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This study aims to monitor and assess the penetration and accumulation of titanium dioxide nanoparticles ( $TiO_{2}$ NPs) (25 nm and 60 nm) and the penetration of the $TiO_{2}$ NPs assisted by diode laser radiation (LR) in human normal endometrium (NE) and uterine leiomyoma (UL) tissues. In the 210 min ex vivo experiments, optical coherence tomography (OCT) and diffuse reflectance (DR) spectral measurement were used to study the changes in optical properties of tissues after $TiO_{2}$ NPs suspension administering. The results show that $TiO_{2}$ NPs make the OCT signal intensities and DR spectra of both NE and UL tissues increase with time, and larger NPs produce greater signal enhancement. In addition, there are significant differences between NE and UL tissues in terms of the values of attenuation coefficients. The experiment results indicate that the same size of the NPs penetrate faster in UL tissues than that in NE tissues, and 25 nm $TiO_{2}$ NPs allow larger penetration depth than 60 nm $TiO_{2}$ NPs in tissues. LR can remarkably increase the penetration of $TiO_{2}$ NPs in two types of tissues, especially in UL tissues. Analysis of attenuation coefficients and reflectance intensity reveals that the accumulation of the $TiO_{2}$ NPs in NE and UL tissues has great influence on the tissue optical properties.

The aberrations in microscope system and polarization of the input light beam directly determine the quality of the depletion patterns, which mainly affect the resolution improvement of Stimulated Emission Depletion (STED) microscopy. In the paper, the influences of combining Seidel aberrations and light polarization on the depletion patterns were analyzed comprehensively. And a comparative study about the effects on the resolution was conducted. Simulation results show that the right-handed circularly polarization is the best choice for the depletion patterns in the same condition. And the serious aberration will influence the realization of super-resolution. This study could provide a reliable theoretical basis for a realization of a STED super-resolution system with less aberration.

Mast cell (MC) degranulation is an important step in the healing process. In this study, silver‐nanoparticles‐based surface‐enhanced Raman spectroscopy (SERS) was used to investigate the spectral characteristics of degranulation of MCs activated by low‐intensity laser. The significant spectral changes, such as Raman peak intensities, suggested the concentration variation of some degranulated substances. The Raman intensity ratio of 799–554 cm (−) (1) could be used as a potential internal indicator for the degranulation degree of MCs. Principal component analysis (PCA) was employed to reduce the high dimension of spectra into a few principal components (PCs) while retaining the most diagnostically significant information for sample differentiation. Using the diagnostically significant PC scores (P

Optical whispering-gallery-mode (WGM) microresonator-based sensors with high sensitivity and low detection limit down to single unlabeled biomolecules show high potential for disease diagnosis and clinical application. However, most WGM microresonator-based sensors, which are packed in a microfluidic cell, are a &ldquo, closed&rdquo, sensing configuration that prevents changing and sensing the surrounding liquid refractive index (RI) of the microresonator immediately. Here, we present an &ldquo, open&rdquo, sensing configuration in which the WGM microdisk laser is directly covered by a water droplet and pumped by a water-immersion-objective (WIO). This allows monitoring the chemical reaction progress in the water droplet by tracking the laser wavelength. A proof-of-concept demonstration of chemical sensor is performed by observing the process of salt dissolution in water and diffusion of two droplets with different RI. This WIO pumped sensing configuration provides a path towards an on-chip chemical sensor for studying chemical reaction kinetics in real time.

A novel series of light-harvesting dendrimer zinc-phthalocyanines chromophores labeled-single-wall carbon nanotubes (SWNTs) nanoparticles, in which 0–2 generations dendrimer zinc phthalocyanines covalently linked with SWNTs using either ethylenediamine or hexamethylenediamine as the space linkers were prepared. The structures and morphologies of these nanoconjugates were comprehensively characterized by Raman spectroscopy, transmission electron microscopy and thermal gravimetric analysis methods. Their photophysical properties were investigated by fluorescence and time-resolved spectroscopic methods. The photoinduced intramolecular electron transfer occurred from phthalocyanines (donors) to SWNTs (acceptors). Besides, the electron transfer exchange rates and exchange efficacies between the dendritic phthalocyanines and single-wall carbon nanotubes increased as the length of spacer linker decreased, or as the dendritic generation increased. Cyclic voltammetry (CV) method further confirmed thermodynamics possibility of the electron transfer from phthalocyanines to single-wall carbon nanotubes. These new nanoconjugates are fundamentally important due to the synergy effects of both carbon nanotubes and dendrimer phthalocyanines, which may find potential applications in the fields of drug delivery, biological labeling, or others.

