Isaac Abella
Isaac David Abella (June 20, 1934 – October 23, 2016) was a Professor of Physics at The University of Chicago. He specialized in laser physics, quantum optics, and spectroscopy. Isaac was the cousin of Irving Abella. Isaac Abella was born on June 20, 1934 in Toronto, Ontario. Abella received his Bachelor of Arts degree (1957) from the University of Toronto, Master of Arts (1959) degree, and Ph.D. (1963) in Physics from Columbia University in New York. He studied under Charles H. Townes and was involved in the early research work of laser development. Notably, Abella's thesis under Townes  was among the earliest work on two-photon absorption. He was married to Mary Ann Abella, Professor of Art, Chicago State University. He has a son Benjamin, and daughter, Sarah. Abella was known for his work with laser coherent transients, where photon echo techniques are used to probe metastable excited states in rare gas mixtures such as helium, neon, and argon. These states are produced in a weakly ionized RF plasma discharge, and nitrogen-pumped dye lasers are used to generate the coherent super-position states. The University of Chicago. He was also known for his work in spectroscopy of  rare-earth laser materials. Samples of YLF and YAG crystals doped with erbium, thulium, and holmium are being studied with selective laser excitation in the region of 780 nm, the erbium bands. These materials can be efficiently optically pumped by the AlGaAs-GaAs laser diode arrays, but dye laser excitation is used instead. He was interested in the energy transfer process: Er to Tm, to Ho, which concentrates energy emission at 2.085 µm at room temperature and at liquid nitrogen. The process is a radiationless, almost resonant transfer of energy between sites and depends on the relative concentrations of the  rare earth ions. In particular his experimental interests are measuring decay rates, excited state absorption, and branching ratios and detailed theories of such processes. Isaac Abella died on October 23, 2016 in Chicago, Illinois, at the age of 82.