Ultra-stable photonic fiber ring lasers are demonstrated at 10 and 40 Gpulses/s repetition rate operating under an optical-RF feedback mechanism with the in-ring hard pumped optical amplification. Ultra-stability is achieved when the circulating optical power is forced into saturation and hence acting as a distributed saturation absorber. Temporal diffraction with harmonic detuning are also analyzed and experimentally demonstrated. Further the pulse repetition rate of higher than 100GHz is achieved by incorporating an external temporal diffraction fiber length.
Free-space quantum key exchanges between ground stations and low earth orbiting satellites will be characterized by high link losses, typically of the order of 30 dB or higher. These losses, together with the need to transmit weak Poissonian laser pulses containing on average substantially less than 0.1 photons per transmitted bit to preserve security, will result in exceedingly low channel efficiencies, typically of the order of 10-5. In order to achieve even a relatively modest secure key bit rate of 100 kbps, it will therefore often be necessary to key the transmitter at rates in excess of 10 Gbps. In this paper we outline several different methods of achieving such fast polarization keying including the use of dual drive Mach-Zehnder intensity modulators on lithium niobate in a hybrid fibre-guided modulator structures. We then propose a total integrated polarization keying structure in LiNbO3. We describe the fabrication and testing of such ultra-broadband polarization keyers suitable for use in high loss, short-wave free-space quantum key distribution systems employing silicon photon counters. We also indicate how these devices may be incorporated into quantum key satellite courier payloads and ground station terminals.
The Shape of an object can be determined by analyzing the distortion of optical grating projected onto it. Many available approaches could be used for this kind of analysis, however most of them require massive computation such as Fourier transformation. Alternatively, direct image processing could be used to give an efficient and accurate result. The profile of the object can be expressed in terms of wire-frame or texture mapped model.
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