Liquid-assisted hard tissue ablation by infrared lasers has extensive clinical application. However, detailed studies are still needed to explore the underlying mechanism. In the present study, the dynamic process of bubble evolution induced by Ho:YAG laser under water without and with bone tissue at different thickness layer were studied, as well as its effects on hard tissue ablation. The results showed that the Ho:YAG laser was capable of ablating hard bone tissue effectively in underwater conditions. The penetration of Ho:YAG laser can be significantly increased up to about 4 mm with the assistance of bubble. The hydrokinetic forces associated with the bubble not only contributed to reducing the thermal injury to peripheral tissue, but also enhanced the ablation efficiency and improve the ablation crater morphology. The data also presented some clues to optimal selection of irradiation parameters and provided additional knowledge of the bubble-assisted hard tissue ablation mechanism.

A hybrid microcavity based on the liquid-metal-filled silica microbubble is experimentally demonstrated, which supports both plasmonic and optical whispering gallery modes. The high quality (Q)-factor plasmonic mode of liquid metal is demonstrated via controlling the polarization of the probe laser as well as changing the liquids in the microbubble. Additionally, we reveal an unconventional Q-factor enhancement effect in the bottle microresonator. The liquid metal (mercury) could dissolve various metals and solids, meriting the optofluidic type of sensing. Combining the two kinds of high-Q resonances in the hybrid microcavity, we could probe the optical, mechanical, and thermal properties of solvents in liquid metal, providing a unique experimental platform for realizing multi-parameter optical sensing and making the detection and identification of metal and alloy possible.

An optofluidic microbubble Fabry–Pérot (OMBFP) cavity was investigated. In contrast to plane-plane FP (PPFP) cavities, the optical mode confinement and stability in an OMBFP were significantly enhanced. The optical properties of the OMBFP cavity, including the quality (Q) factor, effective mode area, mode distribution as a function of the core refractive index, microbubble position, and mirror tilt angle, were investigated systematically using the finite element method. In optofluidic lasing experiments, a low lasing threshold of 1.25 µJ/mm2, which was one order magnitude lower than that of the PPFP, was achieved owing to improved modal lateral confinement. Since the microbubble acts as a micro-lens and microfluidic channel in the parallel FP cavity, mode selection and cell-dye laser were easily realized in the OMBFP cavity.

Reduced graphene oxide is utilized as a FRET probe acceptor to quench the fluorescent donor emission. Compared with control group, the fluorescence intensity increased 6.59 times, indicating the probe is promising for detecting trypsin activity.

We investigate a hybrid Fourier-Continuation (FC) method (Bruno and Lyon, J Comput Phys 229:2009---2033, 2010) and fifth order characteristic-wise weighted essentially non-oscillatory (WENO) finite difference scheme for solving system of hyperbolic conservation laws on a uniformly discretized Cartesian domain. The smoothness of the solution is measured by the high order multi-resolution algorithm by Harten (J Comput Phys 49:357---393, 1983) at each grid point in a single-domain framework (Costa and Don, J Comput Appl Math 204(2):209---218, 2007) (Hybrid), as opposed to each subdomain in a multi-domain framework (Costa et al., J Comput Phys 224(2):970---991, 2007; Shahbazi et al., J Comput Phys 230:8779---8796, 2011). The Hybrid scheme conjugates a high order shock-capturing WENO-Z5 (nonlinear) scheme (Borges et al., J Comput Phys 227:3101---3211, 2008) in non-smooth WENO stencils with an essentially non-dissipative and non-dispersive FC (linear) method in smooth FC stencils, yielding a high fidelity scheme for applications containing both discontinuous and complex smooth structures. Several critical and unique numerical issues in an accurate and efficient implementation (such as reasonable choice of parameters, singular value decomposition, fast Fourier transform, symmetry preservation, and overlap zone) of the FC method, due to a dynamic spatial and temporal change in the size of data length in smooth FC stencils in a single-domain framework, will be illustrated and addressed. The accuracy and efficiency of the Hybrid scheme in solving one and two dimensional system of hyperbolic conservation laws is demonstrated with several classical examples of shocked flow, such as the one dimensional Riemann initial value problems (123, Sod and Lax), the Mach 3 shock---entropy wave interaction problem with a small entropy sinusoidal perturbation, the Mach 3 shock---density wave interaction problem, and the two dimensional Mach 10 double Mach reflection problem. For a sufficiently large problem size, a factor of almost two has been observed in the speedup of the Hybrid scheme over the WENO-Z5 scheme.

