Search

We present a miniaturized ROADM implemented on a silicon optical bench platform; for application as drop and continue module in WDM networks. Both optical and opto‐mechanical components of the ROADM, including a silicon beam splitter, a tunable photonic band gap (PBG) filter with MEMS actuators and waveguides are simultaneously fabricated by micromachining of the device layer of a silicon‐on‐insulator wafer. The silicon beam splitter transmits 35% of the incoming WDM (S, C&L bands) signal to the PBG filter, which can be tuned over a range of more than 150nm (S, C&L). The 65% reflected power from the beam splitter containing all WDM channels can be routed to other nodes in the WDM ring.

We have studied the structural and optical properties of ZnO micro rods. These rods are synthesized by low temperature hydrothermal method, which is under the treatment of 80 °c/22 hrs. The synthesized rods have an average length of 5 μm with hexagonal cross section. They are characterized by absorption spectrum, fluorescence spectrum, back scattering, SEM, HRTEM, and SAED. The photoluminescence from the spectrophotometer shows broad visible emission.

Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH3 gas‐sensing technology. The X‐ray diffraction measurements confirmed that the films grown by this technique have good crystalline tetragonal mixed anatase and rutile phase structure. The surface morphology (SEM) of the TiO2 film showed that the nanoparticles are fine Gas sensing properties showed that TiO2 films were sensitive as well as fast in responding to NH3. A high sensitivity for ammonia indicates that the TiO2 films are selective for this gas.

Lead sulphide nanostructured thin films were grown on soda lime glass substrates by chemical bath deposition. The films were then doped with gallium using vacuum evaporation technique. Optical absorption studies in conjunction with photo sensitivity measurements indicated the suitability of the p‐type Ga doped β‐PbS2 thin films in photovoltaic applications due to the blue shift in the band gap to 2.37 eV and the increased photoconductivity of the films.

Surface morphology and kinetic roughness of ZnO thin films grown on Si(100) substrate for different time durations by pulsed laser deposition technique were analyzed using Atomic Force Microscopy images. Dynamic scaling approach was used for quantitatively analyzing the surface topology in terms of height difference correlation function G(rr, t) and interface width w(t). Dynamic scaling approach is used to find roughness exponent α and growth exponent β, which yields the values 0.67 and 0.49 respectively. This α value is in good agreement with the value predicted by surface diffusion driven model. However, value of growth exponent β is higher than the model value. The deviation suggests anisotropy in film growth. X‐ray diffraction data shows the preferential c‐axis growth supporting deviation from the diffusion driven model.

Thin films of Cd1−xZnxSe (x = 0, 0.2, 0.4, 0.6, 0.8 & 1) with variable composition have been deposited onto glass substrates using mechanically mixed CdSe and ZnSe by vacuum evaporation technique. These thin films have been characterized through the XRD, optical and electrical characterization technique. XRD patterns confirm the preferred orientation and polycrystalline nature of the thin films. Absorption edge shifts towards lower wavelength range with the increase of Zn concentration. The variations of energy band gap have been determined and discussed with Zn concentration. The electrical conductivity of so prepared thin films has been determined in the temperature range from room to 413 K. The result indicates that the electrical conductivity decreases with increasing Zn content

Silica based glasses activated by rare earth ions promises to be an efficient material for the photonics applications. Incorporation of holmium as a rare earth dopant finds wide applications in the infrared range of the electromagnetic spectrum. In this work, we report the preparation and the thermo‐optic characterization of the holmium doped silica glasses. The samples are prepared via sol‐gel route. The structural characterization of the samples is carried out using the X‐ray diffraction technique whereas the constituents of the samples are identified using the Fourier Transform Infrared (FTIR) Spectroscopy. The optical properties of the samples are measured using the UV‐VIS absorption spectroscopy. The thermal effusivity values of the samples are evaluated using an open cell photoacoustic technique. Influence of the annealing temperature on the thermal as well as the optical properties of the samples is investigated in detail. Analysis of the results shows that the doping and annealing process influences the thermo‐optic properties in a substantial manner.

