Charis Mesaritakis

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.

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.

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.

Intraband Crosstalk Properties of Add–Drop Filters Based on Active Microring Resonators

The dynamic operation of add-drop filters based on active microring cavities is numerically investigated for the first time to our knowledge, with high bit-rate return-to-zero (RZ) input signals at both the input and the add port. The use of an active ring cavity allows the complete loss compensation, which has been suggested in order to eliminate the intraband crosstalk between the incoming signals. Strong degradation of the dropped and added signals is observed due to the imperfect spectral response of the through and drop ports. A double-stage topology that addresses the inefficiencies of the single add-drop ring is proposed and the successful operation of 40-Gb/s RZ signals is numerically demonstrated.

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

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.

Tunable Master-Oscillator Power-Amplifier Based on Chirped Quantum-Dot Structures

A broadly tunable master-oscillator power-amplifier (MOPA) picosecond optical pulse source is demonstrated, consisting of an external cavity passively mode-locked laser diode with a tapered semiconductor amplifier. By employing chirped quantum-dot structures on both the oscillators gain chip and amplifier, a wide tunability range between 1187 and 1283 nm is achieved. Under mode-locked operation, the highest output peak power of 4.39 W is achieved from the MOPA, corresponding to a peak power spectral density of 31.4 dBm/nm.

Adaptive Interrogation for Fast Optical Sensing Based on Cascaded Micro-Ring Resonators

An adaptive interrogation technique that employs integrated semiconductor micro-ring resonators (MRR) for fast-response sensing applications is proposed and numerically studied. The basic sensing scheme consists of two MRRs in an add/drop signal configuration; the first MRR plays the role of the measuring sensor, while the second one acts as a reference optical filter that converts any frequency shift induced in the spectral characteristics of the measuring sensor into optical power variations. The proposed photonic sensor has the potential to adjust its transfer function dynamically, due to the varying response of the MMRs to different operating conditions, exhibiting either an ultra-low resolution operation capable of detecting extremely small refractive index changes, or an operation with a wide dynamic range. Finally, we propose a more sophisticated approach for simultaneous interrogation that incorporates multiple MRR sensors, based on thermal heaters that modulate the response of each MRR sensor with different modulation frequencies. In contrast to the conventional interrogation techniques, the proposed configurations enable ultra-high sampling rates crucial for studying fast biochemical reactions, such as enzyme kinetics.

Dual ground-state pulse generation from a passively mode-locked InAs/InGaAs quantum dot laser

In this paper, we present experimental results related to tunable dual wavelength passive mode locking of two independent ground state sub-bands in a multi section InAs/InGaAs quantum dot laser. The emission of these sub-bands is related to gain suppression at the center of the ground state emission, whereas their wavelength separation is tunable with injection current. Through the mechanism of passive mode locking two independent pulses were obtained, with typical pulse width in the order of 17 ps.