Zero-dispersion Wavelength Research Articles

Supercontinuum generation in PCF with As2S3/Ge20Sb15Se65 Chalcogenide core pumped at third telecommunication wavelengths for WDM

Chalcogenide-based photonic crystal fibers (PCFs), due to their nonlinear properties, are capable of producing supercontinuum spectra, which can be used in the wavelength division multiplexing (WDM). These types of fibers highly absorb telecommunication wavelengths and hence cannot be used to transmit information over the corresponding wavelengths. We have studied the dispersion engineered chalcogenide PCF numerically, which is important to produce ultra-flat broadband supercontinuum (SC) spectra in all-normal dispersion areas. A 1 mm long, hexagonal chalcogenide PCF made from As2S3/Ge20Sb15Se65 and silica glass pumped at 1550 nm provided a SC bandwidth of 5000 nm with pump power of 1 kW. Here, we have reached zero-dispersion wavelength (ZDW) at third telecommunication window, which in turn has given us a broad spectrum at this window with reasonable efficiency.

Ultraviolet-Extended Supercontinuum Generation in Zero-Dispersion Wavelength Decreasing Photonic Crystal Fibers

Supercontinuum covering the ultraviolet-blue region is highly useful for fluorescence microscopy. Four zero-dispersion wavelength decreasing photonic crystal fibers with different fiber cross structures and taper profiles are fabricated to extend the short wavelength edge of supercontinuum. Both nanosecond and picosecond pump pulses at 1 μm are used to generate supercontinuum. With a 3 ns pump pulse, the short wavelength edge of supercontinuum is extended to below 400 nm in a fiber with high air-hole ratio (named T3). The underlying mechanism of supercontinuum generation is explored. The short and long wavelength edges of supercontinuum are highly related with the phase-matching condition which decided by the group velocity curve of fiber small core end. With a 10 ps pump pulse, the spectral intensity around ∼800 nm increases in all four fibers. However, the intensity in shorter wavelength band decreased in fibers with a high air-hole ratio (named T3, T4). The experimental results imply that a zero-dispersion wavelength decreasing photonic crystal fiber suitable for nanosecond pulse pumping is not necessarily suitable for picosecond pulse pumping, especially for fibers with high air-hole ratio.

Research on determining of cations in GeAsSeI chalcohalide glass

In order to improve the thermal stability of chalcohalide glasses, which is beneficial for fiber drawing, and blue-shifting zero-dispersion-wavelength (ZDW), which is beneficial to generate supercontinuum (SC) spectra, so more germanium (Ge) is needed to be incorporated into the glass network of Ge-As-Se-I. Here, two series of (Ge20AsxSe80-x)85I15 and (GexAs40-xSe60)85I15 glasses are investigated on the optical properties, including absorption edge at short wavelength, optical band gap, linear refractive index and ZDW. The glass transition temperature (Tg) and the soften temperature (Tp) of these glasses are also investigated. In general, as the ratio of Ge/As changes, optical properties of (GexAs40-xSe60)85I15 glasses change regularly, but when the ratio of As/Se changes, those of the (Ge20AsxSe80-x)85I15 glasses keep weak regularity relatively. Generally, the effect of Ge on Ge-As-Se-I glasses’ properties is well presented in this work, and this will show much help to develop novel mid-infrared fiber and device in the future.

Exploiting higher-order mode dispersion of bend M-type chalcogenide fiber in mid-IR supercontinuum generation

Abstract We propose and numerically demonstrate chalcogenide based bend M-type fiber for mid-IR supercontinuum (SC) generation through higher order mode (HOM) of LP02. In order to achieve this, we comprise two glass materials such as As2Se3 in core and Ge10As23.4Se66.6 in cladding. M-type index fiber has a special property that the HOM of LP02 is confined into the core region with help of high index ring. The mode field distribution of the proposed fiber is numerically calculated by a finite element method. By optimizing structural dimensions in each bending case, we realize a zero dispersion wavelength, double zero dispersion wavelength effective area and power fraction in core. The simulation results shows the flat anomalous dispersion in the wavelength range of 2.1–2.6µm and 2.5–6.5µm for the core radius 4 and 10 µm, respectively at bending case of 1, 3, and 5 cm. which is important for employing the mature fiber laser technology at mid-IR regions.

Manipulation of infrared dispersive waves in customized microstructured optical fibers for 1.7 and 2.0 µm light sources.