The present work explains optical properties of semiconducting natural rubber nanoparticles from pristine natural rubber by doping. The studies give evidence that the SbCl5 is an efficient dopant for natural rubber. The mechanism of conduction predominantly involves the formation of conjugated sequence of unsaturated double bond in the polymer backbone. Examination of the UV/Vis study reveals the formation of charge transfer complexes in the polymer back bone. Particle filled elastomeric composites have become attractive owing to their low cost and widespread industrial applications. The arrival of nanometer fillers to polymer materials is a promising channel for their property modification. Natural rubber composite is prepared by mixing the pristine natural rubber with semiconducting natural rubber powder.

In this paper a packaged sensor using fiber Bragg grating for under water level measurement is presented. The sensor is configured by fixing one end of a fiber Bragg grating with a diaphragm made up of polymer kept inside a hollow cylinder and the other end to the cylinder. As the level of water increases in the tank hydrostatic pressure at the bottom also increases. The diaphragm used in is to transfer this pressure to the axial strain on the grating. By utilizing the unique diaphragm‐based grating packaging method, the level sensing range has been effectively enhanced. The results obtained indicate that this packaged sensor have long range, rugged and can be customized depending on the requirement. The sensitivity of the sensor is 6.057×10−6 per cm within the range 0 to 30 cm.

Cr‐doped ZnS nanoparticles with Cr concentration of 2 atm.% were successfully synthesized by the chemical co‐precipitation method using 2‐mercapto ethanol as the capping agent. The structural, optical characteristics and magnetic properties of the prepared samples were studied. Energy Dispersive spectroscopy (EDS) measurements showed the existence of Cr ion in the Cr doped ZnS. No mixed phase was observed from X‐ray diffraction (XRD) studies and all the peaks were indexed to the cubic phase of ZnS. The diameter is in the range of 5–10 nm, it was confirmed by TEM studies. The photoluminescence spectra of all the samples exhibited a broad emission band located around 435 nm. The luminescence intensity decreased by doping Cr. The magnetic behavior of the nanoparticles for Cr doped ZnS was investigated using a vibrating sample magnetometer (VSM). We determined the magnetic parameters such as saturation magnetization (MS), coercivity (HC) and retentivity (MR) with Cr concentration from M‐H loop.

Particle size has significant effect on the magnetic properties of nano‐particles. Nano‐particles of Cu‐Ni ferrite have been synthesized by the co‐precipitation method. Different particle sizes (3nm‐9 nm) were obtained by annealing the prepared samples at various temperatures. The specimens characterized using XRD confirmed the formation of cubic spinel structure. The samples show typical superparamagnetic behaviour above blocking temperature. The particle size increases with increasing the annealing temperature. The saturation magnetization & blocking temperature increases with particle size which is characteristic of superparamagnetism. The hysteresis curves show reduction in saturation magnetization in the case of nanoparticles as compared to their bulk counterpart, which have been explained on the basis that the magnetic moments in the surface layers of a nanoparticle are in a state of frozen disorder. However the saturation magnetization increases with particle size, which is the characteristic property of single domain superparamagnetic particles.

In the current century there is an increased demand for broad band wireless access for satisfying different customer needs. These applications requires large amount of frequency resources for its efficient implementation. Radio Frequency techniques, which dominate the current wireless technology, have the limitation of available frequency spectrum that can be used. Researchers identified Optical Wireless Communication as a potential candidate for solving this problem. Studies shows that white light can also be used as a carrier for wireless communication and this area is generally known as Visible Light Communication. The provision of voice data and visual communications to users by using optical wireless has become a key area of research and product development. This paper discusses a novel method for transmission of voice in real time so that the system can be used for both communication and illumination simultaneously. A prototype of the system is implemented successfully and performance analyses are carried out based on the experimental results. SNR and BER calculations for the designed system is done theoretically and simulated. The developed system is having the advantages of very high band width, no interference with adjacent rooms as walls are opaque, no license is required as it doesn’t cause electromagnetic interference and communication simultaneously with illumination.

A data rate of 10 GHz/70 Mbps signal is externally modulated and transmitted over a long‐haul fiber link in a full‐duplex ROF transport system employing broadband amplified spontaneous emission (ASE) light source and nonlinear distortions suppression scheme in our proposed system. Good bit error rate (BER) performance and clear eye diagram were achieved in our proposed system. Such a proposed full‐duplex ROF transport system is suitable for long‐haul microwave link.

