Study on optical correlation function initiates the development of many quantum techniques, with ghost imaging (GI) being one of the great achievements. Upon the first demonstration with entangled sources, the physics and improvements of GI attracted much interest. Among existing studies, GI with classical sources provoked debates and ideas to the most extent. Toward better understanding and practical applications of GI, fundamental theory, various designs of illumination patterns as well as reconstruction algorithms, demonstrations and field tests have been reported, with the topic of GI very much enriched. In this paper, we try to sketch the evolution of GI, focusing mainly on the basic idea, the properties and superiority, progress toward applications of GI with classical sources, and provide our discussion looking into the future.

Ghost imaging (GI) is a novel imaging technique that has garnered widespread attention and discussion since its inception three decades ago. To this day, ghost imaging has become an effective bridge between the advantages of quantum light sources and the field of imaging. This article begins by tracing the origin of ghost imaging and reviewing its development journey. Subsequently, we introduce some recent and important achievements and research interests of the field, which mainly include two aspects. First, we review recent works that extend GI from the intensity-only target to the complex field domain, that is, ghost holography. Using quantum correlation, traditional holographic techniques have been reproduced at the single-photon level. Second, we review the recent development of GI with the implementation of the intensified charge-coupled device (ICCD). As detection efficiency improves, ghost imaging will gradually become an important platform for studying physical mechanisms and achieving quantum advantage in imaging.

An ultrasonic phase extraction method is proposed for co-cable identification without modifying transceivers in coherent optical transmission systems. To extract the ultrasonic phase, we apply an improved residual frequency offset compensation algorithm, an optimized unwrapping algorithm for mitigating phase noise induced by phase ambiguity between digital signal processing (DSP) blocks, and an averaging operation for improving the phase sensitivity. In a 64-GBaud dual-polarization quadrature phase shift keying (DP-QPSK) simulation system, the phase sensitivity of the proposed method reaches 0.03 rad using lasers with 100-kHz linewidth and a 60-kHz ultrasonic source, with only 400 k-points (kpts) stored data. Also verified by an experiment under the same transmission conditions, the sensitivity reaches 0.39 rad, with 3 kpts of data stored and no averaging due to the equipment limitation. The results have shown this method provides a better choice for low-cost and real-time co-cable identification in integrated sensing and communication optical networks.

Micromagnets, as a promising technology for microscale manipulation and detection, have been the subject of extensive study. However, providing real-time, noninvasive feedback on the position and temperature of micromagnets in complex operational environments continues to pose a significant challenge. This paper presents a quantum imaging device utilizing diamond nitrogen-vacancy (NV) centers capable of providing simultaneous feedback on both the position and temperature of a micromagnet. The device achieves a temporal resolution of 2 s and a spatial resolution of 1.3 µm. Through flux localization analysis, we have determined a positioning accuracy within 50 µm and a temperature accuracy within 0.4 K.

In this paper, we present a remote time-base-free technique for a coherent optical frequency transfer system via fiber. At the remote site, the thermal noise of the optical components is corrected along with the link phase noise caused by environmental effects. In this system, a 1 × 2 acousto-optic modulator (AOM) is applied at the remote site, with the first light being used to eliminate the noise of the remote time base and interface with remote users while the zeroth light is used to establish an active noise canceling loop. With this technique, a 10 MHz commercial oscillator, used as a time base at the remote site, does not contribute to the noise of the transferred signal. An experimental system is constructed using a 150 km fiber spool to validate the proposed technique. After compensation, the overlapping Allan deviation of the transfer link is 7.42 × 10-15 at 1 s integration time and scales down to 1.07 × 10-18 at 10,000 s integration time. The uncertainty of the transmitted optical frequency is on the order of a few 10-19. This significantly reduces the time-base requirements and costs for multi-user applications without compromising transfer accuracy. Meanwhile, these results show great potential for transferring ultra-stable optical frequency signals to remote sites, especially for point-to-multi-users.

