A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation, photonic crystal fiber

In this paper, we report on the simulation of an ultra-broadband coherent mid-infrared supercontinuum (SC) extending from 1.25 to 20 μm generated using a novel AsSe2-As2S5 multimaterial photonic crystal fiber (PCF). The proposed fiber is composed of a core made of AsSe2 glass and a surrounding cladding made of As2S5 glass. The hybrid PCF is designed to have a zero-dispersion wavelength (ZDW) of 3.3 μm with an overall highly engineered group velocity dispersion shifted to the mid-infrared wavelength region. The SC is generated by pumping 50 fs pulses at 4 μm emitted from an optical parameter amplifier with low energy of 0.625 nJ. The pumping wavelength is selected in the anomalous dispersion regime close to the ZDW. The widening of the SC is mainly based on the soliton effects in the anomalous dispersion region combined with self-phase modulation, cross-phase modulation, stimulated Raman scattering, four-wave mixing, and dispersive wave. The obtained SC shows a high degree of coherence and a 15 fs temporal compressed pulse is generated in only 5 mm long AsSe2-As2S5 hybrid PCF. The power proportion of the SC generated beyond 4 μm is 98% with its long wavelength edge up to 20 μm. To the best of our knowledge, the obtained SC is the first broadest spectrum reported in the mid-infrared region with very low energy. Our results highlight the potential of the novel chalcogenide AsSe2-As2S5 multimaterial PCF to emit across the ultra-broadband mid-infrared atmospheric windows and the molecular fingerprint region.

Numerical investigation of an ultra-broadband coherent mid-infrared supercontinuum in a chalcogenide AsSe2-As2S5 multimaterial photonic crystal fiber

In this paper, we design a polarization-maintaining CS2-core photonic crystal fiber (PM-CCPCF). The two air holes in the x direction are infiltrated with C2H5OH in order to introduce birefringence. By optimizing the structure parameters of the PM-CCPCF, it is demonstrated that the x-polarization fundamental mode has an all-normal dispersion profile and the corresponding y-polarization fundamental mode has an anomalous dispersion profile for a pump wavelength of 1.76 μm. Then, we investigate the supercontinuum (SC) generations when different fiber lengths, pump peak powers, and pump pulse widths are chosen, respectively. Simulation results show that for the x-polarization and y-polarization fundamental modes, highly coherent SCs can be generated by appropriately choosing the fiber length and pump pulse parameters. Finally, nonlinear propagation dynamics are analysed when the optimized fiber length and pump pulse parameters are used. The bandwidth of the SCs generated for the x-polarization and y-polarization fundamental modes can be up to 0.82 and 1.26 octave, respectively.

/pdf/highly-coherent-supercontinuum-generation-in-a-polarization-2mp9nbfbm7.pdf

Highly coherent supercontinuum generation in a polarization-maintaining CS2-core photonic crystal fiber.

.................................................................................................................................... III TABLE DES MATIERES ............................................................................................................... IV LISTE DES TABLEAUX................................................................................................................. VI LISTE DES FIGURES ................................................................................................................... VII LISTE DES ABBREVIATIONS ET DES ACRONYMES ........................................................... XI REMERCIEMENTS ..................................................................................................................... XIV AVANT-PROPOS ..........................................................................................................................XV 0. INTRODUCTION .................................................................................................................... 1 0.1 Les motivations ......................................................................................................................................................... 1 0.2 Pourquoi le supercontinuum (en bref...) ? ..................................................................................................... 1 0.3 Pourquoi l’infrarouge moyen? ............................................................................................................................ 2 0.4 Pourquoi la fibre optique? .................................................................................................................................... 4 1. CHAPITRE 1 : BASES THEORIQUES ET APPLICATIONS SUR LA GENERATION DE SUPERCONTINUUM ............................................................................................................... 6 1.1 Applications des sources de supercontinuum .............................................................................................. 7 1.1.1 La télédétection ..................................................................................................................................................................... 8 1.1.2 La microspectroscopie .................................................................................................................................................... 14 1.2 Revue de littérature ............................................................................................................................................. 19 1.2.1 Les lasers de pompage disponibles émettant dans le mid-IR ...................................................................... 19 1.2.2 Les SC pompés par des lasers à l’état solide ......................................................................................................... 28 1.2.3 Les SC pompés par des lasers à fibre optique ...................................................................................................... 33 1.2.4 Conclusion de la revue de littérature ....................................................................................................................... 38 1.3 La fibre optique, sa conception et l’optique linéaire ............................................................................... 39 1.3.1 La fibre optique à saut d’indice ................................................................................................................................... 39 1.3.2 Le choix des verres ............................................................................................................................................................ 40 1.3.3 La constante de propagation et la dispersion de guidage .............................................................................. 44 1.3.4 Les techniques pour ajuster la dispersion de guidage ..................................................................................... 45

