A. Ramdane

Pulse generation at 346 GHz using a passively mode locked quantum-dash-based laser at 1.55 μm

We report on subpicosecond pulse generation at 346 GHz repetition rate based on InAs/InP quantum dash passively mode locked lasers emitting at 1.55 μm. This is achieved owing to the high optical modal gain of the multilayer InAs/InP quantum dash active region.

Subpicosecond pulse generation at 134GHz using a quantum-dash-based Fabry-Perot laser emitting at 1.56μm

We demonstrate passive mode locking in one-section monolithic semiconductor laser diodes based on quantum-dash active layer at very high repetition rate in the 1.5μm window. Transform-limited pulses are generated at 134GHz with subpicosecond width, without any pulse compression scheme. A 50kHz linewidth of the radio-frequency spectrum is also demonstrated at 42GHz, the lowest value reported for any passively mode-locked semiconductor laser. We further show that the saturable absorption section in two-section devices has no significant impact on the mode-locking behavior.

High performance mode locking characteristics of single section quantum dash lasers.

Mode locking features of single section quantum dash based lasers are investigated. Particular interest is given to the static spectral phase profile determining the shape of the mode locked pulses. The phase profile dependence on cavity length and injection current is experimentally evaluated, demonstrating the possibility of efficiently using the wide spectral bandwidth exhibited by these quantum dash structures for the generation of high peak power sub-picosecond pulses with low radio frequency linewidths.

InAs/InP Quantum-Dot Passively Mode-Locked Lasers for 1.55-μ m Applications

This paper reports on recent results on passively mode-locked InAs/InP quantum-dot-based lasers. These low-dimensional structures have proved very attractive in improving most of the properties of these devices. Subpicosecond pulse generation at repetition rates up to beyond 300 GHz has readily been demonstrated. Ultranarrow RF linewidths reach record values of less than 1 kHz. Controlled optical feedback allows a further reduction of this linewidth yielding extremely low timing jitter. A comparison of single-section and standard two-section lasers is given for the first time. These performances open the way to various applications at 1.55 μm, including very high bit rate all-optical signal processing, frequency comb generation, radio over fiber, and low-noise all-optical oscillators.

Short pulse generation using a passively mode locked single InGaAsP/InP quantum well laser

We report on subpicosecond pulse generation using passively mode locked lasers (MLL) based on a low optical confinement single InGaAsP/InP quantum well active layer grown in one epitaxial step. Systematic investigation of the performances of two-section MLLs emitting at 1.54 microm evidenced pulse width of 860 fs at 21.31 GHz repetition rate, peak power of approximately 500 mW and a time-bandwith product of 0.57. A 30 kHz linewidth of the photodetected radio-frequency electrical spectrum is further demonstrated at 21 GHz which is, to our knowledge, the lowest value ever reported for a quantum well device.

Comparison of InAs quantum dot lasers emitting at 1.55 µm under optical and electrical injection

InAs/InGaAsP/InP(113)B quantum-dots are studied as active mediums for laser structures emitting near 1.55 µm under optical and electrical injection. In order to precisely tune the emission wavelength of QDs, the double cap growth procedure is used. Laser emission on the ground states is obtained under optical pumping at room temperature. On equivalent structures doped for electrical injection, laser emission is also observed at low temperatures up to 200 K. The difference between the optical and electrical pumping is ascribed to low carrier injection efficiency due to the presence of a 3 nm InP hole blocking barrier at each quantum dot layer which is inherent to the double cap growth procedure. Room temperature laser emission has been reached when the InP first cap layer is substituted by a quaternary GaInAsP (1.18 µm gap) layer in the double cap growth procedure. The threshold current density of the new structure with QD capped only by quaternary is as low as 840 A cm−2 at room temperature.

Experimental investigation of the timing jitter in self-pulsating quantum-dash lasers operating at 1.55 µm

We report for the first time on the systematic measurement of timing jitter of 40-GHz self-pulsating Fabry-Perot laser based on InAs/InP quantum dashes emitting at 1.55 microm. Two different methods, one based on optical cross-correlation and one on electrical spectrum sideband integration are used and show a good agreement, yielding a jitter of 0.86 ps in the 1 MHz---20 MHz frequency range with a potential of 280 fs for optimized driving conditions. Amplitude noise and high-frequency timing jitter contributions are also discussed.

Low noise performance of passively mode locked quantum-dash-based lasers under external optical feedback

We report on a systematic investigation of the effect of external optical feedback on 17 GHz passively mode-locked two-section lasers based on InAs/InP quantum dashes emitting at 1.58 μm. Narrowing of mode-beating linewidth down to a record value of ∼500 Hz is demonstrated over a large operating range.

Effect of layer stacking and p-type doping on the performance of InAs∕InP quantum-dash-in-a-well lasers emitting at 1.55μm

The authors report the growth of 6-, 9-, and 12-layer InAs∕InP quantum-dash-in-a-well (DWELL) laser structures using gas source molecular beam epitaxy. Broad area laser performance has been investigated as a function of number of layers. The highest modal gain at 48cm−1 is achieved for an optimized nine-DWELL layer structure. The effect of layer stacking and p-type doping on the characteristic temperature is also reported. Nine-DWELL layer single mode ridge waveguide lasers showed high slope efficiency (0.2W∕A per facet) and output power (Pout=20mW), close to those of conventional quantum well devices.

Excitable phase slips in an injection-locked single-mode quantum-dot laser

An experimental study of the dynamics of a single-mode quantum-dot semiconductor laser undergoing optical injection is described for the first time, to our knowledge. In particular, the first observation of excitable pulses near the locking boundaries for both positive and negative detuning is reported, indicating locking via a saddle-node bifurcation for both signs of the detuning. The phase evolution of the slave electric-field during pulsing was measured and confirmed that the pulses result from 2pi phase slips. The interpulse-time statistics were analyzed, and a Kramers-like distribution was obtained.