Hybrid modeling approach for mode-locked laser diodes with cavity dispersion and nonlinearity

Abstract

Semiconductor-based mode-locked lasers, integrated sources enabling the generation of coherent ultra-short optical pulses, are important for a wide range of applications, including datacom, optical ranging and spectroscopy. As their performance remains largely unpredictable due to the lack of commercial design tools and the poorly understood mode-locking dynamics, significant research has focused on their modeling. In recent years, traveling-wave models have been favored because they can efficiently incorporate the rich semiconductor physics of the laser. However, thus far such models struggle to include nonlinear and dispersive effects of an extended passive laser cavity, which can play an important role for the temporal and spectral pulse evolution and stability. To overcome these challenges, we developed a hybrid modeling strategy by unifying the traveling-wave modeling technique for the semiconductor laser sections with a split-step Fourier method for the extended passive laser cavity. This paper presents the hybrid modeling concept and exemplifies for the first time the significance of the third order nonlinearity and dispersion of the extended cavity for a 2.6 GHz III–V-on-Silicon mode-locked laser. This modeling approach allows to include a wide range of physical phenomena with low computational complexity, enabling the exploration of novel operating regimes such as chip-scale soliton mode-locking.

Hybrid modeling technique for on-chip extended cavity semiconductor mode-locked lasers

“…However, the implementation of extended cavities poses a considerable computational challenge since the spatial step size in the TWM is extremely short compared to the cavity length. Hence, this work attempts to alleviate that problem by building further upon the results of [6,7]. The report presents a novel hybrid modeling technique that combines a TWM description of the active segments with the nonlinear Schrödinger equation (NLSE) to account for the propagation in the passive cavity.…”

“…The queue lengths , on the other hand, match the time it takes for the light to traverse the passive cavity once, which is given by with the passive cavity length. More details on the structure of the algorithm can be found in [6,7].…”

Extending hybrid integrated diode lasers to multi-frequency oscillation

“…Such approximations are not needed in numerical approaches, where strong variations of the laser-internal gain and field distribution can be taken into account as well. Typical examples of numerical approaches are the finite difference time domain (FDTD) approach, and the full Maxwell-Bloch equations (see references in [101]). However, these models are typically computationally heavy, because they involve sub-optical period timesteps and sub-wavelength resolution.…”