We study the dynamics of a Quantum Cascade Laser subject to strong optical feedback in the framework of the
Lang-Kobayashi model. In particular, we demonstrate that the continuous wave instability may lead to coherent
multimode oscillations that indicate spontaneous phase-locking among external cavity modes. We recently
predicted that this unique behavior is linked to the absence of relaxation oscillations in unipolar semiconductor
lasers, which are characterized by a fast carriers recombination time (class-A lasers). These theoretical evidences
may help understanding the mechanisms possibly leading to spontaneous mode-locking and pulse generation in
We demonstrate superresolution in position tracking sensing based on feedback interferometry in quantum cascade lasers
(QCLs). QCLs with optical feedback make highly compact sensors since they work as mixer oscillator and detector of
infrared radiation. Additionally, QCL continuous-wave emission remains stable at steady state in strong feedback
regimes, permitting to gain control on the nonlinearity of the QCL active medium. Here, nonlinear frequency mixing in a
QCL-based common-path interferometer is exploited to unveil object’s position with nanometer-scale resolution, far
beyond the intrinsic limit of half-wavelength. Experimental results are in excellent agreement with simulations based on
Lang-Kobayashi model encompassing multiple-target dynamics.
We demonstrate a common-path optical interferometer based on a quantum-cascade laser (QCL), in which the QCL acts
both as source and detector of the infrared radiation. The collinear arms of the interferometer are terminated by a plastic
surface (acting as the beam splitter) and by a metallic one (acting as the mirror). The different reflectivity of the surfaces
allows for high contrast feedback-interferometry fringes exhibited on the laser-emitted power and revealed by voltage
compliance measurement at the QCL terminals. The displacement of each surface can be identified and measured with
sub wavelength resolution. The experimental results are in excellent agreement with the numerical simulations based on
the Lang-Kobayashi model for multiple cavities. Applications to microfluidics and resonant chemical detection can be
We consider a multi-transverse mode Vertical Cavity Surface Emitting Laser (VCSEL) subject to optical feedback.
When the field profile can be described in terms of few Gauss-Laguerre modes we show that the self-mixing
interferometric signal exhibits features peculiar of the spatial distribution and/or polarization state of the re-injected
field. Based on these results we provide both theoretically and experimentally the proof-of-principle of
an operational scheme for a sensor that can be used to simultaneously measure target translations along the
optical axis and target rotations in the orthogonal plane.
The recent development of ultrafast laser ablation technology in precision micromachining has dramatically increased
the demand for reliable and real-time detection systems to characterize the material removal process. In particular, the
laser percussion drilling of metals is lacking of non-invasive techniques able to monitor into the depth the spatial- and
time-dependent evolution all through the ablation process. To understand the physical interaction between bulk material
and high-energy light beam, accurate in-situ measurements of process parameters such as the penetration depth and the
removal rate are crucial. We report on direct real time measurements of the ablation front displacement and the removal
rate during ultrafast laser percussion drilling of metals by implementing a contactless sensing technique based on optical
feedback interferometry. High aspect ratio micro-holes were drilled onto steel plates with different thermal properties
(AISI 1095 and AISI 301) and Aluminum samples using 120-ps/110-kHz pulses delivered by a microchip laser fiber
amplifier. Percussion drilling experiments have been performed by coaxially aligning the diode laser probe beam with
the ablating laser. The displacement of the penetration front was instantaneously measured during the process with a
resolution of 0.41 μm by analyzing the sawtooth-like induced modulation of the interferometric signal out of the detector
In the plane wave approximation, we study spatio-temporal dynamics of a semiconductor class B laser driven
by a coherent injected field in a Fabry-Perot configuration. Below the lasing threshold, we manage to reduce
the dynamics to a single evolution equation for the carrier density, to analytically compute the stationary field
configurations and to predict their stability. The numerical simulations, performed by implementing an efficient
and accurate split-step code, perfectly agree with the analytical results.
We consider the paraxial model for a nonlinear resonator with a saturable absorber beyond the mean-field limit. We introduce a general stability analysis to evidence modulational-instabilities leading to the destabilization of a homogeneous field profile, eventually causing the formation of 3D structures. Further on, for accessible parametric domains, we show in simulations the phenomenon of total radiation confinement leading to the formation of 3D localized bright structures. Such structures are a direct generalization of 2D Cavity Solitons, recently observed in broad-area VCSELs, but they are confined also in the propagation dimension. At difference from freely propagating light bullets, here the self-organization proceeds from the resonator feedback/dissipation, combined with diffraction and nonlinearity.
We show that such cavity light bullets can be independently excited and erased by appropriate pulses. They can be addressed to form arrays in the transverse field profile as well as serial trains in the longitudinal direction of the resonator thus combining serial and parallel encoding in the same device. Once created, they endlessly travel the cavity roundtrip.