Inst. Festkörperphysik

313 Items

Recent Submissions
Novel technology and device approaches for InP-on-SOI and InP photonic integrated circuits

Keyvaninia, Shahram (2021)

Photonic integrated circuits (PICs) are key components in many areas, e.g., optical data transmission networks, sensor systems, and metrology equipment. They offer small footprint, low power consumption, and enable cost-efficient solutions. For PIC realization, monolithic InP and hybrid/heterogeneous InP on SOI are the most important technology platforms. Both have been developed in parallel an...

Optical analysis of InN and InGaN nanostructures

Ries, Maximilian Daniel Cedric (2021)

Nanostructures of group-III-V materials, such as quantum wells (QWs) or nanowires (NWs), are widely deployed in modern solid-state technology. The applicability of the III-nitride system originates in the direct fundamental bandgap covering the whole visible range and expanding even into the near-infrared and the ultraviolet (UV). Lighting applications based on these materials exhibit extraordi...

A 310 nm optically pumped AlGaN vertical-cavity surface-emitting laser

Hjort, Filip ; Enslin, Johannes ; Cobet, Munise ; Bergmann, Michael A. ; Gustavsson, Johan ; Kolbe, Tim ; Knauer, Arne ; Nippert, Felix ; Häusler, Ines ; Wagner, Markus R. ; Wernicke, Tim ; Kneissl, Michael ; Haglund, Åsa (2020-12-17)

Ultraviolet light is essential for disinfection, fluorescence excitation, curing, and medical treatment. An ultraviolet light source with the small footprint and excellent optical characteristics of vertical-cavity surface-emitting lasers (VCSELs) may enable new applications in all these areas. Until now, there have only been a few demonstrations of ultraviolet-emitting VCSELs, mainly optically...

AlN base layers for UV LEDs

Walde, Sebastian (2021)

In this work, the aim is to improve the quality of AlN base layers on sapphire substrates to enable the fabrication of high performance ultraviolet (UV) light-emitting diodes (UV LEDs). The main issues for UV LEDs are still a limited internal quantum efficiency due to a high amount of threading dislocations, but also a limited light extraction efficiency due to total internal reflection at the ...

MOVPE growth of (In)AlGaN-based heterostructures for thin-film LEDs and VCSELs in the UVB spectral range

Enslin, Johannes-Tobias (2021)

The goal of this work is the development of efficient UVB-LEDs and VCSELs and to identify, analyze and master the challenges that arise in the process. Special attention is paid to the strain state of emitters in the UVB spectral range. The strain state is analyzed and the realization of AlGaN pseudosubstrates with high structural quality by MOVPE is discussed. Superlattice structures are used ...

Two-step MOVPE, in-situ etching and buried implantation: applications to the realization of GaAs laser diodes

Della Casa, Pietro (2021)

This work concerns the use of two-steps epitaxial growth, realized with metalorganic vapor-phase epitaxy (MOVPE), combined with in-situ etching and buried ion implantation, for the realization of GaAs-based edge emitting laser diodes, emitting in the near infrared region around 1 µm wavelength. The fabricated devices fall into two categories: tunable lasers (milliwatt range, monomodal) and high...

Isotopic study of Raman active phonon modes in β-Ga2O3

Janzen, Benjamin M. ; Mazzolini, Piero ; Gillen, Roland ; Falkenstein, Andreas ; Martin, Manfred ; Tornatzky, Hans ; Maultzsch, Janina ; Bierwagen, Oliver ; Wagner, Markus R. (2021-01-11)

Holding promising applications in power electronics, the ultra-wide band gap material gallium oxide has emerged as a vital alternative to materials like GaN and SiC. The detailed study of phonon modes in β-Ga2O3 provides insights into fundamental material properties such as crystal structure and orientation and can contribute to the identification of dopants and point defects. We investigate th...

Thermal stability of emission from single InGaAs/GaAs quantum dots at the telecom O-band

Holewa, Paweł ; Burakowski, Marek ; Musiał, Anna ; Srocka, Nicole ; Quandt, David ; Strittmatter, André ; Rodt, Sven ; Reitzenstein, Stephan ; Sęk, Grzegorz (2020-12-11)

Single-photon sources are key building blocks in most of the emerging secure telecommunication and quantum information processing schemes. Semiconductor quantum dots (QD) have been proven to be the most prospective candidates. However, their practical use in fiber-based quantum communication depends heavily on the possibility of operation in the telecom bands and at temperatures not requiring e...

