Narrowband optical parametric amplification measurements in Ga0.5In0.5P photonic crystal waveguides.

We report the first demonstration of narrowband parametric amplification in a chip scale semiconductor waveguide. A dispersion engineered, Ga0.5In0.5P photonic crystal waveguide with a dispersion function that exhibits two zero crossings was used with a pulsed pump placed in the normal dispersion regime while a tunable probe was scanned on either side of the pump. A peak conversion efficiency of -10 dB was obtained with a peak pump power of only 650 mW. The narrowband nature of the gain spectrum was clearly demonstrated.

Dual-pump parametric amplification in dispersion engineered photonic crystal waveguides.

This paper describes a numerical simulation of narrow band parametric amplification in dispersion engineered photonic crystal waveguides. The waveguides we analyze exhibit group velocity dispersion functions which cross zero twice thereby enabling many interesting pumping schemes. We analyze the case of two pulsed pumps each placed near one of the zero dispersion wavelengths. These configurations are compared to conventional single pump schemes. The two pumps may induce phase matching conditions in the same spectral location enabling to control the gain spectrum. This is used to study the gain and fidelity of 40 G bps NRZ data signals.

Parametric gain in dispersion engineered photonic crystal waveguides.

We present a numerical simulation of parametric gain properties in GaInP PhC dispersion engineered waveguides in which the group velocity dispersion crosses zero twice and where the pump and the signal are 100 ps pulses. The simulations use the M-SSFT algorithm which incorporates dispersive nonlinear coefficients and losses. We concentrate on narrow band parametric gain which occurs for pump wavelengths in the normal group velocity dispersion regime. The effects of structural details, of pump wavelength and of losses are carefully analyzed.

Temporal gap solitons and all-optical control of group delay in line-defect waveguides.

We show that a model based on anticrossing between highly group velocity-mismatched gap-guided and index-guided modes describes gap soliton propagation in photonic crystal waveguides. Such nonlinear solutions can be exploited for exploring new regimes such as all-optical control of group velocity (dispersionless slow light) over a submillimeter length scale, and propagation beyond the linear modal cutoff. The results are validated by means of finite-difference time domain simulations.

Blue self-frequency shift of slow solitons and radiation locking in a line-defect waveguide.

We investigate experimentally resonant radiation processes driven by slow solitons in a dispersion-engineered photonic crystal waveguide in a regime virtually free of dissipative nonlinear processes (two-photon absorption and Raman scattering). Strong (30% energy conversion) Cherenkov-like radiation accompanied by the blue self-frequency shift of the soliton is observed close to the zero dispersion point, and is explained in terms of the soliton-radiation locking of the velocity.

Narrowband optical parametric gain in slow mode engineered GaInP photonic crystal waveguides.

We predict narrowband parametric amplification in dispersion-tailored photonic crystal waveguides made of gallium indium phosphide. We use a full-vectorial model including the dispersive nature both of the nonlinear response and of the propagation losses. An analytical formula for the gain is also derived.

Kerr-induced all-optical switching in a GaInP photonic crystal Fabry-Perot resonator.

We describe nonlinear properties of a GaInP photonic crystal Fabry-Perot resonator containing integrated reflectors. The device exhibits an extremely large static nonlinearity due to a thermal effect. Dynamical measurements were used to discriminate between the thermal and Kerr contributions to the nonlinearity. The high frequency nonlinear response is strictly due to the Kerr effect and the efficiency is similar to that obtained in self-phase modulation and four wave mixing experiments. The waveguide dispersion and the wavelength dependent integrated reflectors yield a series of transmission peaks with varying widths which determine the maximum speed at which the device can operate. Switching and wavelength conversion experiments with 92ps and 30ps wide pulses were demonstrated using pulse energies of a few pJ. The switching process is Kerr dominated with the fundamental response being essentially instantaneous so that the obtainable switching speed is strictly determined by the resonator structure.

Efficient parametric interactions in a low loss GaInP photonic crystal waveguide.

We describe time domain characterizations of dynamic four-wave mixing in a low loss modified W1 GaInP photonic crystal waveguide. Using 32 ps wide pump pulses with peak powers of up to 1.1 W we achieved a very large conversion efficiency of -6.8 dB as well as a 1.3 dB parametric gain experienced by a weak CW probe signal. Time domain simulations confirm quantitatively all the measured results.

Time domain switching/demultiplexing using four wave mixing in GaInP photonic crystal waveguides.

We describe dynamical four wave mixing (FWM) functionalities of an GaInP photonic crystal waveguide. A W1 waveguide was used to wavelength convert 100 ps pulses and for sampling a 10.56 Gbit/s data stream so as to time demultiplex it into 16 or 32 channels. In all cases, the extracted pulses at the idler wavelength are undistorted and have a high signal to noise ratio proving the high efficiency and the versatility of the FWM process in the GaInP PhC waveguides we used.

Anderson localization of near-visible light in two dimensions.

