Manish Tiwari

Bio: Manish Tiwari is an academic researcher from Manipal University Jaipur. The author has contributed to research in topics: Photonic-crystal fiber & Supercontinuum. The author has an hindex of 5, co-authored 32 publications receiving 102 citations. Previous affiliations of Manish Tiwari include YMCA University of Science and Technology & Malaviya National Institute of Technology, Jaipur.

Chalcogenide photonic crystal fiber for ultraflat mid-infrared supercontinuum generation

Abstract: In this Letter, we numerically simulate the generation of a 1–15 μm mid-infrared supercontinuum (SC) from a highly nonlinear Ge11.5As24Se64.5-based photonic crystal fiber (PCF). This ultra-broadband SC is achieved in a 100 mm long PCF pumped using 85 fs laser pulses operated at 3.1 μm and a peak pulse power of 3 kW. The proposed design offers a flat dispersion profile with two zero dispersion wavelengths. This broad and flat dispersion profile of the Ge11.5As24Se64.5 PCF, combined with the high nonlinearity (2474 W−1 km−1), generates an ultra-broadband SC.

Ultrabroad supercontinuum generation in tellurite equiangular spiral photonic crystal fiber

Abstract: Simulations are presented of a very broad and flat supercontinuum (SC) in both the normal and anomalous group velocity dispersion regimes of the same equiangular spiral photonic crystal fiber at low pumping powers. For a pump wavelength at 1557 nm and average pump power of 11.2 mW, we obtained a bandwidth >3 μm (970 nm–4100 nm) at 40 dB below the peak spectral power with fiber dispersion ∼2.1 ps/km nm at 1557 nm. In the same fiber, at pump wavelength 1930 nm and average pump power of 12 mW the SC bandwidth was more than two octaves (1300 nm–3700 nm) and dispersion was ∼1.3 ps/km nm at 1930 nm. This demonstrates the potential use of the fiber for multi-wavelength pumping with commercially available sources at fairly low power.

Mid-infrared supercontinuum generation in Ge 11.5 As 24 Se 64.5 based chalcogenide photonic crystal fiber

Abstract: In this paper, we have numerically investigated a Ge 11.5 As 24 Se 64.5 based chalcogenide photonic crystal fiber and simulated 1–10 μm mid-infrared supercontinuum generation. This mid-infrared broadband supercontinuum is achieved for 100 mm long photonic crystal fiber pumped with 85 femtosecond laser pulses operated at 3.1 μm and peak power pulse is 3 kW. A broad and flat dispersion profile with two zero dispersion wavelengths of Ge 11.5 As 24 Se 64.5 photonic crystal fiber combined with the high nonlinearity and generate ultra flat broadband supercontinuum.

Supercontinuum generation at 1.55 μm in As 2 S 3 core photonic crystal fiber

Abstract: This paper proposes a design and mathematical study of As2S3 chalcogenide photonic crystal fiber (PCF) for broadband supercontinuum generation. The proposed design offers a large nonlinearity coefficient and ultra-flattened dispersion. The proposed design was analyzed using the full-vectorial finite element method. Through this method, it is shown that an ultra-broad supercontinuum spectrum of 0.8-4.5 μm is attained using an As2S3 core PCF design with 20 fs pump pulse width and a length of 10 mm, having 3 kW power at a -40 dB spectral and temporal intensity. The proposed octagonal PCF has shown a low zero dispersion wavelength at the pump wavelength of 1.55 μm.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Supercontinuum generation, photonic crystal fiber

Abstract: A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Millimeter-Wave and Terahertz Spectrum for 6G Wireless

Abstract: With the standardization of 5G, commercial millimeter wave (mmWave) communications has become a reality despite all the concerns about the unfavorable propagation characteristics of these frequencies. Even though the 5G systems are still being rolled out, it is argued that their gigabits per second rates may fall short in supporting many emerging applications, such as 3D gaming and extended reality. Such applications will require several hundreds of gigabits per second to several terabits per second data rates with low latency and high reliability, which are expected to be the design goals of the next generation 6G communications systems. Given the potential of terahertz (THz) communications systems to provide such data rates over short distances, they are widely regarded to be the next frontier for the wireless communications research. The primary goal of this chapter is to equip readers with sufficient background about the mmWave and THz bands so that they are able to both appreciate the necessity of using these bands for commercial communications in the current wireless landscape and to reason the key design considerations for the communications systems operating in these bands. Towards this goal, this chapter provides a unified treatment of these bands with particular emphasis on their propagation characteristics, channel models, design and implementation considerations, and potential applications to 6G wireless. A brief summary of the current standardization activities related to the use of these bands for commercial communications applications is also provided.

Ultraflat, broadband, and highly coherent supercontinuum generation in all-solid microstructured optical fibers with all-normal dispersion

Abstract: High flatness, wide bandwidth, and high-coherence properties of supercontinuum (SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in a combination of the properties, since special dispersion profiles are required, especially when pump pulses with duration over 100 fs are employed. We propose an all-solid microstructured fiber composed only of hexagonal glass elements. The optimized fiber possesses an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55 μm. An SC spectrum spanning from approximately 1030 to 2030 nm (corresponding to nearly one octave) with flatness <3 dB is numerically generated in the fiber with 200 fs pump pulses at 1.55 μm. The results indicate that the broadband ultraflat SC sources can be all-fiber and miniaturized due to commercially achievable 200-fs fiber lasers. Moreover, the SC pulses feature high coherence and a single pulse in the time domain, which can be compressed to 13.9-fs pulses with high quality even for simple linear chirp compensation. The Fourier-limited pulse duration of the spectrum is 3.19 fs, corresponding to only 0.62 optical cycles.