This paper explains the influence of different parameters to the sensitivity of an optical waveguide Mach‐Zehnder Interferometer (MZI) for real time detection of biomolecules. The sensing principle is based on the interaction of evanescence field with the biomolecules that get immobilized on sensing arm. The sensitivity has been calculated by varying the sensing window length, wavelength and concentration of bio‐analyte. The maximum attainable sensitivity for the preferred design is the order of 10−8 RIU at 840 nm wavelength with a sensing window length of 1cm. All the simulation work has been carried out with Opti‐BPMCAD for the optimization of MZI device parameters. The SU8 polymers are used as a core and clad material to fabricate the waveguide. The refractive index of cladding layer is optimized by varying the curing temperature for a fixed time period and the achieved index difference between core and clad is Δn = 0.0151. The fabricated MZI device has been characterized with LASER beam profiler at 84...

Conducting polymer composites are finding novel applications in various fields especially in device technology. In this work an effort has been made to synthesize polyaniline–synthetic rubber (Styrene‐butadiene rubber) composite via ex‐situ technique and its electrochemical properties are investigated. Highly conducting emeraldine form of polyaniline (20 S/cm) is prepared by the oxidative polymerization of aniline in aqueous acidic (CSA) media using ammonium peroxydisulfate as oxidizing agent. These composite films are characterized by UV‐Visible spectroscopy to investigate their optical properties. The dc conductivity studies indicate that these composite films show extremely low percolation threshold.

Liquid Crystal is a phase formed between a crystal and a liquid with a degree of order intermediate between the molecular disorder of liquid and the regular structure of crystal..The optical properties of Liquid Crystals are one of the most interesting and certainly the most beautiful features of the phase. In this paper we studied the properties of light as it propagates through a sample of Nematic Liquid Crystals. Amongst various properties of light; we studied polarization and scattering of light through Nematic Liquid Crystals. Liquid crystal materials generally have several common characteristics. One of the characteristics is the transition temperature which will be measured over temperature range of phases. In present work we studied Cholesteryl Oleate. The results are analyzed with the help Polarizing microscopy (PMS) and Spectroscopic technique using Fabery —Perot Etalon. The phase transition of liquid crystal between various mesomorphic forms occurs at a thermodynamically defined temperature as ...

We propose to use pure phase filter in combination with high NA lens axicon to achieve high efficient longitudinally polarized beam with a subwavelength spot size and large depth of focus using hyper geometric Gaussian beam. Using this system, the spot size is reduced to 0.392 λ and the depth of focus is increased to 7 λ. The efficiency of such system is found to be 87%. This high efficient longitudinally polarized beam generated by hyper geometric Gaussian beam is useful for most of the near‐field optics applications.

The knowledge of the optical parameters of thin films is important for optics and optoelectronics. In the present work, tin sulphide thin films were deposited on glass substrates by chemical bath deposition method. The as grown films were brown in color and highly adherent to the substrate. The films were characterized by X‐ray diffraction (XRD), scanning electron microscopy and spectrophotometric measurements. XRD patterns showed that the films developed were orthorhombic structure. SEM images of tin sulphide thin films confirmed the formation of nanowires. Absorption spectra revealed medium absorption in the visible region and a gradual decrease with higher wavelength. The transmittance of the as‐synthesized films is about 50% in the wavelength range 600–1000 nm. The methodological framework of the Swanepoel’s method for the spectrophotometric determination of optical parameters of tin sulphide thin films using transmittance data was discussed. The Swanepoel’s method is found to be applicable for thin films when measured transmittance spectra have at least one minimum and one maximum. By analyzing the transmission curve, the refractive index and the thickness of the film were evaluated. The energy band gaps are also reported. The optical band gap is direct with a value of 1.79 eV. The values of the optical band gap energy and thickness of the film calculated by Swanepoel’s method were compared with that obtained from absorption spectra and cross sectional SEM photographs respectively. These properties demonstrated that tin sulphide thin films could be used as an absorber layer in the fabrication of heterojunction solar cells.

