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A fiber-optic surface plasmon resonance (SPR) biosensor based on a silver-coated hollow fiber (HF) structure for glucose detection is presented. The sensor surface was immobilized with 4-mercaptophenylboronic acid (PMBA) acting as a glucose recognition monolayer. Then, gold nanoparticles (AuNPs) modified with 2-aminoethanethiol (2-AET) and PMBA were introduced onto the sensor surface after glucose was captured to enhance the wavelength shift of the SPR phenomenon excited by the light transmitted in the wall of the HF sensor. Instead of the conventional one-step sensitization pretreatment commonly used in the deposition process of silver films for fiber-optic SPR sensors, a sensitization-activation two-step activation method was adopted in the fabrication of the proposed sensor. Experiments for glucose detection were performed on the fabricated sensors in the concentration range of 1 nM-1 mM. Results showed that the sensor fabricated by the two-step activation method has a much larger shift of resonance wavelength than the sensor fabricated using the one-step sensitization method. The resonance wavelength shift was found to be linear to the logarithm of the concentration in the range of 1 nM-1 mM. The sensor achieved a limit of detection (LOD) of as low as 1 nM, which is at least an order of magnitude lower than that of other fiber-optic sensors for glucose detection reported previously. The presented HF glucose sensor has the potential for biosensing applications and provides a large reference value in the study of optical fiber SPR sensors for biosensing.

In this paper, the silver-coated large-core suspended-core fiber (LSCF) probe was fabricated by the dynamic chemical liquid phase deposition method for surface-enhanced Raman scattering (SERS) sensing. The 4-mercaptophenylboronic acid (4-MPBA) monolayer was assembled in the LSCF as the recognition monolayer. Taking advantage of the appropriate core size of the LSCF, a custom-made Y-type optical fiber patch cable was utilized to connect the semiconductor laser, Raman spectrometer, and the proposed fiber SERS probe. The SERS signal is propagated in the silver-coated air channels, which can effectively reduce the Raman and fluorescence background of the silica core. Experiments were performed to measure the Raman scattering spectra of the 4-MPBA in the silver-coated LSCF in a non-enhanced and enhanced case . The experiment results showed that the Raman signal strength was enhanced more than 6 times by the surface plasmon resonance compared with the non-enhanced case. The proposed LSCF for SERS sensing technology provides huge research value for the fiber SERS probes in biomedicine and environmental science. The combination of SERS and microstructured optical fibers offers a potential approach for SERS detection.

A dielectric/Ag-coated hollow fiber (HF) temperature sensor based on long-range surface plasmon resonance (LRSPR) is proposed and experimentally demonstrated. The structural parameters, including the dielectric material and layer thicknesses, are optimized through comprehensive theoretical analysis to achieve the best performance. By filling it with a high refractive index (RI) thermosensitive liquid, the GK570/Ag-coated HF temperature sensor with optimal structural parameters is fabricated. Due to the high sensitivity of the LRSPR sensor and the optimized design, the fabricated sensor achieves a temperature sensitivity of 3.6∼20.5 nm/°C, which is almost the highest among the optical fiber temperature sensors based on surface plasmon resonance reported experimentally. Moreover, the detection range of the proposed sensor can be easily tuned up to 170°C by varying the RI of the filled thermosensitive liquid, and the sensor performance remains stable. Considering that most temperature sensors using polydimethylsiloxane have a fixed detection range, this is an outstanding advantage that could expand the application field of the optical fiber temperature sensor.

A novel surface plasmon resonance (SPR) temperature sensor based on a silver-coated multi-hole optical fiber (SMHOF) is presented. The central and surrounding air holes of the SMHOF are filled with two kinds of thermosensitive liquid with high and low refractive index (RI), respectively. Two separated resonance dips, which are related to the high and low RI filled liquid respectively, are observed at different wavelength in the transmission spectrum. Advantageously, the two dips move towards opposite direction with the temperature variation. The interval between the two SPR dips is measured under different environmental temperature and exhibits a good linearity. The proposed sensor with different detection range is fabricated by changing the RIs of the filled thermosensitive liquids. The temperature sensitivity of 7.72 nm/°C and -7.81 nm/°C is obtained in the range of 20-60 °C and -20-20 °C, respectively. Owing to the high temperature sensitivity and tunable detection range, the proposed sensor is expected to find potential applications in biomedicine, health care and environmental monitoring.

