Since the working conditions of classical and quantum signals are very different, how to effectively integrate classical and quantum communication networks without affecting their respective performance has become a great challenge. In this paper, we proposed a scheme to realize classical communication and continuous-variable quantum key distribution (CV-QKD) based on frequency-division multiplexing (FDM), and we verified the feasibility of simultaneously realizing CV-QKD and classical optical communication data synchronous transmission scheme under the same infrastructure. We achieved a 0 bit error rate in 50 frames and a 20 Mb/s bit rate for the classical signal and an average secret key rate of around 5.86 × 105 bit/s for the quantum signal through a 4 dB fiber channel. This work provides a scheme to establish a QKD channel by only reserving a small passband in the entire optical communication instead of an entire wavelength, increasing efficiency and simplifying the integration of QKD and classical communication.

High-resolution label-free dual-mode full-field optical coherence tomography (FFOCT) is developed for simultaneous structural and functional imaging of mouse retinas, achieving both static contrasts gained from structural refractive index gradients and dynamic contrasts induced by endogenous cell motility. Imaging experiments on normal mouse retinas show that static FFOCT images better reveal the relative stationary structures like nerve fibers, vascular walls, and collagens, and dynamic FFOCT images show enhanced contrasts of cells with active intracellular metabolic motions, offering complementary information about major retinal layers. Specifically, dual-mode FFOCT imaging on early ischaemia/reperfusion (I/R) injured mouse retinas highlights the transparent ganglion cells at the cellular level without contrast agent labeling, visualizing their structural and dynamic alterations in early I/R injured retina.

We propose and experimentally demonstrate the monolithic dual-waveguide (DW) distributed feedback (DFB) laser with tunable wavelength spacing. The differences in the chirp sampled grating with various index modulation amplitudes are theoretically elaborated. The wavelength spacing properties of the DW laser at different Bragg spacings are compared and analyzed. To validate the numerical investigation, the DW laser consisting of three sections is fabricated and implemented, where the chirp sampled grating with two equivalent π phase shifts is located. The simulated relationship between the Bragg wavelength spacing and the mode spacing is consistent with the experimental results. Owing to the prominent contribution of the three-section structure and chirp sampled grating, the tuning range of the wavelength spacing is extended significantly, and the cavity of the DW laser becomes compact. The experimental results indicate that the proposed scheme achieves a tuning range from 59.50 to 116.25 GHz. The proposed scheme paves an extraordinary avenue for the integration of laser devices in the applications of optical sensing and THz communication.

In this work, we report on the recent research progress on watt-level all-solid-state single-frequency Pr:LiYF4 (YLF) lasers in the orange spectral region. Combining dual-end pumping and ring-cavity technologies, we have achieved a maximum single-frequency output of 1.19 W at 607 nm with a linewidth of about 20.3 MHz. Based on this study, by inserting a 0.15 mm etalon inside the ring cavity, we find that the 607 nm lasing can be completely suppressed and a single-frequency laser at 604 nm with a 0.69 W output power and a linewidth of about 16.7 MHz can also be obtained. Moreover, the wavelengths of the two single-frequency lasers can be tuned from 607.16 to 607.61 nm and from 603.99 to 605.02 nm, respectively. Furthermore, the single-frequency Pr:YLF laser can also operate in a state of the two orange wavelengths, simultaneously, with a maximum output power of 0.97 W. We believe that this is the highest output power of a direct generation of single-frequency orange lasers and the first demonstration of the wavelength-tuned operation of the achieved single-frequency orange lasers, which could bring opportunities for the application of single-frequency orange lasers.

Imaging through scattering media remains a formidable challenge in optical imaging. Exploiting the memory effect presents new opportunities for non-invasive imaging through the scattering medium by leveraging speckle correlations. Traditional speckle correlation imaging often utilizes a random phase as the initial phase, leading to challenges such as convergence to incorrect local minima and the inability to resolve ambiguities in object orientation. Here, a novel method for high-quality reconstruction of single-shot scattering imaging is proposed. By employing the initial phase obtained from bispectral analysis in the subsequent phase retrieval algorithm, the convergence and accuracy of the reconstruction process are notably improved. Furthermore, a robust search technique based on an image clarity evaluation function successfully determines the optimal reconstruction size. The study demonstrates that the proposed method can obtain high-quality reconstructed images compared with the existing scattering imaging approaches. This innovative approach to non-invasive single-shot imaging through strongly scattering media shows potential for applications in scenarios involving moving objects or dynamic scattering imaging scenes.

