Nonlinear spectroscopy and microscopy techniques are ubiquitous in a wide range of applications across physics biology. However, these usually rely on high-powered pulsed laser systems. A promising alternative is to exploit entangled two-photon absorption (ETPA), which can lead tens orders magnitude lower incident fluxes than conventional schemes. the role different degrees freedom ETPA was unc...

Recent progress in femtosecond (fs) tera-watt (TW) laser development has raised a new fundamental question in atomic and molecular physics, i.e., how atoms and molecules react against an intense electromagnetic field. As is well known, an atom exposed to photons of relatively low flux density is ionized only if the photon energy exceeds the ionization potential of the atom. On the other hand, w...

BACKGROUND Two-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs) is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used and their low two-photon absorption (2PA...

Current constraints on photon velocity variability are summarized and displayed in terms of an energy dependent vacuum refraction index. It is shown that the energy-momentum balance of high energy Compton scattering is very sensitive to the outgoing photon speed. A missing energy observation in HERA Compton polarimeter data indicates that photons with 12.7 GeV energy are moving faster than ligh...

An empirical Compton up-scattering model is described which reproduces both the fractional amplitude (RMS) vs. energy and the soft time lags in the ≈ 830 Hz QPO observed in 4U1608-52 on Mar. 3, 1996. A combination of two coherent variations in the coronal and soft photon temperatures (with their relative contributions determined by enforcing energy conservation) gives rise to the QPO’s energy d...

This paper lays out the mechanics of creation in the 3-spaces model of an electron-positron pair as a photon of energy 1.022 MeV or more is destabilized when grazing a heavy particle such as an atom's nucleus, thus converting a massless photon into two massive .511 MeV/c particles charged in opposition. An alternate process was also experimentally discovered in 1997, that involves converging tw...

Studies on the structure of the photon are presented by means of the extraction of a leading order effective parton distribution in the photon and measurements of inclusive jet differential cross sections in photoproduction. Measurements of the internal structure of jets have been performed and are also presented as a function of the transverse energy and pseudorapidity of the jets. Dijet cross...