Nonlinear Photonics
The research covers several aspects of ‘Nonlinear Photonics’ with fundamental and applicative aspects, in particular the understanding of the complex nonlinear processes determining (and partially limiting) the performance of semiconductor-based photonic devices and lasers, their control and the utilization of nonlinearities for applications. Focus is on understanding and controlling the highly nonlinear dynamics of semiconductor lasers, especially VCSELs. On the fundamental side many activities have strong interdisciplinary aspects being connected to self-organization phenomena in nonequilibrium system ubiquitous in Nonlinear and Complexity Science, technology and nature. It is performed in close cooperation with the Computational Nonlinear Optics and Quantum Optics Group within the Optics Division.
Former projects
Light does not stay confined to small regions in space or time, but wave packets of light have the natural tendency to broaden. For technical applications, it is important to counteract this natural tendency and to confine light to the smallest possible dimensions. Though great partial success was achieved by linear optical element as optical fibres, it was always the dream of researchers to confine light by self-action. This is why the concept of solitary waves received a lot of attraction during the last decades.
Semiconductor quantum dots are an exciting new material for photonics and quantum information because their properties can be tailored to a wide extent. In a first approximation, they can be considered as artificial atoms which strongly interact with their environment. This provides challenges as well as opportunities.
The band within the electromagnetic spectrum between about 300 GHz and 3 THz is often referred to as terahertz radiation. Terahertz radiation is considered to be an upcoming technology in material inspection, quality control, gas sensing, surveillance and security applications, and wireless, short-haul communication. We study a method to produce THz radiation by mixing two cw infrared lasers in a special kind of semiconductor (low-temperature grown GaAs).
We study nonlinear effects due to optical pumping using hot sodium vapour. Beside technical advantages, such as high optical quality, easy variation of parameters over a broad range, high resonant nonlinearity, the benefit of using an atomic vapour is that the equations governing the light-matter interaction can be derived directly from quantum mechanics via the density matrix approach. A large buffer gas presure of molecular nitrogen ensures that atomic motion can be simply decsribed by diffusion and that depolarization from radiation trapping is negligible.
Latest News
Spontaneously Sliding Multipole Spin Density Waves in Cold Atoms.
Spontaneously Sliding Multipole Spin Density Waves in Cold Atoms reported in Physical Review Letters
Generating Multiparticle Entangled States by Self-Organization.
Generating Multiparticle Entangled States by Self-Organization of Driven Ultracold Atoms reported in Physical Review Letters
Invited book chapter: Vector vortex solitons.
Invited book chapter “Vector vortex solitons and soliton control in vertical-cavity surface-emitting lasers” in Dissipative Optical Solitons (Springer); preprint on arXiv
Review: Self-Organization in Cold Atoms Mediated by Diffractive Coupling.
Review on self-organization with single-mirror feedback “Self-Organization in Cold Atoms Mediated by Diffractive Coupling” in atoms
MSCA-ETN ColOpt funded.
Thorsten Ackemann coordinates MSCA-European Training Network ColOpt (Collective Effects and Optomechanics in Ultra-cold Matter)
Recent publications
Spontaneously sliding multipole spin density waves in cold atoms.
Physical Review Letters
132,
(2024).
Generating multiparticle entangled states by self-organization of driven ultracold atoms.
Physical Review Letters
131,
(2023).
Quantum enhanced SU(1,1) matter-wave interferometry in a ring cavity.
Physical Review A
108,
043302
(2023).
Long-range interactions in a quantum gas mediated by diffracted light.
Physical Review Research
5,
L032004
(2023).
