Ni-Ti tube is used as a supporting tube for the infrared hollow fiber to obtain flexibility and strong mechanical strength. The loss of hollow optical fiber is inversely proportional to the cube of the inner diameter. Considering this, it is expected that the large-diameter hollow optical fiber has a low loss. Even with a large inner diameter of 700 μm, the Ni-Ti tube with a wall thickness of 75 μm can be bent easily to a bending radius as small as 15 mm. Therefore, 700-μm-bore hollow optical fiber based on Ni-Ti tube was fabricated. In order to reduce roughness of inner surface of Ni-Ti tube which causes the additional transmission loss, an acrylic-silicon resin material is used as a buffer layer to the inner wall of Ni-Ti tube for a low-loss characteristic. For the dielectric inner-coating layer, cyclic olefin polymer (COP) is used to lower the transmission loss. The COP layer is formed by using liquid-phase coating method. The hollow fibers with optimized COP inner film thickness for CO2 laser light were fabricated and reasonable transmission losses were demonstrated.
A hollow fiber (HF) surface plasmon resonance (SPR) sensor based on the gold-coated HF is proposed. Different from previous HF SPR sensors, gold is adopted as the thin metal layer material instead of silver. Because gold is much more stable than silver, the durability and scope of the application of the proposed HF sensor are improved. The thin gold film is uniformly coated on the inner wall of the HF by the chemical solution deposition technique. The proposed sensors with different gold layer thickness are fabricated. The transmission spectra of the fabricated sensors filled with liquid of different refractive index are measured. Experimental analyses were carried out to evaluate the performances of the sensors, such as sensitivity and figure of merit (FOM). The highest experimentally achieved sensitivity and FOM are 7054 nm/RIU and 92 RIU-1, respectively. Compared to the silver coated HF SPR sensor, it has much narrower resonance dip and thus higher FOM, which indicates that the coated gold layer is more uniform than the silver layer. The technique of coating uniform gold film in the hollow core of optical fibers has potential in the research of the other optical fiber sensors.
Ni-Ti tube is used as a supporting tube for the infrared hollow fiber to obtain flexibility and strong mechanical strength. The loss of Hollow optical fiber is inversely proportional to the cube of the inner diameter. Considering this, it is expected that the large-diameter hollow optical fiber has a low loss. Even with a large inner diameter of 800 μm, the Ni-Ti tube with a wall thickness of 0.1 mm can be bent with a small force to a bending radius of 15 mm. Therefore, 800-μm-bore hollow optical fiber based on Ni-Ti tube was fabricated. In order to reduce roughness of inner surface of Ni-Ti tube which causes the additional transmission loss, an acrylic-silicon resin material is used as a buffer layer to the inner wall of Ni-Ti tube for a low-loss characteristic. For the dielectric inner-coating layer, cyclic olefin polymer (COP) is used to lower the transmission loss. The COP layer is formed by using liquid-phase coating method. The hollow fibers with optimized COP inner film thickness for CO2 laser light were fabricated and reasonable transmission losses was demonstrated.
Ni-Ti tube is used as a supporting tube for the infrared hollow fiber to obtain flexibility and strong mechanical strength. In order to reduce roughness of inner surface of Ni-Ti tube which causes the additional transmission loss, an acrylic-silicon resin material is used as a buffer layer to the inner wall of Ni-Ti tube for a low-loss characteristic. For the dielectric inner-coating layer, cyclic olefin polymer (COP) is used to lower the transmission loss. The COP layer is formed by using liquid-phase coating method. The hollow fibers with optimized COP inner film thickness for CO2 laser light were fabricated and reasonable transmission losses was demonstrated.
Extremely flexible hollow optical fibers with 75-μm-bore size were developed for infrared laser light delivery. The hollow fiber was inner coated with silver and dielectric layers to enhance the reflection rate at an objective wavelength band. The silver layer was inner-coated by using the conventional silver mirror-plating technique. Concerning the fabrication parameters used up to now for 320-μm-bore size fibers, the target flowing rate for plating solutions was 10 ml/min. Parallel arranged bundles of silica capillaries were used to increase the cross-sectional area of the air core. To achieve the flow-rate target, four bundles of 300 pieces of silica capillaries with an inner/outer diameter of 75/150-μm and a length of 20 cm were bundled. To increase the flow rate, four bundles with an inner diameter of 75-μm and a length of 20 cm, together with three silica capillaries with an inner diameter of 530-μm and a length of 50 cm were connected in parallel. The spectrum loss measured by an optical spectrum analyzer for the 75-μm-bore size, 10-cm-length silver hollow optical fiber was around 5 dB at the wavelength of 1-μm. Thin dielectric layer was formed by using liquid-phase coating method for low-loss transmission of Er:YAG laser light.
A high performance hollow fiber (HF) refractive index (RI) sensor utilizing Tamm plasmon polariton is proposed. The structure of the sensor is a HF with the one dimensional photonic crystal (1DPC)/metal multi-films coated on the inner surface of supporting tube. Theoretical analysis based on a ray transmission model is carried out to evaluate the performance of the designed sensor. Because the lights transmitted in the HF have much larger incident angles than those in the prism based sensors, the center wavelength of the 1DPC should shift to longer wavelength. The origin of multiple resonance dips in the transmission spectrum is investigated by calculating the electric field distribution in the 1DPC/metal structure. The variation of the RI detection range of the sensor with different bilayer period is also analyzed. The optimal bilayer period of the sensor for achieving the highest figure of merit (FOM) at different sensed RI is obtained. Compared to the convention HF surface plasmon resonance sensors which can only detect sensed medium with RI higher than that of the supporting tube material, the RI detection range of the proposed sensor is largely extended to 1.33-1.60 while the FOM is enhanced several times.
