Glass Fiber Tip Research Articles

Evaluation of Er:YAG and Er,Cr:YSGG lasers on intraradicular bonding using modified glass fiber tips.

The aim of this study was to determine whether erbium laser irradiation emitted by modified glass-fiber tips would improve the intraradicular bonding of fiber posts. Forty human canines were endodontically treated and prepared for fiber-post placement. Roots were divided into five groups (n=8); according to the laser-tip combinations (2,940 nm Er:YAG and 2,780 nm Er,Cr:YSGG). Non-irradiated root canals served as control. Posts were cemented with self-adhesive resin cement and subjected to push-out test. Failure modes were characterized, and intraradicular bonded interfaces were analyzed by SEM and submitted to nanoleakage evaluation. Data were analyzed by two-way ANOVA and Tukey test (α=0.05). No significant differences were observed in cervical and middle sections (p>0.05), while significantly higher bond strengths were observed in apical sections (p<0.05). Laser irradiation reduced adhesive failures, cement-dentin gap formation, and nanoleakage apically. Laser-irradiation protocols employing end- or radial-firing tips improved bonding to apical intraradicular dentin contributing to more uniform bonded interfaces.

Tunable nanopillar array on a quartz-fiber tip for surface enhanced Raman scattering (SERS) detection

Abstract In this work, a simple two-step method to create tunable self-assembled three-dimensional nanostructure array-like nanoantennas directly on the tip of an optical quartz glass fiber is described. The structures are prepared by using dry etching of the fiber tip. For the etching process, gold nanoparticles fabricated by thermal dewetting technique were used as template. The structures are applied as sensors for label-free analysis of organic substances in ppb range, such as drug residues in liquid solutions. The measurements are carried out by a portable Raman device with an exchangeable sensor head utilizing the SERS-effect. This method allows in situ applications. In order to characterize the SERS cells, para-thiocresol and diclofenac sodium are used as model substances. For optimization of the substrate performance, different thicknesses of the dewetting-layer (6, 9, 12 nm), different etching times for formation of the pillars (6, 8, 10 and 12 min), and different thicknesses of SERS-metallization (25, 50, 75 nm) of gold and silver are compared. In order to show the applicability of the structure on the tip of a fiber, measurements from the upper side and from the underside of the substrate on quartz plates are compared. Reproducible SERS enhancement factors up to 10 7 {10^{7}} were achieved.

Ag+ ion emission from a sharp Ag2O-Al2O3-P2O5-SiO2 glass-fiber emitter

Ag+ ion conducting xAg2O·(30 − x)Al2O3·55P2O5·15SiO2 (x = 20 and 25, mol%) glasses were prepared using a conventional melting method, and structures and glass transition temperature were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), ultraviolet-visible (UV–Vis) and Fourier transform infrared (FTIR) spectroscopies. Impedance measurement reveals the glass with x = 25 shows a high Ag+ ion conductivity of 3 × 10−3 S cm−1 at 300 °C. Ag+ ion emission measurement was carried out using a sharpened glass fiber tip less than 1 μm, and the emission current was successfully observed above the acceleration voltage of 4 kV at 300 °C and 4 × 10−5 Pa. Silver particles were confirmed on the target substrate after the Ag+ emission measurement. A good linear correlation is obtained between log(current) and square root of the voltage, suggesting the emission of Ag+ ion from the tip of glass fiber is expressed by Schottky model. In this ion emission method, a plasma is not required for ionization and the ion emission mechanism is simple, and various ion conducting glasses can be applied for the emitter of ion gun.

Bismuth-doped glass microsphere lasers

In this work, a hybrid structure consisting of a multicomponent germanate glass microsphere containing bismuth as a gain medium is proposed and presented. The bismuth-doped germanate glass microspheres were fabricated from a glass fiber tip with no precipitation of the bismuth metal. Coupling with a fiber taper, the bismuth-doped microsphere single-mode laser was observed to lase at around 1305.8 nm using 808 nm excitation. The low threshold of absorbed pump power at 215 μW makes this microlaser appealing for various applications, including tunable lasers for a range of purposes in telecommunication, biomedical, and optical information processing.

Mapping the local particle plasmon sensitivity with a scanning probe.

We probe the local sensitivity of an optically excited plasmonic nanoparticle by changing the local dielectric environment through a scanning glass fiber tip. Recording the particle plasmon scattering spectrum for each tip position allows us to observe spectral resonance shifts concurrent with changes in scattering intensity and plasmon damping. For the tip-induced spectral shifts we find the strongest sensitivity at the particle edges, in accordance with the spatial plasmonic field profile. In contrast, the strongest sensitivity occurs at the center of the particle if the scattering intensity is probed at the short wavelength slope of the plasmon resonance instead of the resonance position. This bears important implications for plasmonic sensing, in particular when done at a single light wavelength.

