Marco Peccianti

Route to Nonlocality and Observation of Accessible Solitons

We develop a general theory of spatial solitons in a liquid crystalline medium exhibiting a nonlinearity with an arbitrary degree of effective nonlocality. The model accounts the observability of accessible solitons and establishes an important link with parametric solitons.

Observation of Optical Spatial Solitons in a Highly Nonlocal Medium

We report on the observation and quantitative assessment of self-trapped pulsating beams in a highly nonlocal nonlinear regime. The experiments were conducted in nematic liquid crystals and allow a meaningful comparison with the prediction of a scalar theory in the perturbative limit, while addressing the need for beyond-paraxial analytical treatments.

Routing of anisotropic spatial solitons and modulational instability in liquid crystals

In certain materials, the spontaneous spreading of a laser beam (owing to diffraction) can be compensated for by the interplay of optical intensity and material nonlinearity. The resulting non-diffracting beams are called ‘spatial solitons’ (refs 1–3), and they have been observed in various bulk media. In nematic liquid crystals, solitons can be produced at milliwatt power levels and have been investigated for both practical applications and as a means of exploring fundamental aspects of light interactions with soft matter. Spatial solitons effectively operate as waveguides, and so can be considered as a means of channelling optical information along the self-sustaining filament. But actual steering of these solitons within the medium has proved more problematic, being limited to tilts of just a fraction of a degree. Here we report the results of an experimental and theoretical investigation of voltage-controlled ‘walk-off’ and steering of self-localized light in nematic liquid crystals. We find not only that the propagation direction of individual spatial solitons can be tuned by several degrees, but also that an array of direction-tunable solitons can be generated by modulation instability. Such control capabilities might find application in reconfigurable optical interconnects, optical tweezers and optical surgical techniques.

All-optical switching and logic gating with spatial solitons in liquid crystals

Using mW light beams to generate spatial solitons in nematic liquid crystals, all-optical switching/logic can be performed on a signal launched in the soliton-induced waveguides. Through the collisional behavior of solitons in a nonlocal medium, the signal can be steered in angle and output position. A power-dependent X junction, AND, and NOR gates are demonstrated.

Demonstration of a stable ultrafast laser based on a nonlinear microcavity.

Ultrashort pulsed lasers, operating through the phenomenon of mode-locking, have played a significant role in many facets of our society for 50 years, for example in the way we exchange information, measure and diagnose diseases, process materials and in many other applications. The ability to phase-lock the modes of the high-quality resonators recently exploited to demonstrate optical combs, would allow mode-locked lasers to benefit from their high optical spectral quality in order to realize novel sources such as precision optical clocks for applications to metrology, telecommunications, microchip-computing, and many other areas. We demonstrate the first mode-locked laser based on a micro-cavity resonator. It operates via a new mode-locking method we termed Filter-Driven (FD) Four-Wave-Mixing, and is based on a CMOS-compatible high quality factor micro-ring resonator. It achieves stable self-starting oscillation with negligible amplitude noise at ultrahigh repetition rates, and spectral linewidths well below 130 kHz.Ultrashort pulsed lasers, operating through the phenomenon of mode-locking, have had a significant role in many facets of our society for 50 years, for example, in the way we exchange information, measure and diagnose diseases, process materials, and in many other applications. Recently, high-quality resonators have been exploited to demonstrate optical combs. The ability to phase-lock their modes would allow mode-locked lasers to benefit from their high optical spectral quality, helping to realize novel sources such as precision optical clocks for applications in metrology, telecommunication, microchip-computing, and many other areas. Here we demonstrate the first mode-locked laser based on a microcavity resonator. It operates via a new mode-locking method, which we term filter-driven four-wave mixing, and is based on a CMOS-compatible high quality factor microring resonator. It achieves stable self-starting oscillation with negligible amplitude noise at ultrahigh repetition rates, and spectral linewidths well below 130 kHz.

Nematicons: Optical Spatial Solitons in Nematic Liquid Crystals

Nematicons are self-trapped light beams in nematic liquid crystalline systems. Thanks to their optically nonlinear, saturable, nonlocal and nonresonant response, they enable light to self-confine and guide additional optical signals, making them an ideal testbed for applications in all-optical information processing.

Spatial soliton all-optical logic gates

We demonstrate some basic all-optical (electrically unbiased) logic gates in azobenzene liquid crystalline cells, exploiting their large nonlinearity for light localization and the trans-cis photoisomerization for all-optical external control. Spatial solitons were excited at microwatt power levels at 632.8 nm, whereas gating and switching were achieved with milliwatt beams at 409 nm

Interplay between nonlocality and nonlinearity in nematic liquid crystals.

Spatial nonlocality has a crucial role in the optical response of bulk liquid crystals. With specific reference to one-dimensional modulation instability, we demonstrate the tuning of transverse nonlocality in the nonlinear response of nematics.

Integrated frequency comb source of heralded single photons

We report an integrated photon pair source based on a CMOS-compatible microring resonator that generates multiple, simultaneous, and independent photon pairs at different wavelengths in a frequency comb compatible with fiber communication wavelength division multiplexing channels (200 GHz channel separation) and with a linewidth that is compatible with quantum memories (110 MHz). It operates in a self-locked pump configuration, avoiding the need for active stabilization, making it extremely robust even at very low power levels.We report an integrated photon pair source based on a CMOS-compatible microring resonator that generates multiple, simultaneous, and independent photon pairs at different wavelengths in a frequency comb compatible with fiber communication wavelength division multiplexing channels (200 GHz channel separation) and with a linewidth that is compatible with quantum memories (110 MHz). It operates in a self-locked pump configuration, avoiding the need for active stabilization, making it extremely robust even at very low power levels.

Low power four wave mixing in an integrated, micro-ring resonator with Q = 1.2 million

We demonstrate efficient, low power, continuous-wave four-wave mixing in the C-band, using a high index doped silica glass micro ring resonator having a Q-factor of 1.2 million. A record high conversion efficiency for this kind of device is achieved over a bandwidth of 20 nm. We show theoretically that the characteristic low dispersion enables phase-matching over a tuning range > 160 nm.We demonstrate efficient, low power, continuous-wave fourwave mixing in the C-band, using a high index doped silica glass micro ring resonator having a Q-factor of 1.2 million. A record high conversion efficiency for this kind of device is achieved over a bandwidth of 20nm. We show theoretically that the characteristic low dispersion enables phasematching over a bandwidth > 160nm.