We report here flattened supercontinuum (SC) generated in tellurite-phosphate and chalcogenide-tellurite hybrid microstructured optical fibers (HMOFs) whose chromatic dispersion spectra are tailored with high freedom due to large refractive index difference (∆n) between the core and cladding glasses. It is shown in the simulation that the tellurite-phosphate HMOF whose chromatic dispersion spectrum is near-zero and flattened with three zero-dispersion wavelengths (ZDWs) over a wide wavelength range from 1000 to 4000 nm is beneficial to obtain broad and flattened SC spectra. By using a large ∆n of 0.49, the tellurite-phosphate HMOF which has flattened chromatic dispersion and three ZDWs is successfully fabricated. When a 20-cm-long tellurite-phosphate HMOF is pumped at 1550 nm with a 1560-W peak power, an SC extended from ~800 to 2400 nm where ~5-dB spectral flatness in the wavelength ranges from 890 to 1425 nm and from 1875 to 2400 nm (~1060-nm bandwidth in total) is observed. In addition, a flattened SC spectrum with ~6-dB spectral flatness over a broad wavelength range from 950 to 3350 nm (2400-nm bandwidth in total) is generated by pumping a 1-cm-long chalcogenide-tellurite HMOF at 2300 nm with a 40-MW peak power.
Chalcogenide microstructured fibers (MOFs) have great advantages for supercontinuum (SC) generation in mid-infrared
(MIR) region, because they possess the properties of high nonlinearity and wide transmission window, simultaneously.
The nonlinear parameters of chalcogenide MOFs can be higher by several tens or hundreds than those of silica, fluoride
and tellurite fibers depending on the material components and fiber structures. Chalcogenide MOF can be transparent
from visible up to the infrared region of 12 or 15 μm depending on the compositions. In this paper, we demonstrate the
SC generation in two kinds of suspended-core chalcogenide MOFs with different material components and fiber
structures. One is an As2S3 MOF with three-hole structure (Fiber I). The other is an As2S5 MOF with four-hole structure
(Fiber II). For Fiber I, the SC range of 3020 nm (from 1510 to 4530 nm) were obtained in a 2.4 cm fiber, when pumped
by the wavelength at 2500 nm. The SC extends to the wavelengths longer than 4 μm. For Fiber II, the SC range of 4280
nm (from 1370 to 5650 nm) is generated in a 4.8 cm fiber when pumped by the wavelength at 2300 nm, which covers
more than two octaves. Compared to the SC generated in Fiber I, the SC spectral range in Fiber II has been increased by
more than 1200 nm due to the better transmission property of the As2S5 glass; the SC extends to the wavelengths longer
than 5 μm.
Alternative materials to silica glass are necessary for supercontinuum (SC) generation at longer wavelengths in the midinfrared
(MIR) region. The alternative materials should possess the properties of wide transmission window and high
nonlinearity, simultaneously. Chalcogenide glass is the suitable candidate due to its excellent properties of transmission
and nonlinearity in MIR region. In this paper, we demonstrate the SC generation in a suspended-core As2S3 chalcogenide microstructured optical fiber (MOF). The variation of SC is investigated by changing the fiber length, pump peak power and pump wavelength. In the case of long fibers (20 and 40 cm), the SC ranges are discontinuous and stop at the
wavelengths shorter than 3500 nm, due to fiber absorption. In the case of short fiber as 2.4 cm, the SC range is continuous and can extend to the wavelengths longer than 4 μm. The process of SC broadening is observed when the pump peak power increases from 0.24 to 1.32 kW at 2500 nm in the 2.4 cm long fiber. The variation of SC range with the pump wavelength changing from 2200 to 2600 nm is studied. The selected wavelengths correspond to the dispersion of As2S3 MOF from the normal to anomalous region. The SC generation is simulated by the generalized nonlinear Schrödinger equation. The simulation includes the SC difference between 1.3 and 2.4 cm long fiber at 2500 nm pumping and the variation of SC with pump peak power in 2.4 cm long fiber. The simulation agrees well with the experiment.
