Advanced semiconductor lasers for generation of optical frequency combs


Optical frequency combs are a set of equidistant optical lines characterized by low phase and amplitude noise, of extreme interest for applications ranging from high-resolution molecular spectroscopy in biomedicine to free space optical communications. Optical frequency combs can be generated in edge-emitting semiconductor lasers exploiting passive or active mode-locking techniques that have been demonstrated more than 30 years ago. Recently self-generation of combs have been reported in advanced semiconductor lasers such as quantum dot (QD) lasers and quantum cascade lasers (QCLs). This activity is dedicated to the development and application of models to the simulation of semiconductor lasers aimed at generating optical combs, investigating different regions of the electromagnetic spectrum with different technologies.

A first branch of this activity focuses on near-IR lasers (around 980 nm) based on QD active regions. Indeed, over the last ten years, it has been shown that such lasers can generate very broad and stable combs not only in passive mode-locking regimes (i.e., two-section laser with gain and saturable absorber) but also in self-mode locking regimes relying only on the gain session. In this framework, this activity is aimed at developing time-domain traveling wave numerical simulators accounting for the peculiar characteristics of the QD active material (inhomogeneous gain broadening, carrier dynamics in QD confined states, double state emission from both ground state and excited state, spatial hole burning...) for the simulation of passive, active and self-mode locking in QD lasers. The tool is applied to the design of QD lasers at 980 nm for the generation of ultra-short pulses at low (a few GHz) repetition rates for pumping single photon sources, and to study self-generation of optical frequency combs in QD lasers directly grown on silicon.

A second branch of this activity is focused on the mid-IR and THz regions of the electromagnetic spectrum. These windows can be covered with quantum cascade lasers (QCLs). In particular, this branch is aimed at simulating the multimode dynamics of QCLs by solving a set of effective semiconductor Maxwell Bloch Equations. This approach properly accounts for peculiar features of radiation-matter interaction in the QCL such as linewidth enhancement factor and fast gain recovery time mediated by photon-phonon scattering. Both in the standard Fabry-Pérot configuration and in the ring configuration, the latter particularly interesting for integration in photonic chips, the space of realistic geometrical and physical QCL parameters is explored, looking for favorable conditions for efficient four-wave mixing and other nonlinear phenomena that trigger system self-organization in the form of optical frequency combs.

ERC sectors 

  • PE7_5 (Micro- and nano-) electronic, optoelectronic and photonic components
  • PE2_14 Lasers, ultra-short lasers and laser physics
  • PE2_12 Optics, non-linear optics and nano-optics
  • PE7_6 Communication systems, wireless technology, high-frequency technology
  • PE7_3 Simulation engineering and modelling


  • Optical frequency combs
  • Mode-locking
  • Ultrashort pulses
  • Numerical modelling and design
  • Effective semiconductor Maxwell-Bloch equations
  • Self-organization phenomena
  • Quantum cascade lasers
  • Semiconductor quantum dot lasers