With the flourish of deep learning, transformer models have achieved remarkable performance in dealing with many computer vision tasks. However, their applications in infrared small target detection is limited due to two factors: (1) the high computational complexity of the conventional transformer models reduces the efficiency of detection; (2) the small target is easily left out in the visual environment with complex backgrounds. To deal with the issues, we propose a lightweight infrared small target detection method based on a linear transformer named IstdVit, which achieves high accuracy and low delay in infrared small target detection. The model consists of two parts: a multi-scale linear transformer and a lightweight dual feature pyramid network. It combines the strengths of a lightweight feature extraction module and the multi-head attention mechanism, effectively representing the small targets in the complex background at an economical computational cost. Additionally, it incorporates rotational position encoding to improve understanding of spatial context. The experiments conducted on the NUDT-SIRST and IRSTD-1K datasets indicate that IstdVit achieves a good balance between speed and accuracy, outperforming other state-of-the-art methods while maintaining a low number of parameters.

The two-dimensional nanomaterials are characterized by their ultra-thin structure, diverse chemical functional groups, and remarkable anisotropic properties. Since its discovery in 2004, graphene has attracted significant scientific interest due to its potential applications in various fields, including electronics, energy systems, and biomedicine. In medicine, graphene is used for designing smart drug delivery systems, especially for antibiotics, and biosensing. Skin trauma is a prevalent dermatological condition that increasingly contributes to morbidities and mortalities, thus representing a significant health burden. During tissue damage, rapid skin repair is crucial to prevent blood loss and infection. Therefore, drugs used for skin trauma must possess antimicrobial and anti-inflammatory properties. Two-dimensional (2D) nanomaterials possess remarkable physical, chemical, optical, and biological characteristics due to their uniform shape, increased surface area, and surface charge. Graphene and its derivatives, transition-metal dichalcogenides (TMDs), black phosphorous (BP), hexagonal boron nitride (h-BN), MXene, and metal-organic frameworks (MOFs) are among the commonly used 2D nanomaterials. Moreover, they exhibit antibacterial and anti-inflammatory properties. This review presents a comprehensive discussion of the clinical approaches employed for wound healing treatment and explores the applications of commonly used 2D nanomaterials to enhance wound healing outcomes.

Exfoliation of 2D non-Van der Waals (non-vdW) semiconductor nanoplates (NPs) from inorganic analogs presents many challenges ahead for further exploring of their advanced applications on account of the strong bonding energies. In this study, the exfoliation of ultrathin 2D non-vdW chromium sulfide (2D Cr2S3) by means of a combined facile liquid-phase exfoliation (LPE) method is successfully demonstrated. The morphology and structure of the 2D Cr2S3 material are systematically examined. Magnetic studies show an obvious temperature-dependent uncompensated antiferromagnetic behavior of 2D Cr2S3. The material is further loaded on TiO2 nanorod arrays to form an S-scheme heterojunction. Experimental measurements and density functional theory (DFT) calculations confirm that the formed TiO2@Cr2S3 S-scheme heterojunction facilitates the separation and transmission of photo-induced electron/hole pairs, resulting in a significantly enhanced photocatalytic activity in the visible region.

Gold-titanium nitride (Au/TiN), a prominent plasmonic transition metal nitride, exhibits superior advantages in electronic and optical properties, making it adaptable for applications in modern photonics technologies. Herein, novel gold-titanium nitride (Au/TiN) is a typical representative of the plasmonic photo-bleaching metal nitrides, which comprises modified nanoclusters of gold on TiN for enhancing carrier mobility. These materials can be exploited as an ultrafast optical switch, which shows saturable absorption behavior with strong optical nonlinearity. The chemical composition and morphology of as-prepared plasmonic Au/TiN materials are systematically characterized. The plasmonic photo-bleaching material is directly transferring to a piece of tapered fiber (TF) to fabricate the Au/TiN-based broadband nonlinear saturable absorber (SA). Nonlinear optical (NLO) properties of the Au/TiN plasmonic nanomaterial are measured from the 1.06 to 2.0 mu m wavelength regions for the first time to the best of our knowledge. Additionally, stable passively mode-locked lasers based on the Au/ TiN-SA devices are realized with the shortest pulse durations of 250 ps, 1.416 ps, and 0.810 ps at 1.0, 1.5, and 2.0 mu m bands, respectively. These experimental results indicate that the Au/TiN-SA is an effective broadband nonlinear photonic device in an all-fiber ultrafast laser and can also provide new insights into the design of NLO devices for optoelectronics applications.

