Fabrication of 1 × integrated power splitters with arbitrary power ratio for single and multimode photonics.

Compact power splitters are essential components in integrated optics. While 1 × 2 power splitters with uniform splitting are widely used, a 1 × splitter with arbitrary number of ports and arbitrary splitting ratio is yet to be demonstrated. In this work we address this problem.

Subwavelength and broadband on-chip mode splitting with shifted junctions.

We design and fabricate a sub-wavelength on-chip mode splitter based on the implementation of a shifted junction between a single-mode waveguide and a multimode waveguide. A proper choice of the device parameters enables to split the input beam into a combination of different guided modes of the multimode waveguide, minimizing radiation and reflection losses that amount to ∼ 0.4 dB in our experiments.

Mode attraction, rejection and control in nonlinear multimode optics.

Novel fundamental notions helping in the interpretation of the complex dynamics of nonlinear systems are essential to our understanding and ability to exploit them. In this work we predict and demonstrate experimentally a fundamental property of Kerr-nonlinear media, which we name mode rejection and takes place when two intense counter-propagating beams interact in a multimode waveguide. In stark contrast to mode attraction phenomena, mode rejection leads to the selective suppression of a spatial mode in the forward beam, which is controlled via the counter-propagating backward beam.

Near to short wave infrared light generation through AlGaAs-on-insulator nanoantennas.

AlGaAs-on-insulator (AlGaAs-OI) has recently emerged as a promising platform for nonlinear optics at the nanoscale. Among the most remarkable outcomes, second-harmonic generation (SHG) in the visible/near infrared spectral region has been demonstrated in AlGaAs-OI nanoantennas (NAs). In order to extend the nonlinear frequency generation towards the short wave infrared window, in this work we propose and demonstrate via numerical simulations difference frequency generation (DFG) in AlGaAs-OI NAs.

Selective wavelength conversion in a few-mode fiber.

We experimentally demonstrate a means to selectively enhance wavelength conversion of WDM channels on a 100 GHz grid exploiting nonlinear effects between the spatial modes of a few mode fiber. The selectivity of parametric gain is obtained by dispersion design of the fiber such that the inverse group velocity curves of the participating modes are parallel and their dispersion is suitably large. We describe both theoretically and experimentally the observed dependence of the idler gain profile on pump mode (quasi) degeneracy.

40 GHz pulse source based on cross-phase modulation-induced focusing in normally dispersive optical fibers.

We theoretically and experimentally investigate the design of a high-repetition rate source delivering well-separated optical pulses due to the nonlinear compression of a dual-frequency beat signal within a cavity-less normally dispersive fiber-based setup. This system is well described by a set of two coupled nonlinear Schrödinger equations for which the traditional normally dispersive defocusing regime is turned in a focusing temporal lens through a degenerated cross-phase modulation process (XPM). More precisely, the temporal compression of the initial beating is performed by the combined effects of normal dispersion and XPM-induced nonlinear phase shift provided by an intense beat signal on its weak out-of-phase replica co-propagating with orthogonal polarizations.

Intensity noise-driven nonlinear fiber polarization scrambler.

We propose and analyze a novel all-optical fiber polarization scrambler based on the transfer (via the Kerr effect) of the intensity fluctuations of an incoherent pump beam into polarization fluctuations of a frequency-shifted signal beam, copropagating in a randomly birefringent telecom fiber. Optimal signal polarization scrambling results whenever the input signal and pump beams have nearly orthogonal states of polarization. The nonlinear polarization scrambler may operate on either cw or high-bit-rate pulsed signals.

Theory of modal attraction in bimodal birefringent optical fibers.

Nonlinear mode coupling among two beams of different wavelength that copropagate in a bimodal highly birefringent optical fiber may lead to the effect of modal attraction. Under such circumstances, the modal distribution of light at a pump wavelength is replicated at the signal wavelength, nearly irrespective of the input mode excitation conditions of the signal.

Subwavelength diffraction management.

We study light propagation in nanoscale periodic structures composed of dielectric and metal in the visible range. We demonstrate that diffraction can be tailored both in magnitude and in sign by varying the geometric features of the waveguides. Diffraction management on a subwavelength scale is demonstrated by numerical solution of Maxwell equations in the frequency domain.