A tunable fiber polarizer based on the selectively silver-coated large-core suspended-core fiber (LSCF) was proposed. A thin silver layer was coated on the inner surface of two opposite air holes of the LSCF by the chemical liquid-phase deposition method. The $y$-polarized light (parallel to the two silver-coated air holes) will excite surface plasmon resonance and experience large transmission loss, while the $x$-polarized light does not, resulting in a fiber polarizer. By varying the liquid filled in the microchannels of the LSCF, the operating wavelength can be tuned in the visible and near infrared region along with the surface plasmon resonance wavelength. The dependence of the polarization characteristics on the fiber length was experimentally investigated. The maximum polarization extinction ratio (PER) of 20.1 dB, 19.6 dB, and 18.3 dB and insertion loss (IL) of 2.24 dB, 2.56 dB, and 2.08 dB are achieved with the optimal fiber length of 16 cm at the operating wavelengths of 565.4 nm, 626.7 nm, and 739.7 nm, respectively. Compared with the multimode fiber-based polarizers reported previously, the proposed selectively silver-coated LSCF polarizer exhibits higher PER and lower IL.

A novel hollow fiber temperature sensor (HFTS) based on long-range surface plasmon resonance is presented. The HFTS consists of a dielectric/Ag-coated hollow fiber filled with the thermosensitive liquid and two multimode fibers connected at both ends. By measuring the transmission spectra under different temperatures, the performances, including sensitivity and figure of merit (FOM) of the sensors with different structural parameters, such as thermosensitive liquid property, ethylene-vinyl acetate (EVA) and silver layer thicknesses, were investigated experimentally. The results shows that the sensitivity of the optimized HFTS is 1.60nm/°C to 5.21nm/°C in the range from 20°C to 60°C, and the FOM is up to 0.0453°C -1 . Both performances are higher than most reported optical fiber temperature sensors based on surface plasmon resonance. Moreover, the performance of the HFTS is not sensitive to the dielectric layer thickness, which greatly reduces the difficulty of fabrication.

A fiber optic surface plasmon resonance (SPR) sensor based on a silver-coated large-core suspended-core fiber was proposed. A dynamic chemical liquid phase deposition method was adopted to fabricate a set of proposed sensors with different silver layer thicknesses. A stable fully spiced all-fiber sensing system was established to evaluate the performance of the fabricated sensors. The results show that the proposed sensor with a thicker silver layer exhibits higher sensitivity and figure of merit. The performance of the proposed sensor is comparable to those of the conventional solid-core fiber and hollow fiber SPR sensors and much higher than that of the metal nanoparticle functionalized suspended-core fiber sensors.

A long-range surface plasmon resonance (LRSPR) sensor based on GK570/Silver coated hollow fiber (HF) with an asymmetric layer structure is proposed. A set of proposed sensors with different layer thicknesses were fabricated by the liquid phase coating method. Both theoretical and experimental analyses were carried out to evaluate the performances of the fabricated sensors, such as sensitivity, figure of merit (FOM) and detection range. The theoretical results based on the ray modal agreed well with the experimental results. The highest experimentally obtained sensitivity and FOM were over 12500 nm/RIU and 150 RIU -1 , respectively. The FOM was approximately ten times that of the HF SPR sensor. Moreover, compared to the HF LRSPR sensor with a symmetric layer structure, the proposed sensor has a much larger sensitivity and an approximately double FOM without sacrificing other advantages of the HF LRSPR sensor.

