Silica Photonic Crystal Fiber Research Articles

Mixed integer programming with kriging surrogate model technique for dispersion control of photonic crystal fibers

In this paper, mixed integer nonlinear programming (MINLP) optimization algorithm integrated with kriging surrogate-model is newly formulated to optimize the dispersion characteristics of photonic crystal fibers (PCFs). The MINLP is linked with full vectorial finite difference method (FVFDM) to optimize the modal properties of the PCFs. Through the optimization process, the design parameters can take real and/or integer values. The integer values can be used to selectively fill the PCF air holes to control its dispersion characteristics. However, the other optimization techniques deal with real design parameters where the PCF can be optimized using none or predefined infiltrated air holes. The MINLP algorithm is used to obtain an ultra-flat zero dispersion over a broadband of wavelength range from 1.25 to 1.6 μm using silica PCF selectively infiltrated with Ethanol material. To show the superiority of the proposed algorithm, nematic liquid crystal selectively infiltrated PCFs are also designed with high negative flat dispersion over wide range of wavelengths from 1.25 to 1.6 μm for the quasi transverse magnetic (TM) and the quasi transverse electric (TE) modes. Such designs have negative flat dispersions of − 163 ± 0.9 and − 170 ± 1.2 ps/Km nm, respectively over the studied wavelength range. Therefore, the MINLP algorithms could be used efficiently for the design and optimization of selectively filled photonic devices.

Visible to Mid-IR Supercontinuum Generation in Cascaded PCF-Germanate Fiber Using Femtosecond Yb-Fiber Pump

Broadband supercontinuum (SC) fiber sources covering the mid-IR range have many significant applications, largely due to their compactness, reliability, and ease of use. However, most of the existing SC fiber sources cannot boast of either high reliability or a wide bandwidth. Thus, supercontinuum sources based on silica fibers are robust, but are not capable of generating SC in the mid-IR range. Sources based on soft glasses (tellurite, chalcogenide, etc.) generate broadband SC in the mid-IR range but are not used commercially, due to the poor mechanical and chemical characteristics of such fibers. In this work, we propose a new approach consisting of cascade generation of a supercontinuum sequentially in a silica photonic crystal fiber (PCF) and a germanate fiber. Using a standard ytterbium chirped-pulse amplification (CPA) laser system for pumping, we have demonstrated a supercontinuum in the range of 450–2950 nm in PCF and germanate fiber firmly connected by a standard fusion splicing technique. Further optimization of the cascade pump will make it possible to create a compact and reliable all-fiber SC source from the visible to mid-IR range.

Proposal of a novel analytical method for simultaneous ultra-broadband and ultrashort laser pulses generation in photonic crystal fibers with optimized manufacturing process

In this paper, a novel method for simultaneous ultra-broadband and ultrashort femtosecond laser pulse generation in silica photonic crystal fibers is investigated analytically using the fully vectorial effective index method (FVEIM). By reducing the impact of fifth and lower-order dispersions, the method produces narrower laser pulses and wider supercontinuum using a fixed soliton order over a specific distance of the fiber. Additionally, the larger effective areas utilized in this approach make the manufacturing process simpler compared to other samples. These simultaneous features represent the primary innovations of this study.

Novel Bottom-Side Polished PCF-Based Plasmonic Biosensor for Early Detection of Hazardous Cancerous Cells.

