@inproceedings{MeisterAlSaadiFrankeetal.2011, author = {Meister, Stefan and Al-Saadi, Aws and Franke, B{\"u}lent A. and Mahdi, Shaimaa and Szczambura, Miroslaw and Kuhlow, Berndt and Woggon, Ulrike and Zimmermann, Lars and Richter, Harald H. and Stolarek, David and Schrader, Sigurd and Eichler, Hans J.}, title = {Micro-cavities based on width modulated SOI waveguides}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15233}, pages = {199 -- 204}, year = {2011}, abstract = {We have designed, fabricated and investigated one-dimensional (1D) micro-cavities in Silicon-on-Insulator (SOI) waveguides. The single mode waveguides are fabricated in a 220 nm silicon device layer. The 1D micro-cavities in Fabry-Perot structure consist of two Bragg-mirror regions formed by a sinusoidal modulation of the waveguide width. The mirror regions are separated by a sub-micron spacer. The SOI photonic structures are produced in a CMOS environment using 248 nm DUV lithography. The waveguides as well as the width modulated mirror regions are designed using a single mask and are fabricated in a shallow trench process. The transmission spectra of these width modulated micro-cavities with different mirror reflectivities and cavity lengths are investigated. Q-factors up to 855 could be observed at 1550 nm wavelength with low insertion loss of 1.9 dB. The width modulated micro-cavities, including the mirror regions, have lengths of less than 20 microns and widths of maximum 450 nm. These small foot-print cavities act as band pass filters and can be used as resonators for laser or electro-optic modulation of light.}, language = {en} } @inproceedings{WangMeisterMahdietal.2011, author = {Wang, Sha and Meister, Stefan and Mahdi, Shaimaa and Franke, B{\"u}lent A. and Al-Saadi, Aws and Zimmermann, Lars and Richter, Harald H. and Stolarek, David and Lisinetskii, Viktor and Ksianzou, Viachaslau and Schrader, Sigurd and Eichler, Hans J.}, title = {Spontaneous and stimulated Raman scattering in planar silicon waveguides}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15248}, pages = {281 -- 289}, year = {2011}, abstract = {Raman scattering in planar silicon on insulator (SOI) waveguides with 2 μm width, 220 nm height and 2 cm length is investigated. A cw Nd:YAP laser at 1340.6 nm with 7 GHz FWHM spectral width is used as the pump source. A lensed fiber of 2.5 μm focus diameter is used to couple the pump laser into the waveguide. The coupling efficiency is estimated to be around 10\%. Spontaneous Raman scattering is observed with as low as 2.5 mW pump power inside the waveguide. The spontaneous Raman spectrum is measured by an optical spectrum analyzer. The first order Raman peak is measured at around 1441.4 nm corresponding to a Raman shift of 15.6 THz, while the FWHM of Raman spectrum is measured as around 100 GHz. Maximum Raman output of around 90 pW is obtained by around 22 mW pump. The stimulated Raman gain coefficient is estimated as around 56 cm/GW from the relationship between spontaneous Raman output power and pump power. A temperature dependence of Raman frequency shift of about 0.6 GHz/K is measured. The spontaneous anti-Stokes Raman scattering output peak at 1253 nm is also observed with around 35 mW pump. Stimulated Raman amplification measurement is carried out with a SLED white light source as probe signal. With 35 mW pump power, around 0.6 dB gain has been determined with both pump and probe being TE polarized.}, language = {en} } @article{ZeschFinkelsteinRegehlyetal.2026, author = {Zesch, Christoph and Finkelstein, Daniel and Regehly, Martin and Reif, J{\"u}rgen and Schrader, Sigurd}, title = {Efficient nanosecond barium nitrate Raman laser for the visible spectral range}, series = {Optics Express}, volume = {34}, journal = {Optics Express}, number = {4}, publisher = {Optica}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-21320}, pages = {6355 -- 6363}, year = {2026}, abstract = {We report on the design and performance of two solid-state Raman lasers, pumped by a frequency-doubled Nd:YAG laser at 532 nm (8 ns FWHM, 10 Hz, up to 10 mJ), that generate either the first or second Stokes radiation with wavelengths of 563 nm and 598 nm. Barium nitrate crystals with a 1 cm² face area and lengths of 3 cm and 5 cm were used as the Raman-active medium in stable semi-spherical resonators. The Raman lasers produced first Stokes and second Stokes pulses, achieving pulse energies up to 2.3 mJ and conversion efficiencies up to 35\% (first Stokes, 5 cm crystal) and 21\% (second Stokes, 5 cm crystal). The output beams exhibit nearly Gaussian profiles with beam quality factors of M² = 1.67 and M² = 1.83, respectively. The proposed design and characterization demonstrated a Raman laser with high efficiency and superior beam quality. After subsequent frequency doubling, the output appears well dedicated for future differential absorption LiDAR (DIAL) applications.