We present an experimental study of the passive propagation of a long laser pulse in a fluorescent dye medium showing the importance of stimulated emission. Enhanced transmission as well as compression of the laser pulse were observed.
We have developed a self-consistent description, based on the semiclassical radiation theory of the propagation of a light pulse in a dye medium. The multilevel nature of the energy bands of a dye molecule and the solvent cage effect in a solution are taken into account. In the case of light pulses whose duration is much shorter than the solvent-solute relaxation time but much longer than the time of atomic phase memory, the latter being of the order of ${10}^{\ensuremath{-}12}$ sec for dyes, we solve the coupled system of equations for the field and the medium by the perturbation procedure. The hole-burning effect is incorporated into the solution in a natural manner. This is especially clear in the direct transition approximation where all the intermediate transitions are neglected. A recent idea of pulse superposition, consisting in storing the energy of a pulse in the form of population inversion followed by stimulated emission triggered by another pulse, is further discussed. Contrary to the orginal model developed by one of us (S.L.C.), we show that no cw pumping is required. The feasibility of the pulse superposition is supported by some experimental results obtained by sending a train of 10-psec pulses through a glycerine solution of oxazine 1 perchlorate.
A report is given of a study of the amplitude-spectral asymmetry of the stimulated emission of superfluorescence from dye solutions pumped longitudinally by nanosecond laser pulses. This amplitude asymmetry is manifested by the difference between the powers of the forward and backward waves, and it is a function of the rate of pumping and of the optical density of the active medium. The asymmetry of stimulated emission from a ring laser is manifested by the appearance of a wave with a traveling-wave ratio of ~90 in the absence of any optical isolators. The spectral asymmetry of a ring laser is manifested by a difference between the spectra of strong and weak waves traveling in opposite directions. A quantitative analysis is made of the effects based on the solution of the transfer equations for radiation traveling in a nonlinearly absorbing active medium.
This dissertation presents experimental and theoretical studies of transient degenerate four wave mixing (DFWM) in organic dyes. Chapter 1 is an introduction to DFWM. Chapter 2 describes DFWM experiments that were performed in the gain medium of a dye laser. Chapter 3 presents the theory of DFWM of short pulses in three level saturable media. Chapter 4 presents DFWM experiments of femtosecond pulses in the saturable absorber of a passively modelocked ring dye laser. Chapter 5 presents the theory of DFWM of ultrashort pulses in resonant media.