We demonstrate the controllable generation of infrared dispersive waves (DWs) from customized, in-house fabricated silica microstructured optical fibers (MOFs) by manipulating the location of zero dispersion wavelength (ZDW) through the structure of the fibers. The highly enriched shaping mechanism of arrested soliton in the MOFs with two ZDWs provides a technique for efficient energy transfer into the targeted eye-safe wavelengths at 1.7 and 2.0 µm by the virtue of DW formation.

Multiple Mode Couplings in a Waveguide Array for Broadband Near-Zero Dispersion and Supercontinuum Generation

We achieve a broadband near-zero dispersion in a thin silicon nitride waveguide array at near-infrared utilizing the multiple mode couplings. Different orders of modes are coupled at four different wavelengths, generating eight zero dispersion wavelengths (ZDWs). The broadband near-zero dispersion profile within 90 ps/nm/km is achieved, spanning over the spectral range of 1350 $-$ 1900 nm. Using the dispersion engineered waveguide array, an octave-spanning supercontinuum is numerically generated with a pump of 100 fs and 200 pJ. The concept of using multiple mode couplings to obtain broadband near-zero dispersion can be applied to other spectral regimes and material platforms as well, by engineering the structural parameters to shift the positions of the ZDWs.

Broadband tuning of polarization modulation instability in microstructured optical fibers

The wideband tuning of strong bands generated through polarization modulation instability (PMI) in microstructured optical fibers (MOFs) is reported. Tunability is achieved by exploiting the dependence of the phase-matching condition on the fiber's chromatic dispersion and birefringence, which is particularly sensitive when the fiber is pumped near the zero-dispersion wavelength. MOFs designed to accomplish PMI phase-matching when they are infiltrated with ethanol and pumped at 1064 nm were designed and fabricated. Taking advantage of the large thermo-optic coefficient of ethanol, both chromatic dispersion and birefringence were varied through temperature. Wavelength shifts from 937 nm to 863 nm (anti-Stokes) and from 1231 nm to 1387 nm (Stokes) are demonstrated. Such a tuning range corresponds to a frequency shift between the pump and a PMI sideband ranging from 1274cm-1 to 2189cm-1.

Observation of the quasi-discrete supercontinuum at optical event horizon

Numerically study of the formation of the quasi-discrete supercontinuum (SC) with ultrashort pulse sequence in an optical analogue is reported in the paper. The quasi-discrete SC is produced by pumping an intense pulse and a probe on each side of the zero-dispersion wavelength (ZDW) in a fiber. The nonlinear reflection between them causes the emission of new frequencies and gives rise to the generation of ultrashort pulses. Isolated narrow-band sources occur via the spectra interference of the ultrashort pulses, forming the quasi-discrete SC. Ultrashort pulses with different width are generated by changing the central wavelength of probe. Besides, high energy conversion efficiency and maximum frequency shift caused by the soliton–DW interaction also can be manipulated by varying the central wavelength of probe and time delay of the input pulses. So wider supercontinuum and high intensity tunable ultrashort pulses sequence can be acquired.

Design of a photonic crystal fiber for optical communications application

The desire for photonic crystal fibers (PCF) with small mode areas that can be used in nonlinear optics and optical communications is a never-ending and a continuously evolving research quest. By deliberately varying the diameters of air-holes and spacing between holes, a PCF with possible application in optical communications and nonlinear optics is proposed. The zero-dispersion wavelength (ZDW) is easily tailored to be located around 1.55μm. A design of a PCF with high nonlinearity, reduced dispersion and reduced loss due to improper confinement of mode is investigated. The proposed PCF is designed and demonstrated through the commercially available FemSIM software which employs the full-vectorial finite element method. Among the properties demonstrated and analyzed are the; ZDW which is shown to be around 1.55μm, an effective mode area of 1.7256μm2 at 1.55μm are obtained.

Noise figure of distributed Raman amplifier with different pumping configurations in S-band: A new approach

The higher bit rates, lower noise figure, decreasing the nonlinear penalty of fiber system, longer amplifier length, tight channel spacing and operating near the zero-dispersion wavelength are achieved by using Distributed Raman amplifiers (DRAs). In this paper, a new model of noise figure (NF) due to amplified spontaneous emission (ASE) is introduced for the DRA at different pump schemes: co-pumping, counter-pumping and bidirectional pumping.The variation of power conversion efficiency (PCE) with input pump power; input signal power and amplifier length for S-band is also investigated. It is found that, the NF increases exponentially with the fiber length and decreases exponentially with input signal power, power conversion efficiency (PCE) increases exponentially with the fiber length and input signal power and decreases exponentially with the input pump power. The obtained results show that, the noise figure (NF) reaches its minimum value of 8.6, 9.7 and 11 dB, while the PCE reaches its maximum value of 71%, 31% and 7% in counter-pumping, bidirectional pumping and co-pumping, respectively.