This work presents a single-core bowl-shaped bottom-side polished (BSP) photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) concept for the early detection of hazardous cancer cells in human blood, skin, cervical, breast, and adrenal glands. We have studied liquid samples of cancer-affected and healthy samples with their concentrations/refractive indices in the sensing medium. To induce a plasmonic effect in the PCF sensor, the bottom flat section of a silica PCF fiber is coated with a 40nm plasmonic material, such as gold. To strengthen this effect, a thin TiO2 layer of 5 nm is sandwiched between fiber and gold as it strongly holds gold nanoparticles with smooth fiber surface. When the cancer-affected sample is introduced to the sensor's sensing medium, it produces a different absorption peak in the form of a resonance wavelength than the healthy sample. This reallocation of the absorption peak is used to determine sensitivity. Hence, the obtained sensitivities for blood cancer, cervical cancer, adrenal gland cancer, skin cancer, and breast cancer (type-1and type-2) cells are 22,857nm/RIU, 20000nm/RIU, 20714nm/RIU, 20000nm/RIU, 21428nm/RIU, and 25000nm/RIU, respectively, with highest detection limit 0.024. These strong findings indicate that our proposed cancer sensor PCF is a viable choice for early cancer cell detection.

Pure quartic wave modulation in optical fiber with the presence of self-steepening and intrapulse Raman scattering response

Modulational instability (MI) is addressed in an optical fiber under competing effects between pure-quartic dispersion (PQD), self-steepening, and intrapulse Raman response. The self-steepening parameter reduces the maximum MI gain and the frequency bandwidth. Under the combined effects of the self-steepening and intrapulse Raman scattering, more spectral windows appear in the gain spectrum, induced by the increasing Raman effect. Numerical results fully concur with the theoretical predictions. The MI is manifested by the emergence of ultrashort pulses trains and rogue wave breathing trains. Under increasing self-steepening effect, asymmetric sidebands, reversible via the Raman scattering effect, appear in the spectral and temporal evolution of the pulse trains, which probes the tunability of energy transfer between the mode during signal propagation. Our results open up further perspectives for exploring mechanisms to generate ultrashort pulses in PQD optical media under higher-order nonlinearities, with applications to silicon photonic crystal waveguides and silica photonic crystal fibers.

Investigation of space division multiplexing in multimode step-index silica photonic crystal fibers

The feasible distance is presented for space division multiplexed (SDM) transmission along multimode silica step-index photonic crystal fiber (SI PCF) by solving the time-independent power flow equation (TI PFE). These distances for two and three spatially multiplexed channels were determined to depend on mode coupling, fiber structural parameters, and launch beam width in order to keep crosstalk in two- and three-channel modulation to a maximum of 20% of the peak signal strength. We found that the length of the fiber at which an SDM can be realized increases with the size of the air-holes in the cladding (higher NA). When a wide launch excites more guiding modes, these lengths become shorter. Such knowledge is valuable for the use of multimode silica SI PCFs in communications.

Design and modeling of the nonlinear properties of octagonal lattice Ge20Sb5Se75 photonic crystal fibers

Most silica photonic crystal fibers have limited spectral broadening in the infrared region, making them less than ideal in terms of technological applications. In this work, we propose a new Ge20Sb5Se75 chalcogenide octagonal photonic crystal fiber that provides diverse dispersions with all-normal and anomalous regimes and multiple zero-dispersion wavelengths. The nonlinear properties are investigated over a wide wavelength range up to 14 µm by numerically solving Maxwell's wave equations using Lumerical Mode Solutions software. The full-vector finite-difference eigenmode method minimizes the losses so that low confinement losses in the short-wavelength region of 1 − 6 µm are found and nonlinear coefficients as high as thousands of W−1.km−1 are achieved. Three fibers with an all-normal dispersion profile and anomalous dispersion with one or three zero dispersion wavelengths are proposed for supercontinuum generation. The fibers provide small dispersion values of −0.88, 0.08, and 1.646 ps/(nm.km) at suitable pump wavelengths. Furthermore, the very small confinement loss of approximately 10−5 to 10−11 dB/m is the outstanding advantage of these optical fibers. A broadband spectrum with low input power is expected as a result of the proposed fiber-based supercontinuum generation.

