Mukul Chandra Paul

Bio: Mukul Chandra Paul is an academic researcher from Central Glass and Ceramic Research Institute. The author has contributed to research in topics: Fiber laser & Optical fiber. The author has an hindex of 19, co-authored 221 publications receiving 1625 citations. Previous affiliations of Mukul Chandra Paul include Indian Association for the Cultivation of Science & Academy of Scientific and Innovative Research.

Process for making rare earth doped optical fiber

Abstract: The present invention provides an improved process for making rare earth doped preforms and fibres by a combination of MCVD technique and solution doping method, said method comprising developing matched or depressed clad structure inside a silica glass substrate tube followed by deposition of unsintered particulate layer containing GeO2 and P2O5 for formation of the core and solution doping by soaking the porous soot layer into an alcoholic/aqueous solution of RE-salts containing co-dopants like AlCl3 / Al(NO3)3 in definite proportion, controlling the porosity of the soot, dipping period, strength of the solution and the proportion of the codopants to achieve the desired RE ion concentration in the core and minimise the core clad boundary defects and followed by drying, oxidation, dehydration and sintering of the RE containing porous deposit and collapsing at a high temperature to produce the preform and overladding with silica tubes of suitable dimensions and fibre drawing to produce fibres.

Titanium Dioxide (TiO2) film as a new saturable absorber for generating mode-locked Thulium-Holmium doped all-fiber laser

Abstract: We report the generation of mode-locked thulium-holmium doped fiber laser (THDFL) at 1979 nm. This is a first demonstration of mode-locked by using Titanium Dioxide (TiO 2 ) film as a saturable absorber (SA). A piece of 1 mm×1 mm TiO 2 film was sandwiched in between two fiber ferrule in the cavity. Fabrication process of TiO 2 film incorporated a TiO 2 and a polyvinyl alcohol (PVA). The stable 9 MHz repetition rate of mode-locked mode operation with 58 dB SNR was generated under pump power of 902–1062 mW. At maximum pump power, the mode-locked THDFL has output power and pulse energy of 15 mW and 1.66 nJ, respectively. Our results demonstrate the TiO 2 can be used promisingly in ultrafast photonics applications.

Radiation response behavior of high phosphorous doped step-index multimode optical fibers under low dose gamma irradiation

Abstract: This paper revealed the role of various parameters on the radiation response behavior of P 2 O 5 doped step-index multimode (SIMM) fibers having different content of P 2 O 5 (12–6 mol%) at room temperature. Their suitability for use as a radiation sensitive fiber in fiber optic dosimeter was studied under 60 Co-gamma irradiation at different dose rates 0.01–0 Gy/h. The suitable wavelength region is found to be 500–600 nm where the fibers shows the maximum radiation sensitivity due to formation of phosphorous–oxygen hole centers identified from their radiation induced absorption spectra. The influence of each parameter like the doping levels of P 2 O 5 , dose rates, doping region and energy of the radiation source on their sensitivities was examined. The radiation sensitivities recorded at 502, 540 and 560 nm depends strongly on P 2 O 5 content of the fiber at low dose rates within 0.01–1 Gy/h. However, the fibers shows almost dose rate independent behavior at high dose rates (>1.0 Gy/h) under 60 Co-gamma radiation source of energy 1.25 MeV with respect to all the three wavelengths. The fiber shows almost linear relation to the total dose up to saturation levels of 4.0 Gy at all dose rates. Their sensitivities could be explained through analyses of such type of glass as well as behavior of the radiation induced P-related defects generated in the light guiding core region. At low dose rates the fibers becomes more radiation sensitive compared to the high dose rates due to conversion of POHC centers to P 1 (phosphorous E′) defect centers as observed from their induced loss curves during gamma irradiation. At low dose rates 0.1–1 Gy/h under 502 nm transmission wavelength the fibers shows an excellent linear relation with respect to Cs-137 radiation source of energy 0.662 MeV having average sensitivity of 1.0452 ± 0.0346 dB/m/Gy and very low fading behavior at room temperature. The results suggest that P-doped SIMM fiber (40 μm core diameter) containing 16 mol% P 2 O 5 exhibit an excellent linear radiation response property of high sensitivity around 0.89 ± 0.09 dB/m/Gy at 502 nm wavelength with very low recovery and little dose rate dependence within 0.5–10 Gy/h region that makes them a very promising candidate as radiation sensor for use in fiber optic personal dosimeter to detect low dose gamma radiation of 0.002 Gy for human safety purpose.

Wideband EDFA Based on Erbium Doped Crystalline Zirconia Yttria Alumino Silicate Fiber

Abstract: A wideband erbium-doped fiber amplifier (EDFA) is demonstrated using an Erbium-doped zirconia fiber as the gain medium. With a combination of both Zr and Al, we could achieve a high erbium doping concentration of 4320 ppm in the glass host without any phase separations of rare-earths. The Erbium doped fiber (EDF) is obtained from a fiber preform, which is fabricated in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber using a MCVD process. Doping of Er2O3 into Zirconia yttria-aluminosilicate based glass is done through solution doping process. The maximum gain of 21.8 dB is obtained at 1560 nm with 2 m long of EDF and co-pumped with 1480 nm laser diode. At high input signal of -4 dBm, a flat-gain at average value of 8.6 dB is obtained with a gain variation of less than 4.4 dB within the wavelength region of 1535-1605 nm and using 3 m of EDF and 100 mW pump power. The corresponding noise figure is maintained below 9.6 dB at this wavelength region.

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 …

High power fiber lasers: current status and future perspectives [Invited]

Abstract: The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

Rare earths: jewels for functional materials of the future

Abstract: In recent decades, rare earths have become vital to a wealth of advanced materials and technologies including catalysts, alloys, magnets, optics and lasers, rechargeable hydride batteries, electronics, economical lighting, wind- and solar-energy conversion, bio-analyses and imaging. In this perspective article we give a broad overview of rare earth resources and uses first and then of selected applications in dedicated fields such as telecommunications, lasers, photovoltaics (solar-energy conversion), lighting (fluorescent lamps and OLEDs), luminescent probes for bio-analyses and bio-imaging, as well as magnetism and magnetic refrigeration.