Photon-pair generation in arrays of cubic nonlinear waveguides.

We study photon-pair generation in arrays of cubic nonlinear waveguides through spontaneous four-wave mixing. We analyze numerically the quantum statistics of photon pairs at the array output as a function of waveguide dispersion and pump beam power. We show flexible spatial quantum state control such as pump-power-controlled transition between bunching and anti-bunching correlations due to nonlinear self-focusing.

Non-classical interference in integrated 3D multiports.

We demonstrate three and four input multiports in a three dimensional glass platform, fabricated using the femtosecond laser direct-write technique. Hong-Ou-Mandel (HOM) interference is observed and a full quantum characterization is performed, obtaining two photon correlation matrices for all combinations of input and output ports. For the 3-port case, the quantum visibilities are accurately predicted solely from measurement of the classical coupling ratios.

Multi-wavelength gratings formed via cascaded stimulated Brillouin scattering.

We present the experimental observation of multi-wavelength fiber Bragg gratings in As2Se3 fiber. The gratings are internally written via two-photon absorption of 1550 nm pump light and its first and second order Stokes waves generated by cascaded stimulated Brillouin scattering (SBS). We demonstrate a parameter regime that allows for 4 dB grating enhancement by suppression of SBS.

Slow-light dispersion engineering of photonic crystal waveguides using selective microfluidic infiltration.

We experimentally demonstrate dispersion engineering of slow light photonic crystal (PhC) waveguides using selective infiltration of the first two rows of air holes with high index ionic liquids. The infiltrated PhC waveguide exhibits a dispersion window of 3 nm with a nearly constant group velocity of ~c/80 that depends on the liquid physical properties. We investigate how the effective refractive index changes in time due to the dynamics of the liquids in the holes.

Photonic chip based tunable and reconfigurable narrowband microwave photonic filter using stimulated Brillouin scattering.

We report the first demonstration of a photonic chip based dynamically reconfigurable, widely tunable, narrow pass-band, high Q microwave photonic filter (MPF). We exploit stimulated Brillouin scattering (SBS) in a 6.5 cm long chalcogenide (As2S3) photonic chip to demonstrate a MPF that exhibited a high quality factor of ~520 and narrow bandwidth and was dynamically reconfigurable and widely tunable.

Design for broadband on-chip isolator using Stimulated Brillouin Scattering in dispersion-engineered chalcogenide waveguides.

We propose a scheme for on-chip isolation in chalcogenide (As₂S₃) rib waveguides, in which Stimulated Brillouin Scattering is used to induce non-reciprocal mode conversion within a multi-moded waveguide. The design exploits the idea that a chalcogenide rib buried in a silica matrix acts as waveguide for both light and sound, and can also be designed to be multi-moded for both optical and acoustic waves. The enhanced opto-acoustic coupling allows significant isolation (> 20 dB) within a chip-scale (cm-long) device (< 10 cm).

Fiber nonlinearity compensation for OFDM super-channels using optical phase conjugation.

We experimentally demonstrate that mid-link optical phase conjugation (OPC) effectively compensates fiber nonlinearity in coherent optical OFDM super-channels. The OPC was produced by pump × subcarrier degenerate four-wave-mixing in a 1-km highly nonlinear fiber. The nonlinear threshold for the 10 × 80-km 604.

Energy efficient nonlinear optics in silicon: are slow-light structures more efficient than nanowires?

We compare the energy performance of four-wave mixing in nanowires and slow-light photonic crystals and outline the regimes where each platform exhibits salient advantages and limitations, including analysis of the impact of future fabrication improvement. These results suggest a route towards energy efficient silicon integrated photonics.

Photonic crystal nanocavities fabricated from chalcogenide glass fully embedded in an index-matched cladding with a high Q-factor (>750,000).

We have designed and fabricated a 2-D photonic crystal hetero-structure cavity in the chalcogenide glass Ge(11.5)As(24)Se(64.5) that is fully embedded in a cladding with refractive index of 1.

Spatial dispersion of multilayer fishnet metamaterials.

We study the anisotropic properties of multilayer fishnet optical metamaterials and describe topological transitions between the elliptic and hyperbolic dispersion regimes. In contrast to other hyperbolic media, multilayer fishnet metamaterials may have negative components not only in the effective permittivity tensor but also in the effective permeability tensor, thus allowing the realization of magnetic hyperbolic and generalized indefinite media.

Dual wavelength Q-switched cascade laser.

A diode-cladding-pumped dual wavelength Q-switched Ho3+-doped fluoride cascade fiber laser operating in the mid-infrared is demonstrated. Stable pulse trains from the (5)I6 → (5)I7 and (5)I7 → (5)I8 laser transitions were produced, and the μs-level time delay between the pulses from each transition was dependent on the pump power. At maximum pump power and at an acousto-optic modulator repetition rate of 25 kHz, the (5)I6 → (5)I7 transition pulse operated at 3.

Polarization-independent chalcogenide glass nanowires with anomalous dispersion for all-optical processing.

We demonstrate the design and fabrication of square Ge11.5As24Se64.5 (Ge11) nonlinear nanowires fully embedded in a silica cladding for polarization independent (P-I) nonlinear processing.

Optimizing the net reflectivity of point-by-point fiber Bragg gratings: the role of scattering loss.

We present an experimental and theoretical analysis of the influence of scattering losses on the net reflectivity of fiber Bragg gratings inscribed with a femtosecond laser and the point-by-point technique. We demonstrate that the ratio of the coupling strength coefficient to the scattering loss coefficient varies significantly with the inscribing laser pulse energy, and highlight that an optimal pulse-energy range exists for achieving high-reflectivity gratings. These results are critical for exploiting high power fiber laser opportunities based on point-by-point gratings.

