Prof. Ulrich T. Schwarz Profile

Prof. Ulrich T. Schwarz

Professor at Technische Univ. Chemnitz

SPIE Involvement:

Conference Program Committee | Conference Chair | Conference Co-Chair | Author | Editor

Publications (38)

PROCEEDINGS ARTICLE | March 14, 2018

Carrier dynamics and modulation of (Al,In)GaN laser diodes (Conference Presentation)

Proc. SPIE. 10532, Gallium Nitride Materials and Devices XIII

KEYWORDS: Light sources, Modulation, Semiconductor lasers, Frequency combs, Integrated optics, Carrier dynamics, Laser based displays, Virtual reality, Heads up displays, RGB color model

Read Abstract

SPIE Conference Volume | March 27, 2017

Gallium Nitride Materials and Devices XII

SPIE Conference Volume | July 21, 2016

Gallium Nitride Materials and Devices XI

PROCEEDINGS ARTICLE | March 9, 2016

Hybrid polymer waveguide characterization for microoptical tools with integrated laser diode chips for optogenetic applications at 430 nm and 650 nm

Proc. SPIE. 9690, Clinical and Translational Neurophotonics; Neural Imaging and Sensing; and Optogenetics and Optical Manipulation

KEYWORDS: Light sources, Waveguides, Tissues, Polymers, Silicon, Semiconductor lasers, Optogenetics, Bismuth, Polymer multimode waveguides, Brain

Read Abstract

SPIE Conference Volume | April 30, 2015

Gallium Nitride Materials and Devices X

PROCEEDINGS ARTICLE | May 15, 2014

Study of plasmonic nanoparticle arrays for photon management in solar cells

Proc. SPIE. 9140, Photonics for Solar Energy Systems V

KEYWORDS: Plasmonics, Polarization, Nanoparticles, Glasses, Particles, Solar cells, Silicon, Silver, Nanoimprint lithography, Absorption

Read Abstract

PROCEEDINGS ARTICLE | May 15, 2014

The photonic solar cell: system design and efficiency estimations

Proc. SPIE. 9140, Photonics for Solar Energy Systems V

KEYWORDS: Mirrors, Solar cells, Crystals, Dielectrics, Gallium arsenide, Photonic crystals, Photonics systems, Thin film solar cells, Solar energy systems, Absorption

Read Abstract

PROCEEDINGS ARTICLE | March 8, 2014

Microscopic-scale investigation of the degradation of InGaN-based laser diodes submitted to electrical stress

Proc. SPIE. 8986, Gallium Nitride Materials and Devices IX

KEYWORDS: Quantum wells, Luminescence, Diffusion, Quantum efficiency, Semiconductor lasers, Gallium nitride, Laser damage threshold, Indium gallium nitride, Electro optics, Spectroscopes

Read Abstract

PROCEEDINGS ARTICLE | February 27, 2014

Absorption at large reverse bias in monolithic GaN-based short-pulse-multi-section laser diodes

Proc. SPIE. 9002, Novel In-Plane Semiconductor Lasers XIII

KEYWORDS: Quantum wells, Waveguides, Q switching, Semiconductor lasers, Gallium nitride, Solids, Q switched lasers, Lanthanum, Electroluminescent displays, Absorption

Read Abstract

PROCEEDINGS ARTICLE | February 27, 2014

Influence of surface roughness on the optical mode profile in GaN-based violet ridge waveguide laser diodes

Proc. SPIE. 9002, Novel In-Plane Semiconductor Lasers XIII

KEYWORDS: Waveguides, Scattering, Interfaces, Laser scattering, Surface roughness, Semiconductor lasers, Gallium nitride, Diodes, Waveguide lasers, Electroluminescent displays

Read Abstract

PROCEEDINGS ARTICLE | March 5, 2013

Micro-optical system as integration platform for III-N nanowire based opto-chemical detectors

Proc. SPIE. 8613, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics VI

KEYWORDS: Fabrication, Mirrors, Optical design, Polymethylmethacrylate, Sensors, Oxygen, Semiconductor lasers, Beam shaping, Data conversion, Nanowires

Read Abstract

PROCEEDINGS ARTICLE | March 4, 2013

Picosecond pulse generation in monolithic GaN-based multi-section laser diodes

Proc. SPIE. 8625, Gallium Nitride Materials and Devices VIII

KEYWORDS: Quantum wells, Waveguides, Etching, Image processing, Photons, Semiconductor lasers, Scanning electron microscopy, Gallium nitride, Picosecond phenomena, Absorption

