Fiber Delivery Research Articles

A miniature fiber optic ablation probe manufactured via ultrafast laser inscription and selective chemical etching

Picosecond laser ablation has recently emerged as a minimally invasive alternative to conventional surgical resection of early tumors, offering high precision and limited thermal damage to surrounding tissue. Potential clinical application routes include deployment through the working channels of endoscopes or needle bores, which require the delivery of ultrashort high energy pulses through flexible optical fibers with focusing optics at the distal end. The manufacture of distal end optical systems for fiber ablation is challenging, inhibiting translation toward clinical applications. Here, we present a miniature fiber-coupled ablation probe developed using ultrafast laser inscription and chemical etching, employing a hollow-core fiber for pulse delivery. Its design, fabrication, and characterization are detailed, along with a feasibility demonstration for the ablation of stainless steel and chicken tissue.

Evaluation and application of CO2 laser fiber delivery for single port transoral robotic surgery.

Transoral robotic surgery (TORS) using the Single-Port system (SPS) relies on electrocautery, limiting its applications in the upper aerodigestive tract. We evaluated the feasibility of a CO2 delivery system for the SPS. Otolaryngology residents performed a cutting exercise using a handheld CO2 laser and participated in a cadaveric oropharyngeal dissection using the SPS with monopolar cautery (SP+EC) and CO2 laser (SP+CO2 ). Residents completed the System Usability Scale (SUS) questionnaire to evaluate these techniques. The same laser fiber was used for all combined dissections. The handheld CO2 laser, SP+EC, and SP+CO2 demonstrated similar SUS scores. On individual domain scores, SP+CO2 received less favorable ratings compared to the handheld CO2 laser for complexity, integration, and cumbersome experience (p<0.05). On subgroup stratification, less TORS experience was associated with worse SUS scores. SP-guided CO2 laser delivery is a viable alternative to electrocautery in robotic surgery, and should be considered when performing TORS.

Brillouin gain spectrum characterization in an acoustic anti-guided delivery fiber for high power narrow linewidth laser.

The Brillouin gain spectrum (BGS) provides key information for stimulated Brillouin scattering (SBS), such as the Brillouin frequency shift (BFS), Brillouin spontaneous linewidth, and Brillouin gain coefficient. In this study, we theoretically investigate the field distributions and BGS characterization of Ge-doped, Al-doped, and Al/Ge co-doped fibers. Additionally, we analyzed and compared the relationship between the BGS and acoustic refractive index. In particular, we demonstrate the crucial role played by acoustic modes in anti-waveguide structures. The simulation results show that the Brillouin gain coefficient decreases with a decreasing acoustic index in the fiber core region. Furthermore, we experimentally measure the SBS threshold and BGS of the Al/Ge co-doped fiber to examine the validity of the numerical model. The simulated and experimental results are consistent.

Development of bio-inspired multi-functional polymeric-based fibers (BioFiber) for advanced delivery of bacterial-based self-healing agent in concrete

The goal of this research is to develop innovative damage-responsive bacterial-based self-healing fibers (hereafter called BioFiber) that can be incorporated into concrete to enable two functionalities simultaneously: (1) crack bridging functionality to control crack growth and (2) crack healing functionality when a crack occurs. The BioFiber is comprised of a load-bearing core fiber, a sheath of bacteria-laden hydrogel, and an outer impermeable strain-responsive shell coating. An instant soaking manufacturing process was used with multiple reservoirs containing bacteria-laden, hydrophilic prepolymer and crosslinking reagents to develop BioFiber. Sodium-alginate was used as a prepolymer to produce calcium-alginate hydrogel via ionic crosslinking on the core fiber. The dormant bacteria (spore) of Lysinibacillus sphaericus was incorporated in hydrogel as a self-healing agent. Then, an impermeable polymeric coating was applied to the hydrogel-coated core fibers. The impermeable strain-responsive shell coating material was manufactured using the polymer blend of polystyrene and polylactic acid. The high swelling capacity of calcium-alginate provides the water required for the microbially induced calcium carbonate precipitation (MICP) chemical pathway, i.e., ureolysis in this study. The strain-responsive impermeable coating provides adequate flexibility during concrete casting to protect the spores and alginate before cracking and sufficient stress-strain behavior to grant damage-responsiveness upon crack occurrence to activate MICP. To evaluate the behavior of developed BioFiber, the swelling capacity of the hydrogel, the impermeability of shell coating, the spore casting survivability, and MICP activities were investigated.

