Hercules Simos

Investigation of a 2R all-optical regenerator based on four-wave mixing in a semiconductor optical amplifier

The properties of an all-optical 2R regenerator based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) are investigated. The regeneration is based on the nonlinear FWM transfer function and a study of the systems static behavior reveals the operating conditions, under which the transfer function approaches most the ideal, step-like discrimination characteristic function. A fiber Bragg grating (FBG) is employed in order to overcome the SOAs speed limitations due to limited carrier dynamics. The simulations with dynamic input data by means of extinction ratio (ER) and Q-factor calculations, showed satisfactory regenerative behavior up to 40 Gb/s.

Dual-wavelength mode-locked quantum-dot laser, via ground and excited state transitions: Experimental and theoretical investigation

We report a dual-wavelength passive mode locking regime where picosecond pulses are generated from both ground (lambda = 1263 nm) and excited state transitions (lambda = 1180 nm), in a GaAs-based monolithic two-section quantum-dot laser. Moreover, these results are reproduced by numerical simulations which provide a better insight on the dual-wavelength mode-locked operation.

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.

High peak-power picosecond pulse generation at 1.26 µm using a quantum-dot-based external-cavity mode-locked laser and tapered optical amplifier

In this paper, we present the generation of high peak-power picosecond optical pulses in the 1.26 μm spectral band from a repetition-rate-tunable quantum-dot external-cavity passively mode-locked laser (QD-ECMLL), amplified by a tapered quantum-dot semiconductor optical amplifier (QD-SOA). The laser emission wavelength was controlled through a chirped volume Bragg grating which was used as an external cavity output coupler. An average power of 208.2 mW, pulse energy of 321 pJ, and peak power of 30.3 W were achieved. Preliminary nonlinear imaging investigations indicate that this system is promising as a high peak-power pulsed light source for nonlinear bio-imaging applications across the 1.0 μm - 1.3 μm spectral range.

Potential of InGaAs/GaAs Quantum Dots for Applications in Vertical Cavity Semiconductor Optical Amplifiers

The use of InGaAs/GaAs quantum dots (QDs) in vertical cavity semiconductor optical amplifiers (VCSOAs) is proposed and analyzed. The results underline the distinctive differences between practical designs for QD vertical cavity semiconductor lasers and QD-VCSOAs. By means of a QD rate-equation scheme that accounts for both homogeneous and inhomogeneous broadening and the VCSOA cavity characteristics, the effects of material properties are identified. The design routes outlined here ensure the suitability of QD-VCSOAs for high-speed applications (>100 Gb/s) that rely on the fast carrier dynamics.

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

Dynamic Analysis of Crosstalk Performance in Microring-Based Add/Drop Filters

In this paper, the impact of the simultaneous presence of input and add signals in add/drop filters realized with microring resonators is numerically investigated. It is shown that the notch spectral response of output ports is responsible for the intraband crosstalk appearing on the dropped signals in add/drop operation. The investigation of the filter performance is performed with modulated signals at both the input and the add port. The analysis highlights the strong competition between the levels of induced intraband crosstalk and the wavelength selectivity at high bit rate add/drop operation, even in higher order filters. Multistage add/drop topologies that address the inefficiencies of the single-stage add/drop filters are proposed, and successful operation at 40 Gbps nonreturn to zero and return to zero signals is numerically demonstrated.

Two-Section Quantum-Dot Mode-Locked Lasers Under Optical Feedback: Pulse Broadening and Harmonic Operation

In this paper, we numerically investigate the role of gain and absorber dynamics on the operation of monolithic two-section mode-locked quantum-dot lasers under optical feedback. The analysis is carried out by means of a time-domain traveling wave model for propagation in the gain and absorbing sections. The obtained results indicate that in devices with slow dynamics, pulse duration tends to increase significantly with feedback. On the contrary, devices with fast dynamics exhibit an operation that depends primarily on the external cavity length.

Pulse width narrowing due to dual ground state emission in quantum dot passively mode locked lasers

We present an experimental investigation of the emission properties of a multisection InGaAs quantum dot passively mode locked laser under dual waveband emission from the ground state (GS). A mode locking regime directly related to the GS splitting has been depicted. It is related to significant pulse width decrease with increasing injection current under dual peak emission from the GS, leading to generation of pulses with increased peak power with respect to the usual device operation.

Dynamic Properties of a WDM Switching Module Based on Active Microring Resonators

The switching properties of a resonator consisting of two serially cascaded active microrings (MRs) are reported. The switching is achieved through the variation of the refractive index and the losses of the MRs with current injection, which alters the overall output spectral response. The switch is suitable for optical burst switching systems and metro architectures as it provides fast optical switching in the nanosecond scale with contrast ratio higher than 30 dB for 10-Gb/s intensity modulated signals. The capacity of the switch can be remarkably increased if multiwavelength switching is employed.