III-V-on-silicon anti-colliding pulse-type mode-locked laser

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

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.

Linewidth narrowing via low-loss dielectric waveguide feedback circuits in hybrid integrated frequency comb lasers

We present an integrated hybrid semiconductor-dielectric (InP-Si₃N₄) waveguide laser that generates frequency combs at a wavelength around 1.5 μm with a record-low intrinsic optical linewidth of 34 kHz. This is achieved by extending the cavity photon lifetime using a low-loss dielectric waveguide circuit. In our experimental demonstration, the on-chip, effective optical path length of the laser cavity is extended to 6 cm. The resulting linewidth narrowing shows the high potential of on-chip, highly coherent frequency combs with direct electrical pumping, based on hybrid and heterogeneous integrated circuits making use of low-loss dielectric waveguides.

A III-V-on-Si ultra-dense comb laser

Optical frequency combs emerge as a promising technology that enables highly sensitive, near-real-time spectroscopy with a high resolution. The currently available comb generators are mostly based on bulky and high-cost femtosecond lasers for dense comb generation (line spacing in the range of 100 MHz to 1 GHz). However, their integrated and low-cost counterparts, which are integrated semiconductor mode-locked lasers, are limited by their large comb spacing, small number of lines and broad optical linewidth. In this study, we report a demonstration of a III-V-on-Si comb laser that can function as a compact, low-cost frequency comb generator after frequency stabilization. The use of low-loss passive silicon waveguides enables the integration of a long laser cavity, which enables the laser to be locked in the passive mode at a record-low 1 GHz repetition rate. The 12-nm 10-dB output optical spectrum and the notably small optical mode spacing results in a dense optical comb that consists of over 1400 equally spaced optical lines. The sub-kHz 10-dB radio frequency linewidth and the narrow longitudinal mode linewidth (<400 kHz) indicate notably stable mode-locking. Such integrated dense comb lasers are very promising, for example, for high-resolution and real-time spectroscopy applications.

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 (∼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.