A novel high performance optical fiber refractive index (RI) sensor based on the hybrid transverse magnetic (TM) mode of Tamm plasmon polariton (TPP) and surface plasmon polariton (SPP) is proposed. The structure of the sensor is a multi-mode optical fiber with a one dimensional photonic crystal (1 DPC)/metal multi-films outer coated on its fiber core. A simulation study of the proposed sensor is carried out with the geometrical optical model to investigate the performance of the designed sensor with respect to the center wavelength, bilayer period and the thickness of silver layer. Because the lights transmitted in the fiber sensor have much larger incident angles than those in the prism based sensors, the center wavelength of the 1 DPC should shift to longer wavelength. When the coupling between TM-TPP and SPP is stronger, the sensor exhibits better performance because the electromagnetic field of the TPP-SPP hybrid mode is enhanced more in the analyte. Compared to most conventional fiber surface plasmon resonance sensors, the figure of merit of the proposed sensor is much higher while the sensitivity is comparable. The idea of utilizing TPP-SPP hybrid mode for RI sensing in the solid-core optical fiber structure presented in this paper could contribute to the study of the fiber RI sensor based on TPP.

A high performance hollow fiber (HF) surface plasmon resonance (SPR) sensor utilizing one-dimensional photonic crystal (1DPC) is proposed. The performance of the designed sensor is analyzed theoretically with respect to the center wavelength and the bilayer period. Because the light transmitted in the sensor mostly have large incident angles, the center wavelength of the 1DPC should shift to longer wavelength to ensure the band gap covers the spectrum range of the incident light. The sensor exhibits better performance when the detection spectral range is located in the band gap of 1DPC for incident angle larger than 80°. Compared to conventional HF SPR sensor, the figure of merit (FOM) of the proposed sensor is three to four times higher while the sensitivity is comparable. Moreover, within the limited spectrum range of 400 to 800nm, the proposed sensor have much wider refractive index (RI) detection range and can detect sensed medium with low RI very close to the supporting tube.

A new hollow fiber sensor based on metal-cladding waveguide configuration for the detection of the refractive index of liquid is proposed and demonstrated. Due to the existence of both surface and guided modes in the metal-insulator-metal waveguide, the proposed sensor can detect liquid with refractive index either higher or lower than the insulator layer, which significantly extends the detection range. The characteristics of metal-cladding waveguide is analyzed and presented, while the performance of the sensor is numerically calculated and evaluated. The results evince that, the designed fiber sensor can effectively detect both high and low refractive index liquid by respectively exciting surface mode and guided mode.

To investigate the stability and the conversion rules of cantharidin and cantharidic acid contained in the Mylabris aqueous solution under different conditions. The contents of cantharidin and cantharidic acid under different conditions (pH, temperature and light) were determined by HPLC-TQ-MS. The results showed that the content of cantharidin was gradually decreased with the rising of pH value, while on the contrary, the content of cantharidic acid was increased gradually; after Mylabris aqueous solution with different pH values were placed at 25, 40 ℃ and 25 ℃ respectively for lighting for 90 days, the samples were collected for analysis. The results showed the contents of cantharidin and cantharidic acid were changed greatly in the first 10 days, mainly including the decrease of cantharidic acid and increase of cantharidin when the solution was acidic, and the increase of cantharidic acid and decrease of cantharidin when the solution was alkaline. After that, the contents of the above two components basically remained stable. This study revealed that pH was the main factor to affect the contents of cantharidin and cantharidic acid, and they could be converted into each other with the changes of pH value. High temperature and light can accelerate the speed of achieving such balance. The study can provide certain reference for the quality control of the medicines using the Mylabris as raw material., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Chinese Pharmaceutical Association.)