Optoelectronics with excellent long‐term stability is meaningful for practical applications. Herein, for the first time, an A 2 B 2 O 7 type high‐entropy oxide of (La 0.2 Ce 0.2 Nd 0.2 Gd 0.2 Bi 0.2 ) 2 Ti 2 O 7 (ATO) is synthesized and applied for photoelectrochemical photodetection. The lattice distortion, highly dispersed metal composition, and exposed active sites of ATO are beneficial for the fast separation and transmission of photogenerated electron/hole pairs, endowing ATO‐based devices with good photodetection performance. Both the density functional theory calculations and the nondegenerate transient absorption spectroscopy demonstrate the good optoelectronic properties of ATO. The systematic experimental studies reveal the tunable photodetection capability of ATO‐based photodetector (PD) in the visible region. A photocurrent of 772.00 nA cm −2 and a responsivity of 4.02 µA W −1 can be achieved as the PD in 1.0 m KOH with the bias potential of 0.6 V. Importantly, the robust and reproducible ON/OFF signals of the PD can be verified and there is only ≈5.00% attenuation in photocurrent even after 6 months, revealing the great potential of high‐ entropy oxides for practical applications.

$${Ca}^{2+}$$ plays an important role as an intracellular second messenger in the growth and development of cardiomyocytes (CMs), which can be visualized by calcium imaging and be quantified as calcium transient. Based on calcium imaging, the widely applied measurement method for cellular calcium transient requires laborious and inefficient calibration experiments, as well as affected by photobleaching. In this study, we presented a calibration-free method, based on calcium imaging, to calculate cellular calcium transient and correct photobleaching directly from the target video. We also set up image acquisition and calculation system on custom software, applied to calcium transients monitoring of neonatal rat cardiomyocytes. Results showed that the effect of the new method was similar to that of the traditional one with a Pearson correlation coefficient of 0.99 ± 0.01. Moreover, the residual sum of squares of the two methods was only 26.31 ± 26.28 when the area of the region of interest was greater than 8% of the image area. This result indicated that the new method provided a new concept of cellular $${Ca}^{2+}$$ concentration quantification as well as a rapid and adaptive method for monitoring cellular calcium transient.

We report a dual-wavelength tunable passively Q-switched Er3+ -doped ZBLAN fiber laser at ~3 nm using a bulk PtSe2 as a saturation absorber. Stable pulses were generated for average output power of 504.0 mW at 72.9 kHz repetition rate. The corresponding pulse width and pulse energy were measured to be 1.26 μs and 6.92 μJ, respectively. By tuning the feedback angle of the plane ruled grating, the spectra show simultaneous dual-wavelength pulsed operations with tuning range of 51.5 nm (2745.5-2797.0 nm) at the launched pump of 2.27 W.

A 3 mu m passively Q-switched Ho3-/Pr3- co-doped fiber laser by using Au nanocages as saturable absorber is demonstrated. Stable Q-switched pulse trains with a repetition rate of 82. 0 kHz are initially obtained as the pump power increases to 99. 7 mW. When the pump power increases to 347. 1 mW , the largest output power of 50. 7 mW with a pulse duration of 2. 21 mu s and a corresponding repetition rate of 169. 5 kHz is obtained. This study indicates that Au nanocages have a great potential as an outstanding optical modulator for mid-infrared pulses generation.