Fiber-optical parametric amplification (FOPA) has been intensively studied and exploited for various interesting
applications such as wavelength conversion, wavelength division multiplexing, optical signal processing and so on.
However, its efficiency is governed by the fiber nonlinearity and chromatic dispersion. By employing tellurite glass we
propose novel highly nonlinear tellurite hybrid microstructured optical fibers (HMOFs) which have nonlinearity of 6642
W-1km-1 and near-zero flattened dispersion profiles from 1.3 to 2.3 μm with four zero dispersion wavelengths for FOPA applications. The linear phase-mismatch, optical signal gain and gain bandwidth are precisely calculated by using a full propagation constant which includes the contribution of all high-order dispersion parameters. In contrast with silica fibers, the signal gain is shown to be generated in the wavelength regions where Δβ<-4ΥP and the parametric gain coefficient g is imaginary. It is shown that the proposed tellurite HMOFs with short fiber length L<90 cm have the gain bandwidth as broad as 760 nm when it is pumped at 1550 nm. The increase in pump power from 1 to 4 W not only increases the signal gain but also broadens the FOPA gain bandwidth. At 1700-nm pump wavelength, the signal gain
larger than 14 dB is obtained over a very broad gain bandwidth of 1200 nm (from 1290 to 2490 nm). To our best
knowledge, it is the first time that highly nonlinear tellurite HMOFs are demonstrated as attractive candidates for high
performance of FOPA.
Superluminal propagation at negative group velocity was demonstrated in a highly nonlinear fiber embedded in a
Brillouin laser ring cavity. A maximum advancement of 369 ns and strong Stokes lasing power of 482 mW were
achieved when the cavity was pumped with a 1 MHz sinusoidal wave modulated signal at power level of 1 W. The
frequency dependence of fast light in this fiber ring cavity was examined with modulation frequencies of 1 kHz to 15
MHz. a maximum fractional advancement of 0.54 was achieved at 10 kHz and a maximum negative group index of -
9480 was demonstrated at 1 kHz.
The dependence of chromatic dispersion of tellurite microstructured optical fiber on composition and structure was investigated. The material dispersion is mainly dependent on material composition of core glass. And the waveguide dispersion of fiber mainly depends on refractive index distribution in cross-section. The radial step of refractive index produces a peak in waveguide dispersion curve whose value and position are related to both contrast of refractive index and its position. Based on this guidance, some particular dispersion profiles were designed in tellurite fibers.
The hybrid microstructured optical fibers (HMOFs) are emerging due to their capability of tailoring the dispersion. The chromatic dispersion and other related optical properties, such as optical mode confinement and effective index, have been calculated using the finite element method. We have realized four zero dispersion wavelengths (ZDWs) of 1566, 1605, 1726 and 1790 nm. The signal and idler wavelength dependent on pump wavelength is calculated. The gain bandwidth is 134 nm for the pump wavelength of 1761 nm between third and fourth ZDW. The supercontinuum generation is studied for the pump wavelength 1761 nm.
The compositional dependences of glass formation, thermal properties and optical properties are investigated for TeO2-ZnO-Na2O-P2O5 system for hybrid microstructured optical fibers. The refractive indexes at 1.55 μm and glass transition temperature vary in a wide range from 1.513 to 2.036 and from 265°C to 376°C by controlling of the TeO2/P2O5 and ZnO/Na2O content, respectively. These properties endow tellurite-phosphate glasses with large freedom in the hybrid microstructured optical fiber design. The structures of glasses are investigated by Raman spectra to understand the structural dependence on composition. Using the present glasses, some microstructured optical hybrid fibers with particular dispersion profiles are designed and demonstrated.