Improving the Growth and Bioactive Compound Production of Selected Plant Species Using Controlled Genetic and Epigenetic Manipulation

Abstract This review was designed to summarize the present state of research around the genetic and epigenetic modification of selected plant species and the potential for their application in industry. This review summarizes the activity of research groups from the University of Wrocław completed over the last 3 decades which tends to focus on potatoes and flax likely as a result of their centuries-old tradition of cultivation, processing, and use in Poland. The aims of these studies were various and included the creation of pathogen-resistant plants, increased antioxidant production, improved flax fiber quality, and improved oil properties. New plant breeds initially produced using genetic engineering technology provide an excellent basis for improving our understanding of the genes involved in potato and flax productivity and the quality of their products. These results have been published in many papers and have given rise to new methods for plant breeding and product prototypes which have been patented. However, none of the prototypes have been commercialized because of their GMO origins. In addition, later development of a novel, epigenetic method has led to the creation of more diverse products based on the newly obtained variety of flax called Silesia. These developments have facilitated the production of a range of new raw materials from these epigenetically modified plants. These include a modified oil for improved nutrition and regeneration of skin cells, seed- cake extracts that act as anti-infection agents, improved fiber production for use as bandages for chronic wounds, improved fibers for application as bio composite materials for the development of biodegradable packaging materials and scaffolds for tissue engineering, and micronized fiber for drug delivery. These modifications mean that flax has become a more useful and valuable source of a wide range of raw materials applicable in industry, allowing for the application of these materials in zero waste applications.

Suppression of impurities absorption and heterophase inclusions in Ge-As-S glasses

Strong absorption from the impurities and background scattering induced by heterophase inclusions are major issue in the applications of Ge-As-S glass in mid-infrared (MIR). Here, we report that, the absorption of impurities sourced from raw materials can be removed effectively by oxygen getters and hydrogen getters under static vacuum distillation, leading to almost disappearance of the absorption at 3.11 μm due to SH, <4.08 ppm at 4.01 μm due to SH and < 11.03 ppm at 7.5 μm due to As-O, respectively, in Ge10As28S62. The impurities of H2O and CO2 can be further eliminated to near zero by dynamic distillation. On the other hand, the heterophase inclusions, originating from raw materials of sulfur, arsenic and germanium, the silica-container and deoxidizer of Mg, can be eliminated thoroughly by dynamic distillation and optimized melting temperature. We draw the fibers using unpurified and purified glasses and found that, comparing with the fiber loss of 2.87 dB/m at unpurified glass, the optical loss can be decreased to about 1.86 dB/m in purified glass without any visible particles or heterophase inclusions. All the results pave the way of developing low loss Ge-As-S glass fiber for high power laser delivery.

Designing multi-mode anti-resonant hollow-core fibers for industrial laser power delivery

We investigate the design of hollow-core fibers for the delivery of 10s of kilowatt average power from multi-mode laser sources. For such lasers, delivery through solid-core fibers is typically limited by nonlinear optical effects to 10s of meters of distance. Techniques are presented here for the design of multi-mode anti-resonant fibers that can efficiently couple and transmit light from these lasers. By numerical simulation we analyze the performance of two anti-resonant fibers targeting continuous-wave lasers with M2 up to 13 and find they are capable of delivering MW-level power over several kilometers with low leakage loss, and at bend radii as small as 35 cm. Pulsed lasers are also investigated and numerical simulations indicate that optimized fibers could in principle deliver nanosecond pulses with greater than 100 mJ pulse energy over distances up to 1 km. This would be orders of magnitude higher power and longer distances than in typical machining applications using the best available solid core fibers.