A new kind of hollow fiber surface plasmon resonance sensor (HF-SPRS) based on the silver-coated ethylene tetra-fluoro-ethylene (ETFE) hollow fiber (HF) is presented. The ETFE HF-SPRS is fabricated, and its performance is investigated experimentally by measuring the transmission spectra of the sensor when filled by liquid sensed media with different refractive indices (RIs). Theoretical analysis based on the ray transmission model is also taken to evaluate the sensor. Because the RI of ETFE is much lower than that of fused silica (FSG), the ETFE HF-SPRS can extend the lower limit of the detection range of the early reported FSG HF-SPRS from 1.5 to 1.42 approximately. This could greatly enhance the application potential of HF-SPRS. Moreover, the joint use of both ETFE and FSG HF-SPRSs can cover a wide detection range from 1.42 to 1.69 approximately with high sensitivities larger than 1000 nm/RIU.

A long-range surface plasmon resonance (LRSPR) sensor based on dielectric/silver-coated hollow fiber (HF) is proposed. It can detect the refractive index (RI) of sensed liquid filled in the hollow core of the sensor. A HF LRSPR sensor with 90-nm-thick silver layer and 260-nm-thick OC300 layer is fabricated. Experiments are taken to evaluate the performance of the sensor by measuring the transmission spectra. Theoretical analysis based on a ray model is also taken, and the results agree well with the experimental results. The proposed sensor has similar sensitivity but much smaller SPR dip width than the silver-coated HF SPR sensor. Thus figure of merit of the sensor is enhanced approximately five times. The stability of the sensor is also improved because the dielectric layer acts as a protection layer for the damageable silver layer.

A new kind of surface plasmon resonance (SPR) sensor based on silver-coated hollow fiber (HF) structure for the detection of liquids with high refractive index (RI) is presented. Liquid sensed medium with high RI is filled in the hollow core of the HF and its RI can be detected by measuring the transmission spectra of the HF SPR sensor. The designed sensors with different silver thicknesses are fabricated and the transmission spectra for filled liquids with different RI are measured to investigate the performances of the sensors. Theoretical analysis is also carried out to evaluate the performance. The simulation results agree well with the experimental results. Factors that might affect sensitivity and detection accuracy of the sensor are discussed. The highest sensitivity achieved is 6,607 nm/RIU, which is comparable to the sensitivities of the other reported fiber SPR sensors.

A Raman remote spectroscopy system was established by using flexible hollow fibers (HFs) as laser excitation fiber and signal collection fiber. Experimental evaluations with various optical fiber combinations were carried out. Experiments were conducted by using silver-coated HFs as both remote transmission fiber and sample cells for liquid sample detection. Good linearity for concentration detection of liquid was obtained with clean background and signal enhancement. Theoretical analysis was carried out to optimize the length of the liquid cell. Measured data show good agreement with the simulation result. HF has shown potentiality in applications for remote and noninvasive Raman detection.

Flexible and low-loss hollow waveguide has many advantages as an absorption cell for spectroscopic gas sensing. The characteristics of the sensing system are dependent on the parameters of the hollow waveguide cell. In this paper, a mathematical model was proposed to analyze the waveguide cell by considering waveguide loss, effective optical path length, and signal-to-noise ratio of the system. Simulation results show that the gas absorption intensity and system sensitivity are dependent not only on the waveguide length but also on the bore-diameter, signal-to-noise ratio, and the concentration of the target gases. The results provide optimizing methods for the sensing system and algorithms for error compensation. Preliminary experiments on concentration detection of methane gas were carried out and measured data showed good agreements with the simulation results.

Dielectric-coated metallic hollow waveguides (DMHW) are drawing considerable attention for their application in terahertz (THz) waveguiding. This paper theoretically analyzes the multilayer structure to reduce the transmission and bending loss of DMHW. The efficiency of THz multilayer DMHW depends on a proper selection of dielectric materials and geometrical parameters. The low-loss properties are demonstrated by studying the multilayer gold waveguides with a stack of polypropylene (PP) and Si-doped polypropylene (PP(Si)). Comparisons are made with single-layer Au/PP and Au-only waveguides. The effect of dielectric absorption is discussed in detail. It is found that low index dielectric causes more additional loss than that of high index dielectric layers. Several design considerations for the THz multilayer DMHW are pointed out by studying the effects of multilayer structure parameters with a stack of polyethylene (PE) and TiO(2)-doped polyethylene (PE(TiO2)). We conclude that the inner radius of the waveguide and the refractive indices of the dielectrics tend to be larger in order to reduce the influence of material absorption. An optimal value exists for the total number of layers when the dielectrics are absorptive. The absorption tolerances are pointed out to guarantee a smaller loss for multilayer DMHW than that of metal-only waveguide. Finally, a fabrication method for THz multilayer DMHW Ag/PE/PE(TiO2) is proposed based on co-rolling technique.

