Chalcogenide-glass polarization-maintaining photonic crystal fiber for mid-infrared supercontinuum generation

In this paper, we report the design and fabrication of a highly birefringent polarization-maintaining photonic crystal fiber (PM-PCF) made from chalcogenide glass, and its application to linearly-polarized supercontinuum (SC) generation in the mid-infrared region. The PM fiber was drawn using the casting method from As38Se62 glass which features a transmission window from 2 to 10 $\mu m$ and a high nonlinear index of 1.13.10$^{-17}$m$^{2}$W$^{-1}$. It has a zero-dispersion wavelength around 4.5 $\mu m$ and, at this wavelength, a large birefringence of 6.10$^{-4}$ and consequently strong polarization maintaining properties are expected. Using this fiber, we experimentally demonstrate supercontinuum generation spanning from 3.1-6.02 $\mu m$ and 3.33-5.78 $\mu m$ using femtosecond pumping at 4 $\mu m$ and 4.53 $\mu m$, respectively. We further investigate the supercontinuum bandwidth versus the input pump polarization angle and we show very good agreement with numerical simulations of the two-polarization model based on two coupled generalized nonlinear Schr\"odinger equations.Comment: 13 pages, 8 figure

Design of an Efficient Pumping Scheme for Mid-IR Dy3+:Ga5Ge20Sb10S65 PCF Fiber Laser

This letter illustrates the design of a novel medium infrared (Mid-IR) laser based on a photonic crystal fiber made of dysprosium-doped chalcogenide glass, Dy3+:Ga5Ge20Sb10S65. In order to perform a realistic investigation, the simulation is performed by taking into account the spectroscopic parameters measured on the rare earth-doped glass sample. The simulated results show that an optical beam emission close to 4400-nm wavelength can be obtained by employing two pump beams at 2850 nm (pump #1) and 4092 nm (pump #2) wavelengths. The pump beams can be provided by commercial quantum cascade lasers. As example, for the pump powers of 50 mW (pump #1) and 1 W (pump #2), the input mirror reflectivity of 99%, the output mirror reflectivity of 30%, and the optical cavity length of 50 cm, a signal power close to 350 mW at the wavelength of 4384 nm can be generated. This result indicates that the designed source configuration is feasible for high beam quality Mid-IR light generation and it is efficient enough to find applications in optical free propagation links, optical remote sensing, and medicine

Glass and process development for the next generation of optical fibers: A review

Applications involving optical fibers have grown considerably in recent years with intense levels of research having been focused on the development of not only new generations of optical fiber materials and designs, but also on new processes for their preparation. In this paper, we review the latest developments in advanced materials for optical fibers ranging from silica, to semi-conductors, to particle-containing glasses, to chalcogenides and also in process-related innovations.John Ballato, Heike Ebendorff-Heidepriem, Jiangbo Zhao, Laeticia Petit and Johann Trole

Dysprosium-doped chalcogenide Master Oscillator Power Amplifier (MOPA) for Mid-IR emission

The paper describes the design of a medium infrared fiber laser based on a dysprosium-doped chalcogenide glass Dy3+: Ga5Ge20Sb10S65. To obtain a high efficiency, the fiber laser is followed by an optical amplifier. The optimized optical source exploits a master oscillator power amplifier (MOPA) configuration. The MOPA pump and signal wavelengths are 1709 and 4384 nm, respectively. Spectroscopic parameters measured on preliminary samples of chalcogenide glasses are taken into account to fulfill realistic simulations. The MOPA emission is maximized by applying a particle swarm optimization approach. For the dysprosium concentration 6, ×, 1025 ions/m3 and the input pump power of 3 W, an output power of 637 mW can be obtained for optical fiber losses close to 1 dB m-1. The optimized MOPA configuration allows a laser efficiency larger than 21%. By considering the high beam quality provided by photonic crystal fibers, it is a good candidate for medium infrared light generation whose main applications include, but are not limited to, molecular spectroscopy and environmental monitoring

Comparing Deep Learning and MCWST Approaches for Individual Tree Crown Segmentation

Accurate segmentation of individual tree crowns (ITC) segmentation is essential for investigating tree-level based growth trends and assessing tree vitality. ITC segmentation using remote sensing data faces challenges due to crown heterogeneity, overlapping crowns and data quality. Currently, both classical and deep learning methods have been employed for crown detection and segmentation. However, the effectiveness of deep learning based approaches is limited by the need for high-quality annotated datasets. Benefiting from the BaKIM project, a high-quality annotated dataset can be provided and tested with a Mask Region-based Convolutional Neural Network (Mask R-CNN). In addition, we have used the deep learning based approach to detect the tree locations thus refining the previous Marker controlled Watershed Transformation (MCWST) segmentation approach. The experimental results show that the Mask R-CNN model exhibits better model performance and less time cost compared to the MCWST algorithm for ITC segmentation. In summary, the proposed framework can achieve robust and fast ITC segmentation, which has the potential to support various forest applications such as tree vitality estimation

Addition of Ag2O in Er3+doped oxyfluorophosphate glass to allow the drawing of optical fibers

Here, Ag2O containing glasses in the NaPO3–CaF2 glass network were prepared using standard melting process. The addition of Ag2O was found to increase the thermal stability of the glass due to the decrease in the Q2 units at the expense of Q1 units, to decrease the intensity of the upconversion under 980 nm pumping and to have a small impact on the nucleation and growth mechanism. Due to the thermal stability against crystallization of the glass prepared with 4 mol % of Ag2O, we demonstrate that fiber can be drawn from this glass. Despite the formation of Ag nanoparticles at the surface of the fiber although the drawing is a fast process, light can still be confined in the fiber. The fiber exhibits a large emission band centered at 1.5 μm under 980 nm pumping.Peer reviewe

Optical nonlinearity in PbO-SiO2 glass : Kramers-Kronig analyses

Relationship between nonlinear refractivity and two-photon absorption has been studied for PbO–SiO2 glasses using a nonlinear Kramers–Kronig relation. Nonlinear refractive indices, which are determined with z-scan measurements, are consistent with those which are calculated using the relation from two-photon absorption spectra. This consistency suggests that large intensity-dependent refractivity in this glass system arises from resonant two-photon electronic transitions from oxygen 2p to lead 6p states

Broadband mid-infrared supercontinuum generation in dispersion-engineered As2S3-silica nanospike waveguides pumped by 2.8 μm femtosecond laser

International audienceBroadband mid-infrared (IR) supercontinuum laser sources are essential for spectroscopy in the molecular fingerprint region. Here, we report generation of octave-spanning and coherent mid-IR supercontinua in As2S3-silica nanospike hybrid waveguides pumped by a custom-built 2.8 μm femtosecond fiber laser. The waveguides are formed by pressure-assisted melt-filling of molten As2S3 into silica capillaries, allowing the dispersion and nonlinearity to be precisely tailored. Continuous coherent spectra spanning from 1.1 μm to 4.8 μm (30 dB level) are observed when the waveguide is designed so that 2.8 μm lies in the anomalous dispersion regime. Moreover, linearly tapered millimeter-scale As2S3-silica waveguides are fabricated and investigated for the first time, to the best of our knowledge, showing much broader supercontinua than uniform waveguides, with improved spectral coherence. The waveguides are demonstrated to be long-term stable and water-resistant due to the shielding of the As2S3 by the fused silica sheath. They offer an alternative route to generating broadband mid-IR supercontinua, with applications in frequency metrology and molecular spectroscopy, especially in humid and aqueous environments. © 2021 Chinese Laser Pres