Rapid remote detection of Escherichia coli via a reporter-hydrogel coated glass fiber tip

In this work the development of a responsive hydrogel coating for the remote sensing of bacterial enzymes is reported for the selective, sensitive and rapid in situ detection of (pathogenic) bacteria. The approach is based on the combination of a portable optical fiber setup with a self-reporting hydrogel applied as a coating on the glass fiber tip. To implement the enzyme sensing function, chitosan was functionalized with the chromogenic substrate 5-bromo-4-chloro-3-indolyl-β-d-glucuronide (XGlcA), which releases a non-leaching dimerized indigo dye into the hydrogel upon reaction with the enzyme β-glucuronidase (β-GUS), which is secreted by >98% of all known Escherichia coli strains. The intense blue color of the dimerized indole can be detected by bare eye in hydrogel films and, as shown here for the first time, at the tip of a glass fiber sensor. Detailed investigations of the enzymatic reaction in neat enzyme solution as well as in bacterial supernatant revealed the apparent reaction kinetics and allowed us to determine the concentration of β-GUS in the supernatant. Under optimized conditions the portable optical fiber can sense within 5min the presence of β-GUS with a limit of detection of <40nM.

Er:YAG Laser Ablation of Bone versus Conventional Burrs in Otologic Surgery

Objectives: The Er:YAG laser (EYL) provides an efficient means of precise and predictable bone ablation, without intense thermal injury associated with CO2 laser use. Use of the EYL in otology is possible, but must be undertaken with caution as ablation is associated with brief intense acoustic transients up to 120 dB. This study details the use of the EYL in otologic and neuro-otologic surgery and compares ablation using a commercially available EYL with customizable glass fiber tips versus diamond and cutting burrs by means of infrared thermal imaging (IRT) and environmental scanning electron microscopy (ESEM). Methods: Five 0.6 mm diameter cylindrical cuts to a depth of 0.6 mm were made in formalin fixed human squamous temporal bone using a 300 µs EYL with pulse energies of 250 and 400 mJ (corresponding fluence levels of 175 and 280 mJ/cm2) and 0.6 mm diameter cutting and diamond burrs. Copious irrigation was used for all cuts. IRT was used to determine temperature rise. Ablation regions were inspected with ESEM. Results: Peak temperature rises were similar for all methods of ablation, none exceeding the 12 °C threshold required for irreversible bone injury. ESEM revealed rough margins for cuts made using the cutting burr and smooth edges with no sign of microfracture for those made with EYL and diamond burr. Conclusions: EYL ablates bone efficiently and predictably with smooth margins without microfractures or clinically significant temperature rise. When used appropriately, EYL may be a valuable tool for the otologic surgeon.

Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface

We report on two orders of magnitude reduction in the fluorescence lifetime when a single molecule placed in a thin film is surrounded by two gold nanospheres across the film interface. By attaching one of the gold particles to the end of a glass fiber tip, we could control the modification of the molecular fluorescence at will. We find a good agreement between our experimental data and the outcome of numerical calculations.

Understanding the fiber tip thermal runaway present in 3µm fluoride glass fiber lasers

When the tip of a fluoride glass fiber is exposed to ambient air, water vapor reacts with the glass constituents, increasing the OH contaminants at the surface. These OH impurities then diffuse inside the glass according to Fick's laws. Laser radiation at around 3 µm is strongly absorbed by the OH contaminants, causing local heating of the fiber tip resulting in an increase of the diffusion process which ultimately leads to fiber tip destruction. We accurately model this phenomenon by combining the diffusion theory with a basic thermal equation. Experimental measurements are in agreement with the model predictions for a good range of operating conditions.

Generation of broadband longitudinal fields for applications to ultrafast tip-enhanced near-field microscopy

We report on the generation of broadband longitudinal fields within a tightly focused spot by using a segmented wave plate combined with a phase tailored broadband laser pulse. Their field distribution is characterized by observing the scattered light from a gold-coated glass fiber tip as it is scanned across the focused beam spot. It is observed that efficient coupling to the tip-enhanced field can be achieved over a broad bandwidth of more than 100nm, resulting in a positive contrast at the centre of the focus in the spectrally resolved Rayleigh scattering image. Temporal characteristics of the nonlinear excitation at the tip apex observed by using the fringe resolved autocorrelation technique indicate the possibilities of ultrafast spectroscopy by utilizing the tip-enhanced longitudinal fields.