Silica-based Photonic Crystal Fiber for Supercontinuum Generation in the Anomalous Dispersion Region: Measurement and Simulation

We report on numerical simulation and experimental study of the supercontinuum (SC) generation in the anomalous dispersion region of photonic crystal fiber (PCF). The results show that a flat and stable spectrum with bandwidth of 130 nm around the central pump wavelength was achieved with an input power of 4.0 W. Although the measured spectrum is slightly different from the numerical ones, a good consistency can be recognized in the major sideband positions and spectral width. In addition, the chromatic dispersion of air silica PCF was measured at visible and near-infrared wavelengths using the Mach-Zehnder interferometer configuration and then verified by comparison with simulated results.

Modeling nonlinear high-pressure sensors based on degenerate four-wave mixing in photonic crystal fibers.

We propose a high-pressure sensing mechanism in solid-core silica photonic crystal fibers (PCF) that is based on the nonlinear optical process of degenerate four-wave mixing. A quite simple configuration for the pressure sensor is given and is theoretically investigated by obtaining signal gain spectra. We focus on the Stokes and anti-Stokes sidebands that are generated during propagation of the field along the PCF due to the interplay of dispersion and nonlinear optical effects. We have considered wave propagation in the normal dispersion regime with the inclusion of negative fourth-order dispersion. We have also considered a pumping field with wavelength of 1076 nm and peak power of 3000 W that propagates along a PCF with 40 cm of length. We have optimized sensitivity, varying lattice pitch and air-hole diameter, and we have obtained high sensitivities of the Stokes and anti-Stokes lines of 3.672 and -0.146nm/MPa, respectively. The proposed sensors have potential applicability in high-pressure environments.

Theoretical Investigation of Bandwidth in Multimode Step-Index Silica Photonic Crystal Fibers

Solving the time-dependent power flow equation (PFE) provides a useful method to study the transmission bandwidth of step-index silica photonic crystal fibers (SI SPCFs). The transmission bandwidth of these kinds of fibers is determined for different air-hole structures (different numerical apertures (NAs)) and different distribution widths of the Gaussian launch beam. The results indicate that the lower the NA of SI SPCFs, the higher the bandwidth (for example, for a lower NA of SI SPCFs, a bandwidth that is eight times larger is obtained at a fiber length of 3500 m). The narrower launch beam at short fiber lengths results in a wider bandwidth. The longer the fiber (>300 m), the much less the effect of the launch beam width on the bandwidth. The bandwidth becomes independent of the width of the launch beam distribution at the fiber length at which a steady-state distribution (SSD) is reached. These results are useful for some potential applications, such as high capacity transmission optical fiber systems.

Supercontinuum generation in benzene-filled hollow-core fibers

Supercontinuum generation (SG) in fused silica photonic crystal fibers (PCFs) having a core infiltrated with liquid benzene is analyzed. Three PCF designs, with dimensions and chromatic dispersion optimized for SG using off-the-shelf femtosecond pulse lasers (1560 nm, 90 ps), are proposed. F1 fiber with lattice constant Λ = 1.5 μm and linear filling factor f = 0.45 has all-normal dispersion and offers SG in the 700- to 2000-nm band at relative power levels within 15 dB when pumped with 3 nJ pulses. F2 fiber (Λ = 1.5 μm, f = 0.6) enables SG in an anomalous dispersion regime, covering 600 to 2600 nm spectral range at relative power levels within 30 dB when pumped with low-energy pulses (1 nJ). The F3 fiber (Λ = 2.5 μm, f = 0.6) also exhibits mostly anomalous dispersion and makes possible SG in a very broad 600 to 3500 nm range at relative power levels within 30 dB when pumped with 2 nJ pulses.

Method for investigation of mode coupling in multimode step-index silica photonic crystal fibers

We propose a new method for investigation the state of mode coupling in a multimode step-index silica photonic crystal fiber (SI SPCF) with a solid-core by solving the time-independent power flow equation. For various arrangements of air-holes (different numerical apertures (NAs)), as well as a different widths of launch beam distribution, the length Lc for achieving equilibrium mode distribution (EMD) and length zs at which a steady state distribution (SSD) is established are determined for such fiber. We obtained that the larger the air holes in the cladding (higher NA), the longer length of the fiber it takes for the modal distribution-transients to reach their equilibrium and steady state. In the case of a wide launch that excites more guiding modes, these lengths shorten. Such information is of interest for application of multimode SI SPCFs in telecommunication and fiber optic sensors.

