A novel physical layer data encryption scheme using two-level constellation masking in three-dimensional (3D) carrier-less amplitude and phase modulation (CAP) passive optical network (PON) is proposed in this Letter. The chaotic sequence generated by Chua’s circuit model realizes two-level encryption of displacement masking and constellation rotation for 3D constellations. We successfully conduct an experiment demonstrating 8.7 Gb/s 3D-CAP-8 data transmission over 25 km standard single-mode fiber. With two-level constellation masking, a key space size of 2.1 × 10⁸⁵ is achieved to bring about high security and good encryption performance, suggesting broad application prospects in future short-range secure communications.

We propose a concept of wavelength synchronization to ensure the stability of ultra-dense channels in an ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) transmitter. A mode-locked laser is used to provide wavelength references for users. By injection locking the semiconductor laser, the separation of the wavelength reference is realized in an optical line terminal. The downlink and uplink wavelength references are interlaced and distributed to facilitate the synchronization of uplink carriers. In the optical network unit, the uplink optical carriers are filtered by injection locking semiconductor lasers, which achieve wavelength synchronization for the uplink users. In this Letter, an adaptive wavelength synchronization transmitter for UDWDM-PON is realized with a channel spacing of 5 GHz.

We present the generation of the nanosecond cylindrical vector beams (CVBs) in a two-mode fiber (TMF) and its applications of stimulated Raman scattering. The nanosecond (1064 nm, 10 ns, 10 Hz) CVBs have been directly produced with mode conversion efficiency of ～18 dB (98.4%) via an acoustically induced fiber grating, and then the stimulated Raman scattering signal is generated based on the transmission of the nanosecond CVBs in a 100-m-long TMF. The transverse mode intensity and polarization distributions of the first-order Stokes shift component (1116.8 nm) are consistent with the nanosecond CVBs pump pulse.

A novel scheme of photonic aided vector millimeter-wave (mm-wave) signal generation without a digital-to-analog converter (DAC) is proposed. Based on our scheme, a 20 Gb/s 4-ary quadrature amplitude modulation (4-QAM) mm-wave signal is generated without using a DAC. The experiment results demonstrate that the bit error rate (BER) of 20 Gb/s 4-QAM mm-wave signal can reach below the hard-decision forward-error-correction threshold after a delivery over 1 m wireless distance. Because the DAC is not required, it can reduce the system cost. Besides, by using photonic technology, the system is easily integrated to create large-scale production and application in high-speed optical communication.

In order to improve the accuracy and universality of the rotational speed measurement, an instantaneous rotational speed measurement method based on laser Doppler technology is proposed. The composition and working principle of the new system are discussed in detail. Theoretical and experimental results show that the new rotational speed measurement system belongs to the non-contact method, which eliminates the quantization error of the contact method and greatly improves the applicability and accuracy. Compared to the commonly used method, the measurement accuracy of the new rotational speed measurement system will not be affected by the system’s installation angle deviation, and it does not need to measure the radius of the rotating body, so the influence of the radius fluctuation of the rotating body on the measurement accuracy can be avoided while outputting the rotational speed in real time. The relative error of the rotational speed measurement is less than 0.06% (1σ).

The research on nanophotonic devices has made great progress during the past decades. It is the unremitting pursuit of researchers that realize various device functions to meet practical applications. However, most of the traditional methods rely on human experience and physical inspiration for structural design and parameter optimization, which usually require a lot of resources, and the performance of the designed device is limited. Intelligent algorithms, which are composed of rich optimized algorithms, show a vigorous development trend in the field of nanophotonic devices in recent years. The design of nanophotonic devices by intelligent algorithms can break the restrictions of traditional methods and predict novel configurations, which is universal and efficient for different materials, different structures, different modes, different wavelengths, etc. In this review, intelligent algorithms for designing nanophotonic devices are introduced from their concepts to their applications, including deep learning methods, the gradient-based inverse design method, swarm intelligence algorithms, individual inspired algorithms, and some other algorithms. The design principle based on intelligent algorithms and the design of typical new nanophotonic devices are reviewed. Intelligent algorithms can play an important role in designing complex functions and improving the performances of nanophotonic devices, which provide new avenues for the realization of photonic chips.

A novel tiled Ti:sapphire (Ti:S) amplifier was experimentally demonstrated with >1 J amplified chirped pulse output. Two Ti:S crystals having dimensions of 14 mm× 14 mm× 25 mm were tiled as the gain medium in a four-pass amplifier. Maximum output energy of 1.18 J was obtained with 2.75 J pump energy. The energy conversion efficiency of the tiled Ti:S amplifier was comparable with a single Ti:S amplifier. The laser pulse having the maximum peak power of 28 TW was obtained after the compressor. Moreover, the influence of the beam gap on the far field was discussed. This novel tiled Ti:S amplifier technique can provide a potential way for 100 PW or EW lasers in the future.

