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An all-fiber laser using polarization-maintaining and ring-core fibers that are capable of automatically generating stable TE01 and TM01 modes is proposed and demonstrated experimentally. Two vector-mode coupling long-period fiber gratings (LPFGs) fabricated by a high-frequency CO2 laser are used in the fiber laser to realize efficient coupling between HE11 mode and TE01/TM01 mode. The polarization dependence of the LPFGs is simulated using the coupled-mode theory and verified by experiments. A ring-core fiber is employed to support the stable propagation of TE01 and TM01 modes. By carefully aligning the polarization direction of the input light, the mode coupling ratios of both LPFGs exceed 15 dB. The mode purities of TE01 and TM01 modes are 92.4% and 97.3%, respectively. Owing to the all-polarization-maintaining structure, the laser output is highly stable under environmental disturbance. This laser can be used as a stable cylindrical vector beam source for a wide range of applications, including surface plasmon excitation, optical tweezers, high-resolution metrology and so on.

Manipulation of nonlinear processes of orbital angular momentum (OAM) modes in optical fibers is an emerging challenge, providing the potential for a wide variety of applications in parametric amplification, high-dimensional entanglement generation, and frequency conversion. The authors demonstrate low-crosstalk intramodal processes for four-wave mixing between OAM modes in an optical-vortex fiber. By engineering the relative group velocity within a spatial dimension, the phase-matching conditions for OAM modes can be tailored. The proposed scheme may also illuminate further possibilities for generating and manipulating OAM states in fiber systems.

We experimentally demonstrate degenerate intra-modal four-wave mixing (FWM) processes among orbital angular momentum modes in a family designed ring-core fiber. The designed fiber provide both large effective refractive index difference and low dispersion between multiple modes in the C-band. The signal wave with different modes generated by intra-modal FWM processes was examined using mode de-multiplexed system.

In this work, by combining the wavelength- and time-division multiplexing technologies, we demonstrate a multiplexing time-bin entangled photon pair source based on a silicon nanowire waveguide and distribute entangled photons into 3(time) × 14(wavelength) channels independently. The indistinguishability of photon pairs in each time channel is confirmed by a fourfold Hong-Ou-Mandal quantum interference.

Optical quantum states based on entangled photons are the key resource in quantum-information science. The realization of multiplexed multiple entanglement are necessary for developing high-capacity quantum information process. Silicon-on-insulator (SOI) has recently become a leading platform for generating and processing of non-classical optical states. In this work, by combining the wavelength- and time-division multiplexing technologies, we demonstrate a multiplexing time-bin entangled photon pair source based on a silicon nanowire waveguide and distribute entangled photons into 3(time) × 14(wavelength) channels independently. The indistinguishability of photon pairs in each time channel is confirmed by a fourfold Hong-Ou-Mandal quantum interference. Our work paves a new and promising way to achieve a high capacity quantum communication and to generate a multiple-photon non-classical state.

We propose and experimentally demonstrate an ytterbium-doped fiber laser emitting the single high-order cylindrical vector beams with a high efficiency and a high modal purity based on adaptive modal gain control. By the combination of a high-order pump with a self-designed ytterbium-ring doped fiber, modal dependent gain was tailored and specific transverse mode can be selected in the laser cavity. A model based on multimode propagation-rate equations is built up to demonstrate the behaviors of transverse mode competition in the fiber laser. Modal dependent gain of high-order mode pump are simulated numerically, which agree well with our experiment results. The slope efficiency of the fiber laser reaches 79.61% with a low threshold of 47.73mw. The purity of the generated high-order CVBs are in excess of 95%. Such a strategy enables the controllability of modal gain in a fiber laser and reveals the potential to offer a new and promising way to achieve a high-power fiber laser with an arbitrary single high-order transverse modes output.

Silicon-on-chip (SOI) photonic circuit is the most promising platform for scalable quantum information technology for its low loss, small footprint, CMOS-compatible and telecom communications techniques compatible. Multiple multiplexed entanglement sources include: energy-time, time-bin and polarization entangled sources based on 1-cm length single silicon nanowire, all these sources are compatible with (100GHz) dense-wave-division-multiplexing (DWDM) system. Different methods such as two photon interference pattern, Bell-Inequality and quantum state tomography are used to characterize the quality of these entangled sources. Multiple entanglements are generated over more than 5 channel pairs with high raw (net) visibilities around 97% (100%). The emission spectral brightness of these entangled sources reaches 4.2*105 /(s.nm.mW). The quality of the photon pair generated in continuous and pulse pump regimes are compared. High qualities of these multiplexed entanglement sources make them very promising to be used in future minimized quantum communication and computation systems., Comment: Accepted by Physical Review Applied

Silicon-on-chip photonic circuits are among some very promising platforms for generating nonclassical photonic quantum state, because of its low loss, small footprint, and compatibility with complementary metal-oxide-semiconductor (CMOS) and telecommunications techniques. Dense wavelength division multiplexing (DWDM) is a leading technique for enhancing the transmission capacity of both classical and quantum communications. To bridge the frequency gap between silicon-chip and other quantum systems, such as quantum memories, a quantum interface is indispensable. Here, we demonstrate a quantum interface for multiplexed energy-time entanglement states, which are generated on a silicon micro-ring cavity that is based on frequency up-conversion. By switching the pump wavelength, energy-time entanglement from any channel can be selected at will after being up-converted. The high visibilities of two-photon interference over three channels after frequency up-conversion clearly prove that the entanglement is fully preserved during the quantum frequency conversion (QFC) process. Our work provides new perspectives regarding channel capacity enhancement in quantum communications and for quantum resources being transferred between two different quantum systems.