Strong nonlinear optical limiting of resin composed by carbon nanotubes.

The development of solid-state nonlinear optical limiting (NOL) materials is crucial for advancing the practicality in the field of optical limiting. In this paper, we innovatively prepare a new solid NOL material which is spiral carbon nanotubes doped epoxy resin (SCNTs-doped ER, SER) with a simple physical mixing method, and achieve an excellent nonlinear optical limiting performance. We experimentally measured optical limiting of SER with different SCNTs concentrations (0.14, 0.28, and 0.43 mg/mL) and obtained the nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear susceptibility at the wavelength 1064 nm. Z-scan experiment results show that the SER exhibits a large nonlinear absorption coefficient (5.07 ± 0.38) × 10-9 m/W. We also measure the transmittance of the SER to evaluate its nonlinear optical limiting performance. For the SER with 0.43 mg/mL concentration, the linear transmittance and minimum transmittance with NOL effects at 1064 nm are 54.8% and 26.2%, respectively. In addition, the SER also has prominent features such as a high damage threshold and easy fabrication, indicating that the SER is a promising solid material for nonlinear optical limiting.

Frequency selection rule for the HDHF Lissajous scanning imaging with a low-voltage one axis actuated PZT scanner based on an asymmetric fiber cantilever.

Lissajous micro scanners are very attractive in compact laser scanning applications for biomedical endoscopic imaging, such as confocal microscopy, endomicroscopy or optical coherence tomography. The scanning frequencies have a very important effect on the quality of the resulting Lissajous scanning imaging. In this paper, we propose a frequency selection rule for high definition and high frame-rate (HDHF) Lissajous scanning imaging, by deriving the relationship among the scanning field of view (FOV), actuation frequencies and pixel size based on the characteristics of the scanning trajectory. The minimum sampling rate based on the proposed frequency selection rule is further discussed. We report a lead zirconate titanate piezoelectric ceramic (PZT) based Lissajous fiber scanner to achieve HDHF Lissajous scanning imaging. Based on the frequency selection rule, different frequency combinations are calculated, under which the Lissajous fiber scanner can work at the frame rate (FR) of 10 Hz, 20 Hz, 40 Hz and 52 Hz. The trajectory evolution of the Lissajous scanning at the frame rate of 10 Hz has been obtained to verify the applicability of the proposed rule. The measured resolution of the scanner is 50.8 lp/mm at the unit optical magnification, and the measured FOV at the FR of 10 Hz and 40 Hz are 1.620 mm ×1.095 mm and 0.405 mm ×0.27 mm, respectively. HDHF Lissajous scanning images of the customized spatial varying binary pattern are obtained and reconstructed at the FR of 10 Hz and 40 Hz, demonstrating the practicability of the frequency selection rule.

Full-range depth-encoded swept source polarization sensitive optical coherence tomography.

To realize the high sensitivity polarization sensitive optical coherence tomography (PS-OCT) imaging, a fiber-based full-range depth-encoded swept source PS-OCT (SS-PS-OCT) method is proposed. The two OCT images corresponding to the orthogonal polarized input light are located on the high sensitivity imaging region of the opposite sides relative to the zero optical path difference position. The full-range OCT images can be obtained by implementing the spatial phase modulation in the reference arm. The detection sensitivity of the system was measured experimentally to be 67 dB when the imaging depth approaching to 2 mm. The imaging of the biological tissue verifies that the proposed full-range depth-encoded SS-PS-OCT system has the higher detection sensitivity compared with the conventional depth encoded SS-PS-OCT system. Finally, we demonstrated the full-range high sensitivity phase retardation image of the bovine tendon and skin of human fingertip. The fiber-based full-range depth-encoded SS-PS-OCT method can realize the high sensitivity birefringence imaging in the medical diagnosis scenes with the requirements for long imaging range and high detection sensitivity.

Nonlinear optical limiting effect of porous graphene dispersions at 1064 nm.

This work presents a new, to the best of our knowledge, porous graphene dispersion in ethanol that can achieve a good nonlinear optical limiting (NOL) effect at the wavelength of 1064 nm. Using the Z-scan system, the nonlinear absorption coefficient of the porous graphene dispersion with a concentration of 0.01 mg/mL was measured as 9.69×10-9 c m/W. The NOL of the porous graphene dispersions in ethanol under three different concentrations (0.01, 0.02, and 0.03 mg/mL) were measured. Among them, the 1-cm-thick porous graphene dispersion with a concentration of 0.01 mg/mL has the best optical limiting effect, in which the linear transmittance is 76.7%, and the lowest transmittance is 24.9%. By using the pump-probe technique, we detected the formation and annihilation times of the scatter when the suspension interacts with the pump light. The analysis shows that the NOL mechanisms of the novel porous graphene dispersion are mainly nonlinear scattering and nonlinear absorption.

