Optics express最新文献

Scientific-grade spectrometers with high hyperspectral resolution and high spectral accuracy are desirable in miniaturized optical systems to maintain stable and real-time spectral sampling. Fourier transform spectrometers that utilize high-precision moving mirrors generally struggle to enhance their miniaturization and stable real-time performance. A static infrared spectral measurement method is proposed that uses micro/nano-optical devices as the core of static interference and lightweight imaging. The use of micro/nano step mirrors allows for the instantaneous sampling of spectra. By employing an array of micro/nano lenses, interference imaging for each spectral channel can be accomplished. The spectrometer's all-static micro/nano-optical structure results in a reduction in volume and weight of more than half. Enhanced precision in design and fabrication is achieved through optical error analysis via a full-linkage optical field transmission model. An image edge detection-assisted spectral inversion algorithm is proposed, and the sampling stability and reconstruction accuracy are verified. The repeatability accuracy of interference intensity sampling surpasses 2%, and the peak accuracy of the reconstructed spectrum exceeds the resolution.

This paper proposes a reflective metasurface composed of a single unit structure, yet capable of achieving precise control of two degrees of freedom. By grooving two orthogonal slots on the copper ring, it enables the independent conversion of the two orthogonal components of the incident waves. Consequently, incident linearly-polarized waves can be rotated by an arbitrary angle. For circularly-polarized waves, the handedness will be reversed; furthermore, the phase of the reflected wave can cover the full 2π range by rotating the unit cells in a manner similar to that of the Pancharatnam-Berry (PB) phase metasurface. Rigorous theoretical analyses are provided. Numerical validation demonstrates that the cross-polarization reflectance of the metasurface exceeds 0.7 within the frequency range of 0.7044 to 2.0859 THz, corresponding to nearly 100% relative bandwidth. The modulation accuracy of the polarization angle can reach within 1 degree. The proposed metasurface may find applications in communication, imaging, sensing, and other fields.

Coherent lensless imaging usually suffers from coherent noise and twin-image artifacts. In the terahertz (THz) range, where wavelengths are 2 to 4 orders of magnitude longer than those in the visible spectrum, the coherent noise manifests primarily as parasitic interference fringes and edge diffraction, rather than speckle noise. In this work, to suppress the Fabry-Pérot (F-P) interference fringes, we propose a novel method, which involves the averaging over multiple diffraction patterns that are acquired at equal intervals within a sample's half-wavelength axial shift. To address edge diffraction, as well as non-uniform illumination, a normalization operation is applied. As the twin-image disturbances when dealing with a single diffraction pattern, multi-plane configuration is employed. With all these strategies combined, we propose a flyscan THz multi-plane lensless imaging technique that enables subwavelength resolution, and high-quality, full-field, and rapid complex-valued THz imaging. Furthermore, we refine two algorithms for image reconstruction: one based on the regular multi-plane alternating projection and the other based on an optimization model with total variation regularization. We experimentally verify the proposed methods, achieving a lateral resolution of 88 µm (0.74λ) at 2.52 THz, and showcase its potential for biomedical applications by imaging a section of mouse brain tissue.

Using a single optical microfiber (OM) sensor for multi-parameter sensing can lead to significant demodulation error due to ill-conditioned matrices and nonlinear response characteristics. To address these issues, this paper proposes a novel specially packaged optical microfiber coupler combined with a silver mirror (OMCM). OMCM is combined with a mechanically enhanced sensitivity fiber Bragg grating (FBG) to form a temperature-pressure sensor. The temperature sensitivity exceeds -1.7 nm/°C while the pressure sensitivity reaches 53.435 nm/MPa, with a depth resolution of 0.935 cm. According to the characteristics of the sensor spectrum, this paper proposes a new demodulation method, which combines machine learning methods with a traditional wavelength-tracking method to achieve low demodulation error. For temperature and pressure, the mean absolute percentage errors are 0.04% and 1.31%, respectively. This feature facilitates the detection of minute changes in shallow marine environments, lacustrine systems, and other aquatic habitats, thus making it highly suitable for applications such as underwater aquaculture and marine monitoring.

We propose and experimentally demonstrate what we believe to be the first mid-infrared surface plasmon resonance (SPR) fiber optic sensor using a D-shaped multimode silica optical fiber coated with a 105 nm indium tin oxide (ITO) layer. The sensor shows resonance around 2700 nm, with a refractive index sensitivity of 1065.70 nm per refractive index unit (nm/RIU) for refractive indices ranging from 1.33 to 1.42. Since the evanescent wave outside the fiber decays within approximately 1/3 of its wavelength, the use of mid-infrared wavelengths can significantly increase the probing depth of SPR sensors compared to what is obtained when using visible light. This would allow SPR sensors to probe a larger volume, potentially improving sensitivity and signal-to-noise ratio. In addition, the mid-infrared region aligns with the molecular fingerprint region, which can unlock the potential for gas detection.