We evaluate the ablation thresholds of Er:YAG and Er,Cr:YSGG laser for enamel and dentin. A total of 140 dental slices is evenly divided into two groups: the dentin group and the enamel group. Dental tissues are irradiated with either an Er:YAG laser or an Er,Cr:YSGG laser with pulse widths in the order of 100 μs. The laser fluence is increased gradually until the ablation crater is formed. The laser ablation threshold is calculated using probit analysis. The ablation thresholds of the Er:YAG laser for dentin and enamel range from 2.88 to 3.36 J/cm2 and from 2.94 to 3.8 J/cm2, respectively, and the ablation thresholds of the Er,Cr:YSGG laser for dentin and enamel range from 2.92 to 4.2 J/cm2 and from 4.93 to 5.66 J/cm2, respectively.

Liquid-assisted hard biotissue ablation with the pulsed lasers takes advantages in precision and compatibility than mechanical tools in traditional surgery. The objective of this study was to monitor the dynamic process of the cavitation bubble evolution induced by Ho:YAG laser under water and identify the opening time of channel formation between the fiber tip to the target tissue surface. A free-running Ho:YAG laser was used in the experiment. The wavelength was 2.1 μm with a pulse duration of 350 us and pulse energy varied from 500 mJ to 2000 mJ. The high-speed camera (PCO. dimax, Germany, PCO) applied to monitor the whole ablation process was setting at a frame rate of 52000 frames/s. The results showed that the cavitation bubble induced by laser energy experienced an oscillation process including occurrence, expansion, contraction and subsequent collapse. A channel connected the fiber tip and target tissue surface was formed during the dynamic process which allowed the following pulse energy transmitted through the channel with a relative low absorption and directly interacted with the target tissue. The beginning time of channel formation, as well as the duration of channel opening, as functions of incident laser energy were also presented. A micro-explosion was observed near the tissue surface during the bubble collapse, which may contribute to produce a clean cut, reduce the thermal injury and improve the morphology of ablation crater.

Microlasers based on high-Q whispering-gallery-mode (WGM) resonances are promising low-threshold laser sources for bio-sensing and imaging applications. In this talk, we demonstrate a cost effective approach to obtain size-controllable polymer microspheres, which can be served as good WGM microcavities. By injecting SU-8 solution into low-refractiveindex UV polymer, self-assembled spherical droplet with smooth surface can be created inside the elastic medium and then solidified by UV exposure. The size of the microspheres can be tuned from several to hundreds of microns. WGM Lasing has been achieved by optically pumping the dye-doped microspheres with ns lasers. Experimental results show that the microsphere lasers have high quality factors and low lasing thresholds. The self-assembled dye-doped polymer microspheres would provide an excellent platform for the micro-laser sources in on-chip biosensing and imaging systems.

Simultaneous spectral unmixing of excitation and emission spectra (ExEm unmixing) has the inherent ability to resolve donor emission, fluorescence resonance energy transfer (FRET)-sensitized acceptor emission and directly excited acceptor emission. We here develop an ExEm unmixing-based quantitative FRET measurement method (EES-FRET) independent of excitation intensity and detector parameter setting. The ratio factor (rK), predetermined using a donor-acceptor tandem construct, of total acceptor absorption to total donor absorption in excitation wavelengths used is introduced for determining the concentration ratio of acceptor to donor. We implemented EES-FRET method on a wide-field microscope to image living cells expressing tandem FRET constructs with different donor-acceptor stoichiometry.

We report a single-mode dye-doped polymer microbottle resonator (MBR) laser. The selective single-mode lasing from different order whispering gallery modes is achieved by precisely controlling the axial and radial coupling position between a tapered nanofiber and an MBR, respectively. The side-mode suppression ratio is above 20 dB. By doping different fluorescence dyes into the MBR, single-mode lasers at various colors are demonstrated.

The use of erbium,chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser with a wavelength of 2.78 μm for hard bone tissue ablation was evaluated. The surface morphology and microstructure changes of bone tissue treated with Er,Cr:YSGG were analyzed as compared to those treated with diamond drill. The influence of fluence on ablation rate and ablation efficiency as well as microstructure was also examined. The results show that Er,Cr:YSGG laser can perform bone perforation that is more fine and presented a lot of unique advantages compared to traditional methods. An approximately linear relationship was observed between the ablation rate/ablation efficiency and radiant exposure. Increasing the radiant exposure irradiated on bone tissue will produce stronger thermal injury around the crater and result in microstructure changing.

The influence of scanning speed on hard bone tissue ablation is studied with a 10.6-\mum laser. The groove morphology and the thermal damage created in bovine shank bone by pulsed CO2 laser are examined as a function of incident fluence by optical microscope following standard histological processing. The results show that ablation groove width, depth and ablation volume, as well as the zone of thermal injury, increase gradually with incident fluence. As compared to the result for high scanning speed, the lower scanning speed always produces larger ablation volume but thicker zone of thermal injury. It is evident that scanning speed plays an important role in the ablation process. In clinical applications, it is important to select appropriate scanning speed to obtain both high ablation rates and minimal thermal injury.