Local polarization properties extraction using single incident state, single-mode-fiber-based spectral domain polarization-sensitive optical coherence tomography.

We showed the local polarization properties extraction method for the single incident state, all-single-mode-fiber-based spectral domain polarization-sensitive optical coherence tomography (SD-PS-OCT) system that uses the single linear-in-wavenumber spectral camera. Polarization controllers are used in the single-mode-fiber-based SD-PS-OCT system to provide a compact structure with polarization state stability. The local polarization properties of the birefringent sample are extracted from the cumulative polarization properties iteratively. The reconstructed polarization images demonstrate the local polarization properties extraction ability of the system.

Distributed strain and temperature fast measurement in Brillouin optical time-domain reflectometry based on double-sideband modulation.

A novel distributed strain and temperature fast measurement method in Brillouin optical time-domain reflectometry (BOTDR) system based on double-sideband (DSB) modulation is proposed. The single-wavelength probe light is modulated into dual-wavelength probe light with a fixed phase difference by using carrier suppressed DSB modulation. The interaction between the Brillouin scattering signals corresponding to dual-wavelength probe light forms a Brillouin beat spectrum (BBS). The distributed temperature and strain are obtained by only measuring the peak power trace of the BBS and one of the slope power trace of the two Brillouin gain spectrum (BGS) corresponding to dual-wavelength probe light. The proposed method does not require scanning the Brillouin spectrum and does not require using optical fibers with multiple Brillouin scattering peaks as sensing fibers, and thus features fast measurement speed and wide variety of sensing fiber types. In a proof-of-concept experiment, the temperature uncertainty of 1.3 °C and the strain uncertainty of 36.3 µÎµ are respectively achieved over a 4.5-km G.657 fiber with 3 m spatial resolution and 30 s measurement time. The experimental measurement uncertainties of temperature and strain of the proposed method are almost equivalent to that of the method by using BGS scanning and special fibers.

Noise reduction in a Brillouin optical time-domain sensor by a frequency-domain feature filter.

A novel frequency-domain image processing method is proposed, to the best of our knowledge, to filter the noise from data collected by distributed optical fiber sensors based on Brillouin optical time-domain sensing (BOTDS). In the proposed method, we first divide a data image into subimages, and then we filter the noisy subimages by retaining the useful frequency information corresponding to the Lorentz-shape frequency spectrum and Brillouin frequency shift (BFS) transitions. The denoising performance improvements are verified by simulation and experiment. The performances in terms of temperature/strain measurement uncertainty, spatial resolution, and processing time achieved by the proposed filter are then compared with those by using a Gaussian filter and a nonlocal means (NLM) filter. In a proof-of-concept experiment with a 5.2 km length G657 sensing fiber, we achieve a temperature measurement uncertainty improvement of 27% compared with the results obtained by using the Gaussian filtering method. Furthermore, the processing speed of the proposed method is 22 times faster than that of the NLM filter under the same temperature measurement uncertainty.

Third-order optical nonlinearity measurements and optical limiting experiment in Tm: YAG crystal.

In this paper, we investigate the third-order nonlinearities and optical limiting effect of Tm: YAG crystal at a wavelength of 1064 nm. We experimentally measure different energy densities (6.4, 12.8, and 19.2J/cm2) and obtain the nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear susceptibility of Tm: YAG crystal. Z-scan results show that Tm: YAG crystal exhibits a large nonlinear absorption coefficient (3.34×10-9m/W) at the wavelength of 1064 nm. We also measure the transmittance of Tm: YAG crystals of three different lengths (7, 15, and 20 mm) to evaluate its nonlinear optical limiting performance. For the 20 mm Tm: YAG crystal, the maximum transmittance without optical limiting effect and minimum transmittance with nonlinear optical limiting effect at a 1064 wavelength nm are 84.2% and 47.8%, respectively, which indicates that Tm: YAG crystal may be a solid material for nonlinear optical limiting at 1064 nm.

Simultaneous measurement of temperature and acoustic impedance based on forward Brillouin scattering in LEAF.

