Optics letters最新文献

Gas-phase oxidation in a laser-produced plasma is significantly influenced by the availability of oxygen in and around the plume. In this study, we investigate the role of target-derived and ambient oxygen on AlO formation in plasmas generated from aluminum (Al) and Al₂O₃ targets in air and argon, respectively. Our results highlight that gas-phase oxidation occurs early during the evolution of Al₂O₃ plasmas in argon, in contrast to Al plasmas in air, where the initial exclusion of oxygen from the plume delays the chemical reactions.

In this Letter, over-correction of spherical aberration is used to counteract nonlinear effects such as Kerr self-focusing and plasma effects, resulting in more spherical and small-sized femtosecond laser-inscribed voxels within nonlinear materials. By strategically redirecting marginal focusing rays toward the beginning of the laser modification zone, the induced plasma prevents any rays from causing a structural modification beyond this zone, irrespective of any focus elongation caused by nonlinear effects. The method has been effectively validated across a range of materials, including ZnS, ZnSe, BIG, GeS₄, and SiO₂. A significant outcome is the achievement of quasi-spherical and (sub-)micrometer voxels in highly nonlinear materials. These findings open avenues for single-mode active waveguides and high-resolution patterning within nonlinear materials. The experiments are performed using a microscope objective equipped with a correction collar, a widely available tool in laboratories, highlighting the potential and versatility of the technique.

Quantum walks (QW) offer a speed-up advantage over random walks in quantum search applications. We present an experimental study of the transition from quantum-to-classical random walk using an emulation of the decoherence process for polarization qubits that exploits maximally non-separable spin-orbit modes of an intense laser beam for the first, to the best of our knowledge, time. We are able to continuously control the input polarization mode in an all-optical quantum walk circuit to observe transitions associated with quantum, quantum stochastic, and classical random walk distributions. The results are in agreement with theoretical expectations.

The interface with spin defects in hexagonal boron nitride has recently become a promising platform and has shown great potential in a wide range of quantum technologies. Varieties of spin properties of V B- defects in hexagonal boron nitride (hBN) have been researched widely and deeply, like their structure and coherent control. However, little is known about the influence of off-axis magnetic fields on the coherence properties of V B- defects in hBN. Here, by using optically detected magnetic resonance (ODMR) spectroscopy, we systematically investigated the variations in ODMR resonance frequencies under different transverse and longitudinal external magnetic fields. In addition, we measured the ODMR spectra under off-axis magnetic fields of constant strength but various angles and observed that the splitting of the resonance frequencies decreases as the angle increases, aligning with our theoretical calculation based on the Hamiltonian, from which we came up with a solution of detecting the off-axis magnetic field angle. Through Rabi oscillation measurements, we found that the off-axis magnetic field suppresses the spin coherence time. These results are crucial for optimizing V B- defects in hBN, establishing their significance as robust quantum sensors for quantum information processing and magnetic sensing in varied environments.

This work demonstrates that the phase-based decorrelation compensation method outperforms the amplitude-based approach in low signal-to-noise ratio (SNR) regions of phase-sensitive optical coherence tomography (PhS-OCT). Building on this finding, an adaptive decorrelation compensation approach for digital-image-correlation (DIC)-assisted PhS-OCT is introduced. This method utilizes the maximum correlation coefficient from amplitude maps to adaptively determine the need for secondary tracking of decorrelated displacement using the phase-based approach. It significantly improves decorrelation compensation quality while minimizing impacts on computational efficiency. A tensile testing experiment was conducted to validate the method, with results showing that the proposed adaptive compensation method enables previously unmeasurable low SNR regions to become measurable by adaptively retracking only 21.7% of the area.