https://corpus.ulaval.ca/jspui/bitstream/20.500.11794/38229/1/35603.pdf

Génération de supercontinuum dans l'infrarouge moyen à partir de fibres optiques à saut d'indice

The photonic crystal fiber (PCF) with a bunch of air holes enclosing the silica core field has momentous and compelling attributes when compared with the ordinary single-mode fibers. In this work, both the birefringence and dispersion properties of a polarization-maintaining chalcogenide (ChG) photonic crystal fiber are numerically investigated by means of the finite element method. Through simulation, it is found that the birefringence of the proposed $${\mathrm{G}\mathrm{e}}_{11.5}{\mathrm{A}\mathrm{s}}_{24}{\mathrm{S}\mathrm{e}}_{64.5}$$
 PCF can reach as high as $$0.03$$
 when compared with the conventional fiber that has merely $$5\times {10}^{-4}$$
 for wavelengths in the 2–10 
 $$\upmu \mathrm{m}$$
 range. The PCF is designed with zero-dispersion wavelengths for x- and y-polarized modes in the 2–10 
 $$\upmu \mathrm{m}$$
 range. It is also observed that over the entire MIR wavelength range, the GVD remains positive and has a maximum value of 30,000 ps2/nm-km. Hence, the proposed $${\mathrm{G}\mathrm{e}}_{11.5}{\mathrm{A}\mathrm{s}}_{24}{\mathrm{S}\mathrm{e}}_{64.5}$$
 PCF plays the dual role of acting as a very good polarization-maintaining fiber due to its very high birefringence and an excellent dispersion-compensating fiber due to its large positive GVD. This $${\mathrm{G}\mathrm{e}}_{11.5}{\mathrm{A}\mathrm{s}}_{24}{\mathrm{S}\mathrm{e}}_{64.5}$$
 PCF serves as a very good candidate for ultra-broadband high bit-rate transmission. Supercontinuum generation is another important application of PCF. Supercontinuum generation is a generation of coherent and broadband light. SC generation in PCFs has several applications in optical coherence tomography (OCT), optical frequency metrology (OFM), pulse compression, and design of ultrafast femtosecond laser pulses.

/pdf/design-and-analysis-of-dispersion-compensating-chalcogenide-5caoj69rnl.pdf

Design and analysis of dispersion-compensating chalcogenide photonic crystal fiber with high birefringence

We report a polarization maintaining chalcogenide (ChG) photonic quasicrystal fiber (PQF) for wide-band mid-IR (MIR) supercontinuum (SC) generation The numerical demonstration of SC generation in the proposed PQF spans from 2 to 15 μm wavelengths for a pulse power of 2 kW Besides, the proposed PQF offers a high birefringence (10−3 to 10−2) from 35 to 15 μm wavelengths and exhibits a low confinement loss (10−7 to 10−1) for the wavelengths from 2 to 15 μm with single mode behavior The proposed Ge115As24Se645 PQF is designed with zero dispersion wavelengths (ZDWs) at 433 and 446 μm for X and Y polarized modes within the wavelength range of 2–15 μm The polarized spectral broadening of the continuum is realized for the first time from 2 to 15 μm using the proposed PQF with a length of 8 mm Hence, the two orthogonally polarized modes allow the high degree of freedom in tuning the properties of the SC Thus, the proposed PQF-based SC source is a good candidate for applications such as optical sensing, frequency metrology, and optical tomography

Wide-band supercontinuum generation in mid-IR using polarization maintaining chalcogenide photonic quasi-crystal fiber.