}, language = {en} } @inproceedings{PulwerFiebelkornZeschetal.2019, author = {Pulwer, Silvio and Fiebelkorn, Richard and Zesch, Christoph and Steglich, Patrick and Villringer, Claus and Villasmunta, Francesco and Gedat, Egbert and Handrich, Jan and Schrader, Sigurd and Vandenhouten, Ralf}, title = {Endoscopic orientation by multimodal data fusion}, series = {Proc. SPIE 10931, MOEMS and Miniaturized Systems XVIII}, booktitle = {Proc. SPIE 10931, MOEMS and Miniaturized Systems XVIII}, issn = {1996-756X}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-11420}, year = {2019}, abstract = {To improve the feasibility of endoscopic inspection processes we developed a system that provides online information about position, orientation and viewing direction of endoscopes, to support the analysis of endoscopic images and to ease the operational handling of the equipment. The setup is based on an industrial endoscope consisting of a camera, various MEMS and multimodal data fusion. The software contains algorithms for feature and geometric structure recognition as well as Kalman filters. To track the distal end of the endoscope and to generate 3D point cloud data in real time the optical and photometrical characteristics of the system are registered and the movement of the endoscope is reconstructed by using image processing techniques.}, language = {en} } @inproceedings{ZeschSchraderProspositoetal.2019, author = {Zesch, Christoph and Schrader, Sigurd and Prosposito, Paolo and Lux, Oliver and Eichler, Hans J.}, title = {Raman lasers for trace gas detection}, publisher = {SPIE}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15351}, pages = {114 -- 119}, year = {2019}, abstract = {The emission of commercial solid-state lasers is shifted by Raman lasers to selected wavelengths suitable for trace gas detection. High power Raman lasers based on Ba(NO3)2, diamond and silicon detect CO2, O3 and H2O. Raman lasers base on the physical effect of stimulated Raman scattering. Two new Raman crystals (Spodumene and LuAlO3) are investigated and their SRS-spectra is shown.}, language = {en} } @article{VillasmuntaHeiseBreiteretal.2026, author = {Villasmunta, Francesco and Heise, Patrick and Breiter, Manuela and Schrader, Sigurd and Schenk, Harald and Regehly, Martin and Mai, Andreas}, title = {Monolithically Integrated Optical Through-Silicon Waveguides for 3D Chip-to-Chip Photonic Interconnects}, series = {IEEE Journal of Selected Topics in Quantum Electronics}, volume = {32}, journal = {IEEE Journal of Selected Topics in Quantum Electronics}, number = {2}, publisher = {IEEE}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-20828}, year = {2026}, abstract = {The scaling limitations of electrical interconnects are driving the demand for efficient optical chip-to-chip links. We report the first monolithic integration of air-clad optical through-silicon waveguides in silicon, fabricated via Bosch and cryogenic deep reactive-ion etching. Rib, single-bridge, and double-bridge designs with 50 μm cores and up to 150 μm propagation lengths have been evaluated. Cryogenic-etched rib waveguides achieve the highest median transmission (66\%, -1.80 dB), compared to Bosch-etched ribs (62\%, -2.08 dB). Across all geometries, 3 dB alignment windows range from 9.3 μm to 49.2 μm, with Bosch-etched double-bridge waveguides providing the broadest tolerance. We show that geometric fidelity outweighs sidewall roughness for transmission and alignment in these large-core, multimode optical through-silicon waveguides. This technology provides a scalable, complementary metal-oxide semiconductor-compatible pathway toward 3D photonic interconnects.}, language = {en} } @article{SteglichMaiVillringeretal.2021, author = {Steglich, Patrick and Mai, Christian and Villringer, Claus and Dietzel, Birgit and Bondarenko, Siegfried and Ksianzou, Viachaslau and Villasmunta, Francesco and Zesch, Christoph and Pulwer, Silvio and Burger, Martin and Bauer, Joachim and Heinrich, Friedhelm and Schrader, Sigurd and Vitale, Francesco and De Matteis, Fabio and Prosposito, Paolo and Casalboni, Mauro and Mai, Andreas}, title = {Silicon-organic hybrid photonics: an overview of recent advances, electro-optical effects and CMOS integration concepts}, series = {Journal of Physics: Photonics}, volume = {3}, journal = {Journal of Physics: Photonics}, number = {2}, issn = {2515-7647}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13882}, year = {2021}, abstract = {In