Advanced Diode Laser with Specialized Beam-delivery Instrument in Combined Mini Invasive Laser Hemorrhoid Treatment

As the wavelength range of diode lasers expands, they become increasingly attractive for laser medicine because they are compact, allow the use of convenient fiber delivery systems, and are relatively inexpensive and long-lived. Russian diode lasers are based on world-level achievements in nanotechnologies used in their production. The paper presents the results of clinical application of an improved diode laser apparatus “ACT” model of a domestic company “Uricon Group” equipped with unique multifunctional instruments which enable to minimize mucous lesion in treating vascular pathology of the anorectal zone. A dual-frequency apparatus generating at wavelengths of 980 and 1470 nm permitted the development of a combined technique, which was verified by practical clinical application. The study was aimed at improving the mini-invasive method of surgical treatment of vascular anorectal pathology to ensure maximum efficiency of surgery at any stage of the disease, reducing the duration of surgery, minimizing pain during and after surgery. The technique of laser mini-invasive transdermal and subdermal-submucosal destruction, applied in treatment of 362 patients using the diode laser of “ACT” model and the developed specialized instrument, has shown its effectiveness. All patients returned to daily activities 2-3 days after surgery. Economic effect of the developed treatment technology is provided by low price of the equipment and absence of necessity of the patient’s stay in the clinic in the postoperative period.

Lacticaseibacillus paracasei KC39 Immobilized on Prebiotic Wheat Bran to Manufacture Functional Soft White Cheese

In the current study, probiotic Lacticaseibacillus paracasei KC39 was immobilized on wheat bran as a carrier. The immobilized synbiotic biocatalyst was freeze-dried and used as an adjunct during the production of functional soft white cheese. Free freeze-dried Lc. paracasei cells as an adjunct and a control cheese with a commercial starter were used for comparison. In addition to a fiber content of 1.12%, the functional cheese made using the synbiotic biocatalyst showed higher cell viabilities in the gastric and intestinal phases as well as an enhanced microstructure and favorable sensory characteristics. The presented immobilization method could be applied to the production of soft cheese and other functional food products for the stabilized delivery of both probiotics and dietary fibers.

Fast and accurate measurement of the polarization-dependent detection efficiency of superconducting nanowire single photon detectors.

Superconducting nanowire single photon detectors (SNSPDs) have been extensively investigated due to their superior characteristics, including high system detection efficiency, low dark count rate and short recovery time. The polarization sensitivity introduced by the meandering-type superconductor nanowires is an intrinsic property of SNSPD, which is normally measured by sweeping hundreds of points on the Poincaré sphere to overcome the unknown birefringent problem of the SNSPD's delivery fiber. In this paper, we propose an alternative method to characterize the optical absorptance of SNSPDs, without sweeping hundreds of points on the Poincaré sphere. It is shown theoretically that measurements on the system detection efficiencies (SDEs) subject to cases of four specific photon polarization states are sufficient to reveal the two eigen-absorptances of the SNSPD. We validate the proposed method by comparing the measured detection spectra with the spectra attained from sweeping points on the Poincaré sphere and the simulated absorption spectra.

Hollow-core photonic crystal fibers for Power-over-Fiber systems

Research achievements in hollow-core photonic crystal fibers technology allow ascertaining such fibers as outstanding platforms for delivering high-power laser beams. Indeed, the key property underlying the success of this family of optical fibers for high-power beam delivery is their capability of efficiently transmitting light through empty space with minimal interaction with the fiber microstructure. In this context, here we widen the framework of hollow-core fiber-based beam delivery applications by demonstrating their utilization as promising platforms for Power-over-Fiber systems. Thus, we report on the use of a tubular-lattice hollow-core fiber to deliver a watt-level continuous-wave laser beam onto a photovoltaic converter and activate a representative camera circuit. We believe that the experiments reported herein allow identifying hollow-core fibers as eligible candidates for next-generation Power-over-Fiber devices potentially able to lift the power restrictions of current solid-core fiber-based Power-over-Fiber systems.