Pulmonary artery hypertension (PAH) is a severe disease characterized with progressive increase of pulmonary vascular resistance that finally causes right ventricular failure and premature death. Cigarette smoke (CS) is a major factor of Chronic Obstructive Pulmonary Disease (COPD) that can lead to PAH. However, the mechanism of CS-induced PAH is poorly understood. Mounting evidence supports that pulmonary vascular remodeling play an important role in the development of PAH. PDGF signaling has been demonstrated to be a major mediator of vascular remodeling implicated in PAH. However, the association of PDGF signaling with CS-induced PAH has not been documented. In this study, we investigated CS-induced PAH in rats and the expression of platelet derived growth factor (PDGF) and PDGF receptor (PDGFR) in pulmonary artery. Forty male rats were randomly divided into control group and three experimental groups that were exposed to CS for 1, 2, and 3 months, respectively. CS significantly increased right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI). Histology staining demonstrated that CS significantly increased the thickness of pulmonary artery wall and collagen deposition. The expression of PDGF isoform B (PDGF-B) and PDGF receptor beta (PDGFRβ) were significantly increased at both protein and mRNA levels in pulmonary artery of rats with CS exposure. Furthermore, Cigarette smoke extract (CSE) significantly increased rat pulmonary artery smooth muscle cell (PASMC) proliferation, which was inhibited by PDGFR inhibitor Imatinib. Thus, our data suggest PDGF signaling is implicated in CS-induced PAH.

Transmission characteristics at terahertz (THz) frequencies are numerically analyzed for elliptical dielectric-coated metallic hollow fiber (DMHF). Attenuation constants, group velocity, modal birefringence, and modal power fraction in the air core are presented. Optimization of the fiber geometry is investigated to reduce the attenuation and to increase the birefringence simultaneously. Modal birefringence of 3.3 × 10 -2 and attenuation of 2.4 dB/m are expected. It is found that a desirable ellipticity of the air core is around 3. And both the modal birefringence and the attenuation constant are inversely proportional to the cube of the core size. Multiple dielectric layers significantly reduce the attenuation and meanwhile have little influence on the modal birefringence.

We report the optimal design for hollow fiber inner-coated with metallic and multidielectric layers by using ray-optics theory. Transmission characteristics of the multilayer hollow fiber are more dependent on the film surface roughness in the IR region. Comparisons of fibers with smooth and rough films are made and discussed in detail. The optimal design for film thickness, inner radius, and the number of layers and refractive indices is presented. The calculation results are important for structure design, material selection, and fabrication when considering imperfections in film-coating techniques. Multilayer fibers are fabricated based on the calculation and experimental results agree with the theoretical ones.

We report the transmission characteristics of infrared hollow fiber with multi- AgI and SiO(2) inner-coating layers in the mid-infrared region. A three-dielectric-layer hollow glass fiber with a SiO(2)-AgI-SiO(2)-Ag structure was fabricated and low-loss property was obtained in the mid-infrared region. The SiO(2) films were coated by use of the liquid-phase coating method and a semi-inorganic polymer was used as the coating material. For deposition of the AgI film between the two SiO(2) films, a silver film was first plated by use of the silver mirror reaction method. Then the iodination process was conducted to turn the silver layer into silver iodide. A calculation method was also developed to estimate the film thickness of dielectric layers in each fabrication step according to the position of loss peaks in the measured loss spectra. Good agreement between calculated and measured loss spectra was demonstrated by taking into consideration material dispersion and surface roughness of inner-coating films.