Loss is usually considered a problem for photonics, which can seriously deteriorate the performance of most optical devices, and thus has to be suppressed. However, in non-Hermitian passive optical systems without gain, when both eigenvalues and eigenvectors coalesce to form exceptional points (EPs), the addition of loss may, counterintuitively, bring unique advantages, such as improved noise resistance and more stable operation. In this review, we first briefly introduce the underlying mechanisms leading to passive EPs and then examine several implementations based on different electromagnetic structures, including cavities, waveguides, and metasurfaces. We highlight the introduction of losses in each case and discuss their benefits. Finally, we also provide our thoughts on the current limits for those passive realizations as well as potential future projects.

Among super-resolution microscopy techniques, structured illumination microscopy (SIM) shows great advances in low phototoxicity, high speed, and excellent performance in long-term dynamic observation, making it especially suitable for live-cell imaging. This review delves into the principles, instrumentation, and applications of SIM, highlighting its capabilities in achieving high spatiotemporal resolution. Two types of structured illumination mechanics are employed: (1) stripe-based SIM, where the illumination stripes are formed through interference or projection, with extended resolution achieved through Fourier-domain extension; (2) point-scanning-based SIM, where illumination patterns are generated through the projection of the focal point or focal array, with extended resolution achieved through photon reassignment. We discuss the evolution of SIM from mechanical to high-speed photoelectric devices, such as spatial light modulators, digital micromirror devices, galvanometers, etc., which significantly enhance imaging speed, resolution, and modulation flexibility. The review also explores SIM’s applications in biological research, particularly in live-cell imaging and cellular interaction studies, providing insights into disease mechanisms and cellular functions. We conclude by outlining the future directions of SIM in life sciences. With the advancement of imaging techniques and reconstruction algorithms, SIM is poised to bring revolutionary impacts to frontier research fields, offering new avenues for exploring the intricacies of cellular biology.

Ultrafast lasers can produce, beyond single-pulse mode locking, a multitude of robust multi-pulse dynamics, including optical soliton molecules. Based on recent experimental advances using smart fiber lasers, this commentary addresses the open question of using soliton molecules as symbols for digital optical information.

The optical Vernier effect has garnered significant research attention and found widespread applications in enhancing the measurement sensitivity of optical fiber interferometric sensors. Typically, Vernier sensor interrogation involves measuring its optical spectrum across a wide wavelength range using a high-precision spectrometer. This process is further complicated by the intricate signal processing required for accurately extracting the Vernier envelope, which can inadvertently introduce errors that compromise sensing performance. In this work, we introduce a novel approach to interrogating Vernier sensors based on a coherent microwave interference-assisted measurement technique. Instead of measuring the optical spectrum, we acquire the frequency response of the Vernier optical fiber sensor using a vector network analyzer. This response includes a characteristic notch that is highly sensitive to external perturbations. We discuss in detail the underlying physics of coherent microwave interference-based notch generation and the sensing principle. As a proof of concept, we construct a Vernier sensor using two air-gap Fabry–Perot interferometers arranged in parallel, demonstrating high-sensitivity strain sensing through microwave-domain measurements. The introduced technique is straightforward to implement, and the characteristic sensing signal is easy to demodulate and highly sensitive, presenting an excellent solution to the complexities of existing optical Vernier sensor systems.

Laser-driven inertial confinement fusion (ICF) diagnostics play a crucial role in understanding the complex physical processes governing ICF and enabling ignition. During the ICF process, the interaction between the high-power laser and ablation material leads to the formation of a plasma critical surface, which reflects a significant portion of the driving laser, reducing the efficiency of laser energy conversion into implosive kinetic energy. Effective diagnostic methods for the critical surface remain elusive. In this work, we propose a novel optical diagnostic approach to investigate the plasma critical surface. This method has been experimentally validated, providing new insights into the critical surface morphology and dynamics. This advancement represents a significant step forward in ICF diagnostic capabilities, with the potential to inform strategies for enhancing the uniformity of the driving laser and target surface, ultimately improving the efficiency of converting laser energy into implosion kinetic energy and enabling ignition.