Though soft glass such as tellurite or chalcogenide glass is transparent in the range of 3-6 μm, fiber made of it is difficult to generate supercontinuum (SC) to that range because of the high loss, the wavelength limit of pump source, and the challenges in light-coupling. To circumvent these problems, we developed SC light source by using tellurite bulk glass through filamentation. For this scheme, the optical path length in the glass is very short due to the adopted high pump power, so the negative influence of material loss is reduced greatly. The light-coupling is straightforward, and the coupling efficiency is high. The bulk glass for SC generation is cheap, and can be fabricated easily. We adopted a pump wavelength of 1600 nm which is comparatively long. Such a long pump wavelength ensures a large energy ratio of the glass’s bandgap to the incident photon, so the disadvantage of small bandgap of tellurite glass is reduced, and the twophoton absorption is avoided as well. We have shown that under suitable pump condition, the SC generation by filamentation can cover from visible to 6 μm. It is the broadest SC generation by tellurite (including glass and fiber). For the suitable pump condition, the glass was free of optical breakdown. If the interface reflections were deducted, the SC
conversion efficiency was 87%. The SC conversion efficiency was stable. To the best of our knowledge, this is the first report on filamentation in tellurite glass which has a comparatively small bandgap.
We present an all-solid tellurite-phosphate photonic bandgap fiber (PBGF) with high-index rods in the cladding. The
low-index background material is phosphate glass (PZNK) and the high-index rods are made of tellurite glass (TZLB).
The all-solid tellurite-phosphate PBGF has three bandgaps and the first one is wide in frequency. It is easier to draw than
the silicon PBGF due to the phosphate glass has lower fiber-drawing temperature. It can be widely used in the
photoelectron field, compact nonlinear devices and devices which work in the mid-infrared range, such as wavelength
filter, phase-locked high-power lasers, fiber sensors in the mid-infrared for gases detecting, etc.
The microstructured optical fibers have been considered in this paper due to their unique nonlinear properties.
These optical fibers have enormous potential and they are also unrestraint to tailor the design for obtaining promising
dispersion properties. It has been observed that conversion efficiency significantly increases when nonlinear contribution
to propagation constant is considered for phase matching. The phase matching have been obtained for even and higher
order dispersion with the optical pump pulse conditions. The coupled mode theory along with nonlinear Schrödinger
equation has been used to reveal the optical properties of telluride/phospho-tellurite hybrid microstructured optical fiber.
The paper has been focused to investigate the effective index, pulse propagation intensity and quasi phase matching.
We report the fabrication of tellurite composite microstructured optical fiber (CMOF) with ultra-flattened zero dispersion
(±3 ps/nm/Km) over 200nm band. To obtain this dispersion profile together with high nonlinearity, one ring of air holes
and two layers of glass cladding are employed in the tellurite CMOF. The core of fiber is made of TeO2-Li2O-WO3
-MoO3-Nb2O5 (TLWMN) tellurite glass which possesses high linear and nonlinear refractive indices. The refractive
index (n) at 1544nm and nonlinear refractive index (n2) of TLWMN glass is 2.08 and 3.78×10-11 esu, respectively.
TeO2-ZnO-Na2O-La2O3 (TZNL) glass with n of 1.96 at 1544 nm and TeO2-ZnO-Li2O-Na2O-P2O5 (TZLNP) glass with
low refractive index n of 1.63 at 1544 nm are used as the first cladding and the second cladding, respectively. Six small
air holes are located between the core and the first glass cladding. Such kind of fiber with ~1.7 μm core and ~0.6 μm air
holes are fabricated by a rod-in-tube method. The chromatic dispersion of the fiber is calculated by the fully vectorial
finite difference method (FV-FDM) and becomes (±3 ps/nm/Km) in the wide range from 1.53 μm to 1.72 μm. And the
nonlinear coefficient of present fiber is about 3.47 m-1W-1 which is much higher than that of silica MOFs. Furthermore,
broad and flattened supercontinuum generation is demonstrated in 30-cm-long fiber with femtosecond laser pumping at
1557 nm. This kind of fiber has promising potential in nonlinear applications owing to the high nonlinearity and
flattened dispersion profile.