Effects of the induced seed pulse on generation of ultra-short pulse sequences by dark solitons

We study the impact of the seed pulse on ultra-short pulse sequences and narrow-band sources produced by pumping two input pulses that are identical but delayed one with another in a 10-mm long silica photonic crystal fiber with two ZDWs. The collision between the induced seed pulse and input pulses will increase the power of ultra-short pulse sequences in long-wavelength region. The darkness of dark solitons on the red side of pump is influenced by modulation frequencies and depths of the seed pulse. In particular, the energy red-shift of narrow-band sources can be obtained by tuning the parameters of the seed pulse. Besides, initial chirp also influences the generation of ultra-short pulse sequences by dark solitons. We have shown that it is effective to control the power of ultra-short pulse sequences by varying the parameters of the seed pulse.

Optimization of the ultra-flattened normal dispersion in photonic crystal fibers infiltrated with olive oil for supercontinuum generation

This paper proposes a pure silica photonic crystal fiber (PCF), having its core infiltrated with olive oil, which allows achieving an ultra-flattened normal dispersion regime. As a result, the optimization processes allows us to achieve an ultra-flat normal dispersion in the range of over 682 nm within the wavelength range from 1446 to 2128 nm. Besides, the nonlinear coefficient of the selected PCF structure is extremely high (9.54 x 109 W-1.km-1 at 1550 nm). The proposed PCF structure could be very helpful in investigating the supercontinuum generation which has many potential applications in various promising areas such as spectroscopy, medical diagnostics, etc. Full Text: PDF ReferencesJ.M.Dudley, G.Genty and S.Coen, "Supercontinuum generation in photonic crystal fiber", Rev. Mod. Phys. 78(2006). CrossRef T.Udem, R.Holzwarth and T.W.Hänsch, "Optical frequency metrology", Nature 416 233-7(2002). CrossRef S.Moon and D.Y.Kim, "Ultra-high-speed optical coherence tomography with a stretched pulse supercontinuum source", Opt. Express 14 11575-84 (2006). CrossRef G.P.Agrawal. "Chapter 11 - Highly Nonlinear Fibers", Nonlinear Fiber Optics (Oxford: Academic Press 2013) CrossRef V.R.K. Kumar, A.K. George, J.C. Knight, P.S.J. Russell, "Tellurite photonic crystal fiber", Opt. Exp. 11 2641-2645 (2003). CrossRef R. Buczynski, H. T. Bookey, D. Pysz, R. Stepien, I. Kujawa, J. E. McCarthy, A. J. Waddie, A. K. Kar and M. R. Taghizadeh, "Supercontinuum generation up to 2.5 μm in photonic crystal fiber made of lead-bismuth-galate glass", Laser Phys. Lett.7 666-72 (2010). CrossRef F.G.Omenetto, N.A.Wolchover, M.R. Wehner, M. Ross, A. Efimov, A.J. Taylor, V.V.R.K. Kumar, A.K. George, J.C. Knight, N.Y. Joly, P.St.J. Russell, "Spectrally smooth supercontinuum from 350 nm to 3 µm in sub-centimeter lengths of soft-glass photonic crystal fibers.", Opt. Express 14 4928-4934 (2010). CrossRef H. L.Van, V. C. Long, H. T. Nguyen, A. M. Nguyen, R. Buczyński, R. Kasztelanic, "Application of ethanol infiltration for ultra-flattened normal dispersion in fused silica photonic crystal fibers", Laser Physics, 28 115106 (2018). CrossRef J. Pniewski, T. Stefaniuk, H. L. Van, V. C. Long, L. C. Van, R. Kasztelanic, G. Stępniewski, A. Ramaniuk, M. Trippenbach, and R. Buczynski, "Dispersion engineering in nonlinear soft glass photonic crystal fibers infiltrated with liquids", Appl. Opt. 55, 5033-5040(2016). CrossRef H. D. Quang, J. Pniewski, H. L.Van, R. Aleksandr. V. C. Long, B. Krzysztof, D. X. Khoa, K. Mariusz, and R. Buczynski, "Optimization of optical properties of photonic crystal fibers infiltrated with carbon tetrachloride for supercontinuum generation with subnanojoule femtosecond pulses", Applied Optics, Vol. 57, No. 15, 1559-128X (2018). CrossRef M.Chemnitz,M.Gebhardt, C.Gaida, F.Stutzki, J.Kobelke, J.Limpert, A.Tünnermann and M.A. Schmidt, "Hybrid soliton dynamics in liquid-core fibres", Nat. Commun. 8 42 (2017). CrossRef S.Kedenburg, A.Steinmann, R.Hegenbarth, T.Steinle and H.Giessen, "Nonlinear refractive indices of nonlinear liquids: wavelength dependence and influence of retarded response", Appl. Phys. B 117 803-16 (2014). CrossRef E.Sani and A.Dell'Oro, "Spectral optical constants of ethanol and isopropanol from ultraviolet to far infrared", Opt. Mater. 60 137-41 (2016). CrossRef S.T. Wu, "Absorption measurements of liquid crystals in the ultraviolet, visible, and infrared", J. Appl. Phys. 84 4462-4465 (1998). CrossRef Z. Mousavi, B. Ghafary, M.H. Majles Ara, "Fifth- and third- order nonlinear optical responses of olive oil blended with natural turmeric dye using z-scan technique", Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.04.077 CrossRef Web page: Refractive Index Info: https://refractiveindex.info. CrossRef I. Bodurov, I. Vlaeva, M. Marudova, T. Yovcheva, K. Nikolova, T. Eftimov, V. Plachkova, "Detection of adulteration in olive oils using optical and thermal methods", Bulgarian Chemical Communications, Volume 45, Special Issue B (pp. 81-85) (2013) DirectLink