Silver-clad stainless steel pipe is used as the supporting tube for the fabrication of infrared hollow fiber. The hollow fiber has high mechanical strength and is highly durable for use in the medical sterilization process. Film of a cyclic olefin polymer layer or silver iodide (AgI) was coated internally to reduce the transmission loss. A liquid-filling method is proposed for coating the AgI layer. Multiple coating processes proved to be effective to increase the AgI film thickness. A treatment of sodium thiosulfate water solution is also proposed to reduce the film thickness. The film thickness can be accurately controlled by combining the coating and decoating techniques. A loss of less than 0.2 dB was obtained for CO2 laser light for a hollow pipe with a length of 280 mm and an inside diameter of 0.75 mm.

We report calculation results for the transmission characteristics of terahertz hollow fibers with inner coatings of absorptive dielectric and metal layers. The absorption property of the dielectric film has an obvious influence on the transmission property of terahertz hollow fiber, because the optimum thickness of the dielectric layer is several tens of micrometers. Calculations were conducted on the loss properties of the hollow fiber with and without the absorptive dielectric layer. Important results were obtained, such as the optimum refractive index for the absorptive dielectric layer and the absorption tolerances for hollow fibers with various inner diameters.

A method is proposed to evaluate the material dispersion of dielectric film in dielectric-coated silver hollow fiber. Cauchy's formulas that characterize the dispersion property were obtained for several commonly used dielectric materials by using the measured data of loss spectra of the hollow fibers. The wavelengths of the loss peaks and valleys in the loss spectra can be predicted more accurately when taking into consideration of the material dispersion. The derived Cauchy's formulas play an important role in the design of infrared hollow fiber for multiwavelength delivery.

We report on AgI/Ag infrared hollow fiber with low-loss in visible region. Improved methods of silver plating and iodination were proposed to fabricate the hollow fiber. The surface roughness of the silver layer and the silver iodide layer was reduced by the pretreatment with an SnCl2 solution and low iodination temperature. Losses for the Er:YAG and green laser light were 0.4 and 7dB/m. The loss property of green laser beam was low to deliver a pilot beam for the invisible infrared laser light. Owing to the smooth and uniform AgI film, the loss spectrum of the hollow fiber showed clear interference peaks in the visible region. An empirical formula for AgI material dispersion was derived, which is of special importance for the design of high-performance AgI/Ag hollow fiber.

A vitreous material with an optimum reflective index of 1.41 for dielectric metallic hollow fiber is used for what is believed to be the first time. A smooth vitreous film is formed by the treatment of a hardener at room temperature by using the liquid-phase coating technique. Low-loss properties were obtained in both the infrared and visible wavelength regions, and the fibers are of high durability when sterilized. This hollow fiber is promising for use in medical applications or other harsh environments.

The techniques for fabricating a hollow optical fiber with an inner silver layer and a cyclic olefin polymer (COP) layer have been improved to reduce the surface roughness of these two layers. The loss spectrum was thereby drastically reduced over a wide wavelength range, from visible to near infrared. Optimization of the COP layer thickness resulted in low loss simultaneously at several key laser wavelengths. Infrared hollow fiber with low loss was developed for Er:YAG and Nd:YAG lasers. It can also deliver green and red pilot beams with low loss. Use of this fiber in therapeutic and pilot lasers should prove useful for research and development in laser medicine.

We developed hollow fibers with polycarbonate (PC) capillaries for use as a supporting tube. The PC capillaries were prepared by using a glass-drawing technique. Hollow PC fibers are safer and more flexible than hollow glass fibers because no fragments are released when the fibers are broken in various applications. Inner coating layers of silver and cyclic olefin polymer (COP) enhanced the reflection rate at the Er:YAG laser light wavelength. Using these fibers, we attained low loss for Er:YAG laser light transmission. By adjusting the drawing temperature in the fabrication of the PC capillaries, we created a smooth inner surface and uniform PC capillaries. We also demonstrated low-loss properties for visible pilot beams.

