Early diagnosis of brain tumors is often hindered by non-specific symptoms, particularly in eloquent brain regions where open surgery for tissue sampling is unfeasible. This limitation increases the risk of misdiagnosis due to tumor heterogeneity in stereotactic biopsies. Label-free diagnostic methods, including intraoperative probes and cellular origin analysis techniques, hold promise for improving diagnostic accuracy. Polarimetry offers valuable information on the polarization properties of biomedical samples, yet it may not fully reveal specific structural characteristics. The interpretative scope of polarimetric data is sometimes constrained by the limitations of existing decomposition methods. On the other hand, dynamic laser speckle analysis (DLSA), a burgeoning technique, not only does not account for the polarimetric attributes but also is known for tracking only the temporal activity of the dynamic samples. This study bridges these gaps by synergizing conventional polarimetric imaging with DLSA for an in-depth examination of sample polarization properties. The effectiveness of our system is shown by analyzing the collection of polarimetric images of various tissue samples, utilizing a variety of adapted numerical and graphical statistical post-processing methods.

The transport of intensity equation (TIE) is a well-established phase retrieval technique that enables incoherent diffraction limit-resolution imaging and is compatible with widely available brightfield microscopy hardware. However, existing TIE methods encounter difficulties in decoupling the independent contributions of phase and aberrations to the measurements in the case of unknown pupil function. Additionally, spatially nonuniform and temporally varied aberrations dramatically degrade the imaging performance for long-term research. Hence, it remains a critical challenge to realize the high-throughput quantitative phase imaging (QPI) with aberration correction under partially coherent illumination. To address these issues, we propose a novel method for high-throughput microscopy with annular illumination, termed as transport-of-intensity QPI with aberration correction (TI-AC). By combining aberration correction and pixel super-resolution technique, TI-AC is made compatible with large pixel-size sensors to enable a broader field of view. Furthermore, it surpasses the theoretical Nyquist-Shannon sampling resolution limit, resulting in an improvement of more than two times. Experimental results demonstrate that the half-width imaging resolution can be improved to ~345 nm across a 10× field of view of 1.77 mm² (0.4 NA). Given its high-throughput capability for QPI, TI-AC is expected to be adopted in biomedical fields, such as drug discovery and cancer diagnostics.

Nano-kirigami technology enables the flexible transformation of two-dimensional (2D) micro/nanoscale structures into three-dimensional (3D) structures with either open-loop or close-loop topological morphologies, and has aroused significant interest in the fields of nanophotonics and optoelectronics. Here, we propose an innovative kissing-loop nano-kirigami strategy, wherein 2D open-loop structures can transform into 3D kissing-loop structures while retaining advantages such as large deformation heights and multiple optical modulations. Benefited from the unidirectional deformation of the structures, the kissing-loop nano-kirigami exhibits significant asymmetric transmission under x-polarized light incidence. Importantly, the Pancharatnam-Berry geometric phase is experimentally realized in nano-kirigami structures for the first time, resulting in broadband anomalous reflection in the near-infrared wavelength region. The kissing-loop nano-kirigami strategy can expand the existing platform of micro/nanoscale fabrication and provide an effective method for developing optical sensing, spatial light modulations, and optoelectronic devices.

We established a complete model and relationship between laser source characteristics and measurement accuracy of high precision fiber microprobe sensor (FMS) based on phase generated carrier demodulation. The laser carried out high-bandwidth frequency modulation to improve the measurement speed. Meanwhile, the laser also carried out large-amplitude frequency modulation to eliminate tens of nanometers of nonlinear error, thus improving the measurement accuracy. Further, the laser center wavelength is required to be stabilized under the above modulation to achieve a high measurement stability. The conflict between laser frequency modulation and central stability is revealed and analyzed alongside the distortion of measurement accuracy. A modified frequency stabilization method for laser source under high-bandwidth and large-amplitude modulation is proposed for improving measurement accuracy to realize sub-nanometer precision. The experimental results showed that when the modulation bandwidth was 1 MHz and maximum modulation amplitude was 2.61 GHz, the distributed feedback laser central wavelength stability was 2.9 × 10⁻¹⁰ (τ = 1s) according to Allan variance. Additionally, the relative expanded uncertainty of the laser wavelength was demonstrated to be superior to 5 × 10⁻⁸ (k = 2) within 3 hr, which was at least one order of magnitude higher than that of the traditional method. The resolution and stability of FMS is better than 0.4 nm, and the nonlinear error is reduced from tens of nm to 0.8 nm, which meets the requirements of sub-nanometer measurements.

To fulfill the requirements of high-precision common baseline measurement for multiple parameters, such as surface profiling and the curvature radius of large-aperture optical elements on the same instrument, this paper proposes a research on a high-precision large-aperture laser differential confocal-interferometric measurement method. This method is based on the principle of laser differential confocal combined with interferometry. It utilizes a Galilean double-reflection collimation system to generate well large-aperture collimated beams and employs mechanical phase-shifting technology for large-aperture and heavy-load reference lenses to overcome the flaws of existing large-aperture wavelength-tuning phase shifting technology in theory, thus achieving high-precision and high-stable phase-shifting interference in large-aperture surface profiling measurements. By utilizing the laser differential confocal method with anti-scattering and anti-interference properties, high-precision common baseline measurements are achieved for the multiple-parameter of optical elements such as ultra-long focal lengths and ultra-large curvature radii. The measurements of large-aperture surface profiles, the mean PV was 46.0 nm. For the ultra-long focal length, the relative standard deviation was 0.019%, whereas for the ultra-large curvature radius, the relative standard deviation was 0.0036%. This method enables high-precision, high-stable, and high-efficient common baseline measurements for the multiple parameters of optical elements with large, medium, and small apertures thereby providing an effective technical approach for improving the detection and machining precision of optical elements.

