R&D: Integrated Optical Memory Based on Laser-Written Waveguides

Physical Review Applied has published an article written by Giacomo Corrielli^, Istituto di Fotonica e Nanotecnologie–Consiglio Nazionale delle Ricerche and Dipartimento di Fisica–Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italia, Alessandro Seri , Margherita Mazzera, ICFO-Institut de Ciencies otoniques, The Barcelona Institute of Technology, 08860 Castelldefels (Barcelona), Spain, Roberto Osellame, Istituto di Fotonica e Nanotecnologie–Consiglio Nazionale delle Ricerche and Dipartimento di Fisica–Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133 Milano, Italia, and Hugues de Riedmatten, ICFO-Institut de Ciencies otoniques, The Barcelona Institute of Technology, 08860 Castelldefels (Barcelona), Spain, and ICREA-Institució Catalana de Recerca i Estudis Avançats, 08015 Barcelona, Spain.

(a) Microscope picture of the waveguide cross section.
The distance between the damage tracks is    . The red dashed ellipse
indicates the     contour of the guided mode. Scale bar is    .
(b) CCD-acquired near-field intensity profile of the guided mode.
Scale bar is    . (c), (d) Normalized intensity profiles of the waveguide
mode along the   and   sections  indicated in panel (b).
The resulting full widths at half maximum
(FWHM) are       and       (green solid level).
The measured     diameters are       and      
(red dashed level).

Abstract: “We propose and demonstrate a physical platform for the realization of integrated photonic memories based on laser-written waveguides in rare-earth-doped crystals. Using femtosecond-laser micromachining, we fabricate waveguides in   ∶    crystal. We demonstrate that the waveguide inscription does not affect the coherence properties of the material and that the light confinement in the waveguide increases the interaction with the active ions by a factor of 6. We also demonstrate that analogous to the bulk crystals, we can operate the optical pumping protocols necessary to prepare the population in atomic-frequency combs that we use to demonstrate light storage in excited and spin states of the Praseodymium ions. Our results represent a realization of laser-written waveguides in a   ∶    crystal and an implementation of an integrated on-demand spin-wave optical memory. They open perspectives for integrated quantum memories.“