Numerical investigation of a real-time temperature sensor based on high-order soliton compression

Temperature sensors based on photonic crystal fibers (PCFs) have attracted considerable attentions due to their desirable advantages. However, the real-time temperature sensing in the temporal region is rarely studied. Here, an all-fiber real-time high-sensitivity temperature sensor is fabricated based on the high-order soliton compression process. A 1560 nm femtosecond fiber laser is used as the injected pulse source and the alcohol-filled silica PCF is adopted as the temperature sensitive device. Temperature sensing can be realized by detecting the peak values of temporal profiles with an oscilloscope at the change of temperature. The oscilloscope possesses faster response rate than the optical spectrum analyzer and can record the variation of the single pulse. Through numerical simulations, a real-time temperature sensor with the sensitivity of 4.91 W °C−1 is achieved at the fiber length of 21 cm. Our simulated results show that the designed temperature sensors with low cost, compact all-fiber structure and real-time response are competitive for application in temperature measurement devices.

Cascaded-tapered silica photonic crystal fiber for supercontinuum generation

We propose the two-stage cascaded-tapered silica photonic crystal fiber (PCF) for the supercontinuum (SC) generation. The cascaded-tapered silica PCF is designed to have a spatial periodic structure. The physical scenarios of the spectral broadening due to the interaction between the structure-induced periodic dispersion and Kerr nonlinearity under different pulse widths and peak powers are investigated. It is found that when the pump pulses with width of <100 fs and peak power of not more than 10 kW are propagated in the cascaded-tapered silica PCF, the SC with good coherence can be generated. It is believed that the research results have potential applications in the nonlinear photonics and spectroscopy.

Temporal fine structure of all-normal dispersion fiber supercontinuum pulses caused by non-ideal pump pulse shapes.