The supercontinuum generation with Pearcey-Gaussian pulses in an optical fiber

In this paper, the supercontinuum generation in an optical fiber with forward and backward Pearcey-Gaussian pulses near the zero-dispersion wavelength is investigated. By using the split-step Fourier transform to solve the generalized nonlinear Schrödinger equation (GNLSE), we have shown an interesting phenomenon that the spectrum bandwidth of the forward Pearcey-Gaussian pulse is broader than that from hyperbolic secant pulse with the same parameters. By investigating the time–frequency dynamics of the pulse propagation, the underlying mechanism is analyzed.

Refractive index spectroscopy and material dispersion in fused silica glass.

In this study, we aimed to measure material dispersion in fused silica using a low coherence interferometric method. The measurement was carried out quickly and efficiently in a wide spectral range using this method. The refractive index and group index of fused silica were determined by capturing a few interferograms. The material dispersion was modeled using a Sellmeier equation with three resonances. Three different fits were investigated; the most appropriate fit was the one that used both the measured refractive and group indexes to model the dispersion. Second-order dispersion was also quantified, and zero-dispersion wavelength was determined.

Experimental analysis of four-wave mixing effect on next generation Ethernet passive optical network

With the application of wavelength division multiplexing, four-wave mixing (FWM) has an obvious influence on transmission systems. The effects of different channel intervals and numbers of channels on FWM performance in next generation Ethernet passive optical networks are discussed experimentally. When the incident signals near the zero-dispersion wavelength with a 200-GHz channel interval are transmitted over a 25-km fiber, new frequencies are generated, and more than 5-dB sensitivity loss is obtained. With the increase of channel spacing, the performance of FWM decreases significantly. The FWM crosstalk can even be ignored when the channel spacing is set at 800 GHz. In addition, the performance of FWM significantly increases when the number of channels is changed from 3 to 4, at which the power depletion is more severe.

Cascaded telecom fiber enabled high-order random fiber laser beyond zero-dispersion wavelength.

Four-wave mixing induced spectral broadening near the zero-dispersion wavelength (ZDW) of the fiber is a bottleneck factor that limits the further wavelength extending in cascaded random fiber lasers (RFLs). In this Letter, we successfully suppress the spectral broadening near the ZDW of the fiber in the cascaded RFL by simply combining two kinds of commercial telecom fibers with different ZDWs, G655C fiber with ZDW around 1.52 µm and G652D fiber with ZDW around 1.31 µm. As a result, an 8th order Stokes light component at 1721 nm with a maximum output power of 2.1 W and a spectral purity of 96.94% is realized in this telecom-fiber-based cascaded RFL. This work provides a reference of nonlinear effect management in fiber lasers as well as affords a cost-effective way with great potential of realizing high-power widely tunable fiber lasers.

Photonic crystal fibers with high birefringence and multiple zero dispersion wavelengths

Abstract A type of total internal reflection photonic crystal fiber (TIR-PCF) with high birefringence and multiple zero dispersion wavelengths is presented. The optical characteristics are numerically investigated by using the full-vector finite element method. Results show that, by setting the geometrical parameters, the mode birefringence can reach to 2.28 × 10−2 at the wavelength of 1.55 μm, and two zero-dispersion wavelength points appear in the infrared band, one of which emerges near the wavelength of 1.55 μm. It provides a new structure for large birefringence photonic crystal fiber with multiple zero-dispersion wavelengths, and it could be widely used in the fields of fiber polarization control, dispersion management, super-continuum generation and soliton propagation.

Arsenic Sulfide Suspended-core Fiber Simulation with Three Parabolic Air Holes for Supercontinuum Generation

Highly nonlinear suspended-core fibers (SCFs) with tunable dispersion have attracted much attention in the fields of Raman amplification, optical frequency combs, broadband and flat supercontinuum generation (SCG). To address the limitation of applications due to its fragile suspension arms, this study proposes the design of a fiber structure with three parabolic air holes. Numerical simulations are performed to optimize an arsenic sulfide SCF in terms of dispersion management and SCG in the wavelength range from 0.6 µm to 11.6 µm. Results show that the proposed SCF has dual zero-dispersion wavelengths (ZDWs) that can be shifted by adjusting the parabolic coefficient of the air-hole and the equivalent diameter of the suspended core. By means of structural optimization, an SCF with 1 μm equivalent diameter and a parabolic coefficient of 0.18 μm−1 is proposed. The first ZDW of the SCF is blue-shifted to 1.541 μm, which makes it possible to use a commercial light source with a cheaper price, more mature technology and smaller volume as the pump source. SCG is studied by solving the generalized nonlinear Schrödinger equation using the split-step Fourier method, and a 0.6–5.0 μm supercontinuum spectrum is obtained at a pump source peak power of 40 kW.

