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Rajib Chakraborty

Bio: Rajib Chakraborty is an academic researcher from University of Calcutta. The author has contributed to research in topics: Lithium niobate & Coating. The author has an hindex of 10, co-authored 62 publications receiving 288 citations. Previous affiliations of Rajib Chakraborty include Indian Institute of Technology Kharagpur.


Papers
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Journal ArticleDOI
01 Nov 2021-Optik
TL;DR: In this article, the performance of various active materials categorized as organic, inorganic and organic-inorganic hybrid materials and compared their optical performances to select the efficient material with the help of finite difference time domain analysis (FDTD) and Device solutions provided in Lumerical simulator.

5 citations

Journal ArticleDOI
01 Dec 2013-Optik
TL;DR: In this article, an interferometric technique to measure the phase variation of the film surface has been proposed, which is comparable with the surface quality as obtained from AFM images.

4 citations

Journal ArticleDOI
TL;DR: In this work, various types of grating structures on both sides of active solar cell material for light trapping are studied in detail, and a new type of arrangement of optimized grating structure that significantly improves the light absorption is selected.
Abstract: Enhancement of optical to electrical conversion is vital for improving the efficiency of any solar cell. In recent years, use of thin films instead of bulk wafers has resulted in a huge reduction of production cost, and as such, efficiency enhancement of thin-film solar cells is considered in this study. Though this enhancement depends on several factors, most significant among them is the increase in light absorption within the active material of the solar cell. In this work, various types of grating structures on both sides of active solar cell material for light trapping are studied in detail, and a new type of arrangement of optimized grating structure that significantly improves the light absorption is selected. Enhancement of light absorption for change in dielectric material of the grating structure without changing the active material is also observed. Along with structural optimization, simulated electrical characterization of the samples was also performed, which yields a short-circuit current density of 29.27mA/cm2 with conversion efficiency of 14.51%, having a fill factor of 0.83 for a typical ultrathin layer of active material of thickness 2 µm. This is quite significant because typical cells of this category have much lesser conversion efficiency.

4 citations

Journal ArticleDOI
TL;DR: In this article, the surface morphology and angular scattering of the porous silicon formed using this new technique has been studied and it is revealed that etch depth is better than other stain etching methods and possibly vertical which is the reason for using metal assisted porous silicon etching process in making silicon nanowires.
Abstract: Metal assisted Porous Silicon formation has been reported using highly uniform nanometer scale silver films, solution-deposited using a chemical reaction. The surface morphology and the angular scattering of the porous silicon formed using this new technique has been studied. The surface morphology is comparable with that obtained using other methods of metal deposition. Moreover it is also revealed that etch depth is better than other stain etching methods and possibly vertical which is the reason for using metal assisted porous silicon etching process in making silicon nanowires. Thus the proposed method is simple, cheap and maintenance free alternative to the conventional methods of metal assisted porous silicon formation. Being a solution deposition method, it can be used to form porous silicon in interior or inaccessible areas.

4 citations

Journal ArticleDOI
TL;DR: In this paper, a Mach-Zehnder interferometric setup is used and the voltage required for phase reversal of the fringe pattern is noted for single domain and domain inverted sample.
Abstract: Change in the value of half-wave voltage of ${\rm LiNbO}_{3}$ ( $z$ -cut) before and after high electric field domain inversion at room temperature has been reported. For verification, a Mach–Zehnder interferometric setup is used and the voltage required for phase reversal of the fringe pattern is noted for single domain and domain inverted sample. The technique of the used domain inversion process is discussed and confirmation of the domain inversion is also done. As the half-wave voltage decreases after domain inversion, it may be assumed that the overall electro-optic property of ${\rm LiNbO}_{3}$ has been enhanced. This might possibly been caused by the internal field compensating the spontaneous polarization of the crystal.

