In the absence of quantum repeaters, the only way to increase the quantum communication capacity at a given reach is to employ more modes for encoding and transmitting information. While frequency, temporal, and polarization modes have already been exploited for this purpose, the use of many spatial modes over long distances has only recently become possible owing to the development of low-loss few-mode fibers (FMFs). We will discuss the development of two key enablers of quantum communication over FMF spatial modes: 1) spatiallyentangled photon-pair generator and 2) dynamically-reconfigurable spatial-mode de-multiplexer that can perform projective measurements alternating between two sets of mutually unbiased bases in a given spatial mode space. Both devices are based on the spatial-mode-selective quantum frequency conversion process, implemented in either χ(2) (multimode LiNbO3 waveguide) or χ(3) (custom-made FMF) nonlinear medium.
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.
We demonstrated experimentally a new method for generation of linearly chirped light waves with almost perfect linearity over a broad range of about 800 GHz. The external modulation method that we adopt can maintain frequency jitters at a very low level by avoiding relaxation oscillation effects which are an intrinsic property in intra-cavity modulation methods. The linearly chirped light could provide an excellent time-frequency mapping tool for wide-range applications.
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.
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.