In this work, we propose, to the best of our knowledge, the first demonstration of a ~3.5 μm dual-wavelength pumping (DWP) Er3+-doped ZBLAN fiber laser gain switched by 976 nm pulses. The DWP scheme is composed of a pulsed 976 nm laser system and a home-made continuous-wave 1973 nm laser. Stable pulses were obtained with repetition rates ranging between 5.2 kHz and 10 kHz. The maximum output power energy of 50.4 μJ was achieved at 10 kHz with a wavelength of 3445.9 nm. The temporal profile of the pulse trains was characterized by stable relaxation spike pulses containing a series of sub-pulses. The pulse characteristics with respect to the pump energy and the underlying mechanism are discussed. This work makes an effort to better understand the dynamics and theory of the cascade pumping system, and provides a new perspective for the realization of high-power pulses beyond 3 μm.

We report a wavelength-tunable high-repetition-rate passively Q-switched fluoride fiber laser around 3 μm by using Ti 3 C 2 T x MXene as saturable absorber (SA). The Ti 3 C 2 T x MXene was synthesized by selectively etching aluminum layers in Ti 3 AlC 2 . The modulation depth, non-saturation loss and saturation fluence of the SA at 2866 nm were measured to be 43.10%, 25.16%, and 0.50 mJ /cm 2 , respectively. By introducing the Ti 3 C 2 T x SA into a Ho 3+ /Pr 3+ -codoped fluoride fiber, stable Q-switched pulses with a continuously tuning range of 30.8 nm (2868.4 nm-2899.2 nm) were achieved. The repetition rate was as high as 215.3 kHz with an output power of 142 mW at the wavelength of 2879.0 nm. Such compact mid-infrared Q-switched laser source with a high repetition rate is of great importance in various applications such as medicine, high-resolution photoacoustic microscopy, and remote sensing. Our work indicates that the Ti 3 C 2 T x MXene is a promising broadband light modulator for pulsed laser sources around 3 μm.

Due to the complexity of the maxillofacial surgery, the novice should be sufficiently trained before one is qualified to carry on the surgery. To reduce the training costs and improve the training efficiency, a virtual mandible surgical system with haptic feedback is proposed. This surgical simulation system offers users the haptic feedback while simulating maxillofacial surgery. An integrated model is introduced to optimize the system simulation process, which includes force output to a six-degree-of-freedom haptic device. Based on the anatomy structure of the bone tissue, a two-layer mechanism model is designed to balance the requirement of real-time response and the force feedback accuracy. Collision detection, force rendering, and grinding function are studied to simulate some essential operations: open reduction, osteotomy, and palate fixation. The proposed simulation platform can assist in the training and planning of these oral and maxillofacial surgeries. The fast response feature enables surgeons to design a patient-specific guide plate in real-time. Ten stomatology surgeons evaluated this surgical simulation system from the following four indexes: the level of immersion, user-friendliness, stability, and the effect of surgical training. The evaluation score is eight out of ten.

Super-resolution fluorescence microscopy plays an important role in the field of biological science with a tremendous potential, for the capability of observing living cells in real time. Numerous super-resolution methods have been developed to surpass the diffraction limit in recent years. Two-photon structured illumination microscopy (TPSIM) combines structured illumination microscopy (SIM) with two-photon excitation, providing wide field of view with deep penetration, and considerable resolution enhancement simultaneously. Here, we report a new algorithm for TPSIM termed as Fourier ptychographic (FP) technique. The result of simulation is presented to demonstrate that FP scheme is able to reduce the number of raw images with substantial resolution enhancement. The proposed method enables TPSIM to achieve live-cell imaging with fewer effective illumination patterns, shorter acquisition time, deeper imaging depth, and less phototoxicity. In addition, we show that, the number of raw images can further reduce to 4 for acceptable resolution improvement.

