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.
We theoretically and experimentally demonstrate the influence of dispersion on the temporal mode properties of the spontaneous Raman scattering pumped by picosecond pulses in single mode optical fiber. We model the process of the ultrafast spontaneous Raman scattering, calculate and measure the intensity correlation function of the Raman photons with different dispersion by varying the detuning between pump and Raman photons or changing the optical length. The intensity correlation function decreases with the increase of dispersion induced temporal walk-off both by increasing the detuning and by increasing the fiber length. We evaluate the dispersion parameter of the single mode fiber by fitting the measured data with the theoretical equation we deduced. The estimated value is close to the labelled one. Our study provides a new way to evaluate dispersion parameters of the media in which Raman scattering can occur and is beneficial for efficient distillation of entanglement in optical fibers.
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.
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.
Stemming from the pursuit of a simple system to produce squeezed state for long distance continuous variable
quantum communication, we present an all-fibre source of pulsed twin beams at 1550 nm band by using a high
gain fiber optical parametric amplifier. The noise of intensity difference of the twin beams is below the shot noise
limit by 3.1 dB (10.4 dB after correction for losses).
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%.
In this paper, a computer-aided diagnosis system for heart function based on artificial neural networks and fuzzy logic is introduced. Typical parameters reflecting heart function, provided by echocardiography, were used as input of neural networks and their corresponding heart functions as output. To obtain an analytic and discrimination model closer to brain, we combined fuzzy theory with neural network technology, and input parameters are fuzzily treated. During distinguishing morbid style, we used fuzzy interval, fuzzy number and its related possibility distribution concepts, and selected appropriate operator, and so get its corresponding membership, meanwhile membership was put out of interval of linguistic to consist with language expression. The network selected was BP, and back- propagation algorithm was used to train the network. After studying the result evaluated by expert, the neural network was used to appreciate 150 testees' heart function, of which 90.7% was consistent with experts' diagnosis.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.