Collective optomechanical effects in cavity quantum electrodynamics

We investigate a cavity quantum electrodynamic effect, where the alignment of two-dimensional freely rotating optical dipoles is driven by their collective coupling to the cavity field. By exploiting the formal equivalence of a set of rotating dipoles with a polymer we calculate the partition function of the coupled light-matter system and demonstrate it exhibits a second order phase transition between a bunched state of isotropic orientations and a stretched one with all the dipoles aligned. Such a transition manifests itself as an intensity-dependent shift of the polariton mode resonance. Our work, lying at the crossroad between cavity quantum electrodynamics and quantum optomechanics, is a step forward in the on-going quest to understand how strong coupling can be exploited to influence matter internal degrees of freedom.Comment: 6 pages, 3 figure

Ethnobiology : the missing link in ecology and evolution

Evolutionary biologists and ecologists increasingly appreciate the value of local knowledge of human communities for research into the past, present, and future of biodiversity. However, there are often significant problems accessing and interpreting this knowledge. Here, we argue that closer interaction with ethnobiologists, who study the relation between humans and the natural world, will enable local knowledge to be better applied in ecological and evolutionary biological research. This will provide more comprehensive answers to the scientific questions being asked, and will result in improved engagement with both academic and non-academic communities

Matter wave coupling of spatially separated and unequally pumped polariton condensates

Spatial quantum coherence between two separated driven-dissipative polariton condensates created non-resonantly and with a different occupation is studied. We identify the regions where the condensates remain coherent with the phase difference continuously changing with the pumping imbalance and the regions where each condensate acquires its own chemical potential with phase differences exhibiting time-dependent oscillations. We show that in the mutual coherence limit the coupling consists of two competing contributions: a symmetric Heisenberg exchange and the Dzyloshinskii-Moriya asymmetric interactions that enable a continuous tuning of the phase relation across the dyad and derive analytic expressions for these types of interactions. The introduction of non-equal pumping increases the complexity of the type of the problems that can be solved by polariton condensates arranged in a graph configuration. If equally pumped polaritons condensates arrange their phases to solve the constrained quadratic minimisation problem with a real symmetric matrix, the non-equally pumped condensates solve that problem for a general Hermitian matrix.Comment: 3 figures, 16 page

Tourism work and immigrant integration : the case of Finland

The tourism industry in Finland provides many employment opportunities, which is ideal for many immigrants seeking work in the country. Employment is one of the major factors that can affect their integration into local society, due to exposure to the local work culture, building relationships with coworkers, and learning. This paper aims to analyse how working in the tourism and hospitality sectors in Finland has affected immigrants’ integration process, as well as any opportunities for their career development. Immigration is a very relevant topic, and as such has been widely studied in the past. The challenges immigrants face in their new society, whether social, economic, or health related have been documented thoroughly. The host society’s attitudes towards them as well as measures that have been taken to meet the needs of all parties have also been widely studied. In regards to integration processes when working in a specific field, such as tourism, not much discussion has been generated. It is thus important to analyse how the working environment of a specific sector can influence an immigrant’s integration into local society. This essentially means finding out how employers belonging to that sector (in the case of this paper, tourism and hospitality) approach the matter of integration via employment. This paper will focus on the tourism and hospitality sectors of Finland. This paper will approach the subject based on the theory of the “two-way integration”. While there is no concrete definition for two-way integration, this theory largely suggests that proper integration of immigrants requires action from both them and the host society. It provides an excellent opportunity to look into how immigrants try to integrate via their work, while also showing what action employers take to satisfy such needs. The main research question is: How has working in the tourism sector in Finland helped immigrants with integration into society? Sub-questions include: What challenges did the immigrants face while working? How were those challenges addressed? In what ways do employers affect an immigrant’s experiences in the work environment? Research was conducted by referring to previous literature on the subject and interviewing immigrants currently working or residing in Rovaniemi, Finland. The immigrants must be working or have worked in the tourism/hospitality sectors (or sufficiently related) in Finland. The interviews were conducted in April – June 2023. It was found that immigrants’ experiences with their tourism jobs depended largely on how welcome their employer made them feel. Due to many jobs in the sector requiring close coordination with coworkers, some employers invested in teambuilding, which resulted in creating circles of trust between the immigrants and their coworkers. It also allowed them to work without the immediate need for learning the finnish language, although it is still a problem when job-hunting. One employee was left dissatisfied with the employer, but they managed to learn a lot of things about how Finland’s tourism sector operates. Overall, working in Finland’s tourism and hospitality sector proved to be beneficial for the interviewees’ integration, for the reasons just mentioned. The results of this research could be used as reference to what employers in the tourism industry can do to facilitate immigrant integration, and why such steps ar eimportant for tourism in particular

Time resolved scattering relaxation mechanisms of microcavity polaritons

We study the polariton relaxation dynamics for different scattering mechanisms as: Phonon and electron scattering procesess. The relaxation polariton is obtained at very short times by solving the Boltzman equation. Instead of the well-known relaxation process by phonons, we show that the bottleneck effect relaxes to the ground state more efficiently at low pump power intensity when the electron relaxation process is included. In this way, we clearly demonstrate that different relaxation times exist, for which any of these two mechanism is more efficient to relax the polariton population to the ground state.Comment: 10 eps figure

Time-Delay Polaritonics

Non-linearity and finite signal propagation speeds are omnipresent in nature, technologies, and real-world problems, where efficient ways of describing and predicting the effects of these elements are in high demand. Advances in engineering condensed matter systems, such as lattices of trapped condensates, have enabled studies on non-linear effects in many-body systems where exchange of particles between lattice nodes is effectively instantaneous. Here, we demonstrate a regime of macroscopic matter-wave systems, in which ballistically expanding condensates of microcavity exciton-polaritons act as picosecond, microscale non-linear oscillators subject to time-delayed interaction. The ease of optical control and readout of polariton condensates enables us to explore the phase space of two interacting condensates up to macroscopic distances highlighting its potential in extended configurations. We demonstrate deterministic tuning of the coupled-condensate system between fixed point and limit cycle regimes, which is fully reproduced by time-delayed coupled equations of motion similar to the Lang-Kobayashi equation

Spinning nanorods - active optical manipulation of semiconductor nanorods using polarised light

In this Letter we show how a single beam optical trap offers the means for three-dimensional manipulation of semiconductor nanorods in solution. Furthermore rotation of the direction of the electric field provides control over the orientation of the nanorods, which is shown by polarisation analysis of two photon induced fluorescence. Statistics over tens of trapped agglomerates reveal a correlation between the measured degree of polarisation, the trap stiffness and the intensity of the emitted light, confirming that we are approaching the single particle limit.Comment: 7 pages, 4 figure