Thresholdless Transition to Coherent Emission at Telecom Wavelengths from Coaxial Nanolasers with Excitation Power Dependent β‐Factors

Kreinberg, Sören ; Laiho, Kaisa ; Lohof, Frederik ; Hayenga, William E. ; Holewa, Pawel ; Gies, Christopher ; Khajavikhan, Mercedeh ; Reitzenstein, Stephan (2020-11-08)

The ongoing miniaturization of semiconductor lasers has enabled ultra‐low threshold devices and even provided a path to approach thresholdless lasing with linear input–output characteristics. Such nanoscale lasers have initiated a discourse on the origin of the physical mechanisms involved and their boundaries, such as the required photon number, the importance of optimized light confinement in...

Electrically Parallel Three-Element 980 nm VCSEL Arrays with Ternary and Binary Bottom DBR Mirror Layers

Haghighi, Nasibeh ; Lott, James (2021-01-14)

To meet the performance goals of fifth generation (5G) and future sixth generation (6G) optical wireless communication (OWC) and sensing systems, we seek to develop low-cost, reliable, compact lasers capable of sourcing 5–20 Gb/s (ideally up to 100 Gb/s by the 2030s) infrared beams across free-space line-of-sight distances of meters to kilometers. Toward this end, we develop small arrays of ele...

Beam Profile Characterisation of an Optoelectronic Silicon Lens-Integrated PIN-PD Emitter between 100 GHz and 1 THz

Smith, Jessica ; Naftaly, Mira ; Nellen, Simon ; Globisch, Björn (2021-01-06)

Knowledge of the beam profiles of terahertz emitters is required for the design of terahertz instruments and applications, and in particular for designing terahertz communications links. We report measurements of beam profiles of an optoelectronic silicon lens-integrated PIN-PD emitter at frequencies between 100 GHz and 1 THz and observe significant deviations from a Gaussian beam profile. The ...

Strong near-field light–matter interaction in plasmon-resonant tip-enhanced Raman scattering in indium nitride

Poliani, Emanuele ; Seidlitz, Daniel ; Ries, Maximilian ; Choi, Soo J. ; Speck, James S. ; Hoffmann, Axel ; Wagner, Markus R. (2020-12-14)

We report a detailed study of the strong near-field Raman scattering enhancement, which takes place in tip-enhanced Raman scattering (TERS) in indium nitride. In addition to the well-known first-order optical phonons of indium nitride, near-field Raman modes, not detectable in the far-field, appear when approaching the plasmonic probe. The frequencies of these modes coincide with calculated ene...

Developing a photonic hardware platform for brain-inspired computing based on 5 × 5 VCSEL arrays

Heuser, Tobias ; Pflüger, Moritz ; Fischer, Ingo ; Lott, James ; Brunner, Daniel ; Reitzenstein, Stephan (2020-08-25)

Brain-inspired computing concepts like artificial neural networks have become promising alternatives to classical von Neumann computer architectures. Photonic neural networks target the realizations of neurons, network connections and potentially learning in photonic substrates. Here, we report the development of a nanophotonic hardware platform of fast and energy-efficient photonic neurons via...

Tools for the performance optimization of single-photon quantum key distribution

Kupko, Timm ; Helversen, Martin von ; Rickert, Lucas ; Schulze, Jan-Hindrik ; Strittmatter, André ; Gschrey, Manuel ; Rodt, Sven ; Reitzenstein, Stephan ; Heindel, Tobias (2020-03-24)

Quantum light sources emitting triggered single photons or entangled photon pairs have the potential to boost the performance of quantum key distribution (QKD) systems. Proof-of-principle experiments affirmed these prospects, but further efforts are necessary to push this field beyond its current status. In this work, we show that temporal filtering of single-photon pulses enables a performance...