We report on low-loss multiwavelength laser delivery of hollow optical fiber in a wide wavelength region, from the visible to the infrared. Improved methods of liquid-phase coating were used to fabricate the hollow fiber with inner films of a silver and a cyclic olefin polymer (COP) layer. The surface roughness of the silver layer was reduced dramatically by pretreatment on the inner glass surface with an SnCl2 solution. The COP layer roughness was also decreased by using an ambient atmosphere of tetrahydrofuran (THF) solvent during the COP layer formation. Owing to the smooth surfaces, hollow fiber with optimum COP film thickness for CO2 laser light simultaneously yields low losses for a Er:YAG laser and a red pilot beam. The power durability of CO2 and Er:YAG lasers, as well as the loss properties for the pilot beam, is demonstrated.

Background and Objective: Short-pulse solid-state lasers have recently received much attention as new coherent light sources for medical applications, but steady transmission of their high-energy output pulses through a solid quartz fiber is difficult because of the onset of laser-induced breakdown. We previously demonstrated that hollow waveguides could be used to deliver nanosecond laser pulses for tissue ablation. The aim of this study was to determine the optimum laser pulse energy and range of defocused distance for obtaining a deep and sharp ablation channel in myocardial tissue with laser pulses transmitted through a hollow waveguide., Study Design/materials and Methods: Cyclic-olefin-polymer-coated silver hollow waveguides of 1 mm in inner diameter and 1 m in length were used. A vacuum-cored scheme was applied to the waveguides to suppress laser-induced air breakdown. Porcine myocardial tissue was irradiated with 300 laser pulses that were delivered through the waveguide in vitro at various laser energy levels and defocused distances, and depths and diameters of channels were measured. Histological analysis of the ablated tissues was also performed., Results: At an ablation energy of approximately 60 mJ/pulse, deep (>4.5 mm) and sharp (depth-to-diameter ratio of > 6) channels were created in tissue in the range of defocused distances of -4 approximately + 0.5 mm. Under these conditions, waveguide bending did not cause a remarkable change in ablation characteristics. Histological analysis of ablated tissue showed limited thermal damage but suggested a certain extent of mechanical effects in the tissue., Conclusion: With near-infrared, nanosecond laser pulses delivered through a cyclic-olefin-polymer-coated silver hollow waveguide, efficient and sharp ablation of myocardial tissue can be achieved, suggesting the usefulness of the hollow waveguide as a new flexible delivery system for high-intensity laser pulses., ((c) 2005 Wiley-Liss, Inc.)

We have experimentally quantified calculus fragmentation by Er:YAG laser light. Er:YAG laser light was delivered to an underwater target through a sealed hollow optical fiber. Fragmentation efficiency was obtained for an alumina ball used as a calculus model when sealing caps with various focusing effects were used. Three types of human calculus were analyzed, and their absorption properties at the wavelength of Er:YAG laser light were obtained. The relationships among the absorption properties, calculus constituents, and fragmentation efficiency are discussed.