Bone ablation using a Ho:YAG laser

Abstract This study aimed to optimize the ablation depth and duration at a fixed energy using a Ho:YAG laser, considering fiber delivery applications. According to the measurements performed with an optical coherence tomography system, we obtained depths of about 1.4 mm with 500 mJ/pulse applied energy when moving the laser along a 1 cm line for 60 s (corresponding to ~50 pulses per position). Coupling this laser into a flexible fiber (θ= 250 μm) will be the next step for future minimal-invasive bone ablation trials. Furthermore, deeper ablation (~1.5 mm) was also achieved with different energy levels on bone samples.

Laser-induced damage of an anti-resonant hollow-core fiber for high-power laser delivery at 1 µm.

We demonstrate high-power laser delivery exceeding 1 kilowatt through a 5-meter homemade anti-resonant hollow-core fiber (AR-HCF) at 1-µm wavelength. Laser-induced damage to the fiber coating and jacket glass is experimentally observed respectively for different incident laser powers from a few hundred watts up to nearly 1.5 kilowatts. The cladding microstructure of the AR-HCF is free of damage at the incident end when 80% of the 1.5-kW incident power is coupled in. The deviation of an incident laser beam from the core to the cladding causes no damage but only deterioration of the coupling efficiency. The potential of the AR-HCF for higher-power laser delivery is discussed.

Electrospinning Drug-Loaded Alginate-Based Nanofibers towards Developing a Drug Release Rate Catalog.

Electrospinning natural polymers represents a developing interest in the field of biomaterials. Electrospun nanofibers have been shown to facilitate tissue regeneration and emulate body tissue, making them ideal for modern biomedical applications. These water-soluble natural polymers including alginate, have also shown promise as drug delivery vehicles. However, many biopolymers including alginate are inherently charged, making the formation of nanofibers difficult. To better understand the potential of natural polymer-based fibers in drug delivery applications, fiber formulations and drug loading concentrations of alginate-based scaffolds were investigated. It was found electrospinning poly(vinyl alcohol) with alginate facilitated fiber formation while the co-polymer agarose showed minor improvement in terms of alginate electrospinnability. Once uniform fibers were formed, the antibiotic ciprofloxacin was added into the polymer electrospinning solution to yield drug-loaded nanofibers. These optimized parameters coupled with small molecule release rate data from the drug-loaded, alginate-based fibers have been used to establish a catalog of small molecule release profiles. In the future, this catalog will be further expanded to include drug release rate data from other innately charged natural polymer-based fibers such as chitosan. It is anticipated that the cataloged profiles can be applied in the further development of biomaterials used in drug delivery.

Ultrafast Fiber Technologies for Compact Laser Wake Field in Medical Application

Technologies, performances and maturity of ultrafast fiber lasers and fiber delivery of ultrafast pulses are discussed for the medical deployment of laser-wake-field acceleration (LWFA). The compact ultrafast fiber lasers produce intense laser pulses with flexible hollow-core fiber delivery to facilitate electron acceleration in the laser-stimulated wake field near treatment site, empowering endoscopic LWFA brachytherapy. With coherent beam combination of multiple fiber amplifiers, the advantages of ultrafast fiber lasers are further extended to bring in more capabilities in compact LWFA applications.