The detection of the surrounding environment is one of the most fundamental challenges in optical fiber sensors research. In this Letter, we report two new, to the best of our knowledge, phenomena in large effective area fiber (LEAF), which are the linear dependence of the radial acoustic mode induced forward Brillouin scattering (FBS) spectral linewidth on temperature and the linear dependence of the radial acoustic mode induced FBS spectral frequency shift on acoustic impedance. By utilizing these linear relationships, we present a novel temperature and acoustic impedance simultaneous measurement method based on FBS in LEAF. With a fiber Sagnac loop structure, the obtained measurement uncertainties of temperature and acoustic impedance surrounding LEAF are 0.1°C and 0.006kg/(s⋅mm2), respectively. The corresponding measurement uncertainties in the form of relative percentage values are 0.5% and 0.4%, respectively.

Nonlinear optical limiting effect of graphene dispersions at 1064 nm.

We study the nonlinear optical limiting effect of graphene dispersions in ethanol and acetone at a wavelength of 1064 nm. The nonlinear optical limiting effect of graphene dispersion under three different linear transmittances (about 70%, 80%, and 90%), two different thicknesses (1 and 3 cm), and two different solvents (ethanol and acetone) are measured. The influences of concentration, thickness, and solvent on the nonlinear optical limiting effect of the graphene dispersion are analyzed. The experimental results show that the concentration and solution thicknesses have great influence on the optical limiting ability of graphene dispersions. The graphene dispersions with ethanol and acetone as solvents can be used to achieve excellent nonlinear optical limiting effects. The optical limiting ability of the graphene dispersion in acetone is better than that of the graphene dispersion in ethanol.

Design of photonic crystal nonlinear laser power limiter based on topological edge states and optical Kerr effect.

We propose a novel topological photonic crystal nonlinear laser power limiter based on topological edge states and optical Kerr effect. In the proposed laser power limiter, a one-dimensional photonic crystal in topological edge state allows the relatively weak signal light with a certain wavelength to pass through with high transmission, but blocks most of the intense hostile or accidental laser with the same wavelength due to the change of topological edge state generated from optical Kerr effect. Taking a 1064 nm wavelength as an example, we have designed such a nonlinear laser power limiter corresponding to the wavelength. When the optical power density is low (less than 0.12 MW/cm2), the light transmission can reach 82.54%, and the transmission can be reduced to 1.04% when the optical power density is increased to 11.66 MW/cm2. Therefore, this method provides a new promising approach to realize laser protection at the desired wavelength.

Miniaturized precalibration-based Lissajous scanning fiber probe for high speed endoscopic optical coherence tomography.

We present a miniaturized precalibration-based forward-viewing Lissajous scanning fiber probe for high speed endoscopic optical coherence tomography (OCT). The probe is based on an asymmetric fiber cantilever driven by the piezoelectric bender to realize two-dimensional (2D) Lissajous scanning. The stability and repeatability of the Lissajous scanning trajectory of the probe is tested by a position sensitive detector (PSD)-based position calibration setup. The two orthogonal resonant frequencies of the cantilever are measured to be 167.2 and 121 Hz. A 25 µm focal spot is formed at the working distance of 5 mm by the graded-index (GRIN) lens, and the field of view of the imaging probe is around ${1.5}\;{\rm mm} \times {1.5}\;{\rm mm}$1.5mm×1.5mm. The probe is fully packaged in a hypodermic tube for endoscopic imaging. The total rigid length and outer diameter are 35 mm and 3.5 mm, respectively. The probe is incorporated in a 50 KHz swept source OCT system with the axial resolution of 14 µm, and its imaging performance is validated by the 2D en face and 3D volumetric OCT imaging of the phantom and the biological tissue.

Optical limiting effect of C70 solution at 1064 nm.

In this paper, we investigate the optical limiting effect of C70 solution at a wavelength of 1064 nm. We experimentally measured the transmittance of C70 solution under three different concentrations (0.25, 0.5, and 1 mmol/L), three different solution thicknesses (5, 10, and 20 mm), and two different solvents (toluene and xylene) and obtained the values of absorption cross sections and relaxation times in the five-level absorption model of C70 solution. The influences of concentration, thickness, and solvent on the optical limiting effect of the C70 solution are analyzed. We also measured transmittance of C60 solution under the same conditions and compared the results with those of C70 solution. The experimental results show that concentration and solution thicknesses have great influence on the optical limiting ability of C70 solution. The optical limiting effect of C70 solution is better than that of C60 solution at low concentration and worse than that of C60 solution at high concentration.

Nontuberculous Mycobacteria Infection After Autologous Fat Grafting for Cosmetic Breast Augmentation.