Stainless pipe is used as the supporting tube for the infrared hollow fiber to obtain high durability and strong mechanical strength. In order to reduce roughness of inner surface of stainless tubes which causes the additional transmission loss, an acrylic-silicon resin material is used as a buffer layer to the inner wall of stainless tube for a low-loss characteristic. For the dielectric inner-coating layer, cyclic olefin polymer (COP) is used to lower the transmission loss. The COP layer is formed by using liquid-phase coating method. The hollow fiber with optimized COP inner film thickness for CO2 laser light were fabricated and reasonable transmission loss was demonstrated.
Flexible hollow fibers with 530-μm-bore size were developed for infrared laser delivery. Sturdy hollow fibers were fabricated by liquid-phase coating techniques. A silica glass capillary is used as the substrate. Acrylic silicone resin is used as a buffer layer and the buffer layer is firstly coated on the inner surface of the capillary to protect the glass tube from chemical damages due to the following silver plating process. A silver layer was inner-plated by using the conventional silver mirror-plating technique. To improve adhesion of catalyst to the buffer layer, a surface conditioner has been introduced in the method of silver mirror-plating technique. We discuss improvement of transmission properties of sturdy polymer-coated silver hollow fibers for the Er:YAG laser and red pilot beam delivery.
For sturdy silver hollow optical fibers, acrylic silicone resin is newly used as a buffer layer between an inner silver layer and a silica capillary. This acrylic silicone resin film prevents the glass surface from chemical and mechanical micro damages during silver plating process, which deteriorate mechanical strength of the hollow fibers. In addition, it keeps high adhesion of the silver layer with the glass surface. We discuss improvement of mechanical strength of the hollow glass fibers without deterioration of optical properties.
Single-crystal (SC) fibers have the potential of delivering extremely high laser energies. Sapphire fibers have been
the most commonly studied SC fiber and the losses for sapphire fibers have been as low as 0.4 dB/m for a 300-
micron core-only fiber at 3 microns. In this study we report on the growth of SC yttrium aluminum garnet, Y3Al5O12(YAG) fibers from undoped SC source rods using the Laser Heated Pedestal Growth (LHPG) technique. The
advantage of YAG over sapphire is the slight improvement in IR transmission of YAG. The IR transmission of bulk
YAG has been shown to extend to 5 μm where the absorption coefficient is 0.6 cm-1. The garnet family of crystals
is one of the most commonly used oxide crystal hosts for lasing ions in high power solid-state lasers, with the most
commercially common laser host being YAG. Thus, it is reasonable to assume that YAG fibers will have high laser
damage thresholds. The optical losses for 400-μm diameter YAG fibers have been measured to be about 3 dB/m at
2.94 μm. The longest length of YAG fiber grown has been about 60 cm.
Vitreous film based on the structural unit R2SiO, where R is an organic group, is newly used as
the reflection layer in the hollow optical fiber for CO2 laser delivery. A smooth vitreous film is formed
at room temperature by using the liquid-phase coating technique. The vitreous film-coated silver
hollow optical fibers achieve low-loss property for lasers in the infrared regions by properly selecting
fabrication conditions. A hollow fiber with thicker vitreous film designed for CO2 laser light showed
acceptable loss as an output tip. It is shown that the hollow tip is of high durability to withstand
several cycles of autoclave sterilization.
Transmission characteristics of infrared hollow fiber with multi- AgI and SiO2 films are discussed.
Three-dielectric-layer hollow glass fiber with SiO2/AgI/SiO2/Ag structure was fabricated for low-loss
delivery of infrared laser light. The first SiO2 film on the silver layer was coated by using liquid phase
coating method. A semi-inorganic polymer was used as the coating material. A smooth vitreous film was
formed by the treatment of a hardener at room temperature and followed by curing treatment. For the
deposition of the AgI film between the two SiO2 films, an Ag film was first plated on the SiO2 film by
silver mirror reaction method. Then the iodination process was conducted to turn the silver layer into
silver iodide. The second SiO2 layer was deposited on the AgI layer in the same way as the first SiO2 layer.
Fabrication parameters for controlling film thicknesses, such as iodination temperature, silver mirror
reaction time, and solution concentration, are clarified for depositing AgI and SiO2 films with the
theoretical optimum thicknesses. By optimizing the thickness of the three dielectric layers, low-loss in the
loss spectrum of SiO2/AgI/SiO2/Ag hollow glass waveguides can be obtained at the target infrared
wavelengths. A method is proposed to evaluate the film thickness of AgI layer based on the positions of
loss peaks and valleys in the loss spectra. Theoretical calculation for loss spectrum of SiO2/AgI/SiO2/Ag
hollow glass fiber considering material dispersion of dielectric materials is also conducted. Good
agreement with the measured data is demonstrated.
Extremely flexible hollow fibers with 100 μm-bore size were developed for infrared laser
delivery. The hollow fiber was inner coated with silver and a dielectric layer to enhance the reflection
rate at an objective wavelength band. The silver layer was plated by using the conventional silver
mirror-plating technique. And a thin dielectric layer was coated for low-loss transmission of Nd:YAG
and Er:YAG laser light.
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