Evaluation of wood chips and rice hulls as alternative fiber sources in rations self-fed to early-weaned calves

Two experiments were conducted to evaluate the merit of wood chips (WCH, Exp. 1) or rice hulls (RH, Exp. 2) as the sole fiber source in a high-concentrate diet fed to early-weaned calves as well as their method of delivery (hand-feeding versus self-feeder). Rations were formulated to contain similar concentrations of N, energy and NDF and were offered ad libitum. In Exp. 1, 36 Hereford calves (84.4 kg SE 4.5) were randomly allocated to nine pens and one of three dietary treatments: (1) 160 g/kg of sorghum silage (SS) and 800 g/kg of concentrate hand-fed, 2) 80 g/kg of WCH and 920 g/kg concentrate hand-fed, and (3) same ration as in (2) but self-fed. In Exp. 2, 36 early-weaned Hereford calves (97.4 kg SE 1.7) blocked by BW were randomly allocated to nine pens and one of three dietary treatments: (1) 200 g/kg of alfalfa hay (AH) plus 800 g/kg of concentrate hand-fed, (2) 80 g/kg of RH plus 920 g/kg of concentrate hand-fed, and (3) same ration as in 2) but self-fed. In both experiments animals were weighed (BW) every 14 days, dry matter intake (DMI) was measured weekly, and daytime animal behavior was observed. Gain-to-feed ratio (GF), NEg and a sorting index to characterize the selective consumption of specific fractions, were calculated. Data were analyzed according to a randomized complete plot (Exp. 1) or block (Exp. 2) design, with repeated measures. Fiber source and delivery method effects were tested through orthogonal contrasts. In Exp. 1, replacing SS with WCH did not affect body BW gain, DMI, GF, or NEg. No differences were observed either in feed sorting or eating activity (EA). Using a self-feeder to deliver the WCH ration reduced EA (P < 0.05), without affect GF. In Exp. 2, replacing AH with RH did not affect BW gain or DMI but it improved GF (P < 0.05). Higher sorting against large particles (>8 mm) and ADF were observed for AH compared to RH (P < 0.05). Using a self-feeder to deliver the RH ration reduced DMI and EA (P < 0.05) without affecting BW gain and improving GF (P = 0.01) compared to hand-feeding. Also, it increased selective refusal of ADF (P < 0.05) but not of NDF, without affecting rumination. Treatments did not affect peNDF supply. Results from both experiments show the viability of the use of WCH and RH as a source of fiber in high-concentrate rations for early-weaned calves, as well as their suitability for delivery in self-feeders.

Optically powered gas monitoring system using single-mode fibre for underground coal mines

We present an optically powered, intrinsically safe gas monitoring system to measure four essential environmental gases (CH4, CO2, CO and O2), together with ambient temperature and pressure, for underground mines. The system is based on three key technologies developed at UNSW: (1) power-over-fibre (PoF) at 1550 nm using a single industry-standard, low-cost single-mode fibre (SMF) for both power delivery and information transmission, (2) liquid–crystal-based optical transducers for optical telemetry, and (3) ultra-low power consumption design of all electronics. Together, this approach allows each gas monitoring station to operate with less than 150 mW of optical power, meeting the intrinsic safety requirements specified by the IEC60079-28 standard. A 2-month field trial at BMA’s Broadmeadow underground mine proved the cabling compatibility to the mine’s existing optical network and the stability of the system performance. Compared with conventional electrically powered gas sensors, this technology bypasses the usual roadblocks of underground gas monitoring where electrical power is either unsafe or unavailable. Furthermore, using one fibre for both power delivery and communication enables longer distance coverage, reduces optical cabling and increases multiplexing possibilities and data throughput for better awareness of underground environment.

Flexible chalcogenide glass large-core multimode fibers for hundred-watt-level mid-infrared 2-5 µm laser transmission

The rapidly-developed high-power mid-infrared 2-5 µm laser technology requires a compact, flexible low-loss glass fiber for power delivery or laser generation. With the broadest bandwidth of low-loss transmission window in mid-infrared region amongst all mid-infrared glass fibers, chalcogenide glass fiber is the best candidate covering the whole 2-5 µm range. Multi-hundred-watt high-power delivery for 5.4-µm CO laser was previously demonstrated in a multimode chalcogenide fiber with a 1-mm-diameter large core, at the cost of giving up one of the most desirable fiber advantages, the flexibility. Indeed, chalcogenide glass fibers with decent flexibility have never exhibited hundred-watt-level power transmitting capability in the 2-5 µm range. In this paper, we have experimentally demonstrated 100-watt-level power transmission in multimode As2S3 chalcogenide fibers, using a customized high-power 2-µm thulium doped silica fiber laser source. With effective forced cooling, the multimode As2S3 fiber with 200 µm core diameter can resist incident laser power of 120 W and deliver transmitted power of 63 W. Nano-sized scattering center related laser damage mechanism and the cylindrical heat transfer model have been proposed to explain the high-power damage process of chalcogenide glass fibers. The calculation is in good agreement with the experiments. It is promising to further enhance the transmitted power above 100 W in flexible chalcogenide glass large-core fibers.

