Optics and Laser Technology最新文献

With the increasing capacity demands of data communications, mode division multiplexing in on-chip optical interconnect systems is becoming an attractive solution. Compact, broadband, and fabrication-tolerant mode-order converters unaffected by polarizations are considered crucial for the progress of on-chip systems utilizing mode division multiplexing. A proposal for a design scheme for an on-chip mode-order converter that is insensitive to polarization is presented, utilizing a combination of 3D finite-difference time-domain (FDTD) and particle swarm optimization (PSO). The conversion of TE₀/TM₀-to-TE₁/TM₁ mode is achieved through phase matching between a subwavelength grating and an input–output tapered waveguide. Theoretical studies indicate that the TE₀-to-TE₁ and TM₀-to-TM₁ insertion losses are below 0.46 dB and 0.78 dB at a wavelength of 1550 nm. The TE₀-to-TE₁ and TM₀-to-TM₁ insertion loss is under 1.0 dB, with crosstalk below −15 dB within the 190 nm (1432∼1622 nm) and 81 nm (1515∼1596 nm) operating ranges. Experimental data indicates that the device measuring 7 × 1.58 μm² can successfully convert mode orders regardless of polarization within an 81 nm bandwidth (1515∼1596 nm), effectively doubling the data transmission capacity of the MDM system. In addition, the devices fabricated by a standard CMOS process demonstrate the potential for mass production.

Photodetectors based on PbSe quantum dots (QDs) are commonly used for light detection in the near-infrared (NIR) region. Nevertheless, the performance of photodetectors based on PbSe QDs is constrained by ineffective carrier transfer and poor photo and thermal stabilities. Herein, a promising strategy that harnesses PbSe/PbS core/shell QDs structures is developed and demonstrated to enhance the long-term stability of photodetectors, further combining with graphene to form hybrid heterojunctions that effectively promote carrier transfer. As a result, the devices exhibit a broad photoresponse to the incident light at range of 365–1250 nm, and also possess a high photosensitivity of 1.5 × 10⁴ A/W and a high detectivity of 4.0 × 10¹³ Jones. Moreover, the lifetime of graphene-PbSe/PbS core/shell QDs hybrid photodetector was 9 times greater than that of uncoated QDs devices. The enormous boost might be attributed to the passivation and protection provided by the core–shell structure, and graphene’s efficient extraction of charge carriers.

Thermoset composites are vital materials in modern manufacturing due to their exceptional mechanical properties, chemical resilience, and thermal endurance across diverse industries. However, conventional manufacturing methods often struggle to achieve precise control over fabrication processes and optimize material characteristics. The emergence of laser-assisted manufacturing presents a promising solution to these challenges, offering novel avenues for advancing thermoset composite production. By harnessing laser energy’s unique attributes such as localized heating and precise material processing control, laser-assisted manufacturing provides unprecedented opportunities for attaining superior quality, intricate geometries, and tailored properties in thermoset composites. This comprehensive review addresses the pressing needs and gaps in the fundamentals, processes, scientific modeling, challenges, and prospective developments in laser manufacturing processes for thermoset composites. This study examines thermoset composites’ behavior, focusing on structures and properties. Section 3 discusses laser-composite interaction fundamentals, including heating principles and energy absorption mechanisms. Section 4 explores tailored laser manufacturing techniques, and Section 5 covers modeling approaches. Section 6 addresses challenges and future prospects, while Section 7 presents conclusions guiding innovation in laser-assisted manufacturing for thermoset composites. Subsequent sections will explore thermoset composite fundamentals (Section 2) and laser-composite interaction (Section 3), covering heating principles, energy transfer, and thermal effects. Section 4 will examine laser manufacturing techniques, with comparative analysis. Modeling approaches will be discussed in Section 5, while Section 6 addresses challenges and future prospects.