A photonic crystal fiber (PCF) structure which offers exceptional research prospects to design sensors is eccentrically found applicable in wide variety of fields and thus have prompted a lot of interest among researchers. However, intending to determine PCF design configuration producing desired optical response for worthwhile application forcefully necessitates investigating vast search space with suitable topological structure variants. Moreover, the existing Finite Element Method (FEM) based numerical simulation software demands intensively long computation time for each set of design parameters with quite several repetitions and is a challenging task with reduced computational complexity. In this regard, use of Deep Neural Networks (DNN) paves way to predict the outcome in less time. One of the most significant challenges encountered while training a neural network is to generate an extensive data set. With the motive of compensating for the same issue, we propose the use of Autoencoder (AE) network to achieve data augmentation. In this research, a pioneering approach to predict optical parameters of PCF based temperature sensor using AE and DNN is presented. The proposed model is designed to make appropriate predictions of optical properties even for unknown design space parameters. The comparative metric analysis explores the efficient performance of the model with high values of R-squared ( $r^{2}$ ) score and less computation time in contrast to simulation run-time of FEM. Moreover, the proposed DNN model along with AE is proved to show very low collective mean squared error (MSE) in contrast to DNN without AE.

Deep Learning Based Data Augmentation and Behavior Prediction of Photonic Crystal Fiber Temperature Sensor

In this paper, we fabricate and demonstrate Molybdenum Tungsten Disulfide (MoWS2) composite based all-optical gas sensor for environmental monitoring applications. This proposed sensor is fabricated by coating the synthesized MoWS2 nanosheets on a side polished fiber (SPF) and analyzed the sensing performance of three important hazardous gases such as ammonia (NH3), Nitrogen dioxide (NO2) and Carbon monoxide (CO). The MoWS2 nanosheets are synthesized using the hydrothermal exfoliation technique. This novel nanocomposite offers broadband absorption and desorption of gas molecules due to more edge sites, which in turn enhances the sensing properties for various gases. Thus, the MoWS2 coated SPF sensor utilized for sensing three hazardous gases such as NH3, NO2 and CO. Besides, the gas sensor is operated at normal humidity (60–75%) and room temperature for varying gas concentration from 0 to 500 ppm. The sensor shows high sensitivity of 86, 72, and 48% for various gases such as NH3, NO2 and CO respectively. Furthermore, the results exhibit rapid response and fast recovery time, which are measured as 21 s and 60 s for NH3 gas, whereas 42 s and 71 s for NO2 gas and 93 s and 56 s for CO gas. The selectivity test for the sensor is conducted with methane and formaldehyde along with NH3, CO, and NO2 gases in the same experimental condition. Further, the results confirm that the sensor possesses a high degree of selectivity for NH3 gas among the other gases. Hence, the proposed sensor is eminently suitable to detect hazardous gases in high traffic and industrial fields.

All Fiber-Optic Multigas (NH₃, NO₂, and CO) Sensor Based on MoWS₂ Coated Fiber

A photonic crystal waveguide (PhCW) based coupler is numerically designed to realize the operation of wavelength division multi/demultiplexer (MUX/DEMUX). The PhCW coupler consists of Ge2Sb2Se4Te1 phase changing material (PCM) rods arranged in a square lattice pattern in air background. MUX/DEMUX is realized by optical phase changing between coupling and decoupling of PhCWs. Further, the contrast ratio of DEMUX is achieved about 19 and 29 dB for wavelengths 1530 and 1550 nm. The proposed design act as a good candidate in the wavelength division multiplexing and demultiplexing for the application of optical communications.

M. Valliammai

Papers

Wide-band supercontinuum generation in mid-IR using polarization maintaining chalcogenide photonic quasi-crystal fiber.

Deep Learning Based Data Augmentation and Behavior Prediction of Photonic Crystal Fiber Temperature Sensor

All Fiber-Optic Multigas (NH₃, NO₂, and CO) Sensor Based on MoWS₂ Coated Fiber

Phase Changing Material based Multi/Demultiplexer with Photonic Crystal Waveguide Couplers for Optical Communication