Energy storage and two-photon extraction from metastable states

This dissertation presents experimental studies on the energy storage characteristics of excited metastable species and theoretical analysis of optical energy extraction schemes based on stimulated two-photon transitions. The large energy capacity and long lifetime of metastable states offer attractive properties for generating high energy optical pulses for laser fusion and photochemical studies. Recent experimental results on the metastable states of molecular mercury illustrate some of the important properties of energy storage in a gaseous medium. In particular, collisional deactivation of excited metastable species by mutual two-body quenching and by molecular formation are discussed in relation to storage limitations. The optical extraction of energy stored in an inverted metastable system using stimulated two-photon transitions offers nonlinear characteristics not available in the ordinary laser amplifiers. Analytical expressions for the extraction efficiency of an ideal two-photon emission amplifier are derived. The experimental requirements for the proposed systems based on the calculated gains indicate that the currently available pumping methods and trigger laser sources may lead to a demonstration of two-photon amplification and energy extraction.