Read Abstract

PROCEEDINGS ARTICLE | March 4, 2013

Passive mode-locking in the cavity of monolithic GaN-based multi-section laser diodes

Proc. SPIE. 8640, Novel In-Plane Semiconductor Lasers XII

KEYWORDS: Quantum wells, Resonators, Mode locking, Indium, Electroluminescence, Semiconductor lasers, Streak cameras, Epitaxy, Picosecond phenomena, Absorption

Read Abstract

PROCEEDINGS ARTICLE | February 18, 2013

30 W peak-power 3 ns pulse-width operation of a 2 µm electro-optically cavity-dumped VECSEL

Proc. SPIE. 8606, Vertical External Cavity Surface Emitting Lasers (VECSELs) III

KEYWORDS: Semiconductors, Mirrors, Quantum wells, Polarization, Photons, Polarizers, Semiconductor lasers, Electro optics, Disk lasers, Pulsed laser operation

Read Abstract

SPIE Journal Paper | November 13, 2012

Laser processing of gallium nitride-based light-emitting diodes with ultraviolet picosecond laser pulses

Moser, Rüdiger , Kunzer, Michael , Goßler, Christian , Köhler, Klaus , Pletschen, Wilfried , Schwarz, Ulrich , Wagner, Joachim

OE Vol. 51 Issue 11

KEYWORDS: Light emitting diodes, Laser processing, Photomasks, Laser ablation, Picosecond phenomena, Semiconducting wafers, Ultraviolet radiation, Sapphire, Gallium nitride, Laser systems engineering

Read Abstract

PROCEEDINGS ARTICLE | May 9, 2012

Laser processing of GaN-based LEDs with ultraviolet picosecond laser pulses

Proc. SPIE. 8433, Laser Sources and Applications

KEYWORDS: Light emitting diodes, Optical lithography, Laser processing, Laser ablation, Sapphire, Photomasks, Picosecond phenomena, Semiconducting wafers, Pulsed laser operation, Laser systems engineering

Read Abstract

PROCEEDINGS ARTICLE | May 2, 2012

Optimization of angularly selective photonic filters for concentrator photovoltaic

Proc. SPIE. 8438, Photonics for Solar Energy Systems IV

KEYWORDS: Thin films, Photovoltaics, Optical filters, Refractive index, Solar concentrators, Reflection, Solar cells, Gallium arsenide, Photonic crystals, Optical simulations

Read Abstract

PROCEEDINGS ARTICLE | May 2, 2012

Preparation of periodically arranged metallic nanostructures using nanoimprint lithography

Proc. SPIE. 8438, Photonics for Solar Energy Systems IV

KEYWORDS: Lithography, Nanostructures, Nanoparticles, Particles, Solar cells, Silicon, Silver, Platinum, Nanoimprint lithography, Absorption

Read Abstract

PROCEEDINGS ARTICLE | February 28, 2012

Polarization of eigenmodes and the effect on the anisotropic gain in laser structures on nonpolar and semipolar GaN

Proc. SPIE. 8262, Gallium Nitride Materials and Devices VII

KEYWORDS: Quantum wells, Resonators, Waveguides, Polarization, Crystals, Indium, Semiconductor lasers, Gallium nitride, Laser resonators, Laser damage threshold

Read Abstract

PROCEEDINGS ARTICLE | February 28, 2012

Auger effect in nonpolar quantum wells

Proc. SPIE. 8262, Gallium Nitride Materials and Devices VII

KEYWORDS: Quantum wells, Light emitting diodes, Polarization, Crystals, Indium, Quantum efficiency, Gallium nitride, Promethium, Indium gallium nitride, Internal quantum efficiency

Read Abstract

PROCEEDINGS ARTICLE | February 9, 2012

(Al,In)GaN laser diodes with optimized ridge structures

Proc. SPIE. 8277, Novel In-Plane Semiconductor Lasers XI

KEYWORDS: Mirrors, Quantum wells, Resonators, Semiconductor lasers, Gallium nitride, Diodes, Aluminum, Indium gallium nitride, Semiconducting wafers, Waveguide lasers

Read Abstract

PROCEEDINGS ARTICLE | February 17, 2011

Dynamics of GaN-based laser diodes from violet to green

Proc. SPIE. 7953, Novel In-Plane Semiconductor Lasers X

KEYWORDS: Transparency, Light emitting diodes, Photons, Indium, Electroluminescence, Semiconductor lasers, Optical simulations, Laser damage threshold, Picosecond phenomena, Pulsed laser operation