Much more attentions have been attracted to the inspection and prevention of unmanned aerial vehicle (UAV) in the wake of increasing high frequency of security accident. Many factors like the interferences and the small fuselage of UAV pose challenges to the timely detection of the UAV. In our work, we present a system that is capable of detecting, recognizing, and tracking an UAV using single camera automatically. For our method, a single pan–tilt–zoom (PTZ) camera detects flying objects and gets their trajectories; then, the trajectory identified as a UAV guides the camera and PTZ to capture the detailed region image of the target. Therefore, the images can be classified into the UAV and interference classes (such as birds) by the convolution neural network classifier trained with our image dataset. For the target recognized as a UAV with the double verification, the radio jammer emits the interferential radio to disturb its control radio and GPS. This system could be applied in some complex environment where many birds and UAV appear simultaneously.

We report a watt-level passively Q-switched 2.8 μm mid-infrared multi-mode fiber laser by employing multi-layered two-dimensional MXene-Ti3C2Tx as the saturable absorber (SA). The MXene-Ti3C2Tx is fabricated by selectively etching aluminum layers in Ti3AlC2. The non-saturable loss, modulation depth, and saturable intensity of the SA at 2866 nm were measured to be 25.0%, 33.2%, and 0.043 GW/cm2, respectively. The maximum average output power of the Ti3C2TxQ-switched fiber laser reached 1.09 W at 28.23% slope efficiency. The pulse repetition rate, shortest pulse width, pulse peak power, and single-pulse energy were 78.12 kHz, 1.04 μs, 13.4 W, and 13.93 μJ, respectively. This is the first demonstration of watt-level pulse generation in a mid-infrared fiber laser using low dimensional materials, to the best of our knowledge. These results indicate that the Ti3C2Tx is a reliable and superior broadband SA for high power mid-infrared pulsed laser generation.

The mid-infrared fiber lasers in the 2-3.5 mu m spectral regions have been extensively applied in many application fields, such as biomedicine, telecommunications, military and nonlinear optics. With the improvements of the fiber components, the pumping regimes and other related technologies, the mid-infrared fiber lasers have made significant progress over the past decades and gradually become comparable with or supersede the traditional lasers in terms of certain lasing performance. In this review, from the beginning with the overview of fiber materials for the mid-infrared regions, we briefly summarize and review the latest research progress of mid-infrared continuous-wave (CW) and short pulse fiber lasers, including Tm3+-, Ho3+-doped, Tm3+-Ho3+ co-doped silicate fiber lasers for the 2 mu m region and Er3+-, Ho3+-idoped, Ho3+-Pr3+ co-doped ZBLAN fiber lasers for the 2.8-3.5 mu m region. The advances of saturable absorbers applied in the mid-infrared pulse fiber lasers are also explored. Finally, the future prospects and challenges concerning the further development of mid-infrared fiber lasers are discussed and highlighted.

BACKGROUND:Pharyngeal fricative is one typical compensatory articulation error of cleft palate speech. It passively influences daily communication for people who suffer from it. The automatic detection of pharyngeal fricatives in cleft palate speech can provide information for clinical doctors and speech-language pathologists to aid in diagnosis.RESULTS:This paper proposes two features (CSIFs: correlation of signals in independent frequency bands; OSPP: octave spectrum prominent peak) to detect pharyngeal fricative speech. CSIFs feature is proposed to detect the distribution characteristics of frequency components in pharyngeal fricative speech caused by the changed place of articulation and movement of articulators. While OSPP is presented to reflect the concentration degree of prominent peak which is closely related to the place of articulation in pharyngeal fricative, both features are investigated to relate to the altered production process of pharyngeal fricative. To evaluate the capability of these two features to detect pharyngeal fricative, we collected a speech database covering all the types of initial consonants in which pharyngeal fricatives occur. In this detection task, the classifier used to discriminate pharyngeal fricative speech and normal speech is based on ensemble learning.CONCLUSION:The detection accuracy obtained with CSIFs and OSPP features ranges from 83.5 to 84.5% and from 85 to 87%, respectively. When these two features are combined, the detection accuracy for pharyngeal fricative speech ranges from 88 to 89%, with an AUC (area under the receiver operating characteristic curve) value of 93%.