Charge diffusion in the field-free region of charge-coupled devices

The potential well in back-illuminated charge-coupled devices (CCDs) does not reach all the way to the back surface. Hence, light that is absorbed in the field-free region generates electrons that can diffuse into neighboring pixels and thus decreases the spatial resolution of the sensor. We present data for the charge diffusion from a near point source by measuring the response of a back-illuminated CCD to light emitted from a submicron diameter glass fiber tip. The diffusion of electrons into neighboring pixels is analyzed for different wavelengths of light ranging from 430 to 780 nm. To find out how the charge spreading into other pixels depends on the location of the light spot; the fiber tip could be moved with a piezoelectric translation stage. The experimental data are compared to Monte Carlo simulations and an analytical model of electron diffusion in the field-free region. The presented analysis can be used to predict the charge diffusion in other back-illuminated sensors, and the experiment is universally applicable to measure any type of sensors.

Improved fiber optic device for in situ determination of electrolyte stratification in lead-acid batteries

A three-channel, highly sensitive, fiber optic device is presented to measure acid concentration in lead-acid batteries during their operation. The refractive index and thereby the concentration of sulfuric acid is measured by a bent, silica glass fiber tip, stripped off its cladding. Sensor heads of the device are small enough to be inserted at different positions in the cell of an ordinary, flooded lead-acid battery. Measuring the concentration of the electrolyte at different depths of the battery cell, acid stratification can be accurately determined. During the test of the instrument, about 0.3 Hz temporal and 0.05 wt % concentration resolutions were achieved while the temperature drift was found to be -0.25 wt %/degrees C.

Miniature bending manipulator for fetoscopic intrauterine laser therapy to treat twin-to-twin transfusion syndrome

Recent typical therapy for twin-to-twin transfusion syndrome (TTTS) is selective laser photocoagulation of anastomotic communicating vessels on the placenta using the fetoscopic approach. The difficulty of a conventional laser device approach for this procedure depends significantly on the placental location, so a new robotized device is required to bend the direction of laser irradiation flexibly within the narrow uterus. The authors designed a miniature bending mechanism impelled by a wire-guided linkage driving method that provides a stable procedure for bending laser irradiation from -90 degrees to 90 degrees . Using this bending mechanism, the authors developed a bending manipulator with a diameter of 3.5 mm and a hollow central channel with a diameter of 0.8 mm for passing a glass fiber for neodymium:yttrium-aluminum-garnet (Nd:YAG) laser photocoagulation. The bending mechanism is motorized by an electrical actuator and controlled by a grip-type interface with a small joystick. The robotized tip's part and the actuator's part are easily separable for cleaning and sterilization. In performance evaluations of the manipulator, the bending characteristics with a glass fiber were examined. The bending range was -52.6 degrees to 80 degrees, with a very small hysteresis error, and the bending repeatability error was 0.5 degrees +/- 0.2 degrees, which corresponds with the high accuracy of 0.2 +/- 0.1-mm positioning error at the glass fiber's tip. In the evaluation of Nd:YAG laser photocoagulation, the study confirmed that the manipulator performed effective laser photocoagulation of the placental phantom surface (underwater chicken liver). The large bending range, reaching 80 degrees, enabled a flexible approach from various directions with a high irradiation efficiency of no less than 96.6%. The authors' original miniature bending manipulator can change the laser irradiating direction with highly repeatable positioning accuracy for speedy, safe, and effective vessel occlusion in clinical practice.

Near-field imaging and frequency tuning of a high-Q photonic crystal membrane microcavity

We discuss experimental studies of the interaction between a nanoscopic object and a photonic crystal membrane resonator of quality factor Q=55000. By controlled actuation of a glass fiber tip in the near field of the photonic crystal, we constructed a complete spatio-spectral map of the resonator mode and its coupling with the fiber tip. On the one hand, our findings demonstrate that scanning probes can profoundly influence the optical characteristics and the near-field images of photonic devices. On the other hand, we show that the introduction of a nanoscopic object provides a low loss method for on-command tuning of a photonic crystal resonator frequency. Our results are in a very good agreement with the predictions of a combined numerical/analytical theory.

Vectorial modeling of near-field imaging with uncoated fiber probes: transfer function and resolving power

Using exact 3D vectorial simulations of radiation coupling into uncoated dielectric fiber probes, we calculate amplitude transfer functions for conical single-mode fiber tips at the light wavelength of 633 nm. The coupling efficiency of glass fiber tips is determined in a wide range of spatial frequencies of the incident radiation for opening angles varying from 30 degrees to 120 degrees . The resolution in near-field imaging with these tips is considered for field distributions limited in both direct and spatial-frequency space. The characteristics of the transfer functions describing the relation between probed optical fields and near-field images are analyzed in detail. The importance of utilizing a perfectly sharp tip is also examined.