This work reports a hierarchically structured micromotor (HSM) surface-enhanced Raman scattering (SERS) platform comprising 3D tubular configurations with nanostructured outer walls. The HSMs can be powered by an external magnetic field in solution to enrich molecules with promoted adsorption efficiency. The nanostructured outer wall serves as containers to collect molecules and produce strong localized surface plasmon resonance to intensify Raman of the enriched molecules. Further coupling of HSMs after molecular enrichment can produce additional plasmonic hotspots at the sites where the molecules were enriched, providing a solution to manipulate molecules to enter the plasmonic hotspot region. Moreover, functionalizing specific molecules on the outer wall of HSMs enables high-specificity SERS sensing for benzaldehyde (BA) and Cu²⁺ ions in liquid. This SERS platform demonstrates great potential for practical applications in biochemical analysis and environmental monitoring, offering a rapid and sensitive tool for detecting low-concentration analytes in liquid.

We demonstrate the generation of stable femtosecond vortices from a self-started Kerr-lens mode-locked Yb:YAG thin-disk oscillator. By using a defective mirror inscribed with a fine line, 218-fs Hermite-Gaussian (HG) pulses are delivered directly from the thin-disk oscillator with an average power of 12 W at the repetition rate of 105 MHz and subsequently converted to Laguerre-Gaussian (LG) vortices by a cylindrical-lens mode-converter. The average output power of the Hermite-Gaussian pulses is further improved to 19 W by applying a rectangular aperture. This is the highest, to the best of our knowledge, average power obtained from any mode-locked Hermite-Gaussian oscillator to date. This work provides an effective way to generating a high-order and high-power ultrafast vortex beam.

We demonstrate flexible transmissive structural color filters with enhanced color purity and brightness by exploiting resonance overlap within multiple cavities in penta-layered structures. Using an inverse design method that combines optimization and exhaustive search algorithms, the material choices and layer thicknesses are determined through a loss function based on the CIE XYZ color space, optimizing both color purity and brightness. The resulting color gamut is comparable to standard RGB, as assessed in the CIE xy color space, with luminance (Y from CIE 1931 model) values for the fabricated transmissive RGB colors being 0.14, 0.51, and 0.14. The contribution of each cavity is thoroughly analyzed using optical admittance diagrams and resonant mode calculations. Furthermore, the transmissive colors on a flexible substrate exhibit excellent durability, retaining consistent transmission efficiency and color purity even after 4,000 bending cycles and performing reliably at a bending radius of 5 mm. The versatility of this design approach makes them suitable for a wide range of applications, including e-paper displays, image sensors, flexible wavelength-selective optoelectronic devices, and decorations.

We propose a multi-wavelength digital holography based on Kramers-Kronig (KK) relations, introducing a unified angle-multiplexing multi-wavelength KK model to overcome the accuracy and resolution limitations of angle-multiplexing techniques. By linking the real and imaginary parts of the multi-wavelength complex function via the KK relation, the method captures object light waves with the full effective bandwidth from a single interferogram and reference wave intensity. This method greatly improves spectral utilization and measurement accuracy in multi-wavelength interference. We use a three-wavelength multiplexing system to measure the topography of multi-step samples. The results show that our method expands the spectral range more than twice, reduces errors by 39.3%, and improves the peak signal-to-noise ratio and structural similarity index nearly three times compared to the traditional Fourier transform (FT) method. It offers a new, to the best of our knowledge, approach for high-precision multi-wavelength dynamic measurement and has the potential to overcome the limitations of multiplexing technology.

A fiber Bragg grating (FBG) demodulation system based on arrayed waveguide gratings (AWGs) is proposed. We designed the key parameters of the AWG, prepared the AWG chip based on a silica-on-silicon planar light wave circuit (PLC) platform, and integrated the AWG with a PD array. Eight AWG output channels were selected and the output signals from the photodiode (PD) array was connected to the board with gold wire bonding. The demodulation circuitry consists of transimpedance amplifiers (TIAs), analog-to-digital converters (ADCs), and a main control chip. The signal from the PDs are synchronously captured and amplified and then transmitted at high speed through an Ethernet interface. The total volume of the demodulation system is 200 × 100 × 60 mm³. Experiments show that the wavelength demodulation accuracy of the system is 4.24 pm, the demodulation rate is more than 200 kHz, and the average error of the demodulation acceleration is better than 22.8 mg. The proposed demodulation system can be applied in the field of high-frequency vibration sensing of FBGs.