From an optical perspective, depending on the relationship between the real (n) and imaginary (k) parts of its refractive index, three broad categories of materials can be distinguished: metals (k ≫ n), dielectrics (n ≫ k), and materials in which n ≈ k (termed here excitonic materials). The modes and optical resonances that appear in a thin film bounded by two dielectrics with similar refractive index, what we call here a double interface structure, have been widely studied in the case of metals, but not for dielectrics, or materials with n ≈ k. In this work, we propose a new approach, based on employing the phase matching condition to correlate the resonances that appear in the wavelength versus incident angle color maps of the reflected power with the modal analysis of the cross section of the structure. This analysis is performed, using an attenuated total reflection (ATR) setup, for thin film materials that belong to each of the mentioned categories: a metal (gold, Au), a dielectric (titanium dioxide, TiO₂), and a material with n ≈ k (chromium, Cr). The theoretical analysis is supported with experimental results. It is demonstrated that this method enables to identify any resonance at any wavelength or incident angle, being valid for all three types of materials. Therefore, it is considered the suggested approach will help the research in these materials and in the double interface structure in the optics and photonics field.

Dual-band amplified spontaneous emission (ASE) can be used as a spectral analysis technique to detect specific chemical or biological molecules. In this paper, the dual-band ASE properties of blend films containing a small organic molecule N,N’-(4,4′-(1E,1′E)-2, 2′-(1,4-phenylene) bis(ethene-2,1-diyl)) −bis(4,1-phenylene))-bis(2-ethyl-6-methyl-phenylaniline) (BUBD-1) and a conductive polymer Poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) were investigated and optimized. As the doping concentration of BUBD-1 in the PFO was increased from PFO: 1 wt% BUBD-1 to PFO: 5 wt% BUBD-1, the ASE emission wavelength shifted from single- to dual-band and then back. The dual-band ASE performance of the blend film was also improved by introducing a Poly(methyl methacrylate) (PMMA) buffer layer containing silver nanoparticles (AgNPs), which resulted in a significant decrease in the excitation energy threshold of both ASE peaks and a significant increase in the net gain. Due to the LSPR effect of AgNPs, the ASE thresholds for peaks at 460 nm (PFO) and 490 nm (BUBD-1) in the blend film decreased from 12.24 ± 0.49 μJ/pulse to 6.99 ± 0.28 μJ/pulse and from 12.75 ± 0.51 μJ/pulse to 7.03 ± 0.28 μJ/pulse, respectively. The experimental and theoretical simulation demonstrated that the incomplete energy transfer between PFO and BUBD-1 led to a dual-band ASE effect. In addition, the enhanced light absorption, emission, and scattering caused by LSPR in the AgNPs improved the threshold and gain for dual-band ASE. This provides a possibility of realizing dual-band organic semiconductor lasers.

Traditional structured light technique faces challenges in measuring translucent media due to low fringe modulation and strong random noise caused by subsurface scattering, thereby significantly reducing phase quality. In addition, the difficulty in obtaining ground truth makes it hard to assess reliability even though obtaining measured results. Here, we proposed a 3D measurement method for translucent media base on deep Bayesian inference to achieve both fringe enhancement and phase uncertainty evaluation. Specifically, a deep network incorporated with quatuor-branch residual block is developed to significantly enhance the fringe modulation and signal-to-noise ratio (SNR) for accurate phase recovery. Subsequently, a Bayesian inference mechanism is established for probabilistic statistics, which allows for the optimization of fringe output and provides uncertainty self-evaluation based on Monte Carlo (MC) sampling. Furthermore, by incorporating both numerical and physical constraints into the supervised learning, the network can effectively mitigate phase-shifted errors in the final results. The proposed method shows high efficiency and flexibility since it requires no additional patterns or hardware setup. Experiments validate the feasibility of the proposed method.

A vector magnetic field sensor based on enhanced Vernier effect is experimentally demonstrated. The Vernier effect is generated from two microwave photonic filters (MPFs) with close free spectral range (FSR), which is constructed by the fiber ring (FR) and the optical carrier microwave interferometry (OCMI). Linear chirped fiber Bragg grating (LCFBG) is inserted in the FR to act as the dispersion element to provide time delay. By attaching the fiber Bragg grating (FBG) on the magnetostrictive material (MA), the magnetic field can be transferred into the wavelength shift, as well as the time delay of the FR and the frequency response of the FR-MPF. By choosing opposite dispersion of LCFBGs and closer FSRs, cascaded FR-MPFs based sensor can greatly improve the sensitivity. The sensitivities for the magnetic field intensity and direction are 127.71 kHz/Oe, the magnification factor of which is 432, and 418.16 kHz/deg. The proposed scheme has merits of high sensitivity and interference immunity, which is suitable for high precision measurement.

