ABSTRACT
Oxide-confined vertical cavity surface emitting lasers (VCSELs) with anti-waveguiding AlAs-rich core presently attract a lot of attention. Anti-waveguiding cavity enables the maximum possible optical confinement of the VCSEL mode ("λ/2 design"), increases its oscillator strength and reduces dramatically the optical power accumulated in the VCSEL mesa regions outside the aperture. VCSEL designs are suggested that favor single transverse mode operation. Modeling including current-induced and absorption-induced overheating shows that the preference for the transverse fundamental mode persists up to 10 mA current at 5 µm aperture diameter. Error-free data transmission is realized up to 160 Gb/s in digital-multitone (DMT) format using single-mode anti-waveguiding VCSELs. The approach to single-mode anti-waveguiding VCSELs is extended over a broad spectral range realizing error-free high-speed data transmission at both 850 nm and 910 nm.
ABSTRACT
We demonstrate an all-optical label and payload separator based on nonlinear polarization rotation in a semiconductor optical amplifier (SOA). The proposed scheme uses a packet format composed of a label and payload information signal combined with a control signal by using polarization division multiplexing. The control signal is employed to separate the label from the payload signal by exploiting nonlinear polarization rotation in a SOA. Experimental results show a label from payload suppression factor of 22 dB. This scheme operates asynchronously and does not need external control signal. Clean and wide open eye diagrams are obtained for both the payload and the label signal operating at bit-rates of 10 Gbit/s and 625 Mbit/s, respectively.
ABSTRACT
PURPOSE: To report a case of oligodendroglioma originating from the accessory glia of retina. METHOD: Case report of a 72-year-old woman with a tumor in the temporal fundus of the right eye that was suspected to be choroidal melanoma. Enucleation was declined, but 5 years later, because of tumor growth, pain, and loss of light perception, the globe was enucleated. RESULTS: Histopathologic examination disclosed a neuroepithelial tumor with a structure of oligodendroglioma. Melanoma and metastatic tumor were excluded. CONCLUSIONS: Oligodendrogliomas are rare in the retina but may originate from retinal oligodendrocytes. This case suggests that the differential diagnosis of choroidal melanoma should include the possibility of oligodendroglioma.