recent decades, much research effort has been invested in the development of photonic integrated circuits, and silicon-on-insulator technology has been established as a reliable platform for highly scalable silicon-based electro-optical modulators. However, the performance of such devices is restricted by the inherent material properties of silicon. An approach to overcoming these deficiencies is to integrate organic materials with exceptionally high optical nonlinearities into a silicon-on-insulator photonic platform. Silicon-organic hybrid photonics has been shown to overcome the drawbacks of silicon-based modulators in terms of operating speed, bandwidth, and energy consumption. This work reviews recent advances in silicon-organic hybrid photonics and covers the latest improvements to single components and device concepts. Special emphasis is given to the in-device performance of novel electro-optical polymers and the use of different electro-optical effects, such as the linear and quadratic electro-optical effect, as well as the electric-field-induced linear electro-optical effect. Finally, the inherent challenges of implementing non-linear optical polymers on a silicon photonic platform are discussed and a perspective for future directions is given.}, language = {en} } @inproceedings{VillasmuntaSteglichVillringeretal.2024, author = {Villasmunta, Francesco and Steglich, Patrick and Villringer, Claus and Schrader, Sigurd and Schenk, Harald and Mai, Andreas and Regehly, Martin}, title = {Design, fabrication, and characterization of integrated optical through-silicon waveguides for 3D photonic interconnections}, series = {Optical Interconnects XXIV}, volume = {12892}, booktitle = {Optical Interconnects XXIV}, editor = {Chen, Ray T. and Schr{\"o}der, Henning}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-19759}, year = {2024}, abstract = {In the context of an ever-growing volume of data generated by established and emerging technologies, such as 5G, the Internet of Things, artificial intelligence, machine learning, blockchain, and virtual reality, faster communication speed is demanded by data centers and high-performance computing. Transceiver requirements surged from 100 to 400 Gb/s and beyond. In this scenario, photonics aims to enable Tb/s optical communication at energies below 1 pJ/bit. Targeting higher communication rates while maintaining a low power budget can significantly benefit from 3D photonic chip architectures. This paper presents the simulation-based design, fabrication, and characterization of a monolithically integrated optical through-silicon waveguide that facilitates the connection between different surfaces of a silicon chip. Deep reactive ion etching was employed in both the Bosch and Cryogenic variants to evaluate the effect of sidewall roughness on propagation losses. The mechanical stability of the waveguide was ensured by interrupting the annular trench with a bridging structure. The high-refractive-index contrast to air provides tight light confinement for a core size of up to 50 μm and multimode operation at 1550 nm. The morphology was characterized using scanning electron microscopy (SEM), and optical transmission characterization was performed using relative power loss measurements. A tunable laser source was buttcoupled to a waveguide to analyze light transmission efficiency. Preliminary measurements using single-mode fiber show that the transmitted values exceeded 99\% for all structures.}, language = {en} } @article{BauerFursenkoMarschmeyeretal.2019, author = {Bauer, Joachim and Fursenko, Oksana and Marschmeyer, Steffen and Heinrich, Friedhelm and Villasmunta, Francesco and Villringer, Claus and Zesch, Christoph and Schrader, Sigurd}, title = {Spectroscopic reflectometry for characterization of Through Silicon Via profile of Bosch etching process}, series = {Journal of Vacuum Science \& Technology B}, volume = {37}, journal = {Journal of Vacuum Science \& Technology B}, number = {6}, publisher = {American Vacuum Society (AVS)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16093}, year = {2019}, abstract = {Through Silicon Via (TSV) technology is a key in 3D integration of circuits by the creation of interconnects using vias, which go through the full silicon wafer. Typically, a highly-selective Bosch Si etch process is used. It is characterized by a high etch rate at a high aspect ratio, whereby scallops on the sidewalls are generated. In this work, square via arrays with dimensions from 3 to 50 μm and up to 300 μm depth were fabricated and analyzed by spectroscopic reflectometry. The reflectometric data are compared to simulations by a novel theoretical approach. In order to simulate the reflectance spectra of TSV arrays, a combination of 2D and 3D rigorous coupled wave analysis was applied. Besides the via depth, the sidewall angle and the corner radius of the bottom profile were considered in the model. The general requirements on spectral resolution in TSV metrology are discussed.}, language = {en} } @misc{SteglichVillringerPulweretal.2017, author = {Steglich, Patrick and Villringer, Claus and Pulwer, Silvio and Dietzel, Birgit and Ksianzou, Viachaslau and Schrader, Sigurd}, title = {Chip-integrierte photonische Bauelemente}, series = {Wissenschaftliche Beitr{\"a}ge 2017}, volume = {21}, journal = {Wissenschaftliche Beitr{\"a}ge 2017}, issn = {0949-8214}, doi = {10.15771/0949-8214_2017_7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9426}, pages = {55 -- 59}, year = {2017}, abstract = {In unserer hochtechnologisierten Gesellschaft spielt die optische Daten{\"u}bertragung aufgrund der stetig wachsenden Informationsvielfalt eine immer bedeutendere Rolle. In den Anf{\"a}ngen der Nachrichtentechnik waren Datenraten von wenigen bit/s realisierbar. Heute werden mittels optischer Technologien {\"U}bertragungsraten von mehreren Gbit/s umgesetzt. M{\"o}glich wird dies durch neue Entwicklungen in der Chip-integrierten Photonik. Beispiele daf{\"u}r sind Chip-integrierte elektrooptische Modulatoren und Schalter. In diesem Artikel werden neue Entwicklungen in der Chip-integrierten Photonik diskutiert und die experimentelle Charakterisierung der Bauelemente in Form eines Ringresonators beschrieben. F{\"u}r die Experimente wird exemplarisch ein photonisches Bauelement genutzt, das aus einem hybriden Silizium-Polymer-Materialsystem besteht. Die Ergebnisse zeigen, dass diese Materialkombination vielversprechend f{\"u}r zuk{\"u}nftige Chip-integrierte photonische Bauelemente mit extrem geringem Energiebedarf ist.}, language = {de} } @misc{SteglichKsianzouVillringeretal.2018, author = {Steglich, Patrick and Ksianzou, Viachaslau and Villringer, Claus and Pulwer, Silvio and Schrader, Sigurd}, title = {Theorie der Modenlinienspektroskopie zur optischen Charakterisierung von Polymerschichten}, series = {Wissenschaftliche Beitr{\"a}ge 2018}, volume = {22}, journal = {Wissenschaftliche Beitr{\"a}ge 2018}, issn = {0949-8214}, doi = {10.15771/0949-8214_2018_4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10248}, pages = {31 -- 38}, year = {2018}, abstract = {Die Modenlinienspektroskopie kann zur hochpr{\"a}zisen Charakterisierung von Polymerschichten bez{\"u}glich des Brechungsindex verwendet werden. Das vorliegende Manuskript behandelt die Theorie der Modenlinienspektroskopie und beginnt dabei mit den theoretischen Grundlagen eines planaren Wellenleiters, die zum Verst{\"a}ndnis der Modenlinienspektroskopie notwendig sind. Die hier pr{\"a}sentierten expliziten Herleitungen k{\"o}nnen genutzt werden, um die Modenlinienspektroskopie so zu modifizieren, dass auch die Messung des Pockelseffektes m{\"o}glich ist. Eine Anwendungsm{\"o}glichkeit soll in der zuk{\"u}nftigen Bestimmung des Pockelskoeffizienten bestehen, der f{\"u}r die Weiterentwicklung von polymerbasierten elektrooptischen Modulatoren ben{\"o}tigt wird. Zudem werden der Aufbau und die experimentelle Herangehensweisen beschrieben und die Brechungsindexbestimmung wird exemplarisch am Beispiel einer Wirt-Gast-Polymerschicht demonstriert.}, language = {de} } @article{SteglichMaiVillringeretal.2018, author = {Steglich, Patrick and Mai, Christian and Villringer, Claus and Pulwer, Silvio and Casalboni, Mauro and Schrader, Sigurd and Mai, Andreas}, title = {Quadratic electro-optic effect in silicon-organic hybrid slot-waveguides}, series = {Optics Letters}, volume = {43}, journal = {Optics Letters}, number = {15}, issn = {1539-4794}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12148}, year = {2018}, abstract = {This Letter reports on the quadratic electro-optic effect of polymers, observed in a silicon slot-waveguide at low voltages. We demonstrate that in narrow slots, the electro-optic response with respect to refractive index change is strong enough for on-chip wavelength tuning and intensity modulation using voltages as low as 1 V. A silicon slot-waveguide embedded by a nonlinear optical polymer, consisting of the dye Disperse Red 1 in poly(methyl methacrylate), serves as the phase shifter in a racetrack ring resonator. As deduced from the experimental data, the third-order susceptibility of the utilized electro-optic polymer is about 2·10-19 m2/V2. The demonstrated low-voltage operation and inherently thermal stability show the potential for silicon-organic hybrid devices using the quadratic electro-optic effect.}, language = {en} }