Spontaneous emission in the near field of two-dimensional photonic crystals

We show theoretically that photonic crystal membranes cause large variations in the spontaneous emission rate of dipole emitters, not only inside but also in the near field above the membranes. Our three-dimensional finite-difference time-domain calculations reveal an inhibition of more than five times and an enhancement of more than ten times for the spontaneous emission rate of emitters with select dipole orientations and frequencies. Furthermore, we demonstrate theoretically the potential of a nanoscopic emitter attached to the end of a glass fiber tip as a local probe for mapping the large spatial variations of the photonic crystal local radiative density of states. This arrangement is promising for on-command modification of the coupling between an emitter and the photonic crystal in quantum optical experiments.

Formation of glass fiber tips for scanning near-field optical microscopy by sealed- and open-tube etching

A method, sealed-tube etching, for fabricating glass fiber tips used in scanning near-field optical microscopy is reported. Two glass tips are formed simultaneously inside the acrylate jacket of an optical fiber that is sealed at the bottom end with plastic prior to etching in hydrofluoric acid. The qualities of the tips generated from this and conventional tube etching methods are compared in terms of their taper length, surface smoothness, as well as time evolution of the tip shapes. Etching mechanisms are proposed for this method, which provides more insight into the conventional tube etching method than previously considered.

Tomographic Plasmon Spectroscopy of a Single Gold Nanoparticle

We demonstrate a tomographic method for determining the degree of ellipticity and the orientation of a gold nanoparticle. To do this, we attach a single nanoparticle to the end of a sharp glass fiber tip and record its plasmon spectra for different incident polarizations and angles of incidence. Our measurements allow us to identify the plasmon spectra along the three main axes of the particle, therefore resolving its “internal” spectral inhomogeneity. Knowledge of the plasmon resonances and the orientation of a metallic nanoparticle is an important asset for controlled and quantitative studies of its interaction with a single molecule.

Clinical evaluation of an Er:YAG laser for nonsurgical treatment of peri‐implantitis: a pilot study

The aim of this controlled, parallel design clinical study was to compare the effectiveness of an Er:YAG laser (ERL) to that of mechanical debridement using plastic curettes and antiseptic therapy for nonsurgical treatment of peri-implantitis. Twenty patients with moderate to advanced peri-implantitis lesions were randomly treated with either (1) an ERL using a cone-shaped glass fiber tip at an energy setting of 100 mJ/pulse and 10 pps (ERL), or (2) mechanical debridement using plastic curettes and antiseptic therapy with chlorhexidine digluconate (0.2%) (C). The following clinical parameters were measured at baseline, 3 and 6 months after treatment by one blinded and calibrated examiner: Plaque index (PI), bleeding on probing (BOP), probing depth (PD), gingival recession (GR) and clinical attachment level (CAL). At the baseline examination, there were no statistically significant differences in any of the investigated parameters. Mean value of BOP decreased in the ERL group from 83% at baseline to 31% after 6 months (P < 0.001) and in the C group from 80% at baseline to 58% after 6 months (P < 0.001). The difference between the two groups was statistically significant (P < 0.001, respectively). The sites treated with ERL demonstrated a mean CAL change from 5.8 +/- 1 mm at baseline to 5.1 +/- 1.1 mm (P < 0.01) after 6 months. The C sites demonstrated a mean CAL change from 6.2 +/- 1.5 mm at baseline to 5.6 +/- 1.6 mm (P < 0.001) after 6 months. After 6 months, the difference between the two groups was statistically not significant (P > 0.05). Within the limits of the present study, it was concluded that (i) at 6 months following treatment both therapies led to significant improvements of the investigated clinical parameters, and (ii) ERL resulted in a statistically significant higher reduction of BOP than C.

Cover Picture: ChemPhysChem 1/2003

AbstractThe cover picture shows a picture of a Mentha × piperita plant, which has a high pharmaceutical relevance. Raman spectra of extremely high spatial resolution have been recorded of this plant by applying etched and silver‐coated glass fiber tips; a method which has been developed in our group within the scope of a BMBF project FKZ 13N7511 located in the framework of Laser‐Biodynamik. On the right, a picture of such a glass fiber tip illuminated by the Raman laser is shown. The fiber tip is brought extremely close to the sample area to be investigated. The picture also shows the Raman spectrum obtained by applying this fiber‐tip technique. This method allows the recording of Raman spectra of biologically relevant samples with an extremely high spatial resolution (200 nm).