We combine reflectance confocal microscopy (RCM) with multiphoton microscopy (MPM) to image rat esophagus. The two imaging modalities allow detection of layered–resolved complementary information from esophagus. In the keratinizing layer, the keratinocytes boundaries can be characterized by RCM, while the keratinocytes cytoplasm (keratin) can be further imaged by multiphoton autofluorescence signal. In the epithelium, the epithelial cellular boundaries and nucleus can be detected by RCM, and MPM can be used for imaging epithelial cell cytoplasm and monitoring metabolic state of epithelium. In the stroma, multiphoton autofluorescence signal is used to image elastin and second harmonic generation signal is utilized to detect collagen, while RCM is used to determine the optical property of stroma. Overall, these results suggest that the combination of RCM and MPM has potential to provide more important and comprehensive information for early diagnosis of esophageal cancer.

We proposed and theoretically investigated a hybrid plasmonics waveguide consisting of a tiptilted quadrate nanowire, which was embedded in a low-permittivity dielectric and placed on a metal substrate with a small gap distance. Due to the corner effect, the hybrid mode with extremely local field enhancement has the long propagation length and strong coupling strength between the dielectric nanowire and metal. By employing the simulations with different geometric parameters, the proposed waveguide can obtain better performances than the previous hybrid plasmonics waveguide, particularly in the subwavelength confinement (as small as λ2/1600), long-range propagation (millimeter range), and optical trapping forces (2.12 pN/W). The use of a naturally dielectric wedge tip of quadrate nanowire that can be chemically synthesized provides an efficient approach to circumvent the fabrication difficulty of shape wedge tips. The present structure provides an excellent platform for nanophotonic waveguides, nanolasers, nanoscale optical tweezers, and biosensing.

The objective is to investigate the effects of two different sized (60 and 100 nm) titanium dioxide (TiO2) nanoparticles (NPs) penetration and accumulation in in vitro human normal lung (NL) tissue, lung squamous cell carcinoma (LSCC) tissue, and 650-nm diode laser-pretreated tissue on their optical properties studied with optical coherence tomography monitoring and diffuse reflectance (DR) spectra measurement. As with TiO2 NPs penetrating into the tissues, the intensities of DR of the samples increase, and then the enhancements of DR and the attenuation coefficients of the tissues were quantitatively calculated. The results suggest that 650-nm diode laser pretreatment increased the amounts of TiO2 NPs penetration and accumulation in NL and LSCC tissues, and the tissue optical properties were significantly influenced by accumulation of TiO2 NPs.

Liquid-assisted laser ablation has been investigated in laser surface cleaning, laser osteotomy, and dental tissue ablation. However, the actual mechanism of liquid-assisted ablation is not clear yet. The purpose of this study was to investigate the influence of liquid medium with different absorption and the liquid thickness on laser ablation efficiency. A pulsed CO 2 laser was employed to ablate bovine bone tibia under liquid layer which varied from 0.6 mm to 2 mm. The applied pulse power level was set at 5 w and each crater was produced with six laser pulses. The results showed that the ablation cross-section area produced with various levels of pure water thickness (0.6, 0.8, 1 and 2 mm)were lower than under ink, and the ablation depth gradually decreased as the water layer becoming thicker. The biggest cross-section area in liquid thickness of ink was 0.8mm, but as the layer thicker than 0.8 mm the ablation depth decreased suddenly. There was thermal damage seen on samples in all of the groups, but less in pure water.

Several studies have demonstrated that laser-induced hard tissue ablation effects can be enhanced by applying an additional water-layer on tissue surface. However, the related mechanism has not yet been presented clearly. In this paper, the influence of static pressure on dynamic characteristics of cavitation induced by pulse laser in liquid and its effect on bovine shank bone ablation were investigated. The laser source is fiber-guided free-running Ho:YAG laser with wavelength of 2080 nm, pulse duration of 350 μs and energy of 1600 mJ. The tissue samples were immerged in pure water at different depths of 11, 16, 21, 26 and 31 mm. The working distance between the fiber tip and tissue surface was fixed at 1 mm for all studies. The dynamic interaction between laser, water and tissue were recorded by high-speed camera, and the morphological changes of bone tissue were assessed by stereomicroscope and OCT. The results showed that many times expansion and collapse of bubble were observed, more than four pulsation periods were accurately achieved with the most energy deposited in the first period and the bubble became more and more irregular in shape. The longitudinal length (7.49--6.74 mm) and transverse width (6.69--6.08 mm) of bubble were slowly decreased while volume (0.0586--0.0124 mm 3 ) of ablation craters were drastically reduced, with static pressure increasing. The results also presented that the water-layer on hard-tissue surface can not only reduce thermal injury but also improve lubricity of craters, although the water-layer reduced ablation efficiency.

