by employing the time-dependent wave packet approach. A system of K2 molecule in three states (ground state|X, excited state |B and ionized state|X+) serves as a prototype which interacts with pump-probe laser fields. Interacting with an intense pump field, the excited state |B splits into two substates: | and |. Information of the energies and probability distributions of dresses states | and | can be obtained by analysing the photoelectron spectra (PES) of K2 molecule. Meanwhile, the scheme of selective population of dressed states (SPODS) has been put forward according to the dressed states theory of K2 molecule. It is found that regulating the laser intensity can control the dressed state energies, and altering the laser wavelength can make the high selectivity of the dressed state population readied.

Three-state selective population of dressed states via generalized spectral phase-step modulation

We present a joint experimental and theoretical study of selective population of dressed states (SPODS) in a three-level system. Control is exerted by shaped intense femtosecond laser pulses generated by a generalized spectral phase-step modulation function. We show that both control parameters (i.e., the phase-step amplitude and position) can be used to switch population among each three dressed states with high selectivity. The dynamics of the system, and hence the resulting photoelectron signal is studied theoretically by analyzing the time evolution of the adiabatic dressed-state energies and populations.

Strong-field control landscapes of coherent electronic excitation

We report on physical mechanisms behind resonant strong-field coherent control. To this end, we study multi-photon ionization of potassium atoms using intense shaped femtosecond laser pulses. The measured photoelectron spectra are discussed in terms of selective population of dressed states (SPODS). A physically motivated pulse parameterization is introduced which opens up two-dimensional parameter spaces comprising pulse sequences as well as chirped pulses. The control topologies of these subspaces are mapped out experimentally and are presented in the form of strong-field control landscapes (SFCLs). In the SFCLs, complementary realizations of SPODS via photon locking and rapid adiabatic passage are observed. Moreover, the combined effect, termed Multi-RAP, arises when both mechanisms are at play simultaneously. In order to better understand the performance of adaptive optimization procedures, we experimentally study their capability to find optimal solutions on a given parameter space. The evolution of different optimization procedures is visualized by means of control trajectories on the surface of the measured SFCL.

Coherent control of electrons, atoms and molecules with intense shaped light pulses

We report on a physical mechanism of coherent control with intense shaped femtosecond laser pulses. We study photoelectron spectra from multi-photon ionization of potassium atoms and dimers using tailored femtosecond laser pulses. Our results are interpreted in terms of Selective Population of Dressed States (SPODS). Two realizations of SPODS by Photon Locking (PL) via pulse sequences and Rapid Adiabatic Passage (RAP) via chirped pulses are discussed. New physical mechanisms arise, when both PL and RAP are at play simultaneously. Control by the combined effect of PL and RAP is studied by mapping out a two-parameter Quantum Control Landscape (QCL) for selective population of dressed states.

Femtosecond strong-field quantum control with sinusoidally phase-modulated pulses

The quantum control of the ionization of potassium atoms using shaped intense femtosecond laser pulses is investigated. We use sinusoidal phase modulation as a prototype for complex shaped pulses to investigate the physical mechanism of the strong-field quantum control by shaped femtosecond light fields. The influence of all parameters characterizing the sinusoidal phase modulation on strong-field-induced dynamics is studied systematically in experiment and theory. Our results are interpreted in terms of the selective population of dressed states (SPODS) which gives a natural physical picture of the dynamics in intense laser fields. We show that modulated femtosecond pulses in combination with photoelectron spectroscopy are a versatile tool to prepare and to probe SPODS. The decomposition of the excitation and ionization process induced by shaped pulses into elementary physically transparent steps is discussed.

Ultrafast strong field quantum control on K 2 dimers

In this theoretical wave packet study, we demonstrate efficient strong field quantum control by Selective Population of Dressed States (SPODS) on K 2 dimers. Shaped femtosecond pulses are used to switch population transfer among different final states with high selectivity and almost unit efficiency. The physical mechanism of this ultrafast molecular strong field control scenario is analyzed in analogy to the interpretation of recent experimental studies of SPODS on atoms. Criteria for the design of SPODS-pulses are presented along with experimental signatures for the observation of SPODS on molecules.

Quantum control by selective population of dressed states using intense chirped femtosecond laser pulses

The physical mechanism of strong field quantum control using chirped femtosecond laser pulses is investigated. Dressed state control is exerted by making explicit use of the temporal phase changes of the pulse. In our experiment, the dressed state population is mapped by photoelectron spectra from simultaneous excitation and ionization of potassium atoms as a function of the chirp parameter. We show that chirped pulses can be used to selectively steer ground state atoms temporarily into a single dressed state realizing transient Selective Population of Dressed States (SPODS).

Quantum control by ultrafast dressed states tailoring

Strong field quantum control using shaped intense femtosecond laser pulses is investigated. The physical mechanism relies on selective population of dressed states (SPODS). With time resolved photoelectron spectroscopy the ultrafast dressed state population dynamics during the ionization of potassium atoms is directly observed. High selectivity of the dressed state population and tunability of the dressed state energies is demonstrated experimentally. Wave packet simulations on a diatomic model molecule confirm that SPODS is also applicable to molecules. We conclude that SPODS with simple ultrashort optimal pulse shapes is suitable for robust laser control of chemical reactions.

Strong field quantum control by selective population of dressed states

We study the dynamics of potassium atoms in intense laser fields using femtosecond phase-locked pulse pairs in order to extract physical mechanisms of strong field quantum control. The structure of the Autler–Townes (AT) doublet in the photoelectron spectra is measured to analyse transient processes. The analysis shows that the physical mechanism is based on the selective population of dressed states (SPODS). Experimental results of closed loop optimization of SPODS are presented in addition. Applications to decoherence measurements with implications for quantum information are also proposed.