Four wave mixing and supercontinuum from tellurite photonic crystal fibers have been widely researched. Their
efficiencies depend largely on fiber nonlinearity and chromatic dispersion. We have shown that the composite
microstructured optical fibers (CMOFs) can have high flexibility on chromatic dispersion control when refractive index
difference between core and cladding becomes larger. Cladding materials with much lower refractive index than tellurite
glass are required. We report here a novel tellurite core-phosphate cladding CMOF. Phosphate glasses which thermal
expansion coefficient, viscosity, glass transition temperature, deformation and crystallization temperature are close to
those of tellurite 78TeO2 - 5ZnO - 12Li2O - 5Bi2O3 (mol%) (TZLB) glass are systematically investigated. The
phosphate glass we developed has high transparency and a broad transmission region up to 3 μm as well as a notably low
refractive index. Using the phosphate glass doped with mixed alkali oxides obtained in this work, the refractive index
difference between core and cladding becomes as high as 0.5 which is sufficiently high to control the chromatic
dispersion with high freedom. Our work shows that tellurite-phosphate CMOFs are promising candidates as highly
nonlinear fibers with freely controlled chromatic dispersion for nonlinear applications.
We report on fabrication a composite microstructured optical fibre composed of highly nonlinear chalcogenide Ge-Ga-
Sb-S glass core and tellurite TeO2-ZnO-Li20-Bi2O3 glass clad. We aimed at obtaining more flattened chromatic
dispersion for pumping chalcogenide glass based optical fibre by a pulse laser at current telecommunication
wavelengths, i.e. λ = 1.35 - 1.7 μm, which is difficult to achieve by using a single material chalcogenide fibers due to
their high refractive index (n > 2.1). A fibre design exploiting a composite of two glasses and one ring of the air holes
brings similar options for tuning the fibre dispersion such as use of complex multi rings of air-holes approach. A good
choice of glasses, allows for fabricating a composite chalcogenide-tellurite optical fibre benefiting from high
nonlinearity of chalcogenide core glass but exploiting a tellurite glass technology and fibre drawing. In the paper, we
discuss some aspects of CMOF design concerning current chalcogenide and tellurite glass choice. Also, we show the
supercontinuum spectra recorded from current chalcogenide-tellurite CMOF pumped with a custom made femtosecond
fibre laser at λ = 1.55 μm with the pulse duration of 400 fs.
Highly nonlinear tellurite holey fiber can be transparent from visible to 5 μm. Its nonlinearity can be higher than highly
nonlinear silica fiber by more than one order of magnitude. However, the dispersion of tellurite holey fiber is difficult to
tailor because of the difficulties in fabrication. Tellurite glass shows a low viscosity at the fiber drawing temperature.
Moreover the viscosity decreases sharply with increasing temperature. Tellurite holey fiber with a complex
microstructure could be subject to heavy deformation during fabrication process. So far most tellurite highly nonlinear
holey fibers just have a simple structure which results in an unflattened dispersion. It cancels the advantage of high
nonlinearity greatly in practical applications. In this work we try to develop a dispersion flattened tellurite composite
holey fiber (TCHF). The holey structure of the TCHF is composed of only one ring of holes, so the heavy deformation,
which probably occurs for tellurite complex microstructured fiber during the fabrication process, can be avoided. Since
the holey structure is simple, to improve the flexibility in tailoring dispersion, we use two kinds of tellurite glasses which
have different refractive-indices to design and fabricate the TCHF. The holes are formed by two tellurite glasses. The
fiber can be fabricated by a simple rod-in-tube method. By using this structure the dispersion is engineered to be the
most flattened for the highly nonlinear soft glass fiber within 1.5-1.6 μm. More than one octave supercontinuum
generation, mainly broadened by self phase modulation, is demonstrated by using the fabricated TCHF.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.