Spotlight

Kasturi Saha

Kasturi Saha, graduate student, working with Prof. Alexander Gaeta (A&EP) on Quantum and Nonlinear Photonics aims at understanding light-matter interactions with hot atomic vapors (Rubidium) confined inside hollow-core photonic bandgap fibers(HCPBF). Hollow-core photonic crystal fibers offer low-loss guidance over long lengths in a single mode with very low nonlinearities. These fibers can be filled with atoms and molecules to greatly enhance their nonlinear interaction with light confined in the core. For example, two-photon absorption in Rb has always been observed using a few watts of laser power and characterized using fluorescence measurements techniques. In contrast, using mW of input power we expect to observe two-photon absorption such that it is directly measurable from the output coupled light of the fiber. 

Also, in collaboration with the Lipson Group (ECE), she is studying the effect of coupling of evanescent light from silica-nitride waveguides on-chip with an ambient Rb vapor. The advantage of using these on-chip waveguides is that we can tailor the dimensions of the waveguides and add structures like ring resonators coupled to the waveguides and hence have better confinement and control over the light. The goal is to demonstrate optical bi-stability at a few photon number level, ultimately demonstrating single-photon switching, Kasturi explains. Further she hopes to generate an octave spanning frequency comb in on-chip silica nitride waveguides coupled to ring resonators for the purpose of spectroscopy.