2021, 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

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 pumped, and all with low Al-content AlGaN cavities and emission near the bandgap of GaN (360 nm). Here, we demonstrate an optically pumped VCSEL emitting in the UVB spectrum (280-320 nm) at room temperature, having an Al0.60Ga0.40N cavity between two dielectric distributed Bragg reflectors. The double dielectric distributed Bragg reflector design was realized by substrate removal using electrochemical etching. Our method is further extendable to even shorter wavelengths, which would establish a technology that enables VCSEL emission from UVA (320-400 nm) to UVC (<280 nm). © 2020 American Chemical Society. All rights reserved.

2020, Hossain, Maruf, Stoppel, Dimitri, Boppel, Sebastian, Heinrich, Wolfgang, Krozer, Viktor

A fundamental up-converter with high linearity is presented, realized as full Gilbert cell (GC) mixer using a 800 nm transferred substrate (TS) InP-DHBT technology. The LO input of the Gilbert cell conducts from 75 to 100 GHz and requires 5 dBm of input power. The GC attains a single sideband (SSB) conversion gain of 10 ± 1 dB within the frequency from 82 to 95 GHz with a saturated output power of -1 dBm at 86 GHz and >5 dB conversion gain between 75 and 100 GHz. The up-converter exhibits 25 GHz of IF bandwidth. The DC power consumption is only 51 mW. © 2020 The Authors. Microwave and Optical Technology Letters published by Wiley Periodicals, Inc.

2011, Weyers, M., Knauer, A., Einfeldt, Sven, Rodriguez, Hernan, Kneissl, M., Knüller, V., Tessaro, T., Petzke, T

[no abstract available]

2010, Niehardt, Frank, Grzeganek, Merit, Häckel, Marko, Haselton, Kirk, Kerl, Ralf, Sauer, Franziska

[no abstract available]

2004, Hebermehl, G., Schefter, J., Schlundt, R., Tischler, Th., Zscheile, H., Heinrich, W.

Field-oriented methods which describe the physical properties of microwave circuits and optical structures are an indispensable tool to avoid costly and time-consuming redesign cycles. Commonly the electromagnetic characteristics of the structures are described by the scattering matrix which is extracted from the orthogonal decomposition of the electric field. The electric field is the solution of an eigenvalue and a boundary value problem for Maxwell’s equations in the frequency domain. We discretize the equations with staggered orthogonal grids using the Finite Integration Technique (FIT). Maxwellian grid equations are formulated for staggered nonequidistant rectangular grids and for tetrahedral nets with corresponding dual Voronoi cells. The interesting modes of smallest attenuation are found solving a sequence of eigenvalue problems of modified matrices. To reduce the execution time for high-dimensional problems a coarse and a fine grid is used. The calculations are carried out, using two levels of parallelization. The discretized boundary value problem, a large-scale system of linear algebraic equations with different right-hand sides, is solved by a block Krylov subspace method with various preconditioning techniques. Special attention is paid to the Perfectly Matched Layer boundary condition (PML) which causes non physical modes and a significantly increased number of iterations in the iterative methods.

2020, Liero, Armin, Klehr, Andreas, Knigge, Andrea, Heinrich, Wolfgang

This paper presents a pulse-laser source for the generation of ps and ns laser pulses with more than 50 W peak output power. The final stages of the drivers use GaN transistors and are capable of switching currents of 0.8 A with 200 ps minimum pulse width and 50 A with 3 ns minimum pulse width. The pulses can be externally triggered by ECL logic. Both single-pulse and pulse train modes are possible.

2005, Heinrich, W., Brunner, F., Kurpas, P., Meliani, C., Rudolph, M., Sidorov, V., Würfl, J.

[no abstract available]

2017, Kolbe, Tim, Knauer, Arne, Rass, Jens, Cho, Hyun Kyong, Hagedorn, Sylvia, Einfeldt, Sven, Kneissl, Michael, Weyers, Markus

The effects of composition and p-doping profile of the AlGaN:Mg electron blocking layer (EBL) in 310 nm ultraviolet B (UV-B) light emitting diodes (LEDs) have been investigated. The carrier injection and internal quantum efficiency of the LEDs were simulated and compared to electroluminescence measurements. The light output power depends strongly on the temporal biscyclopentadienylmagnesium (Cp 2 Mg) carrier gas flow profile during growth as well as on the aluminum profile of the AlGaN:Mg EBL. The highest emission power has been found for an EBL with the highest Cp 2 Mg carrier gas flow and a gradually decreasing aluminum content in direction to the p-side of the LED. This effect is attributed to an improved carrier injection and confinement that prevents electron leakage into the p-doped region of the LED with a simultaneously enhanced carrier injection into the active region.

2012, Tränkle, G., Erbert, G., Wicht, A., Spiessberger, S.

[no abstract available]

2007, Würfl, J., Behtash, R., Gesche, R., Janke, B., Klockenhoff, H., Krüger, O., Lossy, R., Chaturvedi, N., Heinrich, W., Knigge, St., Liero, A., Mai, M.

[no abstract available]