BACKGROUND: Autologous fat grafting has been widely applied in cosmetic breast augmentation in recent years. However, nontuberculous mycobacteria infection, as one of the multiple complications described in the literature, has been less well discussed. OBJECTIVE: The aims of the study were to report 5 cases of nontuberculous mycobacteria infection after autologous fat injection for the cosmetic breast augmentation and to explore its causes. METHODS: In this noncomparative, retrospective, and interventional case series, we identified 5 patients with nontuberculous mycobacteria infection. All patients had a history of previous autologous fat injection into the breast for cosmetic purpose, performed in different plastic facilities. RESULTS: Five patients developed nontuberculous mycobacteria infection after autologous fat injection for cosmetic breast augmentation and came to our group for treatment. Grafted fat removal through multiple debridement and long-term intravenous and oral antibiotic therapy were required in our cases. CONCLUSIONS: The number of nontuberculous mycobacteria infection after autologous fat injection into the breast is increasing. Surgeons should be aware of the complication, which rarely manifests during the procedure itself. Strict aseptic principles should be obeyed throughout the surgery.

Design of a hybrid on-chip waveguide with giant backward stimulated Brillouin scattering.

On-chip waveguides on insulator with high stimulated Brillouin gain have wide potential application prospects in the field of nanophotonic structures. We propose a new on-chip hybrid silicon-chalcogenide slot waveguide structure consisting of a chalcogenide As2S3 rectangle core with an air slot and a wrapping layer of silicon. In the new hybrid waveguide, the high radiation pressure and electrostriction force, determined by pump and Stokes optical waves, and the acoustic displacement, determined by acoustic wave, can be achieved by adjusting the dimensions of rectangle core, the thickness of wrapping layers and the width of air slot. Therefore, a strong optomechanical coupling between high radiation pressure and transverse acoustic displacement will be generated. In such a way, a nonlinear gain for backward stimulated Brillouin scattering can be theoretically achieved with a high gain coefficient of 2.88×104 W-1m-1. The enhanced gain coefficient in the proposed waveguide is around 2.4 times as that in an on-chip silicon-chalcogenide hybrid slot waveguide on insulator without the wrapping layer. The Stokes amplification reaches 85.7 dB with the waveguide length of 2.5 cm. Therefore, this method provides a new idea to design nanophotonic waveguides for giant backward stimulated Brillouin scattering.

Trench-assisted multimode fiber used in Brillouin optical time domain sensors.

The trench-assisted multimode fiber TA-OM4 is used as a sensing fiber to achieve a higher signal-to-noise (SNR) in Brillouin optical time domain sensors, due to its high stimulated Brillouin threshold and high modulation instability threshold. The Brillouin gain spectrum (BGS), stimulated Brillouin scattering (SBS) and modulation instability (MI) thresholds of TA-OM4 at 1550 nm are characterized and demonstrated theoretically and experimentally. The SNR improvements of TA-OM4 over G655 and G657 at the end of 15.5 km-long fibers, which are respectively 1.1 dB and 2.3 dB are verified experimentally. We achieve a temperature uncertainty of 0.3°C in 15.5 km TA-OM4 with 5 m spatial resolution by use of a Brillouin optical time domain reflectometry (BOTDR) sensor. The good bend resistance and high SBS and MI thresholds of TA-OM4 with better SNR improvements over SMFs works at the extreme bending conditions.

Z-scan measurements of nonlinear refraction and absorption for aluminum-doped zinc oxide thin film.

In this paper, we investigate third-order nonlinearities in aluminum-doped zinc oxide (AZO) thin film by the Z-scan method at a wavelength of 1064 nm. We carried out experiments under different pulse widths (26 ns, 62 ns, and 101 ns) and energy densities (5.3 J/cm2, 10.6 J/cm2, and 15.9 J/cm2) and obtained the nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear susceptibility of AZO thin film. The Z-scan results show that AZO thin film exhibits a larger nonlinear refractive index (-5.48×10-13 m2/W) and third-order nonlinear susceptibility (1.97×10-6 esu) than those of some other semiconductor materials at the wavelength of 1064 nm. This suggests that AZO thin film may be a very promising nonlinear medium for nonlinear photonics applications in the tens of nanoseconds regime.

Research on tumorigenicity of cinnamaldehyde in melanoma cell lines and its mechanism.

