Anti-Resonant Hollow Core Fibers with Modified Shape of the Core for the Better Optical Performance in the Visible Spectral Region-A Numerical Study.

In this paper, we present numerical studies of several different structures of anti-resonant, hollow core optical fibers. The cladding of these fibers is based on the Kagomé lattice concept, with some of the core-surrounding lattice cells removed. This modification, by creating additional, glass-free regions around the core, results in a significant improvement of some important optical fiber parameters, such as confinement loss (CL), bending loss (BL), and dispersion parameter (D). According to the conducted simulations (with fused silica glass being the structure's material), CL were reduced from ~0.36 dB/m to ~0.16 dB/m (at 760 nm wavelength) in case of the structure with removed cells, and did not exceed the value of 1 dB/m across the 700⁻850 nm wavelength range. Additionally, proposed structure exhibits a remarkably low value of D-from 1.5 to 2.5 ps/(nm × km) at the 700⁻800 nm wavelength range, while the BL were estimated to be below 0.25 dB/m for bending radius of ~1.5 cm. CL and D were simulated, additionally, for structures made of acrylic glass polymethylmethacrylate, (PMMA), with similarly good results-DPMMA ∊ [2, 4] ps/(nm × km) and CLPMMA ≈ 0.13 dB/m (down from 0.41 dB/m), for the same spectral regions (700⁻800 nm bandwidth for D, and 760 nm wavelength for CL).

Application of Negative Curvature Hollow-Core Fiber in an Optical Fiber Sensor Setup for Multiphoton Spectroscopy.

In this paper, an application of negative curvature hollow core fiber (NCHCF) in an all-fiber, multiphoton fluorescence sensor setup is presented. The dispersion parameter (D) of this fiber does not exceed the value of 5 ps/nm × km across the optical spectrum of (680-750) nm, making it well suited for the purpose of multiphoton excitation of biological fluorophores. Employing 1.5 m of this fiber in a simple, all-fiber sensor setup allows us to perform multiphoton experiments without any dispersion compensation methods. Multiphoton excitation of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) with this fiber shows a 6- and 9-fold increase, respectively, in the total fluorescence signal collected when compared with the commercial solution in the form of a hollow-core photonic band gap fiber (HCPBF). To the author's best knowledge, this is the first time an NCHCF was used in an optical-fiber sensor setup for multiphoton fluorescence experiments.

Large-mode-area photonic crystal fiber with double lattice constant structure and low bending loss.

We report on a bendable photonic crystal fiber for short pulse high power fiber laser applications. This fiber uses a double lattice structure and enables single mode operation with a very large mode area that reaches 1454 µm² when the fiber is kept straight and 655 µm² in the fiber bent around a 10 cm radius. Single mode operation is enforced by the very large bending loss in excess of 50 dB/m experienced by the higher order modes, whilst bending loss for the fundamental mode is smaller than 0.01 dB/m. We outline the principles of our fiber design and we explore the guiding properties of the fiber.

Extremely large-mode-area photonic crystal fibre with low bending loss.

We report on the design of a novel flexible very large mode area photonic crystal fibre for short pulse high peak power fibre laser and beam delivery applications. This fibre has an extremely large mode area exceeding 2500 microm(2) when kept straight and over 1000 microm(2) when bent over a 10 cm radius at a wavelength of 1064 nm. In addition our fibre exhibits very small fundamental mode bending loss below 10(-2) dB/m. The large difference between the propagation loss levels of fundamental and higher order modes forces efficient single-mode guidance in the fibre core while bent. This allows using the fibre to build compact high power laser systems. The paper further explores the major features of this fibre including: the dependence of the mode field area on the fibre core shape, the influence of the bending radius and of the bending direction as well as the impact of manufacturing tolerances on the fibre specifications.

Endoluminal phototherapy for prevention of restenosis: preliminary results at 6-month follow-up.

OBJECTIVE: The objective of this observational study was to investigate safety and efficacy of laser phototherapy (LPh) in prevention of restenosis after percutaneous coronary intervention (PCI). BACKGROUND DATA: Laser irradiation is known to cause a limitation of the local inflammatory cascade and a stimulation of proliferation of specific cells. Based on the results of previous experiments proving the beneficial effects of laser light on the activity of vascular and inflammatory cells, we attempted to use these properties to prevent restenosis. METHODS: Laser phototherapy was performed in 41 patients after stent implantation or balloon angioplasty. Illumination power of 100 mW and energy dose equal to 9 J/cm(2) was used. Patients were monitored for major adverse cardiac events (MACE) after 30 days and 6 months. At 6 months, angiography as a control was performed to assess the influence of LPh on restenosis rate. RESULTS: Angiographic follow-up (n = 30) revealed restenosis in 9% and 25% of patients after stent implantation and balloon angioplasty, respectively. The MACE rate was 4.5% and 12.5% in stent and balloon-treated patients, respectively. CONCLUSIONS: Laser phototherapy gives very promising results in restenosis prevention, especially after stent implantation. The treatment method is safe, with a low rate of MACE in follow-up.

[Autofluorescence laryngoscopy in the diagnosis of laryngeal cancer--early results]. / Laryngoskopia autofluorescencyjna w diagnostyce zmian nowotworowych krtani--doniesienie wstepne.

BACKGROUND: During oncogenesis significant changes in tissue properties occur that result in alteration of fluorescence characteristics of the tissue. The aim of our study was to determine the usefulness of autofluorescence technique in diagnostic of laryngeal epithelium lesions. MATERIAL AND METHODS: 40 patients admitted to the Department of Otolaryngology Wroclaw Medical University due to different laryngeal lesions were included into the study. They underwent white light laryngoscopy followed by autofluorescence videoendoscopy. AF was induced by blue light of xenon short arc lamp and processed by a D-light AF System (Storz). Autofluorescence and white light images were immediately assessed and later compared with to histopathological findings. RESULTS: Normal laryngeal mucosa showed a typical green fluorescence signal. Squamous cell carcinoma displayed a diminished green fluorescence and in some cases presented reddish-yellow color. CONCLUSIONS: We revealed that autofluorescence laryngoscopy is very helpful, supplementary tool in diagnosis of laryngeal pathology. Autofluorescence laryngoscopy is noninvasive technique designed especially for diagnostic of early and premalignant lesions.