In this study, the effects of purification, dehydration, and coagulation processes on the absorption and reduced scattering coefficients of chicken liver tissues have been investigated by using a single integrating sphere system. The purification process performed on the tissue samples to remove blood residue has been found to cause a slight change in the optical parameters. Although the dehydration process brings about an increase in the absorption coefficient due to the water loss, no direct relationship has been observed between the reduced scattering coefficient and the dehydration level of the tissue. In addition, it has been observed that there was a relatively small increase in the absorption coefficient and a significant increase in the reduced scattering coefficient after the coagulation process. Therefore, it can be said that the optical penetration depth decreased significantly after dehydration and coagulation processes unlike blood purification. Moreover, fluence rate distributions inside the fresh, blood purified, dehydrated, and coagulated tissue models have been investigated by using the Monte Carlo modeling of photon transport in multilayered tissues simulation code.

One-step precipitation of Ag nanoparticles in Ag⁺-doped silicate glasses was achieved through a focused picosecond laser with a high repetition rate. Absorption spectra and transmission electron microscopy (TEM) confirmed that metallic Ag nanoparticles were precipitated within glass samples in the laser-written domain. The surface plasmon absorbance fits well with the experimental absorption spectrum. The nonlinear absorption coefficient β is determined to be 2.47 × 10^-14 m/W by fitting the open aperture Z-scan curve, which originated from the intraband transition in the s-p Ag band. The formation mechanism of Ag-glass nanocomposites is discussed as well.

Recently, the nested Mach–Zehnder interferometer [Phys. Rev. Lett. 111, 240402 (2013)] was modified by adding Dove prisms in a paper [Quantum Stud.: Math. Found. 2, 255 (2015)], and an interesting result is that, after the Dove prisms were inserted, a signal at the first mirror of the nested interferometer was obtained. But, according to the former original paper, the photons have never been present near that mirror. In this work, we interpret this result naturally by resorting to the three-path interference method. Moreover, we find that even though the photons have been somewhere, they can hide the trace of being there.

In this Letter, we present a display system based on a curved screen and parallax barrier, which provides stereo images with a horizontal field of view of 360° without wearing any eyewear, to achieve an immersive autostereoscopic effect. The display principle and characteristics of this display system are studied theoretically in detail. Three consecutive pixels on a curved screen and parallax barrier form a display unit, which can generate separate viewing zones for the left and right eyes, respectively. Simulation and experimental results show that the non-crosstalk effect can be obtained in the viewing zones, which proves the effectiveness of this display system. This study provides some new ideas for the improvement of the autostereoscopic display and to enable envisioned applications in virtual reality technology.

In this Letter, we report an Airy-like beam of magnetostatic surface spin wave (AiBMSSW) supported on the ferromagnetic film, which is transferred from the optical field. The propagation properties of AiBMSSW were verified with micromagnetic simulation. From simulation results, the typical parabolic trajectory of the Airy-type beam was observed with an exciting source encoding 3/2 phase pattern. The simulation results coincide well with design parameters. Furthermore, simulated results showed that the trajectories of the AiBMSSW could be tuned readily with varied external magnetic fields. This work can extend the application scenario of spin waves.

Nanogap plasmonic structures with strong coupling between separated components have different responses to orthogonal-polarized light, giving rise to giant optical chirality. Here, we proposed a three-dimensional (3D) nanostructure that consists of two vertically and twistedly aligned nanogaps, showing the hybridized charge distribution within 3D structures. It is discovered that the structure twisted by 60° exhibits plasmonic coupling behavior with/without gap modes for different circular-polarized plane waves, showing giant chiral response of 60% at the wavelength of 1550 nm. By controlling the disk radius and the insulator layer, the circular dichroism signal can be further tuned between 1538 and 1626 nm.

Recently reported plasmon-induced transparency (PIT) in metamaterials endows the optical structures in classical systems with quantum optical effects. In particular, the nonreconfigurable nature in metamaterials makes multifunctional applications of PIT effects in terahertz communications and optical networks remain a great challenge. Here, we present an ultrafast process-selectable modulation of the PIT effect. By incorporating silicon islands into diatomic metamaterials, the PIT effect is modulated reversely, depending on the vertical and horizontal configurations, with giant modulation depths as high as 129% and 109%. Accompanied by the enormous switching of the transparent window, remarkable slow light effect occurs.

We propose a photonics-assisted equivalent frequency sampling (EFS) method to analyze the instantaneous frequency of broadband linearly frequency modulated (LFM) microwave signals. The proposed EFS method is implemented by a photonic scanning receiver, which is operated with a frequency scanning rate slightly different from the repetition rate of the LFM signals. Compared with the broadband LFM signal analysis based on temporal sampling, the proposed method avoids the use of high-speed analog to digital converters, and the instantaneous frequency acquisition realized by frequency-to-time mapping is also simplified since real-time Fourier transformation is not required. Feasibility of the proposed method is verified through an experiment, in which frequency analysis of Kα-band LFM signals with a bandwidth up to 3 GHz is demonstrated with a moderate sampling rate of 100 MSa/s. The proposed method is highly demanded for analyzing the instantaneous frequency of broadband LFM signals used in radar and electronic warfare systems.