Narrow line width frequency comb source based on an injection-locked III–V-on-silicon mode-locked laser

In this paper, we report the optical injection locking of an L-band (similar to 1580 nm) 4.7 GHz III-V-on-silicon mode-locked laser with a narrow line width continuous wave (CW) source. This technique allows us to reduce the MHz optical line width of the mode-locked laser longitudinal modes down to the line width of the source used for injection locking, 50 kHz. We show that more than 50 laser lines generated by the mode-locked laser are coherent with the narrow line width CW source. Two locking techniques are explored. In a first approach a hybrid mode-locked laser is injection-locked with a CW source. In a second approach, light from a modulated CW source is injected in a passively mode-locked laser cavity. The realization of such a frequency comb on a chip enables transceivers for high spectral efficiency optical communication. (C) 2016 Optical Society of Americ

28 Gb/s direct modulation heterogeneously integrated C-band InP/SOI DFB laser

We demonstrate direct modulation of a heterogeneously integrated C-band DFB laser on SOI at 28 Gb/s with a 2 dB extinction ratio. This is the highest direct modulation bitrate so far reported for a membrane laser coupled to an SOI waveguide. The laser operates single mode with 6 mW output power at 100 mA bias current. The 3 dB modulation bandwidth is 15 GHz. Transmission experiments using a 2 km non zero dispersion shifted single mode fiber were performed at 28 Gb/s bitrate using a 2(7)-1 NRZ-PRBS pattern resulting in a 1 dB power penalty. (C) 2015 Optical Society of Americ

43 Gb/s NRZ-OOK direct modulation of a heterogeneously integrated InP/Si DFB laser

We discuss howInP membrane laser diodes, heterogeneously integrated on SOI can be designed for high speed operation and how one can take advantage of the heterogeneous integration. This is illustrated with several static and dynamic characteristics of fabricated 1550 nm lasers. We show nonreturn to zero on-off keying at 43 Gb/s and report link experiments over 2 km

An analysis of 1.55 mu m InAs/InP quantum dash lasers

Calculations show that electron states are not confined in the dashes in 1.55 mu m InAs/InP quantum dash-in-a-well laser structures. The combination of strain and three-dimensional confinement reduces the calculated density of states (DOS) near the valence band maximum, with the conduction and valence DOS then almost equal close to the band edges. Calculations and photoabsorption measurements show strongly polarized spontaneous emission and gain spectra. Experimental analysis shows the room temperature threshold current is dominated by nonradiative current paths. (C) 2008 American Institute of Physics. (DOI: 10.1063/1.2952194

Coherent WDM transmission using quantum-dash mode-locked laser diodes as multi-wavelength source and local oscillator

Quantum-dash (QD) mode-locked laser diodes (MLLD) lend themselves as chip-scale frequency comb generators for highly scalable wavelength-division multiplexing (WDM) links in future data-center, campus-area, or metropolitan networks. Driven by a simple DC current, the devices generate flat broadband frequency combs, containing tens of equidistant optical tones with line spacings of tens of GHz. Here we show that QD-MLLDs can not only be used as multi-wavelength light sources at a WDM transmitter, but also as multi-wavelength local oscillators (LO) for parallel coherent reception. In our experiments, we demonstrate transmission of an aggregate data rate of 4.1 Tbit/s (23x45 GBd PDM-QPSK) over 75 km standard single-mode fiber (SSMF). To the best of our knowledge, this represents the first demonstration of a coherent WDM link that relies on QD-MLLD both at the transmitter and the receiver

Laterally coupled distributed feedback lasers emitting at 2 μm with quantum dash active region and high-duty-cycle etched semiconductor gratings

Single-mode diode lasers on an InP(001) substrate have been developed using InAs/In0.53Ga0.47As quantum dash (Qdash) active regions and etched lateral Bragg gratings. The lasers have been designed to operate at wavelengths near 2 μm and exhibit a threshold current of 65 mA for a 600 μm long cavity, and a room temperature continuous wave output power per facet >5 mW. Using our novel growth approach based on the low ternary In0.53Ga0.47As barriers, we also demonstrate ridge-waveguide lasers emitting up to 2.1 μm and underline the possibilities for further pushing the emission wavelength out towards longer wavelengths with this material system. By introducing experimentally the concept of high-duty-cycle lateral Bragg gratings, a side mode suppression ratio of >37 dB has been achieved, owing to an appreciably increased grating coupling coefficient of κ ∼ 40 cm−1. These laterally coupled distributed feedback (LC-DFB) lasers combine the advantage of high and well-controlled coupling coefficients achieved in conventional DFB lasers, with the regrowth-free fabrication process of lateral gratings, and exhibit substantially lower optical losses compared to the conventional metal-based LC-DFB lasers

Probabilistic Reconstruction in Compressed Sensing: Algorithms, Phase Diagrams, and Threshold Achieving Matrices

Compressed sensing is a signal processing method that acquires data directly in a compressed form. This allows one to make less measurements than what was considered necessary to record a signal, enabling faster or more precise measurement protocols in a wide range of applications. Using an interdisciplinary approach, we have recently proposed in [arXiv:1109.4424] a strategy that allows compressed sensing to be performed at acquisition rates approaching to the theoretical optimal limits. In this paper, we give a more thorough presentation of our approach, and introduce many new results. We present the probabilistic approach to reconstruction and discuss its optimality and robustness. We detail the derivation of the message passing algorithm for reconstruction and expectation max- imization learning of signal-model parameters. We further develop the asymptotic analysis of the corresponding phase diagrams with and without measurement noise, for different distribution of signals, and discuss the best possible reconstruction performances regardless of the algorithm. We also present new efficient seeding matrices, test them on synthetic data and analyze their performance asymptotically.Comment: 42 pages, 37 figures, 3 appendixe