Read Abstract

PROCEEDINGS ARTICLE | February 17, 2011

Recent results of blue and green InGaN laser diodes for laser projection

Proc. SPIE. 7953, Novel In-Plane Semiconductor Lasers X

KEYWORDS: Continuous wave operation, Waveguides, Laser applications, Semiconductor lasers, Gallium nitride, Diodes, Laser damage threshold, Indium gallium nitride, Pulsed laser operation, Temperature metrology

Read Abstract

Mobile laser projection is of great commercial interest. Today, a key parameter in embedded mobile applications is the optical output power and the wall plug efficiency of blue and green lasers. We report on improvements of the performance of true blue riedge waveguide InGaN lasers at 452nm with cw-output power up to 800mW in overstress and mono mode operation up to 500mW in a temperatures range of 20°C to 80°C. We succeeded in high and almost temperature independent wall plug efficiencies >20% at stable output power levels from 200 to 500mW in cw-operation. Due to several improvements of our blue laser diodes we now estimate life times is in the order of 40khrs for 80mW output power in cw-operation at 40°C. Additional overstress degradation tests at power levels up to 200mW show a strong dependency of lifetime with output power. Furthermore, we present pioneering results on true green InGaN laser diodes on c-plane GaN-substrates. The technological challenge is to achieve In-rich InGaN-quantum wells with sufficiently high material quality for lasing. We investigated the competing recombination processes below laser threshold like nonradiative defect recombination by electro-optical measurements, such confirming that low defect densities are essential for stimulated emission. A model for alloy fluctuations in In-rich InGaN-MQWs based on spectral and time resolved photoluminescence measurements yields potential fluctuations in the order of E₀=57meV for our blue laser diodes. To get a closer insight into the physics of direct green InGaN-Laser we investigated the inhomogeneous broadening of experimentally measured gain curves via Hakki-Paoli-measurements in comparison to calculated gain spectra based on microscopic theory showing the importance of strong LO-phonon coupling in this material system. Investigations of current dependent gain measurements and calculations yield a factor of 2 higher inhomogeneous broadening for our green lasers than for our blue laser diodes on c-plane GaN. Based on the improvements of the material quality and design we demonstrate true green InGaN-Laser in cw-operation at 522nm with more than 80mW output power on c-plane GaN. The combination of low laser threshold ~60-80mA, high slope efficiency ~0.65W/A and low operating voltage 6.9-6.4V of our green monomode RWG-Laser results in a high wall plug efficiency of 5-6% in a temperature range of 20-60°C.

PROCEEDINGS ARTICLE | February 16, 2009

Emission of biased green quantum wells in time and wavelength domain

Proc. SPIE. 7216, Gallium Nitride Materials and Devices IV

KEYWORDS: Quantum wells, Light emitting diodes, Modulation, Spectroscopy, Luminescence, Quantum efficiency, Electroluminescence, Streak cameras, Indium gallium nitride, Green light emitting diodes

Read Abstract

PROCEEDINGS ARTICLE | February 3, 2009

Impact of filamentation on the far-field of high power broad ridge (Al,In)GaN laser diodes

Proc. SPIE. 7230, Novel In-Plane Semiconductor Lasers VIII

KEYWORDS: Superposition, Refractive index, Gaussian beams, Waveguides, Laser beam propagation, Semiconductor lasers, Near field scanning optical microscopy, Near field, Modes of laser operation, Near field optics

Read Abstract

PROCEEDINGS ARTICLE | May 8, 2008

Measurement and simulation of the lateral mode profile of broad ridge 405 nm (Al,In)GaN laser diodes

Proc. SPIE. 6997, Semiconductor Lasers and Laser Dynamics III

KEYWORDS: Superposition, Refractive index, Waveguides, Semiconductor lasers, Near field scanning optical microscopy, Thermal effects, Optical simulations, Modes of laser operation, Temperature metrology, Near field optics

Read Abstract

PROCEEDINGS ARTICLE | May 8, 2008

Spectral measurements and simulations of 405 nm (Al, In)GaN test laser structures grown on SiC and GaN substrate

Proc. SPIE. 6997, Semiconductor Lasers and Laser Dynamics III

KEYWORDS: Quantum wells, Waveguides, Electroluminescence, Semiconductor lasers, Gallium nitride, Aluminum, Optical simulations, Laser damage threshold, Indium gallium nitride, Silicon carbide