One-Pump Phase Sensitive Fiber Optical Parametric Amplifier With Dual-Core Fiber

The gain performance of one pump phase sensitive fiber optical parametric amplifier (PS-FOPA) in the dual-core fiber is numerically investigated without pump depleting. The effects of the core coupling coefficient(C), the pump wavelength and the initial signal phase on the gain of PS-FOPA are analyzed in detail. It shows that, the signal gain is greatly affected by different core coupling coefficients, and a flatter gain is achieved with suitable C value. Also, when the pump wavelength is greater than the zero-dispersion wavelength (ZDW), both the peak gain and gain bandwidth decrease with the increase of C, but the trend is opposite in case of the pump wavelength less than the ZDW. Additionally, the flatter and broader gain spectra are obtained by adjusting the initial signal phase in core 2. This simulation provides a detail analysis for the dual-core PS-FOPA, which is significant for the all optical fiber amplifier systems.

Supercontinuum generation in all-normal dispersion suspended core fiber infiltrated with water

Octave spanning all-normal dispersion supercontinuum generation (SCG) was experimentally demonstrated in a solid, suspended-core fiber (SCF) infiltrated with water. Replacement of air with water in the cladding air-holes leads to a dramatic modification of the dispersion profile of the fiber, significantly flattening the characteristic over the visible and much of the near-infrared wavelength range at normal values. In such a fiber infiltrated with water, all-normal dispersion supercontinuum was generated with the spectral coverage from 435 nm to 1330 nm using femtosecond pumping with the output peak power of 150 kW and 800 nm central wavelength. The SCF without water infiltration – air in the cladding region – had a zero-dispersion wavelength at 760 nm and enabled the generation of the anomalous dispersion dynamics-based SCG in the wavelength range from 450 nm to 1250 nm. We also numerically calculated the coherence of simulated supercontinuum pulses with one-photon-per-mode noise seeds and point out that the all-normal dispersion SCG in suspended-core fiber infiltrated with water has the potential for high temporal coherence, while the fiber without water infiltration shows gradual decoherence of generated supercontinuum pulses with increasing pump power, over similar peak power range.

Supercontinuum generation in all-normal dispersion suspended core fiber infiltrated with water

Octave spanning all-normal dispersion supercontinuum generation (SCG) was experimentally demonstrated in a solid, suspended-core fiber (SCF) infiltrated with water. Replacement of air with water in the cladding air-holes leads to a dramatic modification of the dispersion profile of the fiber, significantly flattening the characteristic over the visible and much of the near-infrared wavelength range at normal values. In such a fiber infiltrated with water, all-normal dispersion supercontinuum was generated with the spectral coverage from 435 nm to 1330 nm using femtosecond pumping with the output peak power of 150 kW and 800 nm central wavelength. The SCF without water infiltration – air in the cladding region – had a zero-dispersion wavelength at 760 nm and enabled the generation of the anomalous dispersion dynamics-based SCG in the wavelength range from 450 nm to 1250 nm. We also numerically calculated the coherence of simulated supercontinuum pulses with one-photon-per-mode noise seeds and point out that the all-normal dispersion SCG in suspended-core fiber infiltrated with water has the potential for high temporal coherence, while the fiber without water infiltration shows gradual decoherence of generated supercontinuum pulses with increasing pump power, over similar peak power range.

Numerical Analysis of Large Negative Dispersion and highly Birefringent Photonic Crystal Fiber

This article deals with a study of proposed PCF in which a fiber core is surrounded by square shaped air holes arranged in circular rings in the cladding region. Parametric variation of proposed fiber is measured by varying the square air hole number in the core region, length of square air hole and also for hole packing density ratio (HPD) variation from visible to near-infrared (NIR) wavelength range. The parametric analysis shows that zero dispersion wavelength (ZDW) varies for all possible parametric variations mentioned above. The maximum negative dispersion value of −810 ps/nm/Km is obtained at 1.55 μm for 3 square air holes in fiber core while minimum confinement loss value is 1.23 × 10-5dB/m at the same wavelength. Besides this, the birefringence and nonlinear coefficient values were also found high as 3.6 × 10-3 and 75 W-1 km-1, respectively at 1.55 μm. Hence, the proposed PCF can be better used in four wave mixing, solitons generation, polarization maintaining fiber and optical sensor applications.