Objective: The aim of this study is the design, realization, and examination of a new x-ray contrast hollow waveguide which will be suitable for x-ray diagnostics or treatment required in medicine, as dentistry, maxiollofacial surgery or oncology., Background Data: With the growing usefulness of laser radiation therapeutic interventions, a strong demand for radiation delivery from the laser source to the interaction place has appeared. For more complicated surgery, especially for internal intervention, an x-ray is necessary. In such cases, as a minimum, the end of the delivery system must be x-ray contrasted to distinguish where the interaction of radiation with tissue would take place. Up to now, neither fiber, hollow waveguide, nor other delivery system have been x-ray opaque., Materials and Methods: A new type of hollow glass waveguide was designed, fabricated, and examined as a delivery system for an endodontic treatment. The system is composed from the cyclic olefin polymer coated silver hollow glass waveguide with special covering for x-ray visibility. The inner diameter of the waveguide was 320 microm, the outer diameter was 630 microm, and its length was 100 mm. After the delivery system was created, the hollow waveguide was checked under an x-ray machine and its opacity was measured. For actual treatment, an Er:YAG laser system generating a mid-infrared radiation was used. The root canals of 10 molars were treated endodontically, and the result of that treatment was compared with the common cleaning methods. During treatment, digital x-ray images were taken with conventional files, using this new designed hollow waveguide., Results: The position of a metal instrument demonstrates the quality of opacity after conventional step-back technique. The hollow waveguide is visible in the left tooth canal. A bone density analysis shows no differences between a left (waveguide) and right (tooth) canal., Conclusion: It was demonstrated that no differences exist between x-ray opacity of the metal instrument used for endodontic treatment and a special hollow waveguide. The digitalized, three-dimensional image helps to detect a precise position of customary instrument or waveguide in root canal.

The penetration depth in water was measured for Er:YAG laser light in a high density relevant to clinical applications. Various types of focusing elements were used to guide the light efficiently. We found that the transmission distance depended strongly on the beam shape in the water. When we used a plano-convex type of focusing cap, the penetration depth was larger than that when a dome- or ball-type cap were used.

A major advantage of fiber-optic beam delivery in laser materials processing is the ability to guide the laser power to the location where it is needed, leaving the laser itself remote and protected from the process. This is of special importance if the processing is to be performed in a hazardous environment. Particular problems are faced by the nuclear industry where weld repair and surface treatment work are required inside radioactive installations. By use of fiber beam delivery, only part of the delivery system and effector optics become contaminated, but the expensive laser system does not. However, in many cases the region where repair is required is not only radioactive but has only limited physical access, e.g., inside tubes or into corners, which prevents use of standard effector optics. We present a new design to deal with such constraints of a 2-mm outer diameter employing a hollow waveguide and gas shielding. This design is optically characterized and its performance assessed in welding and surface treatment applications. The potential of this compact effector optics in limited physical access situations is clearly demonstrated.

An Er:YAG laser light delivery system composed of a polymer-coated silver hollow waveguide and a quartz sealing cap has been developed for calculus fragmentation. Sealing caps with various distal-end geometries were fabricated, and the focusing effects of these caps for Er:YAG laser light were measured both in air and in water. Owing to the high power capability of the quartz a beam of sealing caps, Er:YAG laser light with an output energy of 200 mJ and a repetition rate of 10 Hz was successfully transmitted in saline solution by use of the system. Calculus fragmentation experiments conducted in vitro showed that the delivery system is suitable for medical applications in lithotripsy. We also found that the cap with a focusing effect is more effective in cutting calculi. The deterioration of the sealing caps after calculus fragmentation is also discussed.

We propose sealing techniques for medical hollow fibers to protect the inner surface of fibers from debris or water that scatters from targets. First, hollow fibers are sealed with a film of polymer that is easily formed by use of a dipping technique. The transmission loss of 20-microm-thick sealing film was 0.2 dB for Er:YAG laser light, and the maximum energy that is available for the film was 180 mJ. Second, a sealed glass cap was applied to the output end of hollow fiber. The silica-glass cap with a wall thickness of 400 microm shows a transmission loss of 0.5 dB and was not damaged by radiation of 400-mJ energy pulses.

Flexible hollow fibers for delivery of the second, third, and fourth harmonic pulses of Q-switched Nd:YAG lasers are introduced. For the doubled (532-nm) wavelength, we fabricated a hollow fiber with an internal metal and polymer film by using a silver-mirror plating and a liquid-phase-coating method. For tripled (355-nm) and quadrupled (266-nm) Nd:YAG in the ultraviolet region, we fabricated aluminum hollow fibers with or without an internal polymer layer by using the metal-organic chemical-vapor deposition method. Both types of fiber show high stability for the transmission of high-peak power laser pulses with low transmission losses.