Giuseppe Leo

Advances in integrated parametric sources (Conference Presentation)

The last couple of years have witnessed an unprecedented boost in nonlinear nanophotonics, allowed both by constant technological evolution in the fabrication of integrated micro- and nano-structures, and by a deeper understanding of multipolar magnetic and electric response of all-dielectric sub-wavelength nanoparticles. Besides reviewing the recent progress in the hybrid and monolithic semiconductor platforms that are being employed to demonstrate parametric sources on chip, we will focus on high-contrast nonlinear nanophotonic sources in the near-infrared spectral region, where plasmonic devices fall short of broad applicability. To confine photons at the nanoscale by total internal reflection, metal-less devices rely on a high-refractive-index core surrounded by low-index cladding in one or more dimensions, and therefore they typically consist of semiconductor nanostructures that either lie on an oxide substrate or are suspended in air. We will report on our results on χ(2) AlGaAs suspended nanowires [1] and AlGaAs-on-AlOx nanoantennas [2], with a perspective view on collective nonlinear effects in 1D and 2D arrays. Finally we will comment on the most sought applications of integrated parametric sources, including optical frequency comb generators and optical parametric oscillators on-chip with sub-milliwatt threshold. nnn[1] N. Morais, I. Roland, M. Ravaro, I. Favero, A. Lemaitre, S. Wabnitz, M. De Rosa, and G. Leo, SPIE Nanophotonics Australasia 2017, Melbourne 10-13/12/2017.n[2] V. F. Gili, L. Carletti, A. Locatelli, D. Rocco, M. Finazzi, L. Ghirardini, I. Favero, C. Gomez, A. Lemaitre, M. Celebrano, C. De Angelis, and G. Leo, Opt. Express 24, 15965 (2016).

Observation of spatial optical solitons in nonlinearly coupled waveguides

This paper discusses the observation of quadratic spatial optical solitons in a guided-wave nonlinearly-coupled structure. The experiments, performed at a pump wavelength /spl lambda//sub /spl omega// = 1.319 /spl mu/m, provide a clear evidence of the nonlinear coupling between orthogonally polarized eigenmodes, with maximum conversion when mode matching TE/sub 0/(/spl omega/) with TM/sub 12/(2/spl omega/).

Second harmonic generation in coupled LiNbO/sub 3/ waveguides

Summary form only given. It is known that as proton-exchanged (PE) lithium niobate (LN) undergoes the reverse process (RPE), a partial restoring of lithium-ion content occurs. In z-cut LN substrates, the above phenomenon defines a surface waveguide for TE polarization, and a buried one for TM polarization. Here, we present SHG experiments in unpoled, 17 mm long PE-RPE planar waveguides in z-cut LN.

Novel spatial solitons in reverse proton exchanged lithium niobate waveguides

Summary form only given. A novel type of quadratic spatial solitons is envisaged in coupled waveguide structures in LiNbO/sub 3/. In these novel PE-RPE geometries, vector solitary waves couple orthogonally-polarized guided modes at the fundamental and second harmonic; they support power-dependent self-channeling and frequency-comb filtering of the input light.

Reverse proton exchange for frequency doubling in lithium niobate waveguides

Reverse proton exchange is a promising technique for the fabrication of nonlinear waveguides in unpoled lithium niobate (LN). We have investigated nonlinear processes in these waveguides for the frequency doubling of near infrared light at 1319 nm. After summarizing the technological processes adopted for the fabrication of planar and channel structures in z-cut LN, we report the preliminary experimental results obtained in planar waveguides, along with numerical simulations in both one- and two-dimensional geometries.