Low-level lasers have been used to relieve pain in clinical for many years. But the mechanism is not fully clear. In animal models, nitric oxide (NO) has been reported involving in the transmission and modulation of nociceptive signals. So the objective of this study was to establish whether low-level laser with different fluence could stimulate the production of nitric oxide synthese (NOS), which produces NO in cultured primary dorsal root ganglion neurons (DRG neurons). The primary DRG neurons were isolated from healthy Sprague Dawley rats (8-12 weeks of age) and spread on 35 mm culture dishes specially used for confocal microscopy. 24 hours after spreading, cells were irradiated with 658 nm laser for two consecutive days at the energy density of 20, 40, 60 and 80 mJ·cm -2 respectively. Control groups were not exposed to the laser, but were kept under the same conditions as the irradiated ones. The synthesis of NOS after laser irradiation was detected by immunofluorescence assay, and the changes of NOS were evaluated using confocal microscopy and Image J software. The results showed that all the laser fluence could promote the production of NOS in DRG neurons, especially the 60 mJ·cm -2 . These results demonstrated that low-level laser irradiation could modify protein synthesis in a dose- or fluence- dependent manner, and indicated that low-level laser irradiation might achieve the analgesic effect through modulation of NO production.

The gas NO is a ubiquitous intercellular messenger that modulates a wide range of physiological and pathophysiological functions. But few studies were made to study the role of NO in the Ca 2+ release in dorsal root ganglion (DRG) neurons by confocal microscopy. Thus the objective of this study was to assess if NO has a role in Ca 2+ signaling in DRG neurons using confocal microscopy combined with special fluorescence probe Fluo-3/AM. A 100 μM concentration of the NO donors (Sodium Nitroprusside, Dihydrate, SNP) and NO synthase inhibitor (NG-Monomethyl-L-arginine, Monoacetate salt, L-NMMA) was used in the study. Results showed that the fluorescence intensity increased rapidly after injecting SNP, which indicated that SNP could enhance intracellular Ca 2+ release. And the fluorescence intensity shrank gradually with time and kept at a low level for quite a long period after loading with L-NMMA which indicated that L-NMMA could block intracellular Ca 2+ release. All these results demonstrated that NO was involved in the regulation of intracellular Ca 2+ release in the DRG neurons.

This work reports on the measurement of optical properties from nine normal and cancerous human esophageal stroma pairs using reflectance-based confocal microscopy. It was found that the scattering coefficient of cancerous stroma is significantly lower than that of normal stroma. The results suggest that the decreased scattering in cancerous stroma may provide a possible indicator for differentiating normal and cancerous stroma.

Light dose plays an important role in the non-ablative photorejuvenation based on the theory of selective photothermolysis. However, present techniques for determining the light dose in clinical practice are still not accurate enough. We present a new system which monitors the skin tissue response during the laser irradiation in photorejuvenation by measuring the change of the total attenuation coefficient. We also investigate the relationship between the total attenuation coefficient and the energy density, pulse duration, and pulse repetition. In this procedure, the total attenuation coefficient decreases when the light dose increases and the reduction dependes on the light dose. These experimental results indicate that the new system would be a potential tool for accurate light dose determination.

The feasibility of measuring crater geometries by use of optical coherence tomography (OCT) is examined. Bovine shank bone on a motorized translation stage with a motion velocity of 3 mm/s is ablated with a pulsed CO2 laser in vitro. The laser pulse repetition rate is 60 Hz and the spot size on the tissue surface is 0.5 mm. Crater geometries are evaluated immediately by both OCT and histology methods after laser irradiation. The results reveal that OCT is capable of measuring crater geometries rapidly and noninvasively as compared to histology. There are good correlation and agreement between crater depth estimates obtained by two techniques, whereas there exists distinct difference between crater width estimates when the carbonization at the sides of craters is not removed.

In clinical practice, laser ablation usually works under liquid environment such as water, blood or their mixture. Laser-induced vapor bubble or bubble formation and its consequent dynamics were believed to have important influence on tissue ablation. In the paper, the dynamic process of vapor bubble formation and consequently collapse induced by pulsed Ho:YAG laser in static water was investigated by using high-speed camera. The results showed that vapor channel / bubble can be produced with pulsed Ho:YAG laser, and the whole dynamic process of vapor bubble formation, pulsation and consequently collapse can be monitored by using high-speed camera. The dynamic characteristics of vapor bubble, such as pulsation period, the maximum depth and width were determined. The dependence of above dynamic parameters on incident radiant exposure was also presented. Based on which, the influence of vapor bubble on hard tissue ablation was discussed.