We analyze the single-photon band structure and the transport of a single photon in a one-dimensional coupled-spinning-resonator chain. The time-reversal symmetry of the resonators chain is broken by the spinning of the resonators, instead of external or synthetic magnetic field. Two nonreciprocal single-photon band gaps can be obtained in the coupled-spinning-resonator chain, whose width depends on the angular velocity of the spinning resonator. Based on the nonreciprocal band gaps, we can implement a single photon circulator at multiple frequency windows, and the direction of photon cycling is opposite for different band gaps. In addition, reciprocal single-photon band structures can also be realized in the coupled-spinning-resonator chain when all resonators rotate in the same direction with equal angular velocity. We believe our work opens a new route to achieve, manipulate, and switch nonreciprocal or reciprocal single-photon band structures, and provides new opportunities to realize novel single-photon devices.

pH is an important physiological parameter within organisms, playing a crucial role in functional activities in cells and tissues. Among various pH sensing methods, optical fiber pH sensors have gained a wide attention due to their unique advantages. However, current silica optical fiber-based pH sensors face some challenges such as weak biocompatibility, low biological safety, complex or unstable surface modification. Herein, we develop what we believe to be a novel pH sensor based on a CdSe/ZnS quantum dots-doped polymer optical fiber microprobe (POF MP) grown at the end of the silica optical fiber using the free radical photopolymerization process, which has the advantages of significant compactness, high flexibility, good biocompatibility, easy functionalization, high structural stability and safety. Moreover, the size of the POF MP are controllable, which is highly significant for applications requiring specific probe sizes or those used in special terrains. The proposed sensor is demonstrated to have a sensitivity of 0.18097/pH in a wide pH range from 4.5 to 9.0, while it exhibits a highly linear correlation between fluorescence intensity and pH value (R ² = 0.99448) and good reversibility and reusability. This proposed pH sensor offers a promising solution for pH monitoring in biological environments, contributing to advancements in biosensing, microenvironment monitoring, and potential therapeutic applications.

By utilizing the time inversion of radiation from spatial dipole arrays, we propose a method for constructing the spatial lattice-type skyrmion arrays under 4π focusing conditions, including Néel-, Bloch-, and Anti-skyrmions/merons. The Richards-Wolf vector diffraction theory is applied to analyze the radiation field emitted by dipole arrays, aiming to determine the incident field required under a high numerical aperture (NA=0.95). We construct spatial optical skyrmion arrays consisting of multiple topological points and investigate the distribution characteristics of the tightly focused field. The results indicate that diverse morphologies of optical skyrmions/merons can be achieved by adjusting the vectorial distribution within the unit dipole arrays. The high degree of freedom in combining optical skyrmion arrays holds significant potential for applications in high-density storage and precision measurement.

Significant advancements in integrated photonics have enabled high-speed and energy efficient systems for various applications, from data communications and high-performance computing to medical diagnosis, sensing, and ranging. However, data storage in these systems has been dominated by electronic memories that in addition to signal conversion between optical and electrical domains, necessitates conversion between analog to digital domains and electrical data movement between processor and memory that reduce the speed and energy efficiency. To date, scalable optical memory with optical control has remained an open problem. Here, we report an integrated photonic set-reset latch as a fundamental optical static memory unit based on universal optical logic gates. As a proof of concept, experimental implementation of the universal logic gates and realistic simulation of the latch are demonstrated on a programmable silicon photonic platform. Optical set, reset, and complementary outputs, scalability to a large number of memory units via the independent latch supply light, and compatibility with wavelength division multiplexing scheme and different photonic platforms enable more efficient and lower latency optical processing systems.

In this paper, a high-power UV-pumped BBO optical parametric oscillator (OPO) is presented by increasing the working temperature of the nonlinear crystal to fasten the color center recovery speed and further decrease the color center density. When the working temperature of the BBO crystal was experimentally increased from 135 °C to 185 °C, the output power was scaled up from 1.20 W to 2.17 W. The repetition rate and pulse width of the signal light were 10 kHz and 5.23 ns, respectively. By rotating the BBO crystal, the wavelength of the signal light was tuned from 409.81 nm to 581.87 nm. To the best of our knowledge, it was the highest output power for the 355 nm UV-pumped II-type critical phase-matched BBO OPO. The results are beneficial for the development of OPOs as well as in industrial and scientific research fields.