Wielozłączowe diody laserowe z rozłożonym sprzężeniem zwrotnym -synergia wysokiej mocy optycznej i jednomodowego trybu pracy

The aim of this project is to demonstrate a completely new type of optoelectronic device - a multi-junction distributed feedback (DFB) laser diode (LD). We expect this device to offer unprecedently high optical power and single-mode operation; all from a compact and robust semiconductor chip. The device will be based on GaN and will be operating in the visible spectrum. This ensures many possible applications such as “last mile” telecommunication based on plastic fibers, Li-Fi, Light Detection and Ranging (LIDAR) systems, underwater communication, strontium-based atomic clocks, gas sensing and environmental monitoring. A multi-junction LD consists of have several pn junctions interconnected with tunnel junctions (TJs). The advantage of this device, compared to single pn junction devices, is that for the same current flow, the recombination occurs in each of the active regions. 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. Multi-junction LDs have been demonstrated for conventional semiconductor systems such as GaAs and InP. Devices operating at a wavelength range of 800 to 2000 nm are commercially available and find applications in LIDAR and range finding. Within this project we plan to force the multi-junction LDs to operate in a single mode by coupling of its optical mode to a surface diffraction grating along the full length of the resonator as is done in DFB LDs. The device will operate on high order transversal mode with maxima of the mode in the active regions and minima in the TJs. The multi-section design will enable high optical power while high coupling of the mode to the surface grating will ensure a single-mode operation of the proposed device. The proposed 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). At IHPP PAS the technology of GaN-based LD is being developed for over 20 years. Multi-junction LDs operating in the visible spectrum were elusive until recently. In our laboratory at IHHP PAS we have recently demonstrated GaN-based multi-junction LDs consisting of two and three sections, but without the diffraction grating. The CEZAMAT laboratory offers state-of-the-art lithographic technologies, in particular electron beam lithography, which will be used to make surface diffraction grating on top of the mesa structure. The group of Prof. Schwarz specializes in the spectroscopic investigation of the physical properties of semiconductor devices. He focuses on characterization and simulation of GaN-based LDs. At TU Chemnitz Prof. Schwarz has built a laboratory with unique equipment that will allow to thoroughly investigate the spatial, spectral and temporal characteristics of multi-junction DFB LDs. We expect that close collaboration between the three groups will allow for the first demonstration of multijunction DFB LDs in the world. We plan to use advanced simulation techniques to design and investigate the properties of multi-junction DFB LDs. In particular, we will investigate the coupling strength between the optical mode and grating placed on top of the mesa structure, thermal heating of the device, optical mode distribution and formation of optical gain. We plan to collaborate with Dr Joachim Piprek from the NUSOD Institute, who is the world leading scientist in the field of simulation of optoelectronic devices. Recently, at IHPP PAS we have developed a theoretical model based on Kane theory in order to study the tunneling properties of the TJs. We will use this model to study the influence of thickness, doping and composition of the We expect that work performed within this project and close collaboration between the three groups will allow for the first demonstration of multi-junction DFB LDs in the world.