Two-state passive mode-locking of quantum dot semiconductor lasers: Classical state scenario and novel reverse state dynamics (original) (raw)
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Applied Physics Letters, 2010
Reverse-emission-state-transition mode locking in a two-section InAs/InGaAs quantum dot laser is experimentally investigated and confirmed by simulations. Stable mode locking starts on the first excited state ͑ = 1207 nm͒ and then, with increasing gain current, a transition to stable simultaneous two-state mode locking on excited state and ground state ͑ = 1270 nm͒ takes place. This particular state-transition occurs already at 0 V reverse-bias and at moderate gain-section currents. It is attributed to the strong active region chirping of the gain medium and in particular to a photon pumping process in the saturable absorber section.
Optics Express, 2007
For the first time passive mode-locking in two-section quantum-dot lasers operating at wavelengths around 1.55 µm is reported. Pulse generation at 4.6 GHz from a 9-mm long device is verified by background-free autocorrelation, RF-spectra and real-time oscilloscope traces. The output pulses have a 7 nm optical bandwidth and are stretched in time and heavily up-chirped with a value of 20 ps/nm. From a 7 mm long device Q-switching is observed over a large operating regime. The lasers have been realized using a fabrication technology that is compatible with further photonic integration, and can perform the function of e.g. a mode-comb generator.
Pulse width narrowing due to dual ground state emission in quantum dot passively mode locked lasers
Applied Physics Letters, 2010
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 ͑GS͒. 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.
Analysis of hybrid mode-locking of two-section quantum dot lasers operating at 15 μm
Optics Express, 2009
For the first time a detailed study of hybrid mode-locking in twosection InAs/InP quantum dot Fabry-Pérot-type lasers is presented. The output pulses have a typical upchirp of approximately 8 ps/nm, leading to very elongated pulses. The mechanism leading to this typical pulse shape and the phase noise is investigated by detailed radio-frequency and optical spectral studies as well as time-domain studies. The pulse shaping mechanism in these lasers is found to be fundamentally different than the mechanism observed in conventional mode-locked laser diodes, based on quantum well gain or bulk material.
IEEE Journal of Quantum Electronics, 2000
We present a modified version of the multisection delayed differential equation model, for quantum dot passively mode-locked (ML) lasers when competition between ground state (GS) and excited state (ES) ML takes place. The model takes into account the difference in the group velocity of GS and ES fields. Sole GS, sole ES, and dual-state lasing and ML have been studied. The results are verified with time domain traveling wave simulations and compared, when possible, with experimental results. These tests confirmed the reliability of the model. We found that, in two-section ML lasers, GS lasing and mode locking are always more easily established. For instance, GS lasing can be either self-starting or induced by the initial lasing from the higher energy ES. On the contrary, GS lasing tends to inhibit, to a certain extent, the onset of ES lasing, especially at low injection current and low reverse voltage. Moreover, ES shows less potential to achieve stable ML than GS. Based on these findings, we propose proper theoretical explanation of the achieved lasing and ML regimes in realized devices. Especially, we demonstrate a novel stable dual-state ML regime with remarkable enhanced pulse peak power and pulse width.
2019
We consider a mode-locked quantum-dot edge-emitting semiconductor laser consisting of a reverse biased saturable absorber and a forward biased amplifying section. To describe the dynamics of this laser we use the traveling wave model taking into account carrier exchange processes between a reservoir and the quantum dots. A comprehensive parameter study is presented and an analysis of mode-locking pulse broadening with an increase of injection current is performed. The results of our theoretical analysis are supported by experimental data demonstrating a strong pulse asymmetry in a monolithic two section quantum dot mode-locked laser
Mode locking of InGaAs quantum dot lasers
2004
Extensive mode-locking investigations are performed in InGaAs/InAs/GaAs quantum dot (QD) lasers. Monolithic mode-locked lasers are fabricated using QD material systems grown by MOCVD and MBE techniques and emitting at 1.1µm and 1.3µm, respectively. The mode-locking performance is evaluated using a variety of laser designs, with various ridge waveguide geometries, cavity and absorber lengths. Passive and hybrid mode-locking are studied and compared in 3.9mm long devices emitting at 1.1µm and operating at a repetition rate of 10GHz. Using 2.1mm long devices emitting at 1.3µm, 18GHz passive mode locking with 10ps Fourier transform limited pulses is demonstrated. This confirms the potential of quantum dot laser for low chirp, short optical pulse generation. Preliminary investigation of the timing jitter of QD passively mode-locked lasers and the behaviour of the QD absorber are also presented. Finally, we report 36GHz passive mode-locking with 6ps optical pulse obtained using 1.1mm long QD lasers emitting at 1.3µm.
Dynamical regimes in a monolithic passively mode-locked quantum dot laser
Journal of the Optical Society of America B, 2010
Operation regimes of a two section monolithic quantum dot (QD) mode-locked laser are studied experimentally with InGaAs lasers and theoretically, using a model that takes into account carrier exchange between QD ground state and two-dimensional reservoir of a QD-in-a-well structure. It is shown analytically and numerically that, when the absorber section is long enough, the laser exhibits bistability between laser off state and different mode-locking regimes. The Q-switching instability leading to slow modulation of the mode-locked pulse peak intensity is completely eliminated in this case. When, on the contrary, the absorber length is rather short, in addition to usual Q-switched mode-locking, pure Q-switching regimes are predicted theoretically and observed experimentally.
A passive mode-locked InAs/InP quantum dot laser with pulse duration of less than 300 fs
2009
We have designed and fabricated a quantum dot (QD) gain medium which consists of InAs QDs in an InGaAsP matrix on an InP substrate. By using these InAs/InP QD layers, we have generated femtosecond (fs) pulses with pulse duration of 295 fs from a single-section monolithic Fabry-Perot (F-P) cavity at the repetition rate of 50 GHz around 1560 nm wavelength range without any external pulse compression. The average output power is 40.1 mW at the injection current of 200 mA. Optical signal-to-noise ratio (OSNR) of the proposed QD mode-locked laser (QD-MLL) is up to 50 dB. The lasing threshold current and the external differential quantum efficiency are 23 mA and 30 %, respectively. And the mode beating linewidth was measured to be less than 20 KHz. We have interpreted that several nonlinear optical effects related to interaction of QD excitons with intracavity laser fields could create nonlinear dispersion to compensate intracavity linear dispersion. So total dispersion is minimized and four-wave mixing (FWM) is dramatically enhanced within QD F-P cavity. If spectral bandwidth is broad enough, tens or hundreds of longitudinal modes would lase and their phases would be locked together through FWM process. Eventually a train of fs pulses with a repetition rate corresponding to cavity round-trip time is generated.