Thermal Effects of CO2, KTP, and Blue Lasers with a Flexible Fiber Delivery System on Vocal Folds

To determine the differences in thermal effects on vocal folds between four fiber-routed lasers. In this experimental laboratory study the thermal effects of an AcuPulse Duo CO2 (CO2 AP), UltraPulse Duo CO2 (CO2 UP), KTP, and Blue laser were analyzed using a Schlieren technique on a human tissue mimicking gel model. Power, laser duration, laser fiber distance to tissue and mode (continuous wave [CW] vs pulsed [P] modes) were evaluated in varying combinations in order to compare the effects of the tested lasers and to explore the individual effect on thermal expansion and incision depth of each setting. The model was validated by comparing the results from the Schlieren model with histology of ex vivo fresh human vocal folds after laser irradiation using a selection of the same laser settings, and calculating the intraclass correlation coefficient (ICC). One thousand ninety-eight Schlieren experiments and 56 vocal cord experiments were conducted. In comparison with CW mode, less thermal expansion occurred in P mode in all lasers, while incisions were deeper in the CO2 and more superficial in the KTP and Blue lasers. The mean thermal expansion was found to be minimally smaller, whereas incision depth was pronouncedly smaller in the KTP and Blue compared to the CO2 lasers. Duration of laser irradiation was the most important factor of influence on thermal expansion and incision depth for all lasers in both CW and P modes. The ICC for consistency between the results of the Schlieren model and the vocal cord histology was classified from fair to excellent, except for the thermal expansion of the Blue laser, which was classified as poor. This study demonstrates important differences in thermal effects between CO2, KTP, and Blue lasers which can be explained by the different physical characteristics of the P modes and divergence of the fiber delivery system. The Schlieren imaging model is a good predictor of the relative thermal effects in vocal fold tissue. Our results can be used as a guidance for ENT surgeons using fiber-routed lasers, in order to achieve effective treatment of vocal fold lesions and prevention of functional impairment of vocal folds.

ADVANCED DIODE LASER WITH SPECIALIZED BEAM-DELIVERY INSTRUMENT IN MINI INVASIVE LASER TREATMENT OF ANORECTAL VASCULAR PATHOLOGY

As the wavelength range of diode lasers expands, they become increasingly attractive for laser medicine because they are compact, allow the use of convenient fiber delivery systems, and are relatively inexpensive and long-lived. Russian diode lasers are based on world-level achievements in nanotechnologies used in their production. The paper presents the results of clinical application of an improved diode laser apparatus ACT model of a domestic company “Uricon Group” equipped with unique multifunctional instruments which enable to minimize mucous lesion in treating vascular pathology of the anorectal zone. A dual-frequency apparatus generating at wavelengths of 980 and 1470 nm permitted the development of a combined technique, which was verified by practical clinical application. The study was aimed at improving the mini-invasive method of surgical treatment of vascular anorectal pathology to ensure maximum efficiency of surgery at any stage of the disease, reducing the duration of surgery, minimizing pain during and after surgery. The technique of laser mini-invasive transdermal and subdermal-submucosal destruction, applied in treatment of 362 patients using the diode laser of ACT model and the developed specialized instrument, has shown its effectiveness. All patients returned to daily activities 2-3 days after surgery. Economic effect of the developed treatment technology is provided by low price of the equipment and absence of necessity of the patient’s stay in the clinic in the postoperative period.