A bright triggered twin-photon source in the solid state

Heindel, Tobias ; Thoma, Alexander ; Helversen, Martin von ; Schmidt, Marco ; Schlehahn, Alexander ; Gschrey, Manuel ; Schnauber, Peter ; Schulze, Jan-Hindrik ; Strittmatter, André ; Beyer, Jörn ; Rodt, Swen ; Carmele, Alexander ; Knorr, Andreas ; Reitzenstein, Stephan (2017-04-03)

A non-classical light source emitting pairs of identical photons represents a versatile resource of interdisciplinary importance with applications in quantum optics and quantum biology. To date, photon twins have mostly been generated using parametric downconversion sources, relying on Poissonian number distributions, or atoms, exhibiting low emission rates. Here we propose and experimentally d...

Bright single-photon sources based on anti-reflection coated deterministic quantum dot microlenses

Schnauber, Peter ; Thoma, Alexander ; Heine, Christoph V. ; Schlehahn, Alexander ; Gantz, Liron ; Gschrey, Manuel ; Schmidt, Ronny ; Hopfmann, Caspar ; Wohlfeil, Benjamin ; Schulze, Jan-Hindrick ; Strittmatter, André ; Heindel, Tobias ; Rodt, Sven ; Woggon, Ulrike ; Gershoni, David ; Reitzenstein, Stephan (2015-12-25)

We report on enhancing the photon-extraction efficiency (PEE) of deterministic quantum dot (QD) microlenses via anti-reflection (AR) coating. The AR-coating deposited on top of the curved microlens surface is composed of a thin layer of Ta2O5, and is found to effectively reduce back-reflection of light at the semiconductor-vacuum interface. A statistical analysis of spectroscopic data reveals, ...

Deterministically fabricated quantum dot single-photon source emitting indistinguishable photons in the telecom O-band

Srocka, N. ; Mrowiński, P. ; Große, J. ; Helversen, M. von ; Heindel, Tobias ; Rodt, Sven ; Reitzenstein, Stephan (2020-06-09)

In this work, we develop and study single-photon sources based on InGaAs quantum dots (QDs) emitting in the telecom O-band. Quantum devices are fabricated using in situ electron beam lithography in combination with thermocompression bonding to realize a backside gold mirror. Our structures are based on InGaAs/GaAs heterostructures, where the QD emission is redshifted toward the telecom O-band a...

Deterministically fabricated strain-tunable quantum dot single-photon sources emitting in the telecom O-band

Srocka, N. ; Mrowiński, P. ; Große, J. ; Schmidt, M. ; Rodt, Sven ; Reitzenstein, Stephan (2020-12-01)

Most quantum communication schemes aim at the long-distance transmission of quantum information. In the quantum repeater concept, the transmission line is subdivided into shorter links interconnected by entanglement distribution via Bell-state measurements to overcome inherent channel losses. This concept requires on-demand single-photon sources with a high degree of multi-photon suppression an...

CSAR 62 as negative-tone resist for high-contrast e-beam lithography at temperatures between 4 K and room temperature

Kaganskiy, Arsenty ; Heuser, Tobias ; Schmidt, Ronny ; Rodt, Sven ; Reitzenstein, Stephan (2016-11-29)

The temperature dependence of the electron-beam sensitive resist CSAR 62 is investigated in its negative-tone regime. The writing temperatures span a wide range from 4 K to room temperature with the focus on the liquid helium temperature regime. The importance of low temperature studies is motivated by the application of CSAR 62 for deterministic nanophotonic device processing by means of in si...

Deterministically fabricated spectrally-tunable quantum dot based single-photon source

Schmidt, Marco ; Helversen, Martin V. ; Fischbach, Sarah ; Kaganskiy, Arsenty ; Schmidt, Ronny ; Schliwa, Andrei ; Heindel, Tobias ; Rodt, Sven ; Reitzenstein, Stephan (2020)

Spectrally-tunable quantum light sources are key elements for the realization of long-distance quantum communication. A deterministically fabricated single-photon source with a photon extraction efficiency of η =(20 ± 2) %, a maximum tuning range of ΔE = 2.5 meV and a minimum g(2)(τ = 0) = 0.03 ± 0.02 is presented. The device consists of a single pre-selected quantum dot (QD) monolithically int...