Adenosine exerts a key role in analgesia. In the present study, adenosine-induced Ca(2+) responses were revealed by using confocal microscopy imaging in the rat dorsal root ganglia (DRG) neurons in vitro. Our results showed that adenosine could evoke increases in the intracellular Ca(2+) concentration in the DRG neurons. In addition, by application of selective receptor antagonists, two types of receptors, A1R and A3R, were identified to be involved in the adenosine-induced Ca(2+) release from intracellular stores in neurons. Altogether, these results suggest that confocal microscopy imaging combined with fluorescent dyes could help to detect the analgesic-induced ion signaling in single cell.

Far-field fluorescence microscopy has made great progress in the spatial resolution, limited by light diffraction, since the super-resolution imaging technology appeared. And stimulated emission depletion (STED) microscopy and structured illumination microscopy (SIM) can be grouped into one class of the super-resolution imaging technology, which use pattern illumination strategy to circumvent the diffraction limit. We simulated the images of the beads of SIM imaging, the intensity distribution of STED excitation light and depletion light in order to observe effects of the polarized light on imaging quality. Compared to fixed linear polarization, circularly polarized light is more suitable for SIM on reconstructed image. And right-handed circular polarization (CP) light is more appropriate for both the excitation and depletion light in STED system. Therefore the right-handed CP light would be the best candidate when the SIM and STED are combined into one microscope. Good understanding of the polarization will provide a reference for the patterned illumination experiment to achieve better resolution and better image quality.

Optical microscopy allows us to observe the biological structures and processes within living cells. However, the spatial resolution of the optical microscopy is limited to about half of the wavelength by the light diffraction. Structured illumination microscopy (SIM), a type of new emerging super-resolution microscopy, doubles the spatial resolution by illuminating the specimen with a patterned light, and the sample and light source requirements of SIM are not as strict as the other super-resolution microscopy. In addition, SIM is easier to combine with the other imaging techniques to improve their imaging resolution, leading to the developments of diverse types of SIM. SIM has great potential to meet the various requirements of living cells imaging. Here, we review the recent developments of SIM and its combination with other imaging techniques.

Water plays an important role in laser ablation. There are two main interpretations of laser-water interaction: hydrokinetic effect and vapor phenomenon. The two explanations are reasonable in some way, but they can’t explain the mechanism of laser-water interaction completely. In this study, the dynamic process of vapor channel formation induced by pulsed CO 2 laser in static water layer was monitored by high-speed camera. The wavelength of pulsed CO 2 laser is 10.64 um, and pulse repetition rate is 60 Hz. The laser power ranged from 1 to 7 W with a step of 0.5 W. The frame rate of high-speed camera used in the experiment was 80025 fps. Based on high-speed camera pictures, the dynamic process of vapor channel formation was examined, and the threshold of vapor channel formation, pulsation period, the volume, the maximum depth and corresponding width of vapor channel were determined. The results showed that the threshold of vapor channel formation was about 2.5 W. Moreover, pulsation period, the maximum depth and corresponding width of vapor channel increased with the increasing of the laser power.

The objective of this study was to evaluate the influence of different thickness of water layer on microstructure changes of bone tissue irradiated by pulse CO2 laser. Bovine shank bone was divided into four groups randomly for laser irradiation: without water layer and with a static water layer applied to target tissue surface at thickness of 0.4, 0.8 and 1.2 mm. The wavelength used in the study was 10.64 μm with pulse repetition rate of 60 Hz. The energy density was 50 J/cm2 and the beam diameter of about 400 μm. The microstructure changes of ablation grooves were examined and compared with scanning electron microscope (SEM). It shows that the addition of water layer applied to target tissue surface actually mediated the interaction of laser with tissue and took an important role in microstructure changes. There was a critical thickness of water layer for a given radiant exposure to obtain regular cut profile with sharp-cut edge and smooth inner wall surface

The theory of hard tissue ablation reported for IR lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The microexplosion of the water is the cause of tissue fragments being blasted from hard tissue. The aim of this study is to evaluate the influence of the interdependence of water layer thickness and incident radiant exposure on ablation performance. A total of 282 specimens of bovine shank bone were irradiated with a pulse CO(2) laser. Irradiation was carried out in groups: without a water layer and with a static water layer of thickness ranging from 0.2 to 1.2 mm. Each group was subdivided into five subgroups for different radiant exposures ranging from 18 to 84 J/cm(2), respectively. The incision geometry, surface morphology, and microstructure of the cut walls as well as thermal injury were examined as a function of the water layer thickness at different radiant exposures. Our results demonstrate that the additional water layer is actually a mediator of laser-tissue interaction. There exists a critical thickness of water layer for a given radiant exposure, at which the additional water layer plays multiple roles, not only acting as a cleaner to produce a clean cut but also as a coolant to prevent bone heating and reduce thermal injury, but also helping to improve the regularity of the cut shape, smooth the cut surface, and enhance ablation rate and efficiency. The results suggest that desired ablation results depend on optimal selection of both water layer thickness and radiant exposure.