Broadband tunable ultrafast lasers using mid-infrared (MIR) fibers operating at a 3-5 mu m atmospheric transmission window are attractive sources because of their numerous applications. Tellurite fibers possess the merits of large linear and nonlinear refractive indices, sufficient chemical stability, and wide transparency range up to similar to 5 mu m; also, they are highly suitable for high efficiency MIR ultrafast fiber laser sources based on soliton self-frequency shift (SSFS). We numerically simulate SSFS of MIR femtosecond pulses in step-index tellurite optical fibers. A femtosecond erbium-doped fluoride fiber laser at 3.5 mu m is employed as the pump source. Parameters including the peak power of the input pulse and nonlinear fiber length are optimized for high efficiency broadband tunable MIR ultrafast laser performance. Our results show that a high-efficiency 3.5-6 mu m wavelength-tunable femtosecond laser can be realized by employing SSFS in a 22-cm-long segment of tellurite step-index fiber pumped by femtosecond pulses with 10-300 kW peak powers at 3.5 mu m. Ultra-high energy ratios of the most redshifted solitons to the input pulses of > 50% are obtained across the 3.5-5 mu m tuning range. The presented numerical study provides valuable guidance for SSFS of MIR femtosecond pulses in step-index tellurite fibers and is valuable for future high efficiency wavelength-tunable MIR ultrafast fiber laser development. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

To achieve a simple and fast calibration of parameters for three-dimensional imaging system with structured light, a method of obtaining a large number of calibration data using a homography matrix is presented. First, the image coordinates and the corresponding world coordinates of the rectangular corner points on the left and right sides of a stereo target are obtained, and the homography matrices of the left and right sides of the target surface from the image coordinates to the world coordinates are then calculated respectively. Next, all the pixels in the rectangular frame of the stereo target in the image are applied to the calculated homography matrix to obtain the corresponding world coordinates. Finally, we calibrate the three-dimensional imaging system using the image coordinates of nearly all the pixels on the target surface of the stereo target in the image and the corresponding world coordinates. A stereo target corresponding to the proposed calibration method is designed. Based on the stereo target, the three-dimensional imaging system with structured light is calibrated and experiments are carried out using the calibrated system. The experimental results show that the calibration method has high calibration accuracy, the reconstructed three-dimensional point cloud image has a good visual effect, and the calibration process is simple, which reduces the cost of calibration and is valuable for practical applications.

Q-switched fiber lasers emitting at around 3 μm have been widely applied in various scientific and industrial fields, such as molecular spectroscopy, laser surgery, material processing, remote sensing, and mid-infrared (mid-IR) supercontinuum source generation. Au nanocages (Au-NCs) have attracted much attention recently due to their outstanding saturable absorption properties including broadband absorption, ultrafast optical response (a few picoseconds), and large third-order optical nonlinearity coefficient that caused by local surface plasmon resonance (LSPR). We propose and demonstrate a tunable Er3+ doped ZBLAN fiber laser using Au-NCs as a Q-switcher for the first time. Nonlinear absorption of the Au-NCs was measured by a home-made Ho3+/Pr3+ co-doped mode-locked fiber laser at 2850 nm. The measured modulation depth, saturation intensity and non-saturation loss are 10.73%, 0.11 MW/cm2 and 3.26%, respectively. The central wavelength of the Q-switched pulses could be tuned across 54.1 nm (from 2753.0 to 2807.1 nm). The Q-switched fiber laser delivers a maximum average power of 253.7 mW with corresponding pulse energy of 4.06 μJ and pulse width of 1.30 μs at repetition rate of 62.5 kHz. Our work shows the Au-NCs are promising saturable absorbers (SAs) for 3 μm mid-infrared (mid-IR) pulse generation.