The dynamical control of single-photon scattering in a one-dimensional waveguide coupled to a Floquet atom-cavity system with time-modulated coupling constants is investigated. The analytical expressions for determining the scattering properties are obtained by using an effective Floquet Hamiltonian in real space. The photon transport is extremely sensitive to the time-modulated atom-cavity coupling strengths. Two cases, i.e., the effective Floquet Hamiltonian either includes or excludes a static coupling term, are discussed in detail. The results show that, with such Floquet atom-cavity configuration, an active photonic switch with nearly ideal switching contrast could be implemented. The transmission of the waveguide photons with different frequencies can dynamically be switched on or off via adjusting the modulated amplitude or relative modulated phase no matter whether the static coupling between the atom and the two cavity modes is considered or not. The application of the dynamic modulated atom-cavity coupling strengths instead of a purely static one makes our photonic switch more tunable. These results are expected to be applicable in quantum information processing and in active quantum device design involving dynamical modulation.

The linearity of the laser frequency modulation is a crucial factor that affects the performance of the frequency-modulated continuous wave (FMCW) LiDAR ranging. Nonlinearity can influence ranging resolution and introduce errors. This paper proposes a method for correcting frequency modulation nonlinearity based on waveform preprocessing for the modulation signal of the laser. After correction, the residual nonlinearity (1-r2) of the laser is reduced to $1.85\times 10^{-4}$ for the up-sweeping and $8.47\times 10^{-4}$ for the down-sweeping using the modulation signal with the repetition frequency of 50 kHz. The full-width at half of the maximum (FWHM) of the spectrum decreases by 86% compared to pre-correction, resulting in the ranging error of 0.37% at the distance of 38 cm. With distances of 0.90 m, 1.80 m, 2.89 m, and 4.13 m, respectively, the ranging error stabilizes at 0.2%, and the minimum deflection of distance can reach $8~\mathrm {\mu m}$ .

A multi-wavelength semiconductor optical amplifier (SOA) fiber laser with ultra-narrow wavelength spacing is experimentally demonstrated in this paper. The SOA is used as the primary gain medium due to its inhomogeneous broadening and nonlinear polarization rotation (NPR) effect that allows to achieve stable multi-wavelength output with ultra-narrow wavelength spacing. The combination of PC (polarization controller)-SOA-PC-polarizer and nonlinear optical loop mirror (NOLM) serve as the intensity equalizer for inducing IDL to suppress mode competition effect furtherly, while the NOLM mainly achieves power equalization and improve SMSR in this laser. The Lyot-Sagnac loop mirror is designed to realize different channel spacing, when the length of PMF is 71 m, stable multi-wavelength output has been achieved at room temperature. The number of lasing lines is up to 184 with wavelength spacing of 0.08nm within 10 dB bandwidth from 1549.75 nm to 1664.25 nm, and the multi-wavelength output has no obvious power fluctuation. The side mode suppression ratio (SMSR) is about up to 22dB. Moreover, the maximum value of optical signal-to-noise ratios (OSNR) is 10.7 dB.

Aiming at the difficulty of traditional chaotic-shift-keying (CSK) systems in resisting return map attacks, we propose an optical chaotic communication system based on time-delayed shift keying and common-signal-induced synchronization. This scheme combines amplified spontaneous emission (ASE) noise, phase modulator (PM), and fiber Bragg grating (FBG) to achieve dual masking in both intensity and phase fields, achieving 10Gb/s information transmission. A common-signal-induced method is used to achieve the synchronization of the system. Moreover, by shifting the time delay as the message-feeding method, the return map attack is effectively resisted, to prevent the amplitude and frequency information of the chaotic attractor from being exposed. In terms of confidentiality and communication performance, this scheme demonstrates good performance of time delay signatures (TDSs) concealment and long-distance transmission capability. In addition, this scheme maintains high sensitivity to key parameters and achieves better confidentiality while increasing the key space.

Nonreciprocal single-photon scattering in a one-dimensional waveguide coupled to a giant two-level atom assisted with a time-modulated single-mode cavity is investigated. The analytic expressions of the single-photon scattering amplitudes are derived by using an effective Floquet Hamiltonian in real space. The scattering characteristics are discussed detail in both the Markovian and the non-Markovian regimes, and the corresponding conditions for achieving perfect nonreciprocal single-photon transmission are obtained. In the Markovian regime, a frequency-tunable single-photon diode with an ideal transmission contrast ratio can be realized by adjusting the frequency of the cavity mode, the local coupling phase difference, and the accumulated phase between the two coupling points. Furthermore, the influence of the intrinsic energy dissipations on the photon transport is discussed in detail. It is found that the dissipations of the cavity and the giant atom affect discriminatively the nonreciprocal single-photon scattering process. In the non-Markovian regime, the influence of the non-Markovian retarded effect induced by the time delay on the nonreciprocal single-photon scattering is discussed in detail. The results reveal that, although the retarded effect leads to a complex nonreciprocal scattering spectrum, dynamic tunable perfect nonreciprocal transmission with more abundant physical phenomena suitable for photons with different frequencies within a larger range can also be achieved. Such a nonreciprocal single-photon device can be used as an elementary unit for various quantum information processing and may have potential applications in quantum network engineering.