The purpose of this study was to evaluate the shear bond strength of a self-etch adhesive to caries-affected dentin after caries removal by erbium: yttrium, aluminum garnet (Er:YAG) laser and analyze the resin-dentin interface. The caries-infected dentin of human molars were removed by Er:YAG laser with energy density of 20 J/cm 2 and pulse repetition rate of 20 Hz. The conventional bur was used as control group. After bonding procedures, specimens were subjected to shear bond strength test and the adhesive interface was examined by laser confocal scanning microscope (LCSM). The result showed that Er:YAG laser could effectively remove dentin caries. There was no statistical difference in shear bond strength between two groups and the adhesive interface created on laser-irradiated dentin surface presented similar feature to that on bur-ground surface.

The aim of this study is to develop a light-emitting diode- (LED-) based illumination system that can be used as an alternative light source forin vitrophotodynamic therapy (PDT). This illumination system includes a red LED array composed of 70 LEDs centered at 643 nm, an air-cooling unit, and a specific-designed case. The irradiance as a function of the irradiation distance between the LED array and the sample, the homogeneity and stability of irradiation, and the effect of long-time irradiation on culture medium temperature were characterized. Furthermore, the survival rate of the CNE1 cells that sensitized with 5-aminolevulinic acid after PDT treatment was evaluated to demonstrate the efficiency of the new LED-based illumination system. The obtained results show that the LED-based illumination system is a promising light source forin vitroPDT that performed in standard multiwell plate.

This study was intended to compare the efficacy of proliferation of HeLa cells under three different low-intensity laser irradiation (LIL), that is, 633 nm, 658 nm, and 785 nm. The time-dependent responses of proliferation of HeLa cells after the red laser irradiation and the influence of fetal bovine serum (FBS) at 1%, 2%, 5%, or 10% on the proliferation of cells were also investigated. The results indicated that the proliferation of HeLa cells in 10% FBS was in proliferation-specific homeostasis (PSH) so that it was not modulated with LIL; the proliferation in FBS at 1%, 2%, or 5% was far from PSH so that it may be wavelength dependently modulated with LIL, and the maximum proliferation promotion was conducted with LIL at 633 nm amongst the three different LIL. It was concluded the wavelength-dependent photobiomodulation of LIL on proliferation of HeLa cells may be homeostatic.

A simple method based on total internal reflection is presented for measuring the refractive index of biological tissue. Anarrow laser beam and a semicylindrical lens in contact with a tissue specimen are used in the experimental apparatus. The dependence of the internal reflectivity on the angle of incidence is measured to determine the critical angle and therefore the refractive index of tissue. The experimental results for several tissue samples show that the method is reliable and useful for studying tissue optics. The principal advantages of the method are its elimination of scattering effects, suitability to a small in vitro sample, and excellent accuracy.

The objective of this study was to investigate the influence of an applied water film on bone hard tissue ablation by pulse CO 2 laser. Fresh bovine shank bone in vitro used in the experiment were put on a PC-controlled motorized linear drive stage and moved repeatedly through focused beam of laser without and with a water film of 0.4 mm and 1 mm on target tissue. The wavelength of pulse CO 2 laser was 10.64 P m, pulse repetition rate was 60 Hz, the energy density was 18-84 J/cm 2 and the beam diameter of about 400 P m. The moving speed of stage was 12 mm/s, scanning times was 5. The surface morphology and microstructure of ablation grooves we re examined by stereomicros cope and scanning electron microscope (SEM) respectively. The geometry of the groove was measured with optical coherence tomography (OCT), and the thermal injury was examined by histology. It shows that water film on the target tissue surface plays an important role during the ablation process. A proper thickness of water film applied to target tissue surface could improve the regular of cut shape, smooth the cut surface, pro duce the same or even larger ablation rate and efficiency, and reduce the thermal injury around the groove by compared with dry ablation condition. Moreover, the addition of water could alter the microstructure of bone sample. Keywords: Laser Ablation, Biological Hard Tissue, Water-mediated ablation, CO

