Research Topics

  1. Bullet Nonlinear, dissipative, non-equilibrium systems

  2. Bullet Dynamics of mode-locked fiber lasers

  3. Bullet Laser-controlled self-organization and self-assembly

  4. Bullet Ultrafast fiber laser physics and developlment

  5. Bullet Laser-material processing and laser-surgery in the ablation-cooled regime

Ultrafast optics is well deservedly associated with strong nonlinear responses. In fact, the entire field of ultrafast optics is unthinkable without nonlinear interactions of light with matter, starting with mode-locking of lasers, the process that generates ultrashort pulses in the first place, to the majority of their applications, from material processing and nonlinear microscopy to high-field physics and frequency metrology. However, when the nonlinear effects are too strong, they cause instabilities, even catastrophic damage. It is, perhaps, ironic that the majority of efforts into improving mode-locked lasers has been dedicated to limiting these nonlinearities. Starting in early 2000’s, we have been developing the concept of Nonlinearity Engineering (J. Opt. Soc. Am. B, 2002), which kicked-started the exploration of particular nonlinear waveforms that are resistant to strong nonlinearities inside mode-locked laser cavities, rather than the traditional approach of weakening the nonlinear effects. Albeit being initially met with disbelief, this approach has led to the demonstration of multiple record-breaking lasers, such as the wave-breaking-free (Opt. Lett., 2003), the similariton (Phys. Rev. Lett., 2004) and the soliton-similariton (Nature Photon., 2010) lasers.

Around 2013, we have started applying what we learned from mode-locking to laser-material interactions — despite the physical system (a material vs light field inside a laser cavity) being entirely different, the interactions share essential mathematical similarities. Following this approach, we showed that we could create laser-induced spatial nanostructures on various material surfaces with unprecedented uniformity (Nature Photon., 2013) by locking the modes in space. Later, we have applied the same concept to extremely efficient laser-material ablation (Nature, 2016), creation of self-organized 3D structures deep inside silicon (Nature Photon., 2017), self-assembly of colloidal nanoparticles (Nature Commun., 2017), among others.

Recently, our focus is shifting back to mode-locking. We would like to apply what we learned from complex laser-material interactions to answer some difficult questions in self-organizing, far-from-equilibrium systems. Mode-locking, itself, is a self-organized far-from-equilibrium state, involving the cooperative action of hundreds of thousands of electromagnetic modes, which interact strongly with matter making up the laser cavity. Often overlooked, fluctuations (in the form of laser noise) plays an essential role when nonlinearities are strong. And unlike many other systems, we have excellent control over the experimental parameters, including the amount and spatial distribution of dissipation, nonlinearity, we can externally inject tailored fluctuations into a cavity, we have a precise theoretical description at hand and we can measure most experimental quantities with dynamic ranges spanning multiple orders of magnitude.

In addition, a large fraction of the research effort of UFOLAB is dedicated to physics and practical development of fiber lasers, in particular high-power ultrafast fiber lasers, along with their numerous biomedical and industrial applications.