In this work package we target new functionalities and superior performance characteristics of light sources. We focus on fundamental studies and new source designs for both chip-scale and fiber-based systems. The incorporation of new complex materials allows to strongly increase the wavelength-range or the versatility of these devices. Novel architectures beyond the state-of-the-art are developed by building upon the technology platforms of the partners, such as quantum dots, liquid crystals and active fibers.
2.1 Development of advanced luminescent devices. Devices such as LEDs have undergone a rapid evolution and are actively commercialized nowadays. Next generation components aim for cheaper fabrication, higher efficiency and new emission wavelengths. We contribute to this goal using two approaches: the all-inorganic quantum dot (QD) LED and organic thin film emitters. The all-inorganic QD LED is a very recent realization, which we aim to supersede by achieving IR emission, compatible with silicon photonics.
2.2 Active components with liquid crystals. The objective is to employ liquid crystals (LCs) both as an active medium (based on dye doping), and as a strongly tuneable element. Particular types of active LCs offer the possibility of spontaneously creating useful feedback structures, and only the basic geometries have thus far been studied. As another concrete application we will develop VCSELs with a LC overlayer, so that the intimate interaction between laser light and LC offers strong levels of control. Until now, this concept was only theoretically examined.
2.3 Advances in random fiber lasers. In ideal random lasers, a nonresonant feedback occurs via reflection off a phase scrambling region (like powders), instead of via laser mirrors. Ideally, the emission of such lasers has no spatial coherence and is indefinite in phase. However, in practice, random lasers generate narrow stochastic spikes on top of the laser emission spectrum. We propose to undertake new studies to open the potential to produce spatially incoherent CW radiation tuneable through the whole optical fiber transparency spectrum band in a robust all-fiber integrated format.
2.4 Exploring coherent beam combining. In fiber laser technology, the power available from a single fiber source is limited by nonlinear effects arising in the fiber. Increase of power can be achieved through coherent combining of the beams delivered by a number of regular sources. We will develop all-fiber coherent combining based on the pump-signal induced refractive index changes in active laser fibers (e.g. Yb-doped multicore fibers).
2.5 Extending the wavelength range of fiber lasers. This will be achieved by using Bi-doped fiber lasers (that luminesce in the 1100-1700nm region, covering a range where no other lasers operate), as well as by new studies of supercontinuum generation mechanisms, with special attention to the role of rogue waves.