Signal processing by opto-optical interactions between self-localized and free propagating beams in liquid crystals

The reorientational nonlinearity of nematic liquid crystals enables a self-localized spatial soliton and its waveguide to be deflected or destroyed by a control beam propagating across the cell. We demonstrate a simple all-optical readdressing scheme by exploiting the lens-like perturbation induced by an external beam on both a nematicon and a co-polarized guided signal of different wavelength. Angular steering as large as 2.2 degrees was obtained for control powers as low as 32mW in the near infrared

Time-resolved nonlinear ghost imaging

Terahertz (THz) spectroscopy systems are widely employed to retrieve the chemical and material composition of a sample. This is single-handed the most important driving motivation in the field and has largely contributed to shaping THz science as an independent subject. The limited availability of high-resolution imaging devices, however, still represents a major technological challenge in this promising field of research. In this theoretical work, we tackle this challenge by developing a novel nonlinear Ghost Imaging (GI) approach that conceptually outperforms established single-pixel imaging protocols at inaccessible wavelengths. Our methodology combines nonlinear THz generation with time-resolved field measurements, as enabled by state-of-the-art Time Domain Spectroscopy (TDS) techniques. As an ideal application target, we consider hyperspectral THz imaging of semi-transparent samples with nonnegligible delay contribution and we demonstrate how time-resolved, full-wave acquisition enables accurate spatiotemporal reconstruction of complex inhomogeneous samples

FLEA: Fresnel-limited extraction algorithm applied to spectral phase interferometry for direct field reconstruction (SPIDER)

We present a novel extraction algorithm for spectral phase interferometry for direct field reconstruction (SPIDER) for the so-called X-SPIDER configuration. Our approach largely extends the measurable time windows of pulses without requiring any modification to the experimental X-SPIDER set-up.Comment: 24 pages 26 references 8 figure

CMOS compatible integrated all-optical radio frequency spectrum analyzer

We report an integrated all-optical radio frequency spectrum analyzer based on a ~4cm long doped silica glass waveguide, with a bandwidth greater than 2.5 THz. We use this device to characterize the intensity power spectrum of ultrahighrepetition rate mode-locked lasers at repetition rates up to 400 GHz, and observe dynamic noise related behavior not observable with other technique

Characterization of high-speed balanced photodetectors

We report the characterization of a balanced ultrafast photodetector. For this purpose, we use a recently developed time-domain laser-based vector network analyzer (VNA) to determine the common-mode rejection ratio (CMRR) of the device under test. This includes the frequency-domain response above the single-mode frequency of the coaxial connector. Although the balanced photodetector has a nominal bandwidth of 43 GHz, it generates voltage pulses with frequency components up to 180 GHz. We obtain a CMRR of better than 30 dB up to 70 GHz and better than 20 dB up to 110 GHz. The laser-based measurements are compared with the measurements using a digital sampling oscilloscope and with the frequency-domain measurements using a conventional VNA. We obtain good agreement between the three techniques with the laser-based method providing the largest measurement bandwidth, although it also constitutes the most complicated characterization setup

Self-locked optical parametric oscillation in a CMOS compatible microring resonator: a route to robust optical frequency comb generation on a chip

We report a novel geometry for OPOs based on nonlinear microcavity resonators. This approach relies on a self-locked scheme that enables OPO emission without the need for thermal locking of the pump laser to the microcavity resonance. By exploiting a CMOS-compatible microring resonator, we achieve oscillation featured by a complete absence of “shutting down”, i.e. the self-terminating behavior that is a very common and detrimental occurrence in externally pumped OPOs. Further, our scheme consistently produces very wide bandwidth (>300nm, limited by our experimental set-up) combs that oscillate at a spacing equal to the FSR of the micro cavity resonance

Efficient wavelength conversion and net parametric gain via four wave mixing in a high index doped silica waveguide

We demonstrate sub-picosecond wavelength conversion in the C-band via four wave mixing in a 45cm long high index doped silica spiral waveguide. We achieve an on/off conversion efficiency (signal to idler) of + 16.5dB as well as a parametric gain of + 15dB for a peak pump power of 38W over a wavelength range of 100nm. Furthermore, we demonstrated a minimum gain of + 5dB over a wavelength range as large as 200nm