Ksenia Dolgaleva

Compact highly-nonlinear AlGaAs waveguides for efficient wavelength conversion

We report on the efficient nonlinear optical interactions in AlGaAs strip-loaded waveguides with a wafer composition specifically designed to increase the nonlinear coefficient. We demonstrate a broad-band self-phase modulation with a nonlinear phase shift up to 6π, and four-wave mixing with a 20-nm tuning range and signal-to-idler conversion efficiency up to 10 dB. Our samples are several times shorter than similar devices used for wavelength conversion by XPM and FWM in previous reports, but the efficiency of the observed effects is similar. Our experimental studies demonstrate the high potential of AlGaAs for all-optical networks.

Local-field effects in nanostructured photonic materials

It is well known that the optical response of a medium depends on the local field acting on an individual emitter rather than on the macroscopic average field in the medium. The local field depends very sensitively on the microcopic environment in an optical medium. It is thus possible to achieve a significant control over the local field by intermixing homogeneous materials on a nanoscale to produce composite optical materials. A combination of local-field effects and nanostructuring provides new degrees of freedom for manipulating the optical properties of photonic materials. Especially interesting opportunities open up in the nonlinear optical regime where the material response depends on the local-field correction as a power law. The goal of this review is to present a conceptual overview of the influence of local-field effects on the optical properties of photonic materials, both homogeneous and composite. We also give a summary of recent achievements in controlling the optical properties by local-field effects and nanostructuring.

Robust organic lasers comprising glassy-cholesteric pentafluorene doped with a red-emitting oligofluorene

Doped with a red-emitting oligofluorene, fluid and glassy cholesteric liquid crystal (CLC) films are characterized by similar lasing thresholds and efficiencies. With picosecond excitations the output from a glassy CLC laser is temporally stable, but that from a fluid CLC laser decays with time. The difference in stability is attributable to external perturbations on supramolecular structure in the fluid but not the solid state, such as heating through optical pumping, light-induced pitch dilation, and laser-induced flow.

Broadband self-phase modulation, cross-phase modulation, and four-wave mixing in 9-mm-long AlGaAs waveguides.

We demonstrate efficient self-phase modulation with a nonlinear phase shift of up to 3π, broadband cross-phase modulation, and four-wave mixing with a 14 nm tunability range in AlGaAs waveguides with a specially designed composition. The length of our sample is only 9 mm, but the efficiency of the observed effects is high.

Enhancement of third-harmonic generation in a polymer-dispersed liquid-crystal grating

We report the observation of significant enhancement of one-step third-harmonic generation in a one-dimensional photonic crystal pumped by a near-infrared laser beam tuned to the low-frequency edge of the first photonic band gap. The third-harmonic phase matching can be controlled by changing the angle of incidence of the fundamental radiation, allowing tunability of the third-harmonic wavelength. The observed phenomenon was modeled theoretically using the transfer-matrix method. The enhancement is attributed to the combined action of phase-matching between the pump and harmonic waves and pump-field localization within the photonic crystal.

Tuneable four-wave mixing in AlGaAs nanowires.

We have experimentally demonstrated broadband tuneable four-wave mixing in AlGaAs nanowires with the widths ranging between 400 and 650 nm and lengths from 0 to 2 mm. We performed a detailed experimental study of the parameters influencing the FWM performance in these devices (experimental conditions and nanowire dimensions). The maximum signal-to-idler conversion range was 100 nm, limited by the tuning range of the pump source. The maximum conversion efficiency, defined as the ratio of the output idler power to the output signal power, was -38 dB. In support of our explanation of the experimentally observed trends, we present modal analysis and group velocity dispersion numerical analysis. This study is what we believe to be a step forward towards realization of all-optical signal processing devices.

Integrated optical temporal Fourier transformer based on a chirped Bragg grating waveguide

We experimentally demonstrate the first integrated temporal Fourier transformer based on a linearly chirped Bragg grating waveguide written in silica glass with a femtosecond laser. The operation is based on mapping the energy spectrum of the input optical signal to the output temporal waveform by making use of first-order chromatic dispersion. The device operates in reflection, has a bandwidth of 10 nm, and can be used for incident temporal waveforms as long as 20 ps. Experimental results, obtained through both temporal oscilloscope traces and Fourier transform spectral interferometry, display a successful Fourier transformation of in-phase and out-of-phase pairs of input optical pulses, and demonstrate the correct functionality of the device for both amplitude and phase of the temporal output.

Continuous-wave quasi-phase-matched waveguide correlated photon pair source on a III–V chip

We report on the demonstration of correlated photon pair generation in a quasi-phase-matched superlattice GaAs/AlGaAs waveguide using a continuous-wave pump. Our photon pair source has a low noise level and achieves a high coincidence-to-accidental ratio greater than 100, which is the highest value reported in III–V chips so far. This correlated photon pair source has the potential to be monolithically integrated with on-chip pump laser sources fabricated on the same superlattice wafer structure, enabling direct correlated/entangled photon pair production from a compact electrically powered chip.

Optical frequency conversion in integrated devices

We review our recent progresses on frequency conversion in integrated devices, focusing primarily on experiments based on strip-loaded and quantum-well intermixed AlGaAs waveguides, and on CMOS-compatible high-index doped silica glass waveguides. The former includes both second- and third-order interactions, demonstrating wavelength conversion by tunable difference-frequency generation over a bandwidth of more than nm, as well as broadband self-phase modulation and tunable four-wave mixing. The latter includes four-wave mixing using low-power continuous-wave light in microring resonators as well as hyper-parametric oscillation in a high quality factor resonator, towards the realization of an integrated multiple wavelength source with important applications for telecommunications, spectroscopy, and metrology.

Optical frequency conversion in integrated devices [Invited]

We review our recent progresses on frequency conversion in integrated devices, focusing primarily on experiments based on strip-loaded and quantum-well intermixed AlGaAs waveguides, and on CMOS-compatible high-index doped silica glass waveguides. The former includes both second- and third-order interactions, demonstrating wavelength conversion by tunable difference-frequency generation over a bandwidth of more than nm, as well as broadband self-phase modulation and tunable four-wave mixing. The latter includes four-wave mixing using low-power continuous-wave light in microring resonators as well as hyper-parametric oscillation in a high quality factor resonator, towards the realization of an integrated multiple wavelength source with important applications for telecommunications, spectroscopy, and metrology.