Q-switched induced gain switching of a two-transition cascade laser.

A gain-switched laser transition, of a two-laser-transition cascade laser, that is driven by the adjacent laser transition which is Q-switched is demonstrated using a Ho3+-doped fluoride fiber laser. Q-switching the 5I6 → 5I7 transition at 3.002 µm produces stable gain-switched pulses from the 5I7 → 5I8 transition at 2.

Actively Q-switched 2.9 μm Ho(3+)Pr(3+)-doped fluoride fiber laser.

We report an efficient Q-switched Ho(3+)Pr(3+)-doped fluoride fiber laser, producing a peak power of 77 W, with pulse width of 78 ns. A slope efficiency of 20% with respect to the launched pump power was achieved. A TeO(2) acousto-optic modulator allowed continuous tunability of the pulse repetition frequency from 40 to 300 kHz.

Wide-band negative permeability of nonlinear metamaterials.

We propose a novel way to achieve an exceptionally wide frequency range where metamaterial possesses negative effective permeability. This can be achieved by employing a nonlinear response of metamaterials. We demonstrate that, with an appropriate design, a frequency band exceeding 100% is available for a range of signal amplitudes.

Reconfigurable photonic crystal waveguides created by selective liquid infiltration.

We experimentally demonstrate reconfigurable photonic crystal waveguides created directly by infiltrating high refractive index (n≈2.01) liquids into selected air holes of a two-dimensional hexagonal periodic lattice in silicon. The resulting effective index contrast is large enough that a single row of infiltrated holes enables light propagation at near-infrared wavelengths.

Broadband unidirectional scattering by magneto-electric core-shell nanoparticles.

Core-shell nanoparticles have attracted surging interests due to their flexibly tunable resonances and various applications in medical diagnostics, biosensing, nanolasers, and many other fields. The core-shell nanoparticles can support simultaneously both electric and magnetic resonances, and when the resonances are properly engineered, entirely new properties can be achieved. Here we study core-shell nanoparticles that support both electric and artificial magnetic dipolar modes, which are engineered to coincide spectrally with the same strength.

Actively tunable bistable optical Yagi-Uda nanoantenna.

We propose and theoretically demonstrate a novel type of optical Yagi-Uda nanoantennas tunable via variation of the free-carrier density of a semiconductor disk placed in a gap of a metallic dipole feeding element. Unlike its narrowband all-metal counterparts, this nanoantenna exhibits a broadband unidirectional emission and demonstrates a bistable response in a preferential direction of the far-field zone, which opens up unique possibilities for ultrafast control of subwavelength light not attainable with dipole or bowtie architectures.

Optically tunable compensation of nonlinear signal distortion in optical fiber by end-span optical phase conjugation.

We demonstrate a nonlinear signal processing approach for compensating nonlinear distortion caused by the Kerr effect in optical fiber transmission. The concept relies on propagating the signal through a separate all-optical module outside the link to apply tunable nonlinear distortion and phase-conjugation in series. We show this uniquely enables tunable regeneration of phase-encoded 40 Gb/s signals of different data-formats and number of WDM channels, to allow significantly higher transmission powers through single and multi-span fiber links.

Ultrafast laser-written dual-wavelength waveguide laser.

We report the performance of a dual-wavelength waveguide laser based on a phase-modulated sampled-grating architecture fabricated using the femtosecond laser direct-write technique. The waveguide laser was written in Yb-doped phosphate glass and had a narrow linewidth (<10 pm), high signal-to-noise ratio (>60 dB), 5 mW output power per channel, and wavelength separation of 10 nm.

Photonic-chip-based tunable slow and fast light via stimulated Brillouin scattering.

We report the first (to our knowledge) demonstration of photonic chip based tunable slow and fast light via stimulated Brillouin scattering. Slow, fast, and negative group velocities were observed in a 7 cm long chalcogenide (As(2)S(3)) rib waveguide with a group index change ranging from ~-44 to +130, which results in a maximum delay of ~23 ns at a relatively low gain of ~23 dB. Demonstration of large tunable delays in a chip scale device opens up applications such as frequency sensing and true-time delay for a phased array antenna, where integration and delays ~10 ns are highly desirable.

Ti-free optical waveguiding regions produced by LiNbO3 etching during the indiffusion of Ti.

We report the observation, first to our knowledge, of optical waveguiding found beneath trenches etched in congruent lithium niobate using the recently reported etching during the indiffusion of Ti process. Observations of multi-mode and single-mode guiding at visible wavelengths and preliminary measurements of waveguide insertion losses are presented.

Near-zero anomalous dispersion Ge11.5As24Se64.5 glass nanowires for correlated photon pair generation: design and analysis.

We show that highly nonlinear chalcogenide glass nanowire waveguides with near-zero anomalous dispersion should be capable of generating correlated photon-pairs by spontaneous four-wave mixing at frequencies detuned by over 17 THz from the pump where Raman noise is absent. In this region we predict a photon pair correlation of >100, a figure of merit >10 and brightness of ~8×10(8) pairs/s over a bandwidth of >15 THz in nanowires with group velocity dispersion of <5 ps∙km(-1) nm(-1). We present designs for double-clad Ge(11.

All-optical wavelength conversion for 10 Gb/s DPSK signals in a silicon ring resonator.

We demonstrate all-optical wavelength conversion at 10 Gb/s for differential phase-shift keyed (DPSK) data signals in the C-band, based on four-wave mixing (FWM) in a silicon ring resonator. Error-free operation with a system penalty of ~4.1 dB at 10⁻⁹ BER is achieved.