Comb-based WDM transmission at 10 Tbit/s using a DC-driven quantum-dash mode-locked laser diode

Chip-scale frequency comb generators have the potential to become key building blocks of compact wavelength-division multiplexing (WDM) transceivers in future metropolitan or campus-area networks. Among the various comb generator concepts, quantum-dash (QD) mode-locked laser diodes (MLLD) stand out as a particularly promising option, combining small footprint with simple operation by a DC current and offering flat broadband comb spectra. However, the data transmission performance achieved with QD-MLLD was so far limited by strong phase noise of the individual comb tones, restricting experiments to rather simple modulation formats such as quadrature phase shift keying (QPSK) or requiring hard-ware-based compensation schemes. Here we demonstrate that these limitations can be over-come by digital symbol-wise phase tracking algorithms, avoiding any hardware-based phase-noise compensation. We demonstrate 16QAM dual-polarization WDM transmission on 38 channels at an aggregate net data rate of 10.68 Tbit/s over 75 km of standard single-mode fiber. To the best of our knowledge, this corresponds to the highest data rate achieved through a DC-driven chip-scale comb generator without any hardware-based phase-noise reduction schemes

Photonic integrated circuits based on quantum well intermixing techniques

The passive sections of a monolithic device must have a wider bandgap than the active regions to reduce losses due to direct interband absorption. Such bandgap engineering is usually realized by complicated regrown butt-joint or selective-area growth techniques. We, however, have developed a simple, flexible and low-cost alternative technique – quantum well intermixing (QWI) – to increase the bandgap in selected areas of an integrated device post-growth. To verify the QWI process, we have fabricated the following demonstrators: a 40 GHz semiconductor mode-locked laser producing pulses as short as 490 fs; a 10 GHz passively mode-locked extended cavity laser integrated with surface-etched distributed Bragg reflector (DBR) which can be tuned in both wavelength and pulse repetition rate; four 10 GHz 1.55 μm AlGaInAs/InP mode-locked surfaced-etched DBR lasers integrated combiner, a semiconductor optical amplifier and modulator where the four channels can be operated separately or simultaneously; a CWDM source with 12 nm wavelength separation based on an AlGaInAs/InP integrated distributed feedback laser array; and a 1.55 μm DFB laser monolithically integrated with power amplifier array. In all these applications, QWI has the advantage of eliminating crystal regrowth and the associated stringent tolerance requirements that are required in traditional integration schemes

Self-generation of optical frequency comb in single section Quantum Dot Fabry-Perot lasers: a theoretical study

Optical Frequency Comb (OFC) generated by semiconductor lasers are currently widely used in the extremely timely field of high capacity optical interconnects and high precision spectroscopy. Very recently, several experimental evidences of spontaneous OFC generation have been reported in single section Quantum Dot (QD) lasers. Here we provide a physical understanding of these self-organization phenomena by simulating the multi-mode dynamics of a single section Fabry-Perot (FP) QD laser using a Time-Domain Traveling-Wave (TDTW) model that properly accounts for coherent radiation-matter interaction in the semiconductor active medium and includes the carrier grating generated by the optical standing wave pattern in the laser cavity. We show that the latter is the fundamental physical effect at the origin of the multi-mode spectrum appearing just above threshold. A self-mode-locking regime associated with the emission of OFC is achieved for higher bias currents and ascribed to nonlinear phase sensitive effects as Four Wave Mixing (FWM). Our results are in very good agreement with the experimental ones

Sub-picosecond pulse and terahertz optical frequency comb generation by monolithically integrated linear mode-locked laser

We report on a record broad 3-dB bandwidth of 14 nm (~1.8 THz around 1532 nm) optical frequency comb generated from a passively mode-locked quantum-well (QW) laser in the form of photonic integrated circuits through an InP generic photonic integration technology platform. This 21.5-GHz colliding-pulse mode-locked laser cavity is defined by two on-chip reflectors incorporating intracavity phase modulators followed by an out-of-cavity SOA as booster. Under certain operating conditions, an ultra-wide spectral bandwidth is achieved along with an autocorrelation trace confirming the mode locking nature exhibiting a pulse width of 0.35 ps. The beat note RF spectrum has a linewidth of sub-MHz and 35-dB SNR.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642355 FiWiN5G and Spanish Ministerio de Economia y Competitividad DiDACTIC project TEC201347753-C3-3R

Tunable microwave signal generator with an optically-injected 1310nm QD-DFB laser

Tunable microwave signal generation with frequencies ranging from below 1 GHz to values over 40 GHz is demonstrated experimentally with a 1310nm Quantum Dot (QD) Distributed-Feedback (DFB) laser. Microwave signal generation is achieved using the period 1 dynamics induced in the QD DFB under optical injection. Continuous tuning in the positive detuning frequency range of the quantum dot's unique stability map is demonstrated. The simplicity of the experimental configuration offers promise for novel uses of these nanostructure lasers in Radio-over-Fiber (RoF) applications and future mobile networks. © 2013 Optical Society of America

Injection locking characteristics of indium arsenide quantum dash lasers

The study of injection locking characteristics was performed on an InAs Quantum Dash (QDash) semiconductor laser for the first time. The linewidth enhancement factor(α-parameter) of a QDash laser was measured using an injection locking technique that takes advantage of the asymmetry of the injection range. Studies were performed as functions of injecesed photon density, wavelength, and output power. To understand the behavior of the α-parameter versus wavelength, the Hakki-Paoli method, a technique that utilized the below threshold amplified spontaneous emission spectrum, was used to measure the modal gain over 1550 nm to 1573 nm. The α-parameter was found to have changed dramatically with power, indicating a large nonlinear gain coefficient, ε. Using a curve fit of the α versus power curve taken from the injection locking data, ε was measured to be 1.4*10-14 cm3, 1000 times larger than the typical ε of quantum well lasers, changing the dynamics of the laser. The small α-parameter and giant ε dramatically change the dynamics of the laser. To study the effects of the small α-parameter and giant ε further, an operational map was created using an Agilent Technologies High Resolution Spectrometer (HRS) with a resolution of 1 MHz. The new operational map of the InAs QDash laser has features never before seen with other devices, such as the avoidance of coherence collapse with optical feedback

312-fs pulse generation from a passive C-band InAs/InP quantum dot mode-locked laser.

For the first time, we report femtosecond pulses from a passive single-section InAs/InP quantum-dot (QD) mode-locked laser (MLL) with the active length of 456 microm and ridge width of 2.5 microm at the C-band wavelength range. Without any external pulse compression, the transform-limited Gaussian-pulses are generated at the 92 GHz repetition rate with the 312 fs pulse duration, which is the shortest pulse from any directly electric-pumping semiconductor MLLs to our best knowledge. The lasing threshold injection current and external differential quantum efficiency are 17.2 mA and 38%, respectively. We have also investigated the working principles of the proposed QD MLLs