The purpose of this study was to determine the shear bond strength of a self-etch adhesive to Er:YAG laser-prepared dentin and evaluate the resin-dentin interface. Extracted so und human molars were sectioned and wet-ground to expose flat dentin surfaces. These surfaces were subsequently irradiated by an Er:Y AG laser with a wavelength of 2.94 P m and pulse repetition rate of 20 Hz. Energy density was set at 20 J/cm 2 and spot size was 2 mm. The conventional bur was used as a control group. After surface treatments, a self-etch adhesive was bonded to the irradiated dentin surface and then a resin composite was applied to th e dentin surface. Specimens were subjected to shear bond strength test after 24 h of storage in water. The bonding interface was examined by la ser confocal scanning micros cope (LCSM) after specimens were serially sectioned into multiple slices. The results rev ealed that Er:YAG laser irradiation did not present advantages compared to the conventional bur. Keywords: Shear bond strength, Er:YAG laser, dentin, self-etch adhesive, laser confocal scanning microscope (LCSM)

The physical properties of acupuncture point were important to discover the mechanism of acupuncture meridian. In this paper, we used an optical coherence tomography to monitor in vivo the changes of optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point during laser irradiation on Yangxi acupuncture point. The optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point were obtained by fitting the raw data according to the Beer-Lambert's law. The experimental results showed that the optical attenuation coefficient of Hegu acupuncture point decreased during the laser acupuncture, in contrast to a barely changed result in that of non-acupuncture point. The significant change of optical attenuation coefficient of Hegu acupuncture point indicated that there was a correlation between Hegu and Yangxi acupuncture points to some extent.

In this work, optical properties from normal and cancerous stroma pairs were measured using reflectance-based confocal microscopy. Our results show that the scattering coefficient of cancerous stroma is significantly lower than that of normal stroma, suggesting that the decreased scattering in cancerous stroma may provide a possible indicator for differentiating normal and cancerous stroma.

Near infrared Nd:YAG pulsed laser treatment had been proved to be an efficient method to treat large-sized vascular malformations like leg telangiectasia for deep penetrating depth into skin and uniform light distribution in vessel. However, optimal clinical outcome was achieved by various laser irradiation parameters and the key factor governing the treatment efficacy was still unclear. A mathematical model in combination with Monte Carlo algorithm and finite difference method was developed to estimate the light distribution, temperature profile and thermal damage in epidermis, dermis and vessel during and after 1064 nm pulsed Nd:YAG laser irradiation. Simulation results showed that epidermal protection could be achieved during 1064 nm Nd:YAG pulsed laser irradiation in conjunction with cryogen spray cooling. However, optimal vessel closure and blood coagulation depend on a compromise between laser spot size and pulse duration.

The object of this study is to evaluate the morphological changes of dentin tissue after Er, Cr: YSGG laser Irradiation. The wavelength is 2.78 μm with pulse repetition rate of 20 Hz and pulse duration of 140 μs. The samples extracted from sound intact adult human premolars were cut into 1 mm thick dentin slices, and then polished by abrasive papers. After preparation, specimens were randomly divided into two groups: one group treated with conventional drills (a diamond drill and a fissure bur), and the other group treated with lasers at four different power settings (2W to 3.5W). The morphological alterations produced by the different treatments were observed and compared by scanning electron microscope (SEM). It showed that the dentin surfaces had distinct and characteristic morphological alteration with different power settings. Compared with the samples treated with conventional drills, the irradiated samples revealed an absent smear layer with open dentinal tubules. The ablation of intertubular dentin was more evident than that of peritubular dentin.

Knowledge of laser hard tooth tissue interactions plays an important role in laser dentistry. Pulsed Er:YAG laser was capable of ablating human dentin. The diameter and depth of ablation craters increased with radiant exposure.

The aim of this study was to assess the effect of different power irradiation conditions on human dentin by pulse Er,Cr:YSGG laser. Tissue samples were derived from freshly extracted human molars. The wavelength of pulse Er,Cr:YSGG laser was 2.78 m μ , pulse repetition rate was 20Hz and pulse duration was 140 s μ . Laser power of irradiation varied from 1.5 to 4 W. Laser energy was delivered through a fiber optic system to a handpiece containing a tip with a diameter of 600 m μ . After irradiation, the morphologic characteristics of ablation craters were measured by use of both stereomicroscope and optical coherence tomography (OCT). Then the specimens were prepared for scanning electron microscope (SEM). The results indicated that Er,Cr:YSGG laser was capable of ablating human dentin. The diameter of ablation craters increased with the output power; the crater depth and ablation volume showed a linear growth with the output power.

Pulse Erbium:YAG laser was capable of massive ablation of middle ear bone and similar outcomes as traditional methods were obtained. The morphological changes and thermal damage around incision were assessed.

Surface temperature evolving with time of in vivo skin irradiated by 1064 nm pulsed Nd:YAG laser was measured with infrared thermal camera and simulated with finite difference approach combined with Monte Carlo light modeling.