A facile combustion synthesis route for preparation of Eu and Cu‐doped Na2Zn(PO4)Cl novel phosphors has been described. XRD confirms the preparation of phosphor and this article presents the luminescence properties of Eu2+and Cu+ activated Na2Zn(PO4)Cl under NUV excitation. The prepared phosphors show an efficient broad blue emission. The excitation spectra of the both phosphors are broadband extending from 300 to 400 nm, which are characteristics of near UV excited LED. The effect of the concentration on the luminescence properties of Eu and Cu‐doped Na2Zn(PO4)Cl phosphors is also studied.A facile combustion synthesis route for preparation of Eu and Cu‐doped Na2Zn(PO4)Cl novel phosphors has been described. XRD confirms the preparation of phosphor and this article presents the luminescence properties of Eu2+and Cu+ activated Na2Zn(PO4)Cl under NUV excitation. The prepared phosphors show an efficient broad blue emission. The excitation spectra of the both phosphors are broadband extending from 300 to 400 nm, which are characteristics of near UV excited LED. The effect of the concentration on the luminescence properties of Eu and Cu‐doped Na2Zn(PO4)Cl phosphors is also studied.

This paper presents the design and development of fiber Bragg grating (FBG) temperature sensor suitable for naval applications like temperature monitoring of onboard ships. The Bragg gratings used here have a reflection Bragg wavelength of 1550 nm and are inscribed by phase mask technique using ultraviolet (UV) laser beam at 255.3 nm. The high‐resolution temperature sensor has been designed and developed based on the principle of converting the strain to temperature. This is achieved by using bimetallic configuration. Here lead and tungsten metals are used. The expansion of lead is concentrated on the Bragg grating, thus imparting strain on it. The wavelength shift with change of temperature is recorded with optical spectrum analyzer. The minimum temperature that could be measured accurately by the sensor with repeatability is of the order of 10−2. We have achieved thermal sensitivity of 46 pm/°C and 72 pm/°C for sensor lengths (length of the metallic strips) of 60 mm and 100 mm respectively. The thermal ...

A potentially useful nonlinear optical (NLO) organic material, 1‐(5‐chlorothiophen‐2‐yl)‐3‐(24,5‐trimethoxyphenyl)prop‐2‐en‐1‐one(CTTMP), has been synthesized and grown as a high‐quality single crystal by the slow evaporation technique. The grown crystals were characterized by UV–visible spectroscopy. The material has thermal stability up to its melting point. Single beam Z‐scan technique was employed to study the third order NLO properties of the material.

Bulk Ge20Te80−xInx(x = 0,6,10&16) glasses are prepared by the conventional melt quenching technique. The crystallization mechanism was studied using differential scanning calorimetry (DSC) performed at different heating rates under non‐isothermal conditions. The glass transition temperature (Tg), the peak crystallization temperature (Tp), the thermal stability (Tc‐Tg), the average value of the activation energy for the glass transition, Eg, and the average value of the activation energy for crystallization, Ec, are calculated for the given glass system. The results indicate that the given glass system has 3‐dimensional growth, the average value of the order of the crystallization mechanism, n, is 3.2 and the average value of Eg and Ec are 288.2 and 146.45 kJ/mol respectively.

Single crystals of pure and L‐valine added Ammonium dihydrogen phosphate were grown from aqueous solutions employing slow evaporation solution growth technique at room temperature. The unit cell parameters of the grown crystals were estimated by Single crystal X‐ray diffraction studies. The functional groups responsible for the various modes of vibrations were identified by Fourier transform infrared spectral analysis. The optical transmission studies reveal that the addition of L‐valine has improved the quality of the crystal with higher transparency.

A first‐principles method has been employed to investigate the electronic properties of Be‐chalcogenides namely BeS, BeSe and BeTe. The electron momentum density, autocorrelation function, energy band gap and density of states have been computed using linear combination of atomic orbitals (LCAO) method. The calculated electronic energy band gap and density of states are found to be in good agreement with available earlier data. The bonding in the BeX compounds also been compared on the basis of equal‐valence‐electron‐density profiles and the trend of ionicity is found as BeS>BeSe>BeTe.

