Many traditional investigations of saturation in multiphoton absorbers with the z-scan method use an approximate
analytical formula that assumes a steady-state approximation. Using a numerical simulation for Maxwell’s equations for
laser propagation including diffraction and coupled electron population dynamics, we show that the commonly used
analytical formula for determining saturation in multiphoton absorbers is often incorrect, even when the sample thickness
is only one diffraction length. Using published experimental data on an organic chromophore, we show that saturation, in
fact, does not occur at the laser intensity values predicted for these two and three photon absorbers. We numerically fit
the published experimental z-scan data and obtain new absorption coefficients for multiphoton absorbers that accurately
reflect their intrinsic values. The new values are from three to ten times larger than the published values.
Because multiphoton absorbers are being used more extensively in many applications such as optical limiter, medical
diagnostics and two photon microscopy, it is important to have accurate values for the two and three-photon absorption
coefficients. Knowing the real value of the multiphoton absorber coefficients, even for a single diffraction length, is
therefore of the utmost importance. In particular, the laser intensity at which the absorber saturates can determine which
absorber is useful for a particular application.
Because metamaterials often utilize strong resonances, a strong group delay dispersion (GDD) is also possible. This
property is an important parameter for ultrafast laser pulse propagation. The Multiphoton Intrapulse Interference Phase
Scan (MIIPS) technique was used to measure the GDD directly over the bandwidth of an ultrafast laser. The measured
GDD of a double-chirped dielectric mirror with a strong resonance was an order of magnitude larger than that of a
dispersive optical glass three orders of magnitude thicker and was shown to be highly wavelength dependent. The impact
of the measured dispersion of this dielectric mirror was explored computationally and the impact on pulse shape of
ultrashort pulses of light with a bandwidth comparable to the wavelength-dependent features of the GDD is shown.
Semi-insulating and conducting SiC crystalline transparent substrates were studied after being processed by
femtosecond laser radiation (780nm at 160fs). Z-scan and damage threshold experiments were performed on both SiC
bulk materials to determine each samples' nonlinear and threshold parameters. "Damage" in this text refers to an index
of refraction modification as observed visually under an optical microscope. In addition, a study was performed to
understand the damage threshold as a function of numerical aperture. Presented here for the first time, to the best of our
knowledge, is the damage threshold, nonlinear index of refraction, and nonlinear absorption measured values.
Organic materials exhibiting strong two-photon absorption cross-sections and subsequent up-converted fluorescence have been targeted for use in a variety of applications including optical data storage, nondestructive imaging, frequency up-converted lasing, and microfabrication. In order for these materials to be useful in practical application they must either be coupled with a liquid solvent or doped into a solid host material. The purpose of this study is to examine effects of different host environments on the nonlinear photophysical properties of AF-455, a recently developed organic two-photon absorber. We present results of experiments using both emission and absorption methods to characterize the linear and nonlinear response of AF-455 dissolved in solvents of varying polarity and doped in a polymer (PMMA) matrix.