Experimental investigation of mid-infrared laser action from DY3+ doped fluorozirconate fiber

Efficient continuous-wave laser operation at 2.982 μm is achieved with a Dy3:fluoride fiber pumped using an inhouse-built 1.1 μm ytterbium (III) fiber laser. The laser output power reached is 554 mW, with a maximum slope efficiency of 18% with respect to the launched pump power. Additionally, the measured spontaneous luminescence within the visible wavelength range, under 1.1 μm pumping, is presented and attributed to excited state absorption (ESA). The influence of the ESA on the laser performance is discussed. The results confirm that high output powers from Dy: fluoride fiber laser pumped at 1.1 μm are possible

A Dual Hollow Core Antiresonant Optical Fiber Coupler Based on a Highly Birefringent Structure-Numerical Design and Analysis

With the growing interest in hollow-core antiresonant fibers (HC-ARF), attributed to the development of their fabrication technology, the appearance of more sophisticated structures is understandable. One of the recently advancing concepts is that of dual hollow-core antiresonant fibers, which have the potential to be used as optical fiber couplers. In the following paper, a design of a dual hollow-core antiresonant fiber (DHC-ARF) acting as a polarization fiber coupler is presented. The structure is based on a highly birefringent hollow-core fiber design, which is proven to be a promising solution for the purpose of propagation of polarized signals. The design of an optimized DHC-ARF with asymmetrical cores is proposed, together with analysis of its essential coupling parameters, such as the extinction ratio, coupling length ratio, and coupling strength. The latter two for the x- and y-polarized signals were ~2 and 1, respectively, while the optical losses were below 0.3 dB/cm in the 1500–1700 nm transmission band

Combining Hollow Core Photonic Crystal Fibers with Multimode, Solid Core Fiber Couplers through Arc Fusion Splicing for the Miniaturization of Nonlinear Spectroscopy Sensing Devices

The presence of fiber optic devices, such as couplers or wavelength division multiplexers, based on hollow-core fibers (HCFs) is still rather uncommon, while such devices can be imagined to greatly increase the potential of HCFs for different applications, such as sensing, nonlinear optics, etc. In this paper, we present a combination of a standard, multimode fiber (MMF) optic coupler with a hollow core photonic bandgap fiber through arc fusion splicing and its application for the purpose of multiphoton spectroscopy. The presented splicing method is of high affordability due to the low cost of arc fusion splicers, and the measured splicing loss (SL) of the HCF-MMF splice is as low as (0.32 ± 0.1) dB, while the splice itself is durable enough to withstand a bending radius (rbend) of 1.8 cm. This resulted in a hybrid between the hollow core photonic bandgap fiber (HCPBF) and MMF coupler, delivering 20 mW of average power and 250-fs short laser pulses to the sample, which was good enough to test the proposed sensor setup in a simple, proof-of-concept multiphoton fluorescence excitation-detection experiment, allowing the successful measurement of the fluorescence emission spectrum of 10−5 M fluorescein solution. In our opinion, the presented results indicate the possibility of creating multi-purpose HCF setups, which would excel in various types of sensing applications

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)

100 hrs endurance test of a DUV laser beam delivery via a hollow-core photonic crystal fiber patchcord

International audienceWe report on the development of inhibited-coupling hollow-core photonic crystal fiber with record-low transmission loss of <50 dB/km at 266 nm, and solarization-free. 2 meter-long patchcord with SMA terminations were made and their UV handling and lifespan were tested. A laser beam from a 266 nm wavelength laser-source emitting 1 ns wide and 27 µJ energy pulses was injected into the hollow-core fiber patchcord, achieving a total transmission rate of 93%. The laser beam was kept continuously coupled to the patchcord for over 100 hrs. The results show excellent stability in transmitted power (fluctuations of less than 2.6%) and in mode quality. To our knowledge, this is the first fiber guidance of DUV laser that combines high energy handling and long lifespan. The results mark a major milestone in the adoption of fiber UV laser beam delivery by the industrial community

Yellow laser based on the inhibited-coupling hollow-core photonic crystal fibre technology

International audienceWe report on a Raman laser emitting in the yellow spectral range using a CO2-filled hollow-core photonic crystal fiber. Taking advantage of a state-of-art inhibited-coupling hollow-core photonic crystal fibre, exhibiting minimum transmission loss of ~1 dB/km in the 500-600 nm region, we were able to develop an extremely compact and simple yellow-Raman laser scheme, allowing to emit as much as 60 mW of average power at the 574.5 nm wavelength while using a compact, microchip laser as a pump source. This solution provides an innovative and scalable alternative for the other yellow laser schemes, which are of high demand in the field of biophotonics due to their effective interaction with hemoglobin and melanin

New models and algorithms for RNA pseudoknot order assignment

The pseudoknot is a specific motif of the RNA structure that highly influences the overall shape and stability of a molecule. It occurs when nucleotides of two disjoint single-stranded fragments of the same chain, separated by a helical fragment, interact with each other and form base pairs. Pseudoknots are characterized by great topological diversity, and their systematic description is still a challenge. In our previous work, we have introduced the pseudoknot order: a new coefficient representing the topological complexity of the pseudoknotted RNA structure. It is defined as the minimum number of base pair set decompositions, aimed to obtain the unknotted RNA structure. We have suggested how it can be useful in the interpretation and understanding of a hierarchy of RNA folding. However, it is not trivial to unambiguously identify pseudoknots and determine their orders in an RNA structure. Therefore, since the introduction of this coefficient, we have worked on the method to reliably assign pseudoknot orders in correspondence to the mechanisms that control the biological process leading to their formation in the molecule. Here, we introduce a novel graph coloring-based model for the problem of pseudoknot order assignment. We show a specialized heuristic operating on the proposed model and an alternative integer programming algorithm. The performance of both approaches is compared with that of state-of-the-art algorithms which so far have been most efficient in solving the problem in question. We summarize the results of computational experiments that evaluate our new methods in terms of classification quality on a representative data set originating from the non-redundant RNA 3D structure repository

Corrigendum to “The influence of anchoring group position in ruthenium dye molecule on performance of dye-sensitized solar cells” ((10.1016/j.dyepig.2017.12.029) (Dyes and Pigments (2018) 150 (335–346), (S0143720817323513), (10.1016/j.dyepig.2017.12.029))

The authors would like to apply the following corrections to the above paper: The data presented in Table 1 for the 455 2PF6 have been incorrect and should be changed to: Table 1. Key CV patterns for the investigated molecules: reduction and oxidation peak potentials (Epc and Epa respectively), referred to the Fc+|Fc redox couple; for first reduction and oxidation peaks only: dEp/dlogv slopes; current densities j (normalized for concentration c and square root of potential scan rate v0.5); formal standard potentials E°’ (calculated as the average of Ep,forward and Ep,backward); corresponding HOMO and LUMO energy levels together with the corresponding energy gap Eg. [Table presented] The authors would like to apologize for any inconvenience caused.</p

The influence of anchoring group position in ruthenium dye molecule on performance of dye-sensitized solar cells

The effect of anchoring group position and, in consequence, the orientation of the ruthenium dye molecule on titania surface on the performance of dye-sensitized solar cells has been studied intensively. Three model ruthenium sensitizing dyes bearing carboxylic anchoring group in ortho, meta or para position were synthesized and well characterized by spectroscopic, electrochemical, photophysical and photochemical measurements. The results were confronted with the quantum-mechanical calculations and discussed. The para derivative has been found as the most effective sensitizer with the cells efficiency twice higher than the meta and four times higher than the ortho derivatives.</p