We report on the generation of narrowband photon pairs at telecommunication wavelengths using a periodically poled lithium niobate waveguide that utilizes the nonlinear tensor element d(24) for type-II quasi phase matching. The FWHM bandwidth of the spontaneous parametric downconversion was 1 nm. The brightness of the photon pair source was ~6x10(5)/s/GHz when the pump power was 1 mW. The indistinguishability of the signal and idler photons generated by the degenerate spontaneous parametric downconversion process was studied in a Hong-Ou-Mandel type interference experiment.

SUMMARYLong-distance communication is important for practical quantum key distribution. From the viewpoint of transmission distance, generation of single photons at 1550 nm is desirable for fiber transmission. Making use of parametric down-conversion (signal and idler photons) as a single photon source for quantum key distribution can obtain communication distance longer than using a conventional weak coherent pulse. The reason for this is that the arrival time of the idler photon can be known by the detection of signal photon and therefore the dark count probability can be reduced by operating Bob's detector for a very short time around the photon arrival. In this paper, we report on the generation of the correlated photon pairs in the 1550-nm band using a periodically poled lithium niobate waveguide which has a high conversion efficiency. Our measurements are in agreement with a Poissonian photon-pair distribution. We have deduced that the probability of multi-photonpair generation is sufficiently reduced when the pump is lower than 5 µW with a repetition rate of 800 kHz. We also demonstrated a two-photon interference experiment using a Mach-Zehnder interferometer to confirm the quantummechanical nature of the correlated photon pairs. We found that that visibility was decreased when the pump power was increased due to the multi-photon-pair contribution.

We demonstrate the first fiber–radio–fiber system in beyond 90 GHz using low loss optical modulator and direct photonic down-conversion. We successfully transmitted 32-/64-QAM OFDM and single-carrier signal with a record line rate of 71.4 Gb/s and net data rate of 53.7 Gb/s.

No abstract

In this paper an improved method of performing minority carrier lifetime measurements in silicon is presented. The described procedure is applicable to etched silicon slices and demands no further preparation of the test sample. The method is based on a combination of photon scanning and a liquid rectifying contact. The result is obtained either as a visualization of lifetime variations or as descrete lifetime determinations. By choosing a suitable electrolytic liquid, noncontaminating measurements can be made which makes it possible to map test samples before as well as after processing. The method is suitable for control and analysis of the process and may easily be automated.

No abstract

SUMMARYOn quantum communication technologies based on an optical fiber channel, for example a quantum key distribution, it is essential to generate a single photon and a correlated photon pair at telecom wavelength efficiently. We report on the single-photon generation at 1550 nm using photon pairs generated by the spontaneous parametric down-conversion.

No abstract