We generate quantum correlated photon-pairs at 1550 nm telecom band via pulse-pumped spontaneous four-wave mixing in high-index doped silica glass (HDSG) waveguides. The input and output ports of the 30-cm-long on-chip HDSG spiral waveguide are coupled to standard polarization maintaining fibers, which brings convenience to mode excitation and photon-pair collection. The flattened group velocity dispersion of the TE mode in the spiral waveguide is about 39 ps/km/nm at 1550 nm. When pumping around 1550 nm, the wavelength range of the generated signal (idler) photons can be more than 20 nm. Experimental results show that, in room temperature, the measured coincidence-to-accidental ratio (CAR) is about 200 when the photon-pair production rate is about 2×10-5 pairs/pulse, and the main noise origin of the photon pair source is spontaneous Raman scattering. Our investigations show that the HDSG waveguide, which can be fabricated using CMOS compatible technologies, is a promising candidate for developing miniaturized quantum light sources.
The field-orthogonal temporal modes (TM) of electromagnetic fields form a new framework for quantum information. A lot of efforts have been made to develop the tools for photonic quantum information processing in TM framework. However, the distribution of temporally multiplexed quantum states over long distance optical fibers has not been realized yet. As a first step toward long distance distribution of TMs, we study fourth-order interference and show how the dispersion influence the field spectrum by launching a pulsed field in different temporal modes into a M-Z interferometer with unbalanced dispersion induced by transmission fibers in two arms. The investigation is useful for further investigating the distribution of temporally multiplexed quantum states in fiber network.
Fiber optical parametric amplifier (FOPA), which is based on the four-wave mixing (FWM) effect in optical fibers, is an important amplifier in fiber-based communication systems. To date, FOPAs have extensively studied in variety of single mode fibers. Recently, few-mode fiber (FMF) has attracted much attention because of its potential for providing further increase in per-fiber transmission capacity via mode-division multiplexing (MDM) technology. To amplify the signal of MDM system, few-mode FOPA (FM-FOPA) with high gain and large bandwidth are required. So far, a lot of efforts have been made on proposing the structure and design of FMFs for simultaneously amplifying the telecom band signals in different spatial modes via FWM in FMFs, however, the experimental demonstration has not been carried out yet. In this work, using 90-m-long homemade few-mode dispersion-shifted fiber, we demonstrate the first experimental realization of FM-FOPA and study its gain dependence on polarization and spatial mode. The gain spectra of the intramodal FWMs in LP01 and LP11 modes are in the telecom C and S bands, respectively. When the average powers of pulsed pump in LP01 and LP11 modes are 7 mW and 10 mW, the measured gains are about 24.5 dB and 7 dB, respectively. Moreover, we show that the gain equalized amplification can be realized for 1535 nm seed injection in LP01 and LP11 mode, respectively. Our investigation has potential application in developing low noise amplifier for MDM communication systems.
KEYWORDS: Lithium niobate, Quantum computing, Waveguides, Quantum optics, Communication engineering, Information and communication technologies, Photonics, Quantum communications, Integrated optics, Signal detection
Lithium niobate is widely used in photonics applications because of its large second order nonlinearity and the possibility of integrating nonlinear parametric processes and fast electro-optical reconfigurability. Here we show how these properties can be used for continuous variable quantum optics experiments including the generation, manipulation and characterization and detection of squeezed light.
Based on the spontaneous four wave mixing in micro/nano-fiber (MNF), we report the generation of quantum-correlated
photon pairs. The wavelengths of the signal and idler photons are in the 1310 nm and 851 nm bands, respectively. The
measured ratio between the coincidence and accidental coincidence rates of signal and idler photons is up to 530.
Moreover, we characterize the spectral property of the signal photons in the wavelength range of 1270-1610 nm. The
results reveal that the bandwidth of the photon pairs is much greater than the theoretically expected value due to the
inhomogeneity of the MNF; while the spectrum of Raman scattering in MNF is different from that in conventional
optical fibers and photonic crystal fibers, which may originate from the heating used for fabricating the MNF. Our
investigation shows that the MNF is a promising candidate for developing the sources of quantum light in micro- or
nanometer-scales, and the spectral property of photon pairs can be used to non-invasively test the diameter and
homogeneity of the MNF.
Based on the dispersion property of a given photonic crystal fiber (PCF), we study how to directly generate
frequency de-correlated photon pairs via pulse pumped spontaneous four wave mixing from both the theoretical
and experimental aspects. The numerical investigation shows that to generated the frequency de-correlated
photon pairs, the experimental parameters should be properly optimized by balancing the influences of the
high order dispersion and the intrinsic sinc oscillation of phase matching function, apart from the satisfaction of
specified phase matching condition and the usage of transform limited pump pulses. We also conduct experiment
to verify the numerical simulations, and the experimental results qualitatively agree with the calculations. For
the filter free case, the experimentally obtained maximum g(2) of the individual signal photons is 1.76 ± 0.02.
When this kind of photon pairs is used to realize the heralded single photons, the heralding efficiency can reach
86%.
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