P. Stolarz

Subpicosecond Pulse Generation at Quasi-40-GHz Using a Passively Mode-Locked AlGaInAs–InP 1.55-

We report on subpicosecond pulse generation using passively mode-locked laser diodes based on AlGaInAs 1.55-mum strained multiquantum-wells. Without any external pulse compression, the nearly transform-limited Gaussian pulses are generated at the quasi-40-GHz repetition rate with the 700-fs pulse duration.

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In this paper, we present an experimental and theoretical study of passive mode-locking in semiconductor Fabry-Pérot, quantum-well, lasers operating at around 1550 nm and producing picosecond pulses at a repetition frequency of 40 GHz. The different regimes that occur as the reverse bias voltage applied to the saturable absorber (SA) section or the bias current injected into the amplifier section are characterized both in the time and frequency/wavelength domains. Our results reveal that the lasers display spectral competition between the gain of the amplifier section and the absorption of the SA, with variations of the lasing wavelength up to 25 nm as the bias conditions are changed. These wavelength variations result from the thermal drift of the SA band-edge due to Joule heating by the generated photocurrent and from the competition between two possible lasing regions placed either at the amplifier gain peak or near the band-edge of the SA. The experimental observations are satisfactorily reproduced and explained in the framework of a Traveling Wave Model complemented by a time-domain description of the semiconductor susceptibility.

Strained Quantum-Well Laser

We have fabricated 40-GHz passively mode-locked AlGaInAs-InP 1.55- lasers integrated with surface-etched distributed Bragg mirrors. Numerically optimized gratings provide low-scattering losses and accurate wavelength control. The lasers produce 4.46-ps Gaussian pulses with time-bandwidth product of 0.47.

Spectral Dynamical Behavior in Passively Mode-Locked Semiconductor Lasers

Passively mode-locked laser devices are presented incorporating chirped distributed Bragg reflectors. The Bragg grating sections consist of post-growth, sidewall relief, tapered gratings, offering continuous chirp and modulation of the coupling coefficient. Blue-chirped gratings are found to compensate for the pulse chirp accumulated in the laser gain and absorption sections. Pulses are measured with the largest 3 dB bandwidths, up to 2.3 nm, and smallest pulsewidths, 1.49 ps, achieved in passively mode-locked DBR lasers.

Monolithic 40-GHz Passively Mode-Locked AlGaInAs–InP 1.55-

We characterized the reflectivity and the modal discrimination of intracavity reflectors (ICRs) with different numbers of slots and presented harmonic mode-locking operation of a monolithic semiconductor laser comprising a compound cavity formed by a single deeply etched slot ICR fabricated from 1.55 μm AlGaInAs strained quantum well material. Gaussian pulses were generated at a 161.8 GHz repetition rate with a pulse duration of 1.67 ps and a time-bandwidth product of 0.81.

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The first demonstration of harmonic mode-locked operation from a monolithic semiconductor laser comprising a compound cavity formed by twin deeply etched intracavity reflectors based on 1.55-μm AlGaInAs strained quantum-well material is presented. Nearly transform-limited Gaussian pulses are generated at 160-GHz repetition rate with a 1.67-ps pulse duration.

m MQW Laser With Surface-Etched Distributed Bragg Reflector

We report on the design and experimental evaluation of AlGaInAs/InP multiquantum well epistructures for mode-locked emission at 1.5 μm. We show that mode-locked lasers fabricated on an optimized three quantum well active region with a low optical confinement factor deliver pulses with increased peak power and stability over a much wider biasing range than those fabricated using a standard five quantum well design. Sonogram measurements indicate that sub-ps symmetrical pulses with a substantially reduced linear blue chirp are generated up to nearly three times the laser current threshold.

Passively Mode-Locked Lasers With Integrated Chirped Bragg Grating Reflectors

This work presents an overview of a combined experimental and theoretical analysis on passive mode-locking in semiconductor quantum-well lasers based on reverse biased saturable absorbers. The experimental results describe the dynamics of laser diodes based on Aluminum quaternary materials at 1550 nm and we will also mention recent results related to GaAs Lasers at 830 nm. The experimental facts evidenced the important impact of the dispersion in frequency domain of the saturable absorption as well as the relevance of the dynamical detuning between the gain peak of the amplifying sections and the edge of absorption of the saturable absorber. Reproducing the dispersion of the saturable absorption demanded an important effort on our modeling approach, specially regarding the development of an efficient but reasonably accurate method to describe in time domain the response of the semiconductor material. The successful realization of this endeavor resulted in the development of the free software simulation package FreeTWM that allows to simulate a large class of multi-section devices. I will discuss how our modeling approach reproduces and explains the experimental results. I will conclude on a discussion of the possible improvements to FreeTWM as for instance the consideration of the ultrafast non linearities e.g. the so-called spectral hole burning and carrier heating effects.

160 GHz harmonic mode-locked AlGaInAs 1.55 μm strained quantum-well compound-cavity laser

We report on the detailed characterization of ultrashort pulses emitted from a 1.5- AlGaInAs/InP semiconductor passively mode-locked laser, operating at a repetition frequency of 35 GHz. Both the temporal and phase profiles of the pulses are retrieved using a sonogram technique that utilizes a highly-sensitive two-photon absorption waveguide detector. The system enables full characterization of pulses with energy as low as 10 fJ and peak power level of 5 mW, which is only inaccessible by a limited number of high-sensitivity measurement approaches. We show that the pulses exhibit a prevailing positive linear chirp across a wide range of biasing conditions. Its high sensitivity to the gain section current proves the dominant contribution of the gain conditions to the group delay characteristics of the emitted pulses.

160-GHz Passively Mode-Locked AlGaInAs 1.55-

We study the Mode-Locking dynamics of 40-GHz semiconductor Fabry-Pe´rot lasers with intracavity saturable absorber by using a Traveling-Wave-Model and a time-domain response of the semiconductor material. We analyze the influence of key parameters and compare our predictions with experimental results.