Chalcogenide Photonic Crystal Fiber Research Articles

Mid-infrared supercontinuum generation in As2S3-circular photonic crystal fibers pumped by 4.5 µm and 6 µm femtosecond lasers

A study on As2S3 chalcogenide photonic crystal fiber (PCF) and its potential in supercontinuum generation (SCG) applications is presented. The designed fibers exhibit near-zero flattened chromatic dispersion, facilitating coherent and broad SCG utilizing femtosecond lasers at 4.5 and 6 µm wavelengths. A continuous spectrum spanning from 1.5 to 8 µm is achieved when the initial fiber is stimulated with an input power of 20 kW. With a pulse width of 100 fs and input power of 6 kW, the second fiber provides soliton-induced SCG with 2 to 15 µm spectral bandwidth. Furthermore, the integration of these large core diameter PCFs with high-power laser pulses guarantees the preservation of optical fiber integrity without damage. Consequently, these fibers hold promise for delivering SC spectra characterized by high power density, catering to a diverse range of practical applications including optical communications, spectroscopy, sensing, metrology, and calibration.

Highly coherent supercontinuum generation in a photonic crystal fiber based on GeSe2–As2Se3–PbSe chalcogenide in the mid-infrared region

We numerically demonstrated highly coherent mid-infrared (IR) super-continuum (SC) generation using all-normal dispersion (AND) GeSe2−As2Se3−PbSe chalcogenide photonic crystal fiber (PCF). The structural parameters of this PCF were optimized to obtain an ultra-flat-AND region and high nonlinearity characteristics using the full-vectorial finite difference method with the perfectly matched layer boundary conditions to calculate the linear properties of the fiber. We show that, pumping a light source at 9.8 µm pump wavelength with an input pulse energy of 3.5 nJ and pulse width of 200 fs, corresponding to the peak power of 17.5 kW, into a 10-cm-long fiber, an ultra-flat-coherent mid-IR SC extended from 2851.8 nm to 13538.8 nm (bandwidth of 10687 nm) is obtained. This ultra-wide and flattened spectrum has excellent stability and coherence properties that can be used for mid-IR applications such as biological imaging, optical coherence tomography, and frequency metrology.

Investigation of hybrid chalcogenide photonic crystal fiber for MIR supercontinuum generation and optical communication

Abstract This study describes a wideband supercontinuum generation (SCG) in the mid-infrared range using a chalcogenide multi-material microstructured fiber design with significant non-linearity under optical communication. The fiber has a single core of As2Se3 and three rings of As2S5 rods arranged in hexagonal pattern in the AsSe2 cladding region. The reported PCF design has effective area and nonlinear coefficients as 59.4174 μm2 and 219.36 W−1 km−1 respectively at 5.3 μm pump wavelength. Additionally, it has a chromatic dispersion profile that is nearly zero and flattened over a large wavelength range of 5–15 µm, which is advantageous for broadband supercontinuum spectrum in the mid-infrared region. Specifically, with pulse width and pulse peak power of 200 fs and 10 kW, respectively, for a 100 mm fibre length, this research work illustrates the SCG that expands from 1000 nm to over 15,000 nm. These extremely nonlinear PCFs are robust contenders for applications that are nonlinear in nature, such as the generation of slow-light and supercontinuum.

Numerical simulation of ultrawideband supercontinuum generation covering a 2-20 µm waveband in cascaded all-soft-glass fiber.

We designed a cascaded all-soft-glass fiber structure and simulate midinfrared 2-20µm ultrawideband supercontinuum (SC) generation numerically. The cascaded fiber structure consists of a 1.5m I n F 3 fiber, a 0.2m chalcogenide photonic crystal fiber, and a 0.2m tellurium-based chalcogenide photonic crystal fiber. Using a 2µm pulse pumping this cascaded structure, the generated SC covering the wavelengths longer than 20µm has been demonstrated theoretically. The 30dB bandwidth reaches 20.87µm from 1.44 to 22.31µm. The effect of different pulse widths on SC generation is considered. With the increase of peak power and the decrease of pulse width, the energy of SC in the 15-20µm waveband increases gradually. The mechanism of SC broadening process has also been analyzed. The SC generation of more than 20µm in this cascade structure is caused by the self-phase modulation, soliton effects, four-wave mixing, and redshifted dispersive wave. This method demonstrates the possibility of generating ultrawide bandwidth SCs up to a 20µm waveband by a commercial 2µm pump source and all-fiber structure.

A single-mode chalcogenide photonic crystal fiber for bending resistance with large mode area and wide bandwidth

A single-mode chalcogenide photonic crystal fiber for bending resistance with large mode area and wide bandwidth

Super-flat coherent mid-infrared supercontinuum in all-normal dispersion As39Se61 chalcogenide photonic crystal fiber

We numerically demonstrated the generation of super-flat coherent mid-infrared supercontinuum in all-normal dispersion (ANDi) As39Se61 chalcogenide photonic crystal fiber (PCF). The PCF with flat-ANDi and high nonlinearities is obtained by optimizing the structural parameters of the fiber. When pumping a 50 fs pulse width and 6 kW peak power laser pulses at 3.35 μm, under 3dB spectral flatness the super-flat coherent mid-infrared supercontinuum extended from 2.17 to 7.47 μm is obtianed. Such coherent mid-infrared supercontinuum are enormously required for optical coherence tomography, biological imaging and frequency metrology.

Supercontinuum generation in chalcogenide photonic crystal fiber infiltrated with liquid

Chalcogenide fibers have attracted much attention for multi-octave spanning supercontinuum generation in the mid-infrared range. However, readily optimizing the dispersion characteristics as well as other mode properties is still problematic because it is difficult to fabricate chalcogenide fibers with sophisticated structures. In this work, we numerically investigate the liquid infiltration as a post-processing method to optimize the dispersion shapes, so that the nonlinear dynamics and spectro-temporal properties of supercontinuum generation are efficiently controlled. In particular, water, carbon disulfide (CS2), carbon tetrachloride (CCl4), and bromoform (CHBr3) are selected to fill into all cladding air holes of As38Se62 fibers for dispersion engineering. By pumping a femtosecond laser at 4.5 μm, pulse duration of 250 fs, and pulse energy of 0.1 nJ (peak power of 0.4 kW), the unfilled and CCl4-filled fibers provide soliton-induced supercontinuum generation with a spectral bandwidth of 2.5–6.5 μm and 2.0–5.5 μm, respectively. Whilst, CHBr3-filled fiber offers all-normal dispersion supercontinuum generation with high coherence and spectral bandwidth of 2.2–5.2 μm. In contrast, unfortunately, CS2 and water-filled fibers have complex dispersion shapes and provide narrow bandwidth supercontinua. We also thoroughly numerically investigate the tapered fibers, which assure both high coupling efficiency with laser sources and high nonlinearity, for broad mid-infrared supercontinuum generation. The results point out that liquid-filled tapered fibers can provide both anomalous and all-normal dispersion SC generation with an octave-spanning bandwidth via the same value of input peak power (0.4 kW). With a large core diameter (12 μm) at the input and output fiber ends, the tapered fibers have a potential to couple with high-power laser pulses without fiber damage, therefore, they can provide supercontinuum spectra with broad bandwidth and high spectral power density for practical applications in sensing, gas detection, and LIDAR.

Design of hexagonal chalcogenide photonic crystal fiber with ultra-flattened dispersion in mid-infrared wavelength spectrum

In the last few decades, silica-based photonic crystal fibers (PCFs) have been the subject of extensive research. Traditional silica-based PCFs, however, experience considerable propagation loss when used beyond 3000 nm. On the other hand, soft glasses, notably tellurite, fluoride, and chalcogenide glasses, offer exceptional optical transparency in the mid-IR wavelength region and are a desirable replacement for silica in MIR applications. A comprehensive investigation of chromatic dispersion properties in the hexagonal chalcogenide photonic crystal fibers is presented. The dependency of fiber dispersion on the structural parameters of photonic crystal fibers is thoroughly described in this study. Utilizing the interaction between material and geometrical dispersion, we were able to develop a well-defined framework for making specific predefined dispersion curves. In the mid-infrared wavelength spectrum, we are concerned with flattened, if not ultra-flattened, dispersion behaviors. In the wavelength range of 3500–6500 nm, the hexagonal chalcogenide microstructured fiber was engineered to achieve a typical dispersion profile flattened to within −3.41 to 9.5 ps/[nm–km] for the six-ring structure and −3.91 to 8.17 ps/[nm–km] for the four-ring structure. This proposed chalcogenide PCF can be used for soliton generation, gas sensing, biomedical imaging, supercontinuum generation, and long-distance high-speed communication applications in the mid-infrared wavelength range due to its nearly zero ultra-flattened dispersion characteristics.

Simulation and analysis of supercontinuum generation in the waveband up to 25 µm.

The ultra-wideband supercontinuum generation (SCG) in a Te-based chalcogenide (ChG) photonic crystal fiber (PCF) is simulated in the mid-infrared (MIR) waveband. The PCF core and cladding materials are Ge20As20Se15Te45 and Ge20As20Se17Te43, respectively. The supercontinuum (SC) broadening affected by the core diameter and fiber absorption is considered. The selected PCFs at different pumping wavelengths can demonstrate the generation of ultra-wideband MIR supercontinuum according to the simulated results. We consider SC broadening with and without fiber absorption. A SC range from 3 to 25 µm is demonstrated by simulation in a PCF with a core diameter of 8 µm and a pump wavelength of 6 µm considering the fiber absorption. With the increase of the peak power and the pulse width and the decrease of the core diameter, the degree of coherence gradually degraded. To the best of our knowledge, this is the first demonstration of the possibility of SCG up to the waveband of 25 µm in fiber. Our results highlight the potential of a novel Te-based chalcogenide multi-material PCF for SCG. We also provide a way to generate the SCs to longer wavebands than 20 µm in fiber, especially up to the far-infrared waveband.

Low pedestal sub-17 fs pulse generation through cascaded self-similar compression in photonic crystal fibers

We propose a realistic numerical model based on cascaded self-similar pulse compression to generate low pedestal ultrashort pulses at 2.5 µm. Self-similarity in photonic crystal fibers (PCFs) has been attained by modelling exponentially dispersion decreasing and exponentially nonlinearity increasing chalcogenide PCFs. The tapered PCF (TPCF) model is theoretically designed using the fully vectorial effective index method (FVEIM) to obtain accurate effective refractive index, group velocity dispersion (GVD), and Kerr nonlinearity values with low computation time. Initially, fundamental soliton compression in As2S3 tapered PCF is being investigated for the pedestal-free reduction of the pulse width. Subsequently, the compression factor is further enhanced in the As2Se3 PCF-based nonlinear optical loop mirror. The numerical outcomes reveal a compression of 1 ps pulse down to a pulse width of 16.6 fs with a peak power of 116 W in a total fiber length of L = 61 cm.

Theoretical Investigation of Mid Infrared Temperature Sensor Based on Sagnac Interferometer Using Chloroform Filled Photonic Crystal Fiber

In this paper, a novel Sagnac Interferometer (SI) based chalcogenide Photonic Crystal Fiber (PCF) temperature sensor is theoretically and numerically analyzed operating in the mid infrared (MIR) region. The PCF cladding air holes are proposed to be filled with a highly temperature sensitive liquid chloroform to enhance the temperature sensitivity. The temperature sensing characteristics of three different infiltration technique is investigated theoretically and compared by Finite Element Method (FEM). Simulation results show that full infiltration performs better than partial infiltration. In the numerical analysis two sensing dips with high linearity is achieved for full infiltration which shows sensitivity of −5.77 nm/°C and 8.49 nm/°C when the temperature increases from 25 to 85 °C for the specific fiber length of 1.532 mm. The R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> values are 0.957446809 and 0.97680771 for the respective two sensing dips. The proposed highly sensitive sensor has broad detection window which can be applied in fingerprint unlocking, MIR radiation detection in human body, biomedicine applications, and environmental temperature monitoring.

Mid-infrared broadband all-optical wavelength converter in Ge20Sb15Se65 photonic crystal fiber with flattened dispersion

A chalcogenide photonic crystal fiber (PCF) with flattened dispersion and high nonlinearity in mid-infrared (mid-IR) based on a triangular and circular lattice hybrid cladding structure is proposed. The structural parameters of the PCF are optimized by the full-vectorial finite-difference method. The numerical simulation results show: when d1 = 0.4 µm, d2 = 0.16 µm, d3 = 0.04 µm, Ʌ1 = 0.88 µm, Ʌ2 = 0.8 µm, Ʌ3 = 0.5 µm, the flatten and low dispersion is obtained in the wavelength range of 3.8–5 µm. The dispersion value is between ± 1.2 (ps/nm/km), and the maximum nonlinear coefficient is as high as 2464.2 km-1 W-1 at 2.5 µm. Based on the four-wave mixing (FWM) effect in the proposed PCF, the all-optical wavelength conversion performance is numerically analyzed. When the pumping wavelength is 4.02 µm, the 3 dB conversion bandwidth can reach 4833 nm (from 2.737 µm to 7.57 µm), and the maximum wavelength conversion efficiency is 12.12 dB. The proposed all optical wavelength converter is having large bandwidth and high conversion efficiency in mid-IR band due to the flat dispersion and high nonlinearity of the PCF, which has potential application in future space optical communication network and mid-IR photonic.

Mid-infrared supercontinuum generation using low peak pump power in As38Se62 based chalcogenide photonic crystal fiber

A supercontinuum (SC) based chalcogenide As38Se62 PCF for broadband mid-infrared light source is numerically reported. For the computational studies, the design of the proposed structure is made up of three rings of air holes with circular and elliptical shapes. The proposed structure provides excellent nonlinear coefficient and dispersion optimization. For the analysis, the finite difference frequency domain (FDFD) method is employed. Due to the high nonlinear refractive index and optimizing design of As38Se62 chalcogenide glass, an effective mode area of 40.5972 μm2 is obtained. The dispersion characteristic of the proposed structure has a zero-dispersion wavelength at 3.89 μm. The nonlinear coefficient is 761 W-1km-1 at the wavelength of 4 μm. Dispersion is almost flat from 2 μm up to 10 μm. The supercontinuum spectrum calculated ranges from 2 μm to 9 μm. The presented structure is appropriate for medical imaging, optical coherence tomography and optical communications.

Toward generation of mid-infrared orbital angular momentum beams by tailoring four-wave mixing in chalcogenide photonic crystal fiber

The nonlinear process of orbital angular momentum (OAM) beams in multimode fiber has attracted renewed interest due to its enhanced intermodal nonlinear interactions. Here, we designed and simulated a novel photonic crystal fiber (PCF) based on A s 2 S e 3 glass that supports stable OAM modes. By optimizing the structure parameters of the fiber, both the effective index separation and the phase-matching condition of OAM modes were satisfied in the fiber. Mid-infrared OAM light can be generated by intermodal four-wave mixing in the chalcogenide fiber. The idler conversion efficiency at the 5 µm waveband and the signal optical gain spectrum near 1.9 µm is calculated when the pump light is around 2.8 µm. Furthermore, the crosstalk of the FWM process from the other vector modes vanished due to the lower overlap factor compared with the interacting OAM modes. Our work demonstrates that the vortex beam at 5 µm could be generated, and its conversion efficiency can reach 21.96% with appropriate optimization.

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.

Few-moded ultralarge mode area chalcogenide photonic crystal fiber for mid-infrared high power applications.

We demonstrate a novel few-moded ultralarge mode area chalcogenide glass photonic crystal fiber for mid-infrared high power applications. The numerical simulation indicates that the fiber has ultralarge mode areas of ∼10500 µm2 and ∼12000 µm2 for the fundamental mode LP01 and the lowest higher-order mode LP11, respectively. Dual-moded operation is confirmed experimentally at 2 µm, in good agreement with the numerical simulation. By selectively launching technique, low bending loss of 0.7 dB/m, equivalent to 0.55 dB/turn, has been observed in the fiber with a small bending radius of ∼12 cm, indicating excellent bending resistance of the few-moded fiber with such a large mode area. The fiber has been demonstrated to sustain an incident power density up to 150 kW/cm2 under 2-µm CW laser irradiation, showing the potential of the fiber for high-power applications in mid-infrared.

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

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.

Slow light via stimulated Brillouin scattering in double-clad As2Se3 chalcogenide photonic crystal fibers

Slow light of stimulated Brillouin scattering in double-clad As2Se3 chalcogenide photonic crystal fibers was investigated theoretically. The influence of air hole size of the inner and outer cladding of the PCFs on Brillouin gain spectrum, Brillouin threshold time delay, and Brillouin gain by taking into account the contribution of the high-order acoustic mode was numerical simulated by full vectorial finite element method. The simulated results indicate that the properties of slow light are affected more obviously by varying the air filling fraction in the inner cladding and less affected by the air hole size of the outer cladding. We found that with the time delay up to 705ns, Brillouin gain up to 40dB can be achieved with pump power of only 10mW in a 1m long chalcogenide PCF when the air filling fraction in the inner cladding is 0.9. The pertinent results can be of great importance for studying and designing the optical devices or optical sensors based on this kind of PCF.

Mid-Infrared Supercontinuum Generation in Chalcogenide Photonic Crystal Fibers with a Weak CW Trigger

We numerically demonstrate that noise properties of picosecond mid-infrared (mid-IR) supercontinuum (SC) in the anomalous region of a chalcogenide photonic crystal fiber (PCF) can be effectively controlled by a weak continuous wave (CW) trigger. Detailed simulation results show that in the mid-IR region, the characteristics of SC, including spectral bandwidth, temporal coherence, and signal-to-noise ratio (SNR), can be greatly enhanced by the CW trigger at selected wavelengths. The present study provides valuable insight into the CW-triggered mid-IR SC under the influence of modulation instability (MI) and stimulated Raman scattering (SRS).

All-solid mid-infrared chalcogenide photonic crystal fiber with ultralarge mode area.

In this Letter, we report, to the best of our knowledge, the largest effective single-mode mid-infrared chalcogenide (ChG) fiber. Two thermally matched ChG glasses with a large index contrast of ∼0.35 are chosen for constructing all-solid photonic crystal fiber (PCF) with two rings of "holey" microstructured cladding. Single-mode operation is confirmed in the fabricated ChG PCF with a core diameter of 91.2μm, from both near-field and far-field observation at 4μm. Ultralow numerical aperture of <0.025 has been observed at wavelengths between 2.5 and 4.0μm. The fundamental mode area is calculated to be 5200 μm2 at 4μm, where the propagation loss of the ChG PCF is measured to be 5.2dB/m. Broadband 3.5 and 7.5μm supercontinuum has been generated in a 35-cm-long ultralarge-mode-area PCF.