Role of semiconductor nanoparticles in the different photophysical processes of short‐chain organic dyads having photoswitchable character has been discussed. Further improvements in efficiency of these light energy conversion devices by using metal‐semiconductor core‐shell (hybrid structure) nanocomposites have been hinted at.

A zero‐order normal coordinate analysis was made for 1,2,3,4‐, 1,2,3,5‐, 1,2,4,5‐tetramethylbenzene, 1,2,3‐trimethylbenzene and 2‐nitro‐para‐toluidine by transferring the force constants from our earlier work. The observed and calculated frequencies agree with an average error of 16.4 cm‐1. On the basis of the results obtained Unambiguous vibrational assignments of fundamentals of the five molecules have been made using the potential energy distributions and eigen vectors and several assignments suggested by earlier workers have been revised.

In this paper we present the factors affecting electroluminescent properties of Zinc complexes of oxazole & thiazole derivatives. Electroluminescent spectra of the Zinc (II) complex of bis‐[2‐(2’‐hydroxyphenyl) benzoxazole], [Zn (HPBO)2]2 and 2‐(1’‐hydroxynaphthyl) benzothiazole [Zn (HNBT)2] show unusual broadening and shows structural and photophysical similarity with [Zn (HPBT)2]2, a dimeric complex. The [Zn (HPBO)2]2 complex as an emissive layer in the device structure ITO /PEDOT:PSS /TPD (30nm) /[Zn (HPBO)2]2 (60nm) /BCP (6nm) /Ca (3nm) /Al (200nm) shows a broad bluish green emission, with a full width at half maxima (FWHM1∼70nm). The EL spectra is much broader compared to the PL spectra because of exciplex formation at the interfacial region between the emissive layer (EML) & hole transport layer (HTL). We also show the device performance of Zinc 2‐(1’‐hydroxynaphthyl) benzothiazole [Zn (HNBT)2] complex as emissive layer. Distinctly this device shows a broad greenish yellow emission with a peak maxim...

We have studied the optical gain of Fullerene C60 and Fullerene C70 in toluene solution by variable strip method. The technique involves the comparison of fluorescence emission at different length of pumped material. The gain is found to be positive for a very narrow range of concentration. The optical gain is maximum at 40 μM concentration for both fullerene molecules. Optical gain is highly concentration dependent and milli molar concentration is not the optimum concentration for the measurement of optical gain. But the value of peak gain for fullerene C70 is more than that of fullerene C60. It may be due to the extent of twisted intermolecular charge transfer (TICT) formation in the excited state is larger for fullerene C70. Therefore, optical gain for fullerene C60 is less than fullerene C70. This is thus an important distinguishing parameter of two sister molecules.

Cobalt‐Manganese and Cobalt‐Nickel oxide (CoMnO and CoNiO) nanoparticles were synthesized via chemical co‐precipitation method by decomposition of their respective metal sulfides and sodium carbonate using ethylene diamene tetra acetic acid as the capping agent. The samples were heated at 400, 600 and 800 °C. The average particle sizes were determined from the X‐ray line broadening. The diffractogram were compared with JCPDS data to identify the crystallographic phase and cubic structure of the particles. The samples were characterized by XRD, FTIR and UV analyses. The internal elastic micro strains were calculated and it was seen that as the particle size increases strain decreases. The FTIR studies have been used to confirm the metal oxide formation. The chemical compositions of the samples were verified using EDX spectra. The surface morphologies of the samples were studied from the SEM images. The absorption spectra of the materials in the UV‐Vis‐NIR range were recorded. From the analysis of the absor...