We report on the observation of Anderson localization of near-visible light in two-dimensional systems. Our structures consist of planar waveguides in which disorder is introduced by randomly placing pores with controlled diameter and density. We show how to design structures in which localization can be observed and describe both the realization of the materials and the actual observation of Anderson localized modes by near-field scanning microscopy.

Theory of slow light enhanced four-wave mixing in photonic crystal waveguides.

The equations for Four-Wave-Mixing in a Photonic Crystal waveguide are derived accurately. The dispersive nature of slow-light enhancement, the impact of Bloch mode reshaping in the nonlinear overlap integrals and the tensor nature of the third order polarization are therefore taken into account. Numerical calculations reveal substantial differences with simpler models, which increase with decreasing group velocity. We predict that the gain for a 1.3 mm long, unoptimized GaInP waveguide will exceed 10 dB if the pump power exceeds 1 W.

Highly efficient four wave mixing in GaInP photonic crystal waveguides.

We report highly efficient four wave mixing in a GaInP photonic crystal waveguide. Owing to its large bandgap, the ultrafast Kerr nonlinearity of GaInP is not diminished by two photon absorption and related carrier effects for photons in the 1550 nm range. A four-wave-mixing efficiency of -49 dB was demonstrated for cw pump and probe signals in the milliwatt range, while for pulsed pumps with a peak power of 25 mW the conversion efficiency increased to -36 dB. Measured conversion efficiency dependencies on pump probe detuning and on pump power are in excellent agreement with a simple analytical model from which the nonlinear parameter gamma is extracted. Gamma scales approximately with the square of the slow down factor and varies from 800 W(-1) m(-1) at a pump wavelength lambda(p)=1532 nm to 2900 W(-1) m(-1) at lambda(p)=1550 nm. These values are consistent with those obtained from self phase modulation experiments in similar devices.

Resonance enhanced large third order nonlinear optical response in slow light GaInP photonic-crystal waveguides.

We report a large nonlinear response in a 1.3mm long GaInP photonic crystal waveguide. The wide band gap of GaInP (1.9 eV) ensures that no two photon absorption takes place for photons at 1.55mm improving the nonlinear performance. The nonlinearity is enhanced by a resonance effect due to the waveguide end facet reflectivities as well as by the low group velocity exhibited by the waveguide. A low CW input pump power of approximately 2mW causes a very large change in the nonlinear refractive index coefficient which manifests itself in a large, approximately p /3 phase shift in the Fabry Perot fringes. The extracted effective nonlinear coefficient g varies from 3.4 x 105W-1m-1 at short wavelengths to 2.2 x 106W-1m-1 near the band edge. These values are several orders of magnitude larger than those obtained in reported nonlinear experiments which exploit the Kerr effect. We postulate therefore that the observed nonlinearity is due to a hybrid phenomenon which combines the Kerr effect and an index change which is induced by local heating that results from the residual linear absorption. The efficient nonlinear phase shift was also exploited in a fast dynamic experiment where we demonstrated wavelength conversion with 100ps wide pulses proving the potential for switching functionalities at multi GHz rates. The index change required for this switching experiment can not be obtained, at the power levels used here, with a g value of a few thousands W-1m-1 which is a typical Kerr coefficient in similar waveguides. Hence, we conclude that the hybrid nonlinearity is sufficiently fast to enable switching with a time scale of at least 100ps.

Near field imaging of a GaAs photonic crystal cavity and waveguide using a metal coated fiber tip.

We report optical near field characterization of a GaAs photonic crystal waveguide which is side coupled to a nano cavity. We observe the effect of the metal coated probe on the resonance wavelength and the intensity distribution. The measurements fit well to finite difference time domain simulations.

Disorder-induced coherent scattering in slow-light photonic crystal waveguides.

Light transmission measurements and frequency-delay reflectometry maps for GaAs photonic crystal membranes are presented and analyzed, showing the transition from propagation with a well-defined group velocity to a regime completely dominated by disorder-induced coherent scattering. Employing a self-consistent optical scattering theory, with only statistical functions to describe the structural disorder, we obtain excellent agreement with the experiments using no fitting parameters. Our experiments and theory together provide clear physical insight into naturally occurring light localization and multiple coherent-scattering phenomena in slow-light waveguides.

Detailed analysis by Fabry-Perot method of slab photonic crystal line-defect waveguides and cavities in aluminium-free material system.

A single-line-defect low-loss photonic crystal waveguide based on a perforated GaAs membrane in an aluminium-free material system is demonstrated. The GaInP lattice is matched to GaAs as the cladding/sacrificial layer. Fabry-Perot resonances are analyzed to obtain the group velocity dispersion for a 1-mm long guide. The losses are deduced to be close to 5 dB/cm, taking into account the wavelength dependent reflectivity of the guide extremities. In this framework, side-coupled nanocavities are also investigated. Feasibility of low-loss photonic-crystal-based devices combined with a reliable industrial material systems is thus demonstrated.