We experimentally investigate the spectro-temporal characteristics of coherent supercontinuum (SC) pulses generated in several implementations of silica and soft-glass all-normal dispersion (ANDi) photonic crystal fibers optimized for pumping with Erbium (Er):fiber femtosecond laser technology. We characterize the resulting SC using time-domain ptychography, which is especially suitable for the measurement of complex, spectrally broadband ultrashort pulses. The measurements of the ANDi SC pulses reveal intricate pulse shapes, considerable temporal fine structure, and oscillations on time scales of < 25 femtoseconds, which differ from the smoothness and simplicity of temporal profiles obtained in numerical simulations and observed in previous experiments. We link the measured complex features to temporal sub-structures of the pump pulse, such as pre- and post-pulses and low-level pedestals, which are common in high pulse energy ultrafast Er:fiber systems. We also observe spectro-temporal structures consistent with incoherent noise amplification in weakly birefringent fiber samples. Our results highlight the importance of the pump source and polarization-maintaining (PM) fibers for high-quality SC generation and have practical relevance for many ultrafast photonics applications employing ANDi fiber-based SC sources.

Accurately Shaping Supercontinuum Spectrum via Cascaded PCF.

Shaping is very necessary in order to obtain a wide and flat supercontinuum (SC). Via numerical simulations, we accurately demonstrated shaping the SC using the fiber cascading method to significantly increase the width as well as the flatness of the spectrum in silica photonic crystal fiber (PCF). The cascaded PCF contains two segments, each of which has dual zero-dispersion frequencies (ZDFs). The spectral range of the SC can be expanded tremendously by tuning the spacing between the two ZDFs of the first segmented cascaded PCF. Increasing the pump power generates more solitons at the red edge, which accelerates solitons trapping and improves the spectral flatness of the blue edge. Furthermore, cascading the second segmented PCF by choosing appropriate fiber parameters ensures the flatness of the red end of SC. Therefore, a cost-effective alternative method for broad and flat supercontinuum generation in the near-infrared range is proposed here, which can be implemented easily in any photonics laboratory, where dual ZDFs PCFs are commonly found.

Hollow Silica Photonic Crystal Fiber Guiding 101 Orbital Angular Momentum Modes Without Phase Distortion in C+L Band

We propose a new hollow ring core silica photonic crystal fiber that can support 101 orbital angular momentum (OAM) modes, maintaining a high mode quality without phase distortion, a low confinement loss, and a large effective index difference between the adjacent modes, which could open a new avenue of OAM mode multiplexing applications. The fiber consists of three layers: the circular central air hole, silica ring core, and circumferencing silica-air hole porous inner cladding. Using the full-vectorial finite element method (FEM), the modal characteristics of individual OAM modes in the proposed fiber were thoroughly analyzed by varying the number of air-holes in the circularly symmetric cladding. We found a general selection rule for the number of air-holes in the first layer and the topological charge to cause the phase distortion of OAM modes, for the first time. The phase distribution of the guided OAM modes was thoroughly investigated to select usable modes for mode division multiplexing. Parametric analyses of the proposed PCF are reported to optimize optical properties of the OAM modes.

Ultra-low-noise supercontinuum generation with a flat near-zero normal dispersion fiber.

A pure silica photonic crystal fiber with a group velocity dispersion (β2) of 4 ps2/km at 1.55μm and less than 7 ps2/km from 1.32μm to the zero dispersion wavelength (ZDW) 1.80μm was designed and fabricated. The dispersion of the fiber was measured experimentally and found to agree with the fiber design, which also provides low loss below 1.83μm due to eight outer rings with increased hole diameters. The fiber was pumped with a 1.55μm, 125fs laser and, at the maximum in-coupled peak power (P0) of 9kW, a 1.34-1.82μm low-noise spectrum with a relative intensity noise below 2.2% was measured. The numerical modeling agreed very well with the experiments and showed that P0 could be increased to 26kW before noise from solitons above the ZDW started to influence the spectrum by pushing high-noise dispersive waves through the spectrum.