To face the challenge of the fast, large area, and high-precision manufacturing for flexible structural color films, a strategy based on soft lithography to fabricate polydimethylsiloxane (PDMS) structural color films was proposed in this paper. The large area periodic structures as the template were obtained by means of laser interference lithography. After soft lithography, SEM images showed that the morphology and period are completely inversed with the templates. The colors of the films have an obvious angle dependence which was proved by an angle-resolved spectrometer(ARM), in which the peak position of the reflectance spectrum changed ∼267 nm as the angle increasing from 10° to 25° for the period ∼2.126 μm. In addition, the peaks of reflectance spectra have also an obvious redshift of ∼162 nm with increasing elongation ratio up to 40 %. Furthermore, the reflection peak of the flexible film will stably change between ∼697 nm and ∼617 nm before and after stretching from 0 to 40 % for 11 times. In conclusion, we explore an efficient way with the fast, large area, and high precision to fabricate flexible structural color films in the atmospheric environment, showing the potential application in optical anti-counterfeiting and mechanical sensor.

Overcoming inverse design problems in fiber Bragg gratings (FBGs) can be challenging due to the significant nonlinearity of the problem and the intricate relationship between structural properties and optical characteristics. Here, we present a novel artificial intelligence-based approach that effectively addresses these challenges. We introduce a methodology centered on applying deep learning (DL) to estimate the reflective spectrum of FBGs. The results highlight DL’s exceptional capability in designing chirped apodized FBGs, with our model demonstrating significantly enhanced computational efficiency relative to traditional numerical simulations. Notably, our DL-based approach exhibits the remarkable ability to tackle the inverse design challenges of FBGs, thereby eliminating the reliance on trial-and-error or empirical methodologies. The predictive losses for both the forward and inverse models are impressively minimal, with low loss values of 2.2 × 10^-2 and 1.6 × 10^-2, respectively. The FBG configurations derived via DL are ideally suited for optical communications, heralding significant advancements in all-optical signal processing.

Traditional machining methods face significant challenges in removing and processing diamond due to its high hardness, brittleness and wear resistance. A promising solution is laser-induced plasma-assisted ablation (LIPAA), which has gained attention as a reliable technology for processing transparent, hard and brittle materials, especially diamond. However, the complexity of the machining mechanism of LIPAA limits its widespread application. This study aimed to investigate the characteristics of LIPAA processing on diamond through experimental and simulation analysis. The experimental results revealed that the amorphization threshold of laser energy density is 3.36 J/cm², the deposition threshold is 3.89J/cm², and the etching threshold is 4.07 J/cm². When employing an infrared laser with a repetition rate of 115 kHz, the range of laser single pulse energy for LIPAA etching on single crystal diamond is from 115μJ to 145μJ, the range of the laser energy density is from 4.07 J/cm².to 5.13 J/cm². In addition, the width, depth and material remove rate of the diamond microgrooves increases with the increasing laser energy. A simulation model employing molecular dynamics (MD) technology was developed to examine the impact of copper plasma bombardment on single crystal diamond. The simulation results show that the deposition velocity threshold of copper ion bombardment on single crystal diamond is 1.062 × 10⁴ m/s, while the etching velocity threshold is 1.143 × 10⁴ m/s. The degree of amorphization on the diamond surface increased with the increase of bombardment speeds and system temperatures. The morphology, element distribution, and the graphite layer quality of the microgrooves were analyzed, and the formation mechanism of the microgrooves was explored. By combining experiments and simulations, it is concluded that the mechanism of LIPAA processing single crystal diamond is the formation of amorphous regions on the diamond surface by ion bombardment, while high-energy laser beams and plasma ablate the amorphous regions to form grooves.