Electrical switching in bulk Ge20Te80−xInx(x = 0,6,10,14 & 16) glasses has been investigated. The glasses studied are found to exhibit current controlled negative‐resistance behaviour and memory switching. Further, the switching voltage (Vt) is found to increase linearly with sample thickness in the range of 0.2mm to 0.45mm. It is observed that the variation of switching voltage (Vt) of Ge‐Te‐In glasses show a maximum value at an average coordination number 〈r〉 = 2.52 (at x = 6, onset of rigidity percolation), there after decreases and a minimum is seen in the switching voltage at an average coordination number 〈r〉 = 2.68 (at x = 14), which is likely to be the chemical threshold of the system. Beyond x = 14, switching voltage is found to increase again with composition.Electrical switching in bulk Ge20Te80−xInx(x = 0,6,10,14 & 16) glasses has been investigated. The glasses studied are found to exhibit current controlled negative‐resistance behaviour and memory switching. Further, the switching voltage (Vt) is found to increase linearly with sample thickness in the range of 0.2mm to 0.45mm. It is observed that the variation of switching voltage (Vt) of Ge‐Te‐In glasses show a maximum value at an average coordination number 〈r〉 = 2.52 (at x = 6, onset of rigidity percolation), there after decreases and a minimum is seen in the switching voltage at an average coordination number 〈r〉 = 2.68 (at x = 14), which is likely to be the chemical threshold of the system. Beyond x = 14, switching voltage is found to increase again with composition.

Planetary surface exploration is one of the vital aspects to be carried out for a better knowledge of a planet’s interior or surface that paves the way in understanding the planet’s evolution. Such a space application depends heavily on landers and rovers to carry highly specialized instruments to the surface of planetary bodies. Amidst the variety of instruments that were flown/to be flown in space missions, the instruments based on Raman spectroscopy are the best‐suited tools for analyzing minerals on planetary surfaces with an additional advantage of detecting water, ice and hydrous minerals. Owing to the constraints space such as size, weight and power, instrument’s adoptability to miniaturization too plays an important role in realization. Currently we are in an effort to realize a rover‐based miniature Laser Raman Spectroscope (MLRS) to perform in‐situ mineralogical studies. Here, in‐situ corresponds to a distance in order of 200‐300 mm, instead of meters of distance. This paper sheds the light on t...

The performance of laser communication systems operating in the atmosphere is degraded by atmospheric turbulence effects, which causes irradiance fluctuations in the received signal and result in a random signal fades. We propose to simulate this effect in laboratory using an optical turbulence generator chamber and to measure the level of turbulence using CMOS array.

To realize direct image of faint object which is in the close proximity of very bright object could be technologically feasible by introducing asymmetric apodization. The point spread function (PSF) of an optical system with asymmetric apodization has been found to possess a so‐called good side and a bad side. The good‐side has decreased side lobes whereas the bad‐side shows increased side lobes. This has been observed when the aperture is divided into three parts viz. two semi‐circular edge rings and a central region with an apodizer. The asymmetry in the PSF has been found to increase with the width of the edge rings and is seen to decrease with the increased apodization of the central region.

We investigate the possibility of electromagnetically induced transparency (EIT) phenomenon in a three level V‐type atomic system considering both homogenous and inhomogeneously (Doppler) broadened media. Although reduction (dips) in the absorption lines have been experimentally reported in various three‐level systems, a certain ambiguity remains as to whether these results are consequences of EIT or a similar phenomenon known as Autler‐Townes (AT) splitting. The latter phenomenon has a signature that looks very similar to that of EIT. Both phenomena display a reduction in absorption where a maximum is expected in the absence of the coupling field. We present results to demonstrate that EIT occurs in an inhomogeneous Doppler broadened medium, whereas it is not possible to observe EIT in a homogenous medium. The reduced absorption of probe in a homogenous medium is due to Autler‐Towns effect (AT).

Photonic crystals grown using self‐assembly from Rhodamine‐B dye‐doped polystyrene colloids show a systematic angle‐dependent suppression of spontaneous emission in the wavelength range of the photonic stop band, an enhancement at the band edge, spectral narrowing near the band edge and a laser threshold when excited with the second harmonic of Nd: YAG laser under certain conditions. Various designs of photonic crystal‐based microcavities are presented and their performance in emission is compared.

Polypyrrole (pure) and its metal halide composites have been synthesized by chemical oxidation polymerization technique with ammonium peroxisulphate (oxidant) in aqueous hydrochloric acid medium These pure and doped samples were named as S1(as prepared),S2 (100% Co),S3 (Co Ni 50%),S4 (Ni100%). Further investigation these pure and doped samples were annealed at 200 °C for 4 hrs. The amorphous nature of these annealed and as prepared samples was confirmed by XRD. FTIR spectra & SEM images of all the samples were taken at room temperature, which indicates in significant changes in annealed samples. FTIR spectra give the chemical structure of these samples. Characterization through SEM gives the information of surface morphology, from this it is found that surface of as prepared samples is not smooth but in annealed samples the surface shows fine structure as compared to as prepared samples. The absorption spectra were recorded by USB‐2000 spectrophotometer at room temperature in the wave length range 300–800...