Melanoma is a highly malignant tumor originating from melanocytes. This disease is characterized by inconspicuous onset, high malignancy, and poor prognosis. The aim of this study is to explore the effect of cinnamaldehyde on melanoma tumorigenicity and its mechanism. Melanoma cells were subcutaneously injected into a nude mouse to establish the tumour model. A comparison was made for the difference in formation and growth of melanoma cell tumor between normal saline and cinnamaldehyde. A comparison was also made for the number of new vessels between the normal saline group (the control group) and the cinnamaldehyde group (the experimental group) through immumohistochemical staining. The western blot was used to detect the difference in expression levels of vascularization related proteins. The results indicated that the volume of tumors formed and the number of new vessels in melanoma cells of the cinnamaldehyde group decreased significantly compared with those in the cells of the normal saline group. A further study indicated that the expression of hypoxia-inducible factor-a (HIF-α) and vascular endothelial growth factor (VEGF) in the melanoma of the cinnamaldehyde group decreased significantly. In conclusion, cinnamaldehyde plays a certain role in inhibiting the occurrence and progression of melanoma and its action mechanism may be manifested by inhibiting expression of VEGF and HIF-α, thus blood vessel simulation and formation of new blood vessels of melanoma cells, and growth of tumors accordingly.

Quantitative assessment of the association between XPC Lys939Gln polymorphism and cutaneous melanoma risk.

Previous studies evaluating the association between XPC Lys939Gln polymorphism and cutaneous melanoma risk reported conflicting findings. We searched PubMed and Embase databases up to May 16, 2013 to identify eligible studies on the association between XPC Lys939Gln polymorphism and cutaneous melanoma risk. Finally, a total of seven case-control studies including 3,971 cases of cutaneous melanoma and 5,873 controls were included in the meta-analysis. Statistical analysis was performed with STATA version 11.0. Odds ratios (ORs) with 95 % confidence intervals (95 % CIs) were used to assess the strength of the association. Overall, there was no association between XPC Lys939Gln polymorphism and cutaneous melanoma risk under all five genetic models (Gln vs. Lys: OR = 1.11, 95 % CI = 0.98-1.26, P = 0.10; GlnGln vs. LysLys: OR = 1.26, 95 % CI = 0.98-1.61, P = 0.07; LysGln vs. LysLys: OR = 1.04, 95 % CI = 0.88-1.22, P = 0.64; GlnGln/LysGln vs. LysLys: OR = 1.10, 95 % CI = 0.92-1.31, P = 0.29; GlnGln vs. LysLys/LysGln: OR = 1.19, 95 % CI = 0.99-1.43, P = 0.06). Subgroup analysis in Caucasians showed that there was an obvious association between XPC Lys939Gln polymorphism and cutaneous melanoma risk in Caucasians (GlnGln vs. LysLys/LysGln: OR = 1.12, 95 % CI = 1.00-1.25, P = 0.05). Sensitivity analysis by omitting one study in turns showed that the significance of the pooled ORs was not stable. In addition, there was some evidence of publication bias in the meta-analysis, and meta-analyses of the studies with large sample size did not find the obvious association between XPC Lys939Gln polymorphism and cutaneous melanoma risk in Caucasians. Therefore, there is little evidence for the association between XPC Lys939Gln polymorphism and cutaneous melanoma risk.

In vitro modeling of recurrent Dermatofibrosarcoma Protuberans: Assessment of 5-aminolevulinic acid photodynamic therapy efficacy.

BACKGROUND: Dermatofibrosarcoma Protuberans (DFSP) is a rare, low-grade malignant tumor of the dermis with a high recurrence rate post-surgery. Current treatments, including surgery, radiotherapy, and targeted therapy, have limitations. Photodynamic therapy (PDT) with 5-aminolevulinic acid (5-ALA) is a promising non-invasive approach, but its efficacy in DFSP treatment remains underexplored. METHODS: This study aimed to evaluate the anti-tumor efficacy of 5-ALA PDT using an in vitro model derived from a recurrent DFSP patient. The cells were treated with varying concentrations of 5-ALA and exposed to red light, followed by assessments of cell viability, proliferation, apoptosis, migration, invasion, angiogenesis, and expression of DFSP-related genes and proteins. RESULTS: 5-ALA PDT significantly reduced DFSP cell viability in a dose-dependent manner and induced apoptosis. It also effectively inhibited cell proliferation, migration, and invasion, as well as suppressed angiogenic activity in conditioned media. Furthermore, 5-ALA PDT downregulated the expression of COL1A1 and PDGFRB, key genes in DFSP pathogenesis. CONCLUSIONS: The findings provide the first evidence of 5-ALA PDT's in vitro anti-tumor efficacy against DFSP, suggesting its potential as a novel therapeutic approach for DFSP. Further studies are warranted to explore the clinical utility of 5-ALA PDT in preventing DFSP recurrence.