In this paper, we present a method to expedite multi-wavelength photoelasticity for efficient stress analysis. By modulating two slightly different-wavelength illumination beams and simultaneously capturing dark-field and bright-field images, our approach acquires four essential polarized images. Spatial filtering of Fourier transforms streamlines inner stress computation, enabling multi-wavelength photoelasticity with a single detector exposure. Theoretical foundations are outlined, and proof-of-principle experiments validate the feasibility with a measurement error below 6.4%. The high measurement speed, determined by the detector’s frame rate, facilitates dynamic sample measurements at video frequency, offering promising advancements in material stress analysis.

This study proposes a method for real-time monitoring of lithium-ion battery (LiB) internal temperatures through the temperature response of an embedded fiber Bragg grating (FBG) sensor. This approach overcomes the limitations of most methods that can only detect the external temperature at limited places by providing the advantages of sensing both the internal temperature and external temperature at multiple points simultaneously for precise condition monitoring. In addition, a numerical LiB cell model was developed to investigate the heat generation and temperature gradient using the finite element analysis method. The outcomes show that this model can be used to predict the temperature with less than 5% discrepancy (1.5°C) compared with experimental results. Thereby, this proposed method can be effectively used to monitor the safety and state of health of LiBs and other types of rechargeable batteries in real-time.

Optical bistability can be used to explore key components of all-optical information processing systems, such as optical switches and optical random memories. The hybrid integration of emerged two-dimensional layered PtSe2 with waveguides is promising for the applications. We demonstrated the optical bistability in the PtSe2-on-silicon nitride microring resonator induced by a thermo-optic effect. The fabricated device has a resonance-increasing rate of 6.8 pm/mW with increasing optical power. We also established a theoretical model to explain the observation and analyze the device’s performance. The study is expected to provide a new scheme for realizing all-optical logic devices in next-generation information processing systems.

Ultra-short pulse, ultra-intense (USUI) lasers have become indispensable tools for scientific research. High-energy pump lasers are crucial for ensuring adequate energy and beam quality of these USUI lasers. Pump lasers with rod amplifiers are a cost-effective and reliable option for meeting high-energy pump requirements. However, there is a notable dearth of comprehensive reports on the design of high-energy rod amplifiers. This study provides a detailed analysis of rod amplifiers, focusing primarily on the pump unit utilized at SULF-10 PW and SEL-100 PW prototypes. The analysis covers aspects such as gain management, thermal effects, and spatiotemporal evolution.

Mode-locked lasing operations at 1064 and 910 nm wavelengths are demonstrated, respectively, in two all-fiber laser oscillators using our homemade Nd3+-doped silica fiber (NDF) as the gain medium. The Al3+/Nd3+ co-doped silica core glass was fabricated by the modified sol–gel method with 18,300 × 10-6 Nd3+ doping concentration. The NDF drawn by the rod-in-tube method has a core of 4 µm in diameter and a numerical aperture (NA) of 0.14. At 1064 nm, we measure an average laser output power of 18 mW with a pulse duration of 5.75 ps, a pulse energy of 1.14 nJ, and a slope efficiency of 7.2%. Using the same NDF gain fiber of a different length, a maximum average laser output power is 3.1 mW at 910 nm with a pulse duration of 877 ns, a pulse energy of 2.7 nJ, and a slope efficiency of 1.44%.

The miniaturization of spectrometers has received much attention in recent years. The rapid development of metasurfaces has provided a new avenue for creating more compact and lightweight spectrometers. However, most metasurface-based spectrometers operate in the visible light region, with much less research on near-infrared wavelengths. This is possibly caused by the lack of effective metasurface filters for the near-infrared light. We design and fabricate a polarization-insensitive amorphous silicon metasurface that exhibits unique transmission spectra in parts of the visible and near-infrared wavelengths. By passing the light to be measured through a metasurface filter array and measuring the transmitted power, we achieve the precise reconstruction of unknown spectra in the visible and near-infrared range (450–950 nm) using an algorithm matched to the filter model. Our approach is a step towards miniaturized spectrometers within the visible-to-near-infrared range based on metasurface filter arrays.