The millimeter‐wave properties of optically controlled Quasi‐Read Double Drift InP IMPATT diodes are studied for the first time at elevated junction temperature. The study indicates that the un‐illuminated device is capable of generating a CW power of 13.0 W at 145 GHz frequency; however it reduces significantly in case of optically‐controlled devices. The optical‐illumination studies on the high frequency properties of the Top Mounted and Flip‐Chip device reveals that the photo‐generated leakage current reduces the RF power output and negative resistance of the devices along with an upward shift of operating frequency. The performances of the Quasi‐Read devices are further compared with those of its flat‐profile counterparts. It is interesting to observe that Quasi‐Read diodes are performing much better as far as RF‐power, efficiency and negative resistances are concerned. In addition to this the study indicates that Quasi‐Read diodes are much more photo‐sensitive than flat‐profile diodes. It is further interesting to note that Flip‐Chip diodes are more photo‐sensitive than Top‐Mounted diodes.

Bottom‐up colloidal synthesis of photonic band gap (PBG) materials or photonic crystals (PC) has attracted considerable interest over the top‐down approaches due to their simple processing steps and prospect of economic production of complex 3‐dimensional structures. Here we report a template assisted bottom‐up synthesis of long range order three‐dimensional (3D) Poly (methyl methacrylate)‐gold (PMMA‐gold) metallodielectric PC structures and their robust inverse opals. PMMA opals prepared by dip coating of the PMMA particles, synthesized in our laboratory, onto indium tin oxide (ITO) substrates were used as templates into which gold metal was deposited by electrodeposition method and their inverse opals were prepared by a combination of chemical dissolution and controlled temperature treatment steps. The angle‐resolved optical reflectance of these structures was measured using an optical bench set up. The spectrum obtained at an incident angle of 10° with respect to the normal show a broad band centered at 715 nm for the gold inverse opal, which show an almost non‐dispersive character at all increasing incident angles. The paper presents the interesting spectral features of the opals and their inverse opal and their fabrication method in detail.

Experimental and Simulation works of Nanostructured Solar Cells Using CdSe Quantum Dots have been analyzed and investigated. CdSe quantum dots have been synthesized from non coordinating and high boiling solvent Octadecene and a series of increasing CdSe particle sizes are produced. The synthesized CdSe quantum dots are highly examined under a Transmission Electron Microscope and four images of different sizes of CdSe quantum dots (5.8 nm, 6.4 nm, 7.0 nm and 7.7 nm) have been obtained. A 1.1×1.1 cm2 TiO2 electrode is prepared using indium tin oxide conducting glass and TiO2 nanoparticles. The Oleic acid terminated CdSe quantum dots are separated from the octadecene by using 100% ethanol and centrifuge machine of spin about 4000 rpm until the shaking gave no longer suspension. The CdSe quantum dot (5.8 nm) was adsorbed on TiO2 photoelectrode and used as sensitizer. The relationship of Bandgap energy, Emission wavelength with respect to quantum dot size have been simulated and investigated. In this paper wo...

Films of polyaniline (PANi) and PANi‐ ZnO nanocomposites have been synthesized by spin coating technique. Fourier transform infrared and UV‐Vis spectroscopic studies of PANi and PANi‐ ZnO nanocomposite films indicated the presence of interaction between nano ZnO particles and molecular chains of PANi. The resistivity measurement shows that molecular chain constitution of polyaniline is the most important carrier in polyaniline‐ nano‐ZnO composite.

We investigate theoretically coherent pump‐probe spectroscopy of four level systems in degenerate double Λ, tripod and N‐configurations and discuss electromagnetically induced transparency, lasing without population inversion, effect of laser phase fluctuations and the possibility of realizing negative refractive index.