Read Abstract

PROCEEDINGS ARTICLE | April 21, 2008

Analysis of the emission characteristics of photonic crystal LEDs

Proc. SPIE. 6989, Photonic Crystal Materials and Devices VIII

KEYWORDS: Semiconductors, Diffraction, Refractive index, Mirrors, Light emitting diodes, Finite-difference time-domain method, Interfaces, Photonic crystals, Solids, Indium gallium nitride

Read Abstract

PROCEEDINGS ARTICLE | February 15, 2008

True-blue InGaN laser for pico size projectors

Proc. SPIE. 6894, Gallium Nitride Materials and Devices III

KEYWORDS: Quantum wells, Magnesium, Luminescence, Laser applications, Reflectivity, Doping, Semiconductor lasers, Projection systems, Laser damage threshold, Indium gallium nitride

Read Abstract

PROCEEDINGS ARTICLE | November 19, 2007

Optical gain in 407nm and 470nm InGaN/GaN heterostructures: signature of quantum-dot states

Proc. SPIE. 6782, Optoelectronic Materials and Devices II

KEYWORDS: Quantum wells, Polarization, Indium, Semiconductor lasers, Gallium nitride, Lab on a chip, Integrated optics, Indium gallium nitride, Heterojunctions, Statistical modeling

Read Abstract

PROCEEDINGS ARTICLE | March 23, 2007

Analysis of substrate modes in GaN/InGaN lasers

Proc. SPIE. 6468, Physics and Simulation of Optoelectronic Devices XV

KEYWORDS: Semiconductors, Refractive index, Waveguides, Dispersion, Metals, Semiconductor lasers, Gallium nitride, Optical simulations, Waveguide modes, Near field optics

Read Abstract

PROCEEDINGS ARTICLE | February 13, 2007

Measurement of the internal quantum efficiency of InGaN quantum wells

Proc. SPIE. 6486, Light-Emitting Diodes: Research, Manufacturing, and Applications XI

KEYWORDS: Quantum wells, Light emitting diodes, Magnesium, Luminescence, Doping, Gallium nitride, Indium gallium nitride, Electron holes, Internal quantum efficiency, Temperature metrology

Read Abstract

PROCEEDINGS ARTICLE | February 8, 2007

Investigation and comparison of optical gain spectra of (Al,In)GaN laser diodes emitting in the 375nm to 470 nm spectral range

Proc. SPIE. 6485, Novel In-Plane Semiconductor Lasers VI

KEYWORDS: Near ultraviolet, Quantum wells, Data modeling, Electrons, Indium, Semiconductor lasers, Optical simulations, Indium gallium nitride, Gallium, Standards development

Read Abstract

PROCEEDINGS ARTICLE | April 14, 2006

Time-resolved scanning near-field microscopy of InGaN laser diode dynamics

Proc. SPIE. 6184, Semiconductor Lasers and Laser Dynamics II

KEYWORDS: Quantum wells, Waveguides, Etching, Microscopy, Semiconductor lasers, Near field scanning optical microscopy, Near field, Indium gallium nitride, Oscilloscopes, Waveguide modes

Read Abstract

PROCEEDINGS ARTICLE | April 14, 2006

Simulation and design of optical gain in In(Al)GaN/GaN short wavelength lasers

Proc. SPIE. 6184, Semiconductor Lasers and Laser Dynamics II

KEYWORDS: Optical design, Quantum wells, Luminescence, Crystals, Semiconductor lasers, Gallium nitride, Optical simulations, Laser damage threshold, Indium gallium nitride, Temperature metrology

Read Abstract

PROCEEDINGS ARTICLE | April 12, 2005

Formation of Ince-Gaussian modes in a stable laser oscillator

Proc. SPIE. 5708, Laser Resonators and Beam Control VIII

KEYWORDS: Monochromatic aberrations, Mirrors, Reticles, Oscillators, Resonators, Output couplers, Crystals, Semiconductor lasers, Diodes, Laser crystals

Read Abstract

PROCEEDINGS ARTICLE | April 1, 2005

Near-field and far-field dynamics of (Al,In)GaN laser diodes

Proc. SPIE. 5738, Novel In-Plane Semiconductor Lasers IV

KEYWORDS: Refractive index, Beam steering, Waveguides, Semiconductor lasers, Monte Carlo methods, Near field scanning optical microscopy, Near field, Wave propagation, Solids, Waveguide modes

Read Abstract