  Entangled photon spectroscopy is a nascent field that has important
implications for measurement and imaging across chemical, biology, and
materials fields. Entangled photon spectroscopy potentially offers improved
spatial and temporal-frequency resolutions, increased cross sections for
multiphoton and nonlinear measurements, and new abilities in inducing or
measuring quantum correlations. A critical step in enabling entangled photon
spectroscopies is the creation of high-flux entangled sources that can use
conventional detectors, as well as provide redundancy for the losses in
realistic samples. Here, we report a periodically poled, chirped, lithium
tantalate platform that generates entangled photon pairs with a $10^{-7}$
efficiency. For a near watt level diode laser, this results in a near
$\mu$W-level flux. The single photon per mode limit that is necessary to
maintain non-classical photon behavior is still satisfied by distributing this
power over up to an octave-spanning bandwidth. The spectral-temporal photon
correlations are observed via a Michelson-type interferometer that measures the
broadband Hong-Ou-Mandel two-photon interference. A coherence time of 245 fs
for a 10 nm bandwidth in the collinear case and a 62 fs for a 125 nm bandwidth
in the non-collinear case is measured using a CW pump laser, and, essentially,
collecting the full photon cone. We outline in detail the numerical methods
used for designing and tailoring the entangled photons source, such as changing
center wavelength or bandwidth, with the ultimate aim of increasing the
availability of high-flux UV-Vis entangled photon sources in the optical
spectroscopy community.
