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.

Current projects

Self-Organization in Cold Atoms
Self-Organization in Cold Atoms

Group Ackemann
Supersolids and quantum droplets via light mediated interactions
Supersolids and quantum droplets via light mediated interactions

Group Ackemann
Nonlinear Laser Dynamics and Spin VCSELs
Nonlinear Laser Dynamics and Spin VCSELs

Vertical-cavity surface-emitting lasers (VCSELs) are a rather new type of semiconductor laser diode, in which – in contrast to conventional edge emitters – the direction of the light emission is parallel to the epitaxial growth direction. We study the connection between the carrier spin and the polarization of the emitted light of VCSELs.
VECSEL and spin-optoelectronics
VECSEL and spin-optoelectronics

Group Ackemann

Former projects

Solitons and vector vortex beams in broad-area VCSELs
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.

Solitons and vector vortex beams in broad-area VCSELs
Nonlinear Optics of Quantum Dots
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.

Nonlinear Optics of Quantum Dots
THz Generation
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).

THz Generation
Optical Pattern Formation in hot Na vapour
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.

Optical Pattern Formation in hot Na vapour

Latest News

Recruiting Postdocs!

For the starting EPSRC funded project Supersolids and quantum droplets via light mediated interactions we are looking for two motivated postdoctoral researchers with a start date from February 2026.

Nov 18, 2025
Recruiting Postdocs!
Supersolids and quantum droplets via light mediated interactions.

A colloboration between the Experimental Quantum Optics and Photonics Group (T. Ackemann, E. Haller) and Computional Nonlonerar and Quantum Optics Group (G. Robb, P. Kirton) obtained funding from EPSRC for the investigation of Supersolids and quantum droplets via light mediated interactions.

Nov 18, 2025
Supersolids and quantum droplets via light mediated interactions.
Self-organized length scales beyond the linear Talbot effect.

In a collaboration with the INPHYNI in Nice and the TU Vienna which just appeared in Physical Review A we are looking now at the interplay of diffraction within the atomic cloud and diffraction in vacuum. It turns out that for most situations it is sufficient to look at the linear Talbot effect but things get more involved, if one puts the mirror “into the cloud”. If you are curious, how to do this and what the resulting length scales are, please look at Phys. Rev. A 111, 063506.

Jun 5, 2025
Self-organized length scales beyond the linear Talbot effect.
Spin Polarization in InGaAs quantum dots for spin-optoelectronics.

New paper in Applied Physics Letter on how the efficiency of introducing a spin polarization in InGaAs quantum dots depends on pump wavelength. Unfortunately, the wavelengths for best spin polarization and best quantum efficiency are not the same. If you are interested, please look at Appl. Phys. Lett. 126, 191102 (2025).

May 15, 2025
Spin Polarization in InGaAs quantum dots for spin-optoelectronics.
Spontaneously Sliding Multipole Spin Density Waves in Cold Atoms.

Spontaneously Sliding Multipole Spin Density Waves in Cold Atoms reported in Physical Review Letters

Apr 5, 2024
Spontaneously Sliding Multipole Spin Density Waves in Cold Atoms.
See all

Recent publications

G. Labeyrie, I. Krešić, R. Kaiser, T. Ackemann, Optical pattern formation in self-focusing and self-defocusing diffractively thick media. Physical Review A 111, (2025).

Cite DOI

N. Alhosiny, S. S. Alharthi, J. Doogan, E. Clarke, T. Ackemann, Optimizing spin polarization in quantum dot vertical-gain structures through pump wavelength selection. Applied Physics Letters 126, (2025).

Cite DOI

H. Souissi, M. Gromovyi, I. Septembre, V. Develay, C. Brimont, L. Doyennette, E. Cambril, S. Bouchoule, B. Alloing, E. Frayssinet, J. Zúñiga-Pérez, T. Ackemann, G. Malpuech, D. D. Solnyshkov, T. Guillet, Mode-locked waveguide polariton laser. Optica 11, 962–970 (2024).

Cite DOI

G. Labeyrie, J. Walker, G. Robb, R. Kaiser, T. Ackemann, Spontaneously sliding multipole spin density waves in cold atoms. Physical Review Letters 132, (2024).

Cite DOI

G. R. M. Robb, J. G. Walker, G. Oppo, T. Ackemann, Continuous acceleration sensing using optomechanical droplets. Atoms 12, (2024).

Cite DOI

See all

Open Positons

Please find openings below.

Self-organized magnetic and droplet states for quantum technologies
We are looking at the spontaneous emergence of intriguing spatial structures (stripes, hexagons, droplets …) and their dynamics in cold atoms via light-mediated interactions. The investigations timely link the fundamental field of emergent phases in many-body open quantum systems to potential applications in quantum technologies.
Jun 25, 2024
Self-organized magnetic and droplet states for quantum technologies