Digital holography technique has wide range of applications in the field of science and engineering. It consists of two processes i.e. recording and reconstruction. The reconstruction procedure influences the accuracy of the measurement. The present study proposes a novel approach for the reconstruction process based on the superposition principle. The effectiveness of this proposed approach has been presented for 3D distribution of the particle field using both simulated data and experimental data. The 3D particle field has been experimentally generated using the mixture of copper particle and gelatin solution between two glass cover slip. The enhancement of resolution is subsequently achieved by implementing the lens based holographic technique. This technique is capable of providing both 3D geometrical and compositional details of crystals and biological cells etc. A single hologram provides 3D distribution and morphology of the object field.

Three Cu(I) halide complexes [Cu(L)(PPh3)X] (L = 1,10‐phenanthroline, X = Cl (1), Br (2) and I (3), PPh3 = triphenylphosphine) have been synthesised and characterised by spectroscopic techniques. Further structure of the complex 1 was confirmed by single crystal X‐ray diffraction analysis. The nonlinear optical properties of the complexes were investigated at 532 nm using single beam Z‐scan technique with nanosecond laser pulses. The complexes showed strong optical limiting behavior due to effective three‐photon absorption (3PA). The values of 3PA coefficients (γ) for 1, 2 and 3 were found to be 3.2×10−24 m3/W2, 6.0×10−25 m3/W2 and 1.2×10−23 m3/W2 respectively, which are comparable to good optical limiting materials. These studies demonstrate that the Ligand→copper coordinative bonds facilitate the polarization of the electronic π‐system which optimizes the third‐order NLO response in the reported complexes.

Holographic Optical Tweezers (HOT) is a technique in which the phase of trapping laser is modulated for generating steerable, multiple optical traps in a sample chamber. An indigenously developed HOT set‐up at Raja Ramanna Centre for Advanced Technology, Indore has been used to trap thermo‐responsive poly(N‐isopropylacrylamide‐co‐acrylic acid) (pNIPAM‐co‐AAc) spherical particles of 1.6 μm diameter suspended in aqueous medium. The videos of the trapped particles were digitally processed to track the particle positions as a function of time. From these measurements lateral trap stiffness for pNIPAM‐co‐AAc particles was determined as a function of trap power and temperature using Equipartition and Boltzmann Statistics methods. Both the methods gave similar results and the value for the trap stiffness at 25 °C with trapping laser power of 33 mW was estimated to be 0.14±0.01 μN/m. Since the optical trap stiffness depends on particle size and refractive index which vary as a function of temperature the variatio...

Nano crystalline mixed ferrites can be prepared through different methods. In the present work a comparison was made on sol‐gel auto combustion method and co‐precipitation method by preparing Nickel Zinc Ferrite. The prepared samples were calcined at different temperatures and were characterized by powder XRD, FTIR. X‐ray diffraction analysis indicated the formation of ferrite in nanophase. The lattice parameter was found to be in the range 8.31–8.41Ao. This confirms that nano crystalline ferrite samples are in the cubic spinel structure. An average nano crystalline size was estimated from XRD by the Scherrer’s equation. FTIR study also confirms the formation of ferrites. Sol‐gel auto combustion technique was superior to co‐precipitation method for producing single phase nano particles with smaller crystallite size.

Bulk glasses of compositions Se85−xTe15Inx (x = 3,6,9,12) are prepared by melt quenching technique and Differential scanning calorimetry (DSC) is employed to study the thermal stability, crystallization mechanism as well as specific heat of these glasses. It is found that the addition of indium increases the glass transition temperature. From the heating rate dependence of the glass transition temperature the activation energy of glass transition is determined using Kissinger’s equation for non‐isothermal crystallization of materials. An attempt has been made to explain the variation in the value of Tc, Tp and ΔCp for the composition Se73Te15In12 using rigidity percolation threshold (RPT). From the values of (Tc‐Tg) the stable glass system is determined.

At present, there is a lot of interest in the functioning of the marine environment. Unmanned or Autonomous Underwater Vehicles (UUVs or AUVs) are used in the exploration of the underwater resources, pollution monitoring, disaster prevention etc. Underwater, where radio waves do not propagate, acoustic communication is being used. But, underwater communication is moving towards Optical Communication which has higher bandwidth when compared to Acoustic Communