Than Singh Saini

Broadband Mid-Infrared Supercontinuum Spectra Spanning 2–15 μm Using As 2 Se 3 Chalcogenide Glass Triangular-Core Graded-Index Photonic Crystal Fiber

In this paper, we report analysis, design, and numerical modeling of mid-infrared supercontinuum generation across 2-15 μm molecular “fingerprint region” using a new design of triangular-core graded-index photonic crystal fiber (PCF) pumped with 50 fs laser pulses of peak power of 3.5 kW at 4.1 μm. Proposed PCF design offers the nonlinear coefficient as high as 1944 W-1 · Km -1 at pump wavelength. To the best of our knowledge, the supercontinuum in PCF with such broadband spectra has been reported first time. Proposed PCF design has potential applications in gas sensing, food quality control, and early cancer diagnostics.

Analysis and Design of Single-Mode As 2 Se 3 -Chalcogenide Photonic Crystal Fiber for Generation of Slow Light With Tunable Features

Theoretical investigation leading to design of a single-mode As2Se3-chalcogenide photonic crystal fiber is reported for generation of a tunable slow light. Maximum allowable pump power for undistorted output pulse, Brillouin gain, and time-delay experienced by the pulse propagating in designed photonic crystal fibers are simulated. We have found that Brillouin gain upto ~88 dB/m and time delay up to ~137 ns can be obtained from 1-m-long photonic crystal fiber pumped with 100 mW. Simulated results indicate that the time delay experienced by the pulse can be tuned with the pump power and structural parameters of As2Se3-chalcogenide photonic crystal fiber.

Slow light generation in single-mode tellurite fibers

Theoretical investigations of stimulated brillouin scattering-based tunable slow light in (i) Er-doped tellurite and (ii) undoped tellurite fibers are reported. Maximum allowable pump power for undistorted output pulse, Brillouin gain, time-delay, figure-of-merit, and time-delay slop efficiency of both the fibers has been obtained. We have found that (i) Brillouin gain up to ~91 dB and time delay of 140 ns can be achieved using 1100 mW pump power in 2 m Er-doped fiber and (ii) Brillouin gain up to ~86 dB and time delay of ~227 ns using 23 mW pump power in 100 m undoped tellurite fiber can be achieved. Simulated results indicate that the time delay in fibers can be tuned with the pump power to obtain tunable slow light features in these fibers. We feel that detailed theoretical investigations and simulations carried out in the study have potential impact in the design and development of slow light-based photonic devices.

Design and analysis of equiangular spiral photonic crystal fiber for mid-infrared supercontinuum generation

A design of equiangular spiral photonic crystal fiber (PCF) in As2Se3 chalcogenide glass is reported for mid-infrared supercontinuum generation. Supercontinuum covering the 1.2–15 μm molecular fingerprint region is achieved using only 8 mm long designed PCF pumped with 50 fs laser pulses of 500 W peak power. The structural parameters have been tailored for all-normal dispersion characteristic. Proposed structure has high nonlinearity (γ = 12474 W−1 km−1) at 3.5 μm with very low and flat dispersion −2.9 [ps/(nm × km)]. Supercontinuum with such broadening and high coherence degree is applicable for mid-infrared spectroscopy, gas sensing, early cancer diagnostics and free space communication.

Selectively filled large-mode-area photonic crystal fiber for high power applications

A large-mode-area (LMA) single-mode (SM) photonic crystal fiber (PCF) structure for applications in high power fiber lasers, amplifiers and sensors is proposed. In the proposed structure the center air hole has been removed to form the core and the six elliptical air holes of inner ring around the center core have been selectively filled with high refractive index material. Effects of design parameters on SM operation and mode area are numerically investigated by using the full vectorial finite-element method. Structure offers large-mode-area exceeding 835 μm2 at 1.064 μm wavelength. A PCF with such a large-mode-area would significantly reduce the nonlinear effects and would be useful for high power applications.

Design and modelling of dispersion-engineered rib waveguide for ultra broadband mid-infrared supercontinuum generation

Abstract We report a dispersion-engineered As2Se3 chalcogenide glass rib waveguide structure for ultra broadband mid-infrared supercontinuum generation across molecular ‘fingerprint region’. The proposed rib waveguide structure offers non-linear coefficient as high as 18,250 W−1 km−1 at 2.5 μm. Supercontinuum spectrum spanning 2–15 μm, which not only covers the both atmospheric transparent windows (3–5 μm and 8–13 μm) in the mid-infrared domain but also covers the important molecular ‘fingerprint domain’, is obtained using only 4 mm-long rib waveguide structure. To the best of our knowledge, such broadband mid-infrared supercontinuum spectrum in As2Se3-based chalcogenide waveguide geometry is reported for the first time. The proposed design of rib waveguide has potential for robust, integrated and low-cost supercontinuum sources in various applications including frequency comb generation, chemical sensing, food quality control and early cancer diagnostics.

Large-mode-area single-polarization single-mode photonic crystal fiber: design and analysis

A rectangular core photonic crystal fiber structure has been presented and analyzed for single-polarization single-mode operation. Single-polarization is obtained with asymmetric design and by introducing different loss for x-polarization and y-polarization of fundamental modes. Single-polarization single-mode operation of the proposed photonic crystal fiber is investigated in detail by using a full vector finite element method with an anisotropic perfectly matched layer. The variations of the confinement loss and effective mode area of x-polarization and y-polarization of fundamental modes have been simulated by varying the structural parameters of the proposed photonic crystal fiber. At the optimized parameters, confinement loss and effective mode area is obtained as 0.94 dB/m and 60.67  μm2 for y-polarization as well as 26.67 dB/m and 67.23  μm2 for x-polarization of fundamental modes, respectively, at 1.55 μm. Therefore simulation results confirmed that, 0.75 m length of fiber will be sufficient to get a y-polarized fundamental mode with an effective mode area as large as 60.67  μm2.

Highly Nonlinear Triangular Core Photonic Crystal Fiber with All Normal Dispersion for Supercontinuum Generation

New design of triangular-core PCF in As2Se3 glass with all-normal dispersion has been proposed for supercontinuum generation. Structure possesses nonlinear coefficient as high as 5400 with -2 dispersion at 4400 wavelength.

Rib waveguide in Ga-Sb-S chalcogenide glass for on-chip mid-IR supercontinuum sources: Design and analysis

Recently, highly nonlinear Ga-Sb-S chalcogenide glasses have been reported for promising mid-infrared applications such as thermal imaging, nonlinear optics, and infrared lasers. However, the nonlinear optical fiber and waveguide geometries in Ga-Sb-S chalcogenide glasses have not been reported to date. In this paper, we numerically investigate the design of the dual zero dispersion engineered rib waveguide in Ga8Sb32S60 chalcogenide glass by employing MgF2 glass as a lower and upper cladding material. The waveguide structure possesses nonlinearity as high as 24 100 W−1 Km−1 and 14 000 W−1 Km−1 at 2050 and 2800 nm, respectively. The reported waveguide is able to generate a mid-infrared supercontinuum spectrum spanning from 1000 to 7800 nm when it pumped with 97 femtosecond laser pulses of a peak power of 1 kW at 2050 nm. We have also showed that the supercontinuum spectrum can be extended to the spectral range of 1000–9700 nm using pumping with 497 fs pulses of a peak power of 6.4 kW at 2800 nm. To the be...

Design and analysis of a highly nonlinear composite photonic crystal fiber for supercontinuum generation: visible to mid-infrared

A composite photonic crystal fiber structure has been designed with tellurite as the cladding and chalcogenide as a core material. To increase nonlinearity, rods of the chalcogenide glass material have been inserted around the core region. The reported structure offers very high nonlinearity of 1042  W-1 Km-1 at 2800 nm pump wavelength with low and flattened dispersion of approximately -11  ps·nm-1 Km-1. An effective mode area of 6.46  μm2 of the propagating mode has been achieved as at pump wavelength. Such a highly nonlinear composite photonic crystal fiber structure is a potential candidate for nonlinear applications, such as slow-light and supercontinuum generation. Pumping at 2800 nm results in a supercontinuum spectrum spanning 0.5-4.7 μm using 8 mm long photonic crystal fiber pumped with femtosecond laser pulses with peak power of 3 kW.