Enhanced Control and Characterization of Complex Molecules with Ultrashort Lasers

Abstract

Quantum control employs ultrashort-pulse laser fields to observe and guide atoms and molecules by manipulating the wave-like interference between quantum pathways, generating constructive interference favoring a target product state.

As technology has developed, especially tools for femtosecond pulse generation and shaping,

the range of systems investigated by quantum control has grown from simple dilute atomic gases to complex condensed phase molecules.

This thesis applies the tools of quantum control to optically-sensitive biochemical protein sensors and switches.

A primary focus of this work is the enhanced control of Optogenetic switching by non-linear pulsed excitation. Optogenetics enables optical control of \emph{in vivo} biological functions by inserting light-sensitive switches into cells. However, spectral cross-talk between switch states (their overlapping steady-state absorption and emission spectra) prevents full-range control.

We introduce a novel nonlinear optical technique to overcome cross-talk by exploiting differences in the excited state dynamics of the active and inactive switch states.

We effectively demonstrate the feasibility of this control mechanism and begin characterizing the dependence of the enhancement factor on laser control parameters to discover the laser controls which most effectively maximize the dynamic range of the optogenetic switch.

This proof of principle work is a first step toward multiplexed control of multiple optogenetic switches.

We also quantitatively characterize mixtures of Fluorescent Proteins (FPs) suffering from cross-talk by employing Optimal Dynamic Discrimination (ODD), which amplifies differences in the excited state dynamics of quantum systems using optimally tailored control fields.

ODD enables accurate concentration determination of mixtures of Enhanced Blue and Enhanced Cyan FPs, advancing the technique toward the simultaneous monitoring of many biochemical processes by multiplexed ODD of several FPs, leading to the ultimate goal of implementing ODD to control multiple sensors and switches for multiplexed control and observation of biochemical processes.

This thesis also presents a novel capability to map concentrations of intermixing fluids in colliding micro-droplets using planar laser induced fluorescence of a chemically-sensitive dye, revealing details of early-stage mixing; as well as an evaluation of new and developing ultrafast optical technologies to suggest tools for future development of optimal quantum control experiments.