We report on modeling, development, and optical characterization of fused silica photonic crystal fiber with germanium doped microinclusion placed in the middle of the core. The fiber is designed to ...efficiently couple and guide LP02 mode. It offers high optical density in the center region, large mode separation, low losses, and small dispersion with relatively flat profile for both LP01 and LP02 modes in 1-1.6 µm wavelength range. We demonstrate that by changing geometrical and material parameters of the inclusion partially independent tuning of propagation constants of individual modes is possible, what might be found is a variety of potential applications, e.g., in nonlinear optics. We also show that diffraction-limited propagation of LP02 mode in free space can be exploited in microscopy or lab-on-a-chip systems, where the proposed fiber can be used for light delivery.
We propose a new approach to developing of graded-index chalcogenide fibers. Since chalcogenide glasses are incompatible with current vapor deposition techniques, the arbitrary refractive index ...gradient is obtained by means of core nanostructurization by the effective medium approach. We study the influence of graded-index core profile and the core diameter on the fiber dispersion characteristics. Flat, normal dispersion profiles across the mid-infrared transmission window of the assumed glasses are easily obtained for the investigated core nanostructure layouts. Nonlinear propagation simulations enable to expect 3.5-8.5 µm spectrum of coherent, pulse preserving supercontinuum. Fabrication feasibility of the proposed fiber is also discussed.
We present a novel method for the development of a micro lenslets hexagonal array. We use gradient index (GRIN) micro lenses where the variation of the refraction index is achieved with a structure ...of nanorods made of 2 types of glasses. To develop the GRIN micro lens array, we used a modified stack-and-draw technology which was originally applied for the fabrication of photonic crystal fibers. This approach results in a completely flat element that is easy to integrate with other optical components and can be effectively used in high refractive index medium as liquids. As a proof-of-concept of the method we present a hexagonal array of 469 GRIN micro lenses with a diameter of 20 µm each and 100% fill factor. The GRIN lens array is further used to build a Shack-Hartmann detector for measuring wavefront distortion. A 50 lens/mm sampling density is achieved.
Dissipative soliton resonance (DSR) is a promising operation regime in fiber lasers where unlimited pulse energy boost is expected. However, several phenomena classified as anti-DSR performance were ...reported recently. Here pulse shrinkage of DSR pulses is investigated in a fiber laser. By setting a central-wavelength-drifting Gaussian filter, after DSR performance of pulse broadening with increasing gain, the pulse shrinkage occurs when the gain continues to increase. A central-wavelength-drifting bimodal filter can also achieve pulse shrinkage. In addition, pulse shrinkage together with period doubling can be observed by changing the initial settings.
•We observed pulse shrinkage phenomenon in simulation by using a central-wavelength-drifting Gaussian filter.•We observed similar results when changing the Gaussian filter to a bimodal filter.•We also observed pulse shrinkage phenomenon with period doubling.
The series of SiO2-Bi2O3-PbO-ZnO-BaO and SiO2-TiO2-Bi2O3-PbO-Na2O glasses were synthetized to obtain non-crystallizing materials, dedicated to fabrication of photonic crystal fibers. During ...composition development, the thermal properties were investigated according to the change of chemical composition. The glasses contain high concentrations of heavy metal oxides for high refractive index, large nonlinear refractive index and spectrally broad transmission window from 0.5 to 4.5 μm. Their thermal properties are optimized to enable drawing of all-solid glass photonic crystal fibers in tandem with previously designed highly nonlinear glass PBG81 based on SiO2-Ga2O3-Bi2O3-PbO-CdO system. This creates novel dual glass combinations for PCF fibers. We have also investigated influence of melting conditions on the final thermal and optical properties, including absorption from water contamination at around 2.8 μm.
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•Thermal properties of SiO2-Bi2O3-PbO-ZnO-BaO and SiO2-TiO2-Bi2O3-PbO-Na2O glass systems were investigated.•Developed glass composition of 50SiO2-10Bi2O3-20PbO-15ZnO-5BaO, is suitable for fabrication of nonlinear all-solid photonic crystal fibers.•The influence of various synthesis conditions on final thermal and optical properties have been determined.•Glass absorption coefficient at 2.8–3.3 μm was reduced to 0.12 cm−1 by proper synthesis conditions and air rinsing of glass melt during synthesis.
Intensity stability and wavelength correlations of near-infrared supercontinuum generation are studied in all-normal flattened dispersion, all-solid soft glass photonic crystal fiber. We use ...dispersive Fourier transformation method to measure shot-to-shot resolved spectra under pumping from a sub-picosecond, fiber-based chirped pulse amplification (CPA) system. For the first time to our knowledge, we demonstrate how unconverted radiation from pump, propagating in the photonic cladding of the fiber, improves the measured degree of coherence in the spectrum and influences its wavelength correlation by seeding of multiple four-wave-mixing / Raman scattering components. The presented results suggest a convenient and simple way of stabilizing of shot-to-shot coherence in sub-picosecond fiber laser pumped, normal-dispersion supercontinuum sources by direct, pump-related seeding.
A unique type of refractive index (RI) sensor is proposed using a dual Mach-Zehnder interferometer (MZI) structure based on side-hole fibers (SHFs). The MZI structure contains two single-mode fibers ...(SMFs), two coreless fiber (CLF) sections and an SHF section, which are spliced together in the order of SMF-CLF-SHF-CLF-SMF. The SMFs and the CLFs enable light lead in/out and beam splitting/combining, respectively. As a special feature of the structure, one hole of SHF is exposed for liquid filling and to form two MZIs as well. Three types of sensors are fabricated, namely S1, S2 and S3. Numerical simulation and experimental studies have been conducted to characterize the sensing performance. The RI sensitivity of the S1 using the ~550 μm long SHF section reaches 14,000 nm/RIU. When a shorter SHF section is used in S2, the detectable RI range is broadened due to larger FSR. When the closed hole of SHF in S3 is filled with liquid to introduce the Vernier effect, the sensitivity can be further enhanced to over 44,000 nm/RIU (i.e., Refractive Index Unit), which corresponds to the detection limit at the level of 1.0 × 10 -5 RIU. This sensor design is original and easy to package, which gives it potential for label-free biochemical analyses.
In this work we present a numerical study on attenuation of the fundamental mode in a suspended-core photonic crystal fibre (SC-PCF) made of fused silica, when a biological layer with various ...thickness and complex refractive index is present on the struts supporting the core and the photonic cladding (channels) is filled with water. In such a fibre structure both the effective refractive index and the mode area increase nonlinearly with the refractive index and with the thickness of the bio-layer, that in turn causes the increase of the attenuation of the fundamental (highest-neff) mode. For the calculation wavelength of 1μm the increase is intensified when the refractive index of the bio-layer exceeds 1.42, what is usually the case when even thin bio-layer is concerned. It is shown that it is possible to use such a fibre as a label-free sensor of a certain bio-layer deposited on a functionalised inner surface of the fibre.
•Attenuation of a suspended-core photonic crystal fibre with a biolayer is studied.•Biolayer covers the struts supporting the core and the cladding is water-filled.•The fibre can be used as a label-free sensor of a certain bio-layers.•Detection of bio-layer growth in real time is also possible.
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