Intelligent food packaging with the multisensory analysis is promising as the next generation technology of food packaging. The oxygen content in food packaging is one of the crucial parameters affecting the food quality and shelf life. Caviar is among the most nutritious and costly food sources. Here, a photonic oxygen-sensing system, based on the time-resolved phosphorescence spectroscopy of a platinum complex, is developed for non-contact, non-intrusive, and real-time vacuum packaging quality control, and implemented for caviar packaging. The sensor is embedded in protective polyethylene layers and excited with a short-pulsed light emitting diode (LED) source. Integration of a blue pulsed light source, a fast and amplified silicon photodiode controlled by the Spartan-6 field programmable gate array (FPGA), and a long lifetime platinum complex results in a photonics-based oxygen sensor with a fast response and high sensitivity to the vacuum packaging damage, which is suitable for caviar. It is revealed that applying the polyethylene layers protects the caviar from the platinum complex, leaching while not interfering with the sensor functionality. Characterizing the photonic system based on its sensitivity, repeatability, stability, and long-term operation demonstrates its capability for this application.

In this paper, a new concept of forward-pumped random Raman fiber laser (RRFL)-based liquid refractive index sensing is proposed for the first time. For liquid refractive index sensing, the flat fiber end immersed in the liquid can act as the point reflector for generating random fiber lasing and also as the sensing head. Due to the high sensitivity of the output power of the RRFL to the reflectivity provided by the point reflector in the ultralow reflectivity regime, the proposed RRFL is capable of achieving liquid refractive index sensing by measuring the random lasing output power. We theoretically investigate the effects of the operating pump power and fiber length on the refractive index sensitivity for the proposed RRFL. As a proof-of-concept demonstration, we experimentally realize high-sensitivity half-open short-cavity RRFL-based liquid refractive index sensing with the maximum sensitivity and the sensing resolution of –39.88 W/RIU and 2.507 5 × 10-5 RIU, respectively. We also experimentally verify that the refractive index sensitivity can be enhanced with the shorter fiber length of the RRFL. This work extends the application of the random fiber laser as a new platform for highly-sensitive refractive index sensing in chemical, biomedical, and environmental monitoring applications, etc.

The effectiveness of monitoring and early-warning systems for ground deformation phenomena, such as sinkholes, depends on their ability to accurately resolve the ongoing ground displacement and detect the subtle deformation preceding catastrophic failures. Sagging sinkholes with a slow subsidence rate and diffuse edges pose a significant challenge for subsidence monitoring due to the low deformation rates and limited lateral strain gradients. In this work, we satisfactorily illustrate the practicality of the Brillouin optical time domain analysis (BOTDA) to measure the spatial-temporal patterns of the vertical displacement in such challenging slow-moving sagging sinkholes. To assess the performance of the approach, we compare the strain recorded by the distributed optical fiber sensor with the vertical displacement measured by high-precision leveling. The results show a good spatial correlation with the ability to identify the maximum subsidence point. There is also a good temporal correlation with the detection of an acceleration phase in the subsidence associated with a flood event.

In this work, we present the investigation of the quantum dot color filter (QDCF) micro-light emitting diode (micro-LED) display. Green and red quantum dot photoresist (QDPR) materials are patterned into a pixelated array and precisely bonded with an all-blue micro-light emitting diode (micro-LED) substrate, forming a red, green, and blue (RGB) full color display through color conversion. A few factors that influence the achievable color gamut are further investigated. The resulting 1.1-inch 228-pixels per inch (ppi) display demo shows the good performance. The findings in this paper pave a way to the future industrialization of the micro-LED display.

In view of the problem that the sensing characteristics of the multi-mode interferometric fiber sensors cannot be accurately analyzed, an analysis method based on the fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) is proposed and demonstrated theoretically and experimentally. The suitabilities of the rectangular window function with the narrow main lobe (high spectrum resolution) and low side lobe (high main mode energy leakage) and the Hanning window function with the wide main lobe (low spectrum resolution) and high side lobe (high energy concentration) in this kind of sensor analysis are discussed, respectively. This method can not only realize the sensing performance analysis of the various modes, but also overcome the inconsistency of the different interference wavelength (dip) sensing characteristics in the conventional analysis methods. At the same time, this method is also beneficial to solve the repetitive problem of such sensors.

In this paper, a cost-effective and miniaturized instrument is proposed, which is based on a tunable modulated grating Y-branch (MG-Y) laser for rapid temperature measurement using a Fabry-Perot interferometer (FPI) sensor. The FPI sensor with a 1 463-μm cavity length is a short segment of a capillary tube sandwiched by two sections of single-mode fibers (SMFs). This system has a broad tunable range (1 527 nm–1 567 nm) with a wavelength interval of 8 pm and a tuning rate of 100 Hz. Temperature sensing experiments are carried out to investigate the performance of the system by demodulating the absolute cavity length of the FPI sensor using a cross-correlation algorithm. Experimental results show that the sensor can reach the response time as short as 94 ms with the sensitivity of 802 pm/℃. Benefiting from the homemade and integrated essential electrical circuits, the entire system has the small size, low cost, and practical application potential to be used in the harsh environment for rapid temperature measurement.

Miniaturized fiber-Bragg-grating (FBG) interrogators are of interest for applications in the areas where weight and size controlling is important, e.g., airplanes and aerospace or in-situ monitoring. An ultra-compact high-precision on-chip interrogator is proposed based on a tailored arrayed waveguide grating (AWG) on a silicon-on-insulator (SOI) platform. The on-chip interrogator enables continuous wavelength interrogation from 1 544 nm to 1 568 nm with the wavelength accuracy of less than 1 pm [the root-mean-square error (RMSE) is 0.73 pm] over the whole wavelength range. The chip loss is less than 5 dB. The 1 × 16 AWG is optimized to achieve a large bandwidth and a low noise level at each channel, and the FBG reflection peaks can be detected by multiple output channels of the AWG. The fabricated AWG is utilized to interrogate FBG sensors through the center of gravity (CoG) algorithm. The validation of an on-chip FBG interrogator that works with sub-picometer wavelength accuracy in a broad wavelength range shows large potential for applications in miniaturized fiber optic sensing systems.

Latent fingerprints (LFPs) at the crime scene are served as important clues to locate the trajectory of criminal behavior and portray the characteristics of the suspect. Therefore, visualizing LFPs is of considerable significance. In this work, the europium metal-organic framework (Eu-MOF) sensor was successfully constructed for sensitive detection of gallic acid (3,4,5-trihydroxybenzoic acid, GA) and visualization of the sweat LFPs. The boric-acid-modified Eu-MOF was prepared by using the simple one-pot solvothermal method using Eu as the metal ion center and 3,5-dicarboxybenzeneboronic acid (BBDC) as the organic ligand. The sensor showed desirable photoluminescent performance through the chelating of BBDC with Eu3+. The sensor exhibited the satisfactory linear relationship to GA in the range of 1 nM to 20 nM with a low detection limit of 0.34 nM under the optimized conditions. The prepared sensor with ideal selectivity to GA was successfully applied for visualizing LFPs on porous substrates with the high contrast and superior stability. Given the good performance of the sensor, all fingerprint images obtained from 1 200 samples presented clear friction ridges and met the identification criteria. Notably, the sensor had less impact on the subsequent deoxyribonucleic acid (DNA) detection, displaying a promising perspective for applications in extracting physical evidence of site investigation.