4 citations


Cited by
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Proceedings Article
01 Jan 1999
TL;DR: In this paper, the authors describe photonic crystals as the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures, and the interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

2,722 citations

Journal ArticleDOI
TL;DR: In this article, a new optical waveguide technology for integrated optics, based on propagation of long-range surface plasmon polaritons (LR-SPPs) along metal stripes embedded in dielectric, is presented.
Abstract: New optical waveguide technology for integrated optics, based on propagation of long-range surface plasmon polaritons (LR-SPPs) along metal stripes embedded in dielectric, is presented. Guiding and routing of electromagnetic radiation along nanometer-thin and micrometer-wide gold stripes embedded in polymer via excitation of LR-SPPs is investigated in the wavelength range of 1250-1650 nm. LR-SPP guiding properties, such as the propagation loss and mode-field diameter, are investigated for different stripe widths and thicknesses. A propagation loss of /spl sim/6 dB/cm, a coupling loss of /spl sim/0.5 dB (per facet), and a bend loss of /spl sim/5 dB for a bend radius of 15 mm are evaluated for 15-nm-thick and 8-/spl mu/m-wide stripes at the wavelength of 1550 nm. LR-SPP-based 3-dB power Y-splitters, multimode interference waveguides, and directional couplers are demonstrated and investigated. At 1570 nm, coupling lengths of 1.9 and 0.8 mm are found for directional couplers with, respectively, 4- and 0-/spl mu/m-separated waveguides formed by 15-nm-thick and 8-/spl mu/m-wide gold stripes. LR-SPP-based waveguides and waveguide components are modeled using the effective-refractive-index method, and good agreement with experimental results is obtained.

417 citations

Journal ArticleDOI
TL;DR: A comprehensive inventory of the progresses achieved so far is gathered, to allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs.
Abstract: High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

171 citations

Journal ArticleDOI
TL;DR: In this article, three types of fiber Bragg grating-based vibration sensors have been classified based on the difference of vibration-strain coupling way to FBG in this survey, which are pasted FBG-based, axial property of FBGbased and transverse property, respectively.
Abstract: Vibration sensing is critical to monitor and ultimately preserve the health state of engineering systems. These systems with a large structure are typically working in some harsh environments including strong magnetic fields. However, traditional electrical sensors are difficult to accurately measure the vibration under harsh environments. Besides these instinct advantages of normal fiber optic sensors (FOS) sensors such as compact size, passive sensing, resistance to electromagnetic interference, etc., fiber Bragg grating (FBG) sensors have a capability of distributed sensing based on wavelength demodulation and resistance to light intensity fluctuation and unwanted fiber bending losses. Such merits lead them to be a hot topic in FOS field and excellent candidates for vibration sensing. Three types of FBG-based vibration sensors have been classified based on the difference of vibration-strain coupling way to FBG in this survey, which are pasted FBG-based, axial property of FBG-based and transverse property of FBG-based, respectively. FBG-based vibration sensors' principles and designs have been introduced and discussed. Recent advances in the applications of FBG-based vibration sensors have been investigated. The limitations and prospects of the FBG-based vibration sensing technologies have been analyzed and discussed.

91 citations

Journal ArticleDOI
TL;DR: A significant reduction in patient healing time with less loss of mechanical strength of implants has been achieved after coating with hydroxyapatite (HA), and a comparative study of these techniques is presented.
Abstract: To facilitate patient healing in injuries and bone fractures, metallic implants have been in use for a long time. As metallic biomaterials have offered desirable mechanical strength higher than the stiffness of human bone, they have maintained their place. However, in many case studies, it has been observed that these metallic biomaterials undergo a series of corrosion reactions in human body fluid. The products of these reactions are released metallic ions, which are toxic in high dosages. On the other hand, as these metallic implants have different material structures and compositions than that of human bone, the process of healing takes a longer time and bone/implant interface forms slower. To resolve this issue, researchers have proposed depositing coatings, such as hydroxyapatite (HA), polycaprolactone (PCL), metallic oxides (e.g., TiO2, Al2O3), etc., on implant substrates in order to enhance bone/implant interaction while covering the substrate from corrosion. Due to many useful HA characteristics, the outcome of various studies has proved that after coating with HA, the implants enjoy enhanced corrosion resistance and less metallic ion release while the bone ingrowth has been increased. As a result, a significant reduction in patient healing time with less loss of mechanical strength of implants has been achieved. Some of the most reliable coating processes for biomaterials, to date, capable of depositing HA on implant substrate are known as sol-gel, high-velocity oxy-fuel-based deposition, plasma spraying, and electrochemical coatings. In this article, all these coating methods are categorized and investigated, and a comparative study of these techniques is presented.

82 citations