The optical properties of hybrid core–shell nanostructures composed of a metallic core and an organic shell of molecular J-aggregates are determined by the electromagnetic coupling between plasmons localized at the surface of the metallic core and Frenkel excitons in the shell. In cases of strong and ultra-strong plasmon–exciton coupling, the use of the traditional isotropic classical oscillator model to describe the J-aggregate permittivity may lead to drastic discrepancies between theoretical predictions and the available experimental spectra of hybrid nanoparticles. We show that these discrepancies are not caused by limitations of the classical oscillator model itself, but by considering the organic shell as an optically isotropic material. By assuming a tangential orientation of the classical oscillators of the molecular J-aggregates in a shell, we obtain excellent agreement with the experimental extinction spectra of TDBC-coated gold nanorods, which cannot be treated with the conventional isotropic shell model. Our results extend the understanding of the physical effects in the optics of metal–organic nanoparticles and suggest an approach for the theoretical description of such hybrid systems.

Broadband, low-drive voltage electro-optic modulators are crucial optoelectronic components in the new-generation microwave photonic links and broadband optical interconnect network applications. In this paper, we fabricate a low-loss thin-film lithium niobate complementary dual-output electro-optic modulator chip with a 3 dB electro-optic bandwidth of 59 GHz and a half-wave voltage (Vπ) of 2.5 V. The insert-loss of the packaged modulator is 4.2 dB after coupling with polarization-maintaining fiber. The complementary dual-output modulator also shows a common-mode rejection ratio of 18 dB and a signal enhancement of 6.2 dB when adapted in microwave photonic links, comparable to commercial bulk lithium niobate devices.

Optical modulation is significant and ubiquitous to telecommunication technologies, smart windows, and military devices. However, due to the limited tunability of traditional doping, achieving broadband optical property change is a tough problem. Here, we demonstrate a remarkable transformation of optical transmittance in few-layer graphene (FLG) covering the electromagnetic spectra from the visible to the terahertz wave after lithium (Li) intercalation. It results in the transmittance being higher than 90% from the wavelengths of 480 to 1040 nm, and it increases most from 86.4% to 94.1% at 600 nm, reduces from ∼80% to ∼68% in the wavelength range from 2.5 to 11 µm, has ∼20% reduction over a wavelength range from 0.4 to 1.2 THz, and reduces from 97.2% to 68.2% at the wavelength of 1.2 THz. The optical modification of lithiated FLG is attributed to the increase of Fermi energy (Ef) due to the charge transfer from Li to graphene layers. Our results may provide a new strategy for the design of broadband optical modulation devices.

In this Letter, a kind of optoelectronic chip based on III-nitride is developed as a versatile platform for both fiber-optic sensing and optical communication. The optoelectronic chip consists of a light-emitting diode (LED) and a photodiode (PD), which are fabricated with the same multi-quantum well (MQW) structure and monolithically integrated on a sapphire substrate. By integrating the chip with a polydimethylsiloxane (PDMS) encapsulated silica fiber-optic sensor, it can effectively detect the bending-induced light intensity change and generate the photocurrent to point out the angle changes. Besides, such an optoelectronic chip can also be treated as a transceiver, enabling duplex communication for real-time audio and video transmission. The proposed optoelectronic chip has the advantages of miniaturization, versatility, and ease of massive manufacturing, making it promising in integrated optical sensing and communication (IOSAC) systems.

Facing escalating demands for high-speed, large-bandwidth, and low-latency wireless data links, laser communication technology has emerged as a promising technology. While free-space optical communication conventionally utilizes near-infrared light sources, there has been growing interest in exploring new spectral resources, including visible lasers. Recently, laser-based white light has been demonstrated in visible light communication (VLC), with a unique capability to seamlessly integrate with illumination and display systems. This review summarizes the key devices and system technologies in semiconductor-laser-based white light for VLC-related applications. The recent advances and many emerging applications in the evolution of lighting, display, and communication are discussed.