Laser polishing (LP) is considered an effective method for generating ultrasmooth surfaces owing to its precision, flexibility, and material compatibility. However, a lack of understanding of the evolution of surface topography during LP significantly limits the achievable surface roughness in practice. In this work, for the first time, by employing optical time-stretch quantitative interferometry (OTS-QI), we recorded the entire evolution of surface topography during LP with nanosecond-level temporal resolution, providing insight into the mechanisms involved in the surface roughness evolution, such as the Marangoni effect and the formation mechanism of mid-frequency waviness (MFW). Assisted by numerical calculations, we reveal that a ‘perfect polishing point’ exists, i.e., the optimal interaction time for LP at a specific laser power density, at which the surface roughness can be minimised without the formation of an MFW owing to the Marangoni effect and non-uniform removal. This OTS-QI system harnesses the rapid repetition rate of femtosecond lasers, achieving a remarkable measurement speed exceeding 100,000,000 times per second while preserving a measurement accuracy comparable to that of existing white light interferometers (WLIs), setting a new benchmark as the fastest recorded roughness measurement. In addition to LP, the proposed method can be applied for real-time and in situ monitoring of many machining scenarios involving highly dynamic phenomena.

Silicon photonics is currently the leading technology for the development of compact and low-cost photonic integrated circuits. However, despite its enormous potential, certain limitations, such as the absence of a linear electro-optical (EO) effect because of the symmetric crystal structure of silicon remain. In contrast, barium titanate (BTO) exhibits a strong Pockels effect. In this study, we demonstrated a high-quality transferred barium titanate ferroelectric hybrid integrated modulator on a silicon-on-insulator platform. The proposed hybrid integration of BTO on silicon Mach-Zehnder interferometers exhibited EO modulation with a V_πL as low as 1.67 V·cm, thereby facilitating the realisation of compact EO modulators. The hybrid integration of BTO with SOI waveguides is expected to pave the way for the development of high-speed and high efficiency EO modulators.

Side-pumping fibre combiners offer several advantages in fibre laser design, including distributed pump absorption, reduced heat load, and improved flexibility and reliability. These benefits are particularly important for all-fibre lasers and amplifiers operating in the mid-IR wavelength range and based on soft-glass optical fibres. However, conventional fabrication methods face limitations due to significant differences in the thermal properties of pump-delivering silica fibres and signal-guiding fluoride-based fibres. To address these challenges, this work introduces a design for a fuse-less side-polished (D-shaped) fibre-based pump combiner comprising multimode silica and double-clad fluoride-based fibres. The results demonstrate stable coupling efficiency exceeding 80% at a 980-nm wavelength over 8 hours of continuous operation under active thermal control. The developed pump combiner has also been successfully integrated into a linear Er-doped fibre laser cavity, showing continuous-wave generation at 2731 or 2781-nm central wavelength with an output power of 0.87 W. Overall, this innovative approach presents a simple, repeatable, and reproducible pump combiner design that opens up new possibilities for leveraging fibre-based component technology in soft glass matrices and other emerging fibres with unique compositions.

Compact micro-spectrometers have gained significant attention due to their ease of integration and real-time spectrum measurement capabilities. However, size reduction often compromises performance, particularly in resolution and measurable wavelength range. This work proposes a computational micro-spectrometer based on an ultra-thin (~250 nm) detour-phased graphene oxide planar lens with a sub-millimeter footprint, utilizing a spectral-to-spatial mapping method. The varying intensity pattern along the focal axis of the lens acts as a measurement signal, simplifying the system and enabling real-time spectrum acquisition. Combined with computational retrieval method, an input spectrum is reconstructed with a wavelength interval down to 5 nm, representing a 5-time improvement compared with the result when not using computational method. In an optical compartment of 200 μm by 200 μm by 450 μm from lens profile to the detector surface, the ultracompact spectrometer achieves broad spectrum measurement covering the visible range (420−750 nm) with a wavelength interval of 15 nm. Our compact computational micro-spectrometer paves the way for integration into portable, handheld, and wearable devices, holding promise for diverse real-time applications like in-situ health monitoring (e.g., tracking blood glucose levels), food quality assessment, and portable counterfeit detection.

In the past several decades, photonic integrated circuits (PICs) have been investigated using a variety of different waveguide materials and each excels in specific key metrics, such as efficient light emission, low propagation loss, high electro-optic efficiency, and potential for volume production. Despite sustained research, each platform shows inherit shortcomings that as a result stimulate studies in hybrid and heterogeneous integration technologies to create more powerful cross-platform devices. This is to combine the best properties of each platform; however, it requires dedicated development of special designs and additional fabrication processes for each different combination of material systems. In this work, we present a novel hybrid integration scheme that leverages a 3D-nanoprinted interposer to realize a photonic chiplet interconnection system. This method represents a generic solution that can readily couple between chips of any material system, with each fabricated on its own technology platform, and more importantly, with no change in the established process flow for the individual chips. A fast-printing process with sub-micron accuracy is developed to form the chip-coupling frame and fiber-guiding funnel, achieving a mode-field-dimension (MFD) conversion ratio of up to 5:2 (from a SMF28 fiber to 4 µm × 4 µm mode in polymer waveguide), which, to the best of our knowledge, represents the largest mode size conversion using non-waveguided 3D nanoprinted components. Furthermore, we demonstrate such a photonic chiplet interconnection system between silicon and InP chips with a 2.5 dB die-to-die coupling loss, across a 140 nm wavelength range between 1480 nm to 1620 nm. This hybrid integration plan can bridge different waveguide materials, supporting a much more comprehensive cross-platform integration.