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Matthias Gross

Publications and source records attributed to Matthias Gross.

8 recordsLinked to original sources
PubMed2006

Optical bistability in vertical-cavity semiconductor optical amplifiers.

We present an overview of the properties and applications of optical bistability in vertical-cavity semiconductor optical amplifiers (VCSOAs). The basic physics and analytical models of this optical nonlinearity are discussed. Experimental results obtained from a VCSOA operated in the 850 nm wavelength region are presented. Counterclockwise hysteresis loops are obtained over a range of initial phase detuning and bias currents. One hysteresis loop is observed experimentally with an input power as low as 2 muW when the device is biased at 98% of its lasing threshold. Numerical simulations based on the Fabry-Perot resonator model and rate equations we developed show good agreement with our experimental observations. In addition, a low input intensity high contrast (10:1) optical and gate and 2R regeneration are demonstrated. We believe that bistable VCSOAs can significantly advance the prospect of a dense two-dimensional array of low-switching-intensity all-optical logic and memory elements.

Journal Article↗
PubMed2006

Adnexal torsion in a patient with bichorial twin pregnancy in the 21st week of gestation treated by open laparoscopy: a case report.

Adnexal torsion is a rare finding during pregnancy. Here we report a patient with bichorial twin pregnancy in the 21st week of gestation with adnexal torsion. She was admitted with acute abdominal pain. Open laparoscopy was performed and the left adnexa was unwinded successfully. The postoperative follow-up was uneventful. Adnexal torsion as differential diagnosis of acute abdomen in pregnancy should be considered seriously to avoid irreversible lesions of the ovary and (salpingo-) oophorectomy.

Adnexal Diseases↗
PubMed2005

Micro gradient-index conical lenses: simulation and fabrication methods.

In this paper, a micro gradient-index conical lens, which has a larger acceptance angle than a conventional microlens, is presented. Methods on how to simulate these lenses in commercial optical design software CodeV are introduced, and the effects of several index profiles and cone shapes are compared in simulation. Results show that a micro gradient-index conical lens has a four times larger acceptance angle compared with a microlens. Additionally, conical lenses with a Gaussian-index profile show a larger acceptance angle than those with a solid refractive index. Fabricated conical lenses show an acceptance angle of more than 27 degrees for a detection threshold of 50%, which agrees with the simulation result.

Journal Article↗
PubMed2004

Polarization anisotropy in vertical-cavity semiconductor optical amplifiers.

The polarization-dependent gain (PDG) characteristics of a vertical-cavity semiconductor optical amplifier (VCSOA) are measured, and the case of the PDG is determined. It is often assumed that the polarization states of a VCSOA are degenerate because of the circular geometry of the device. This assumption is not true in practice, and it is found that VCSOAs possess a dominant linear polarization state and a small difference in frequency between polarization states. The difference in resonant frequencies causes the PDG of the VCSOA. Measurements of the polarization state show that the cause of the splitting is electro-optic birefringence.

Journal Article↗
PubMed2004

Role of teichoic acids in Staphylococcus aureus nasal colonization, a major risk factor in nosocomial infections.

Colonization of the anterior nares in approximately 37% of the population is a major risk factor for severe Staphylococcus aureus infections. Here we show that wall teichoic acid (WTA), a surface-exposed staphylococcal polymer, is essential for nasal colonization and mediates interaction with human nasal epithelial cells. WTA-deficient mutants were impaired in their adherence to nasal cells, and were completely unable to colonize cotton rat nares. This study describes the first essential factor for S. aureus nasal colonization.

Animals↗
PubMed2002

When ecology and sociology meet: the contributions of Edward A. Ross.

Edward A. Ross, a key figure in the early history of American sociology, developed a conceptualization of natural and social changes of the material environment that is virtually forgotten today. In this paper, these topics are discussed and located vis-à-vis Ross's intellectual contemporaries and their general take on the nature/society relationship. It is argued that ecological and sociological ideas in the early twentieth century influenced one another and, in the case of Ross, produced a perspective of social change that tried to include the dynamics of nature.

Ecology↗