Eugenia Roditi

Ultrafast all-optical AND logic operation based on four-wave mixing in a passive InGaAsP-InP microring resonator

An all-optical AND logic gate based on the four-wave mixing (FWM) effect in an InGaAsP-InP microring resonator side-coupled to a bus waveguide, is proposed and simulated. Using an ultrafast nonlinear process such as FWM, operation at a bit rate up to 160 Gb/s is demonstrated for the return-to-zero modulation format.

IMPROVED PERFORMANCE OF A WAVELENGTH CONVERTER BASED ON DUAL PUMP FOUR-WAVE MIXING IN A BULK SEMICONDUCTOR OPTICAL AMPLIFIER

Very high conversion efficiency (6.5 dB for 23.4 nm down-wavelength shift and 4.5 dB for 16 nm up-wavelength shift) is reported, using four-wave mixing in a bulk semiconductor optical amplifier. Based on a dual pump configuration where wavelength conversion is achieved by shifting one of the pumps, superior performance has been achieved in terms of both efficiency and the converted signal-to-background amplified spontaneous emission noise ratio, especially for very large wavelength shifts. Simple theoretical considerations are also discussed for the explanation of the improved performance of the converter.

40-gb/s NRZ and RZ operation of an all-optical AND logic gate based on a passive InGaAsP/InP microring resonator

The properties of an all-optical AND logic gate based on the four-wave mixing (FWM) effect in an InGaAsP/InP microring resonator side coupled to a bus waveguide are investigated. Using an ultrafast nonlinear process such as FWM, operation at a bit rate of 40 Gb/s is demonstrated for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) modulation formats. The gate operation in terms of microring structural parameters and operating conditions is studied

Study of polarization-insensitive wave mixing in bulk semiconductor optical amplifiers

A detailed experimental investigation of polarization-insensitive dual-pump wave mixing in bulk, polarization-insensitive semiconductor optical amplifier (SOA) is reported. Measurements of the phase conjugated, polarization-insensitive four-wave mixing (FWM) efficiency are reported versus: (1) pump-signal wavelength spacing while keeping the wavelength spacing between the two orthogonally polarized pumps constant and (2) wavelength spacing between the pumps while keeping the signal wavelength constant. The achieved wavelength conversion bandwidth of the polarization-insensitive scheme is approximately 60 nm with efficiency between 8 and -20 dB. The obtained results are in good agreement with theoretical predictions.

Investigation of an all-optical wavelength converter with reshaping properties based on four-wave mixing in passive microring resonators

The properties of an all-optical wavelength converter with reshaping characteristics, based on four-wave mixing (FWM) in a passive GaAs-AlGaAs microring resonator side-coupled to a bus waveguide, are investigated in this paper. The reshaping properties are based on the nonlinear FWM transfer function as a result of the two-photon absorption enhanced by the resonance effect. A detailed study of the static and dynamic reshaping characteristics of the wavelength converter has been carried out. Its performance, evaluated by extinction ratio and Q-factor calculations, showed satisfactory regenerative properties up to 10 Gb/s.

Direct Modulation Properties of 1.55-

The modulation properties of 1.55-mum InGaAsP/InP microring lasers are investigated using a multimode rate equation model. A detailed study, with respect to Q-factor and extinction ratio calculations, is carried out as a function of different microrings key design and operating parameters. The modulators performance study shows the possibility for a successful operation at a bit rate of 2.4 Gb/s for radii between 30 and 50 mum and proper values for the bus waveguide reflectivity.

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An enhanced low frequency relative intensity noise due to mode hopping induced from the asymmetric gain suppression in InGaAsP-InP microring lasers, is observed experimentally for the first time. The experimental results are in good agreement to those predicted by a multimode model based on the rate equation approximation accounting for both symmetric and asymmetric nonlinear gain suppression

InGaAsP/InP Microring Lasers

We present an experimental study on the effect of optical feedback in both ground and excited emission of a GaAs quantum dot passively mode locked laser. The experimental setup consisted of a long external cavity with variable cavity length and feedback level ranging from –50 to –20dB. The obtained experimental results show dependence of the emission properties on the cavity length regarding both the ground and excited state. In addition a strong tolerance of the laser operation to feedback at the excited state operation regime is observed.

Low-Frequency Relative Intensity Noise due to Nonlinear Mode Competition in InGaAsP–InP Microring Lasers

A novel approach for realization of all-optical pulse reshaping in an integrated microring resonator is proposed. The concept presented in this study is based on four-wave mixing in a passive GaAs/AlGaAs microring resonator side coupled to a bus waveguide, taking into account all higher order non-linear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), pump depletion and two-photon absorption (TPA), the latter being the dominant process here. We also include in the description changes in absorption and refractive indexes induced by free-carriers generated by TPA. This scheme is investigated for its regenerative characteristics using an optical pump modulation scheme. The application of the modulation bit stream in the pump wave leads in a conjugate wave power being proportional to the square of the pump power, resulting in a corresponding extinction ratio improvement. Because of the strong TPA, enhanced by the resonance effect, the converted signal power saturates as pump power increases, providing noise suppression at high power levels. A detailed study of the static and dynamic reshaping characteristics of the wavelength converter has been carried out. Its performance, evaluated by extinction ratio (ER) and Q factor calculations, showed satisfactory regenerative properties up to 10Gb/s.

Effect of optical feedback to the ground and excited state emission of a passively mode locked quantum dot laser

This paper presents a detailed investigation of the performance of a wavelength conversion scheme. The converter is based on four wave mixing in semiconductor optical amplifiers using two parallel polarised pumps. Measurements of the conversion efficiency and the signal to background noise ratio of the two replicas of the signal, for the cases of the signal polarisation being either parallel or orthogonal relative to the pump waves have been carried out. These measurements will reveal the polarisation sensitivity of this scheme which appears to be less than 1 dB when the wavelength spacing between the signal and its closest spaced pump is larger than 12 nm. The experimental results are supported in a satisfactory way by theoretical considerations. A simple theoretical expression describing the polarisation sensitivity have been derived and the theoretical results are in good agreement with those experimentally obtained. A performance comparison of the conversion scheme using semiconductor optical amplifiers with different lengths but the same structure is also performed. Through the following study the optimum operational conditions for this wavelength conversion scheme will be determined.