OPUS +LAP for Unipress
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National Science Center (NCN) announced the results of OPUS 26+LAP/Weave for the bilateral projects conducted with partners in Germany. Dr. Grzegorz Muzioł from MBE Laboratory of our Institute received funding for the project „Multi-junction distributed-feedback laser diodes - synergy of high optical power and single-mode operation”.
The project will develop a completely new optoelectronic device - a multi-junction distributed-feedback laser diode (DFB LD), which is shown schematically in Figure 1.
Multi-junction LDs have several pn junctions interconnected with tunnel junctions (TJs). The advantage of this scheme, compared to single junction devices, is that for the same current flow, the recombination occurs in each of the quantum wells (QW). In principle, one can expect an N-fold increase in output power of the multi-junction LD with N sections. This results in differential efficiency (photons per injected electrons) higher than 100%, which comes at the cost of additional voltage required for each section. The DFB grating placed on the surface of the device, as shown in Figure 1, will ensure strong coupling to the optical mode and lasing at only one wavelength – the one that matches the grating.
The demonstration of visible multi-junction DFB LDs will open a new field of GaN-based devices and stimulate new research directions. Abstract of the project is available here.
The project will be conducted in collaboration between Institute of High Pressure Physics Polish Academy of Sciences (IHPP PAS), CEZAMAT Warsaw University of Technology and group of Prof. Ulrich Theodor Schwarz from Technische Universität Chemnitz (TU Chemnitz).
Figure 1. (a) A schematic showing the concept of a multi-junction distributed feedback laser diode composed of three sections interconnected with tunnel junctions (TJ). The third order optical mode is drawn with maxima in the three quantum well (QW) regions. The light propagating in the device couples to the DFB grating that is placed on the surface and ensures lasing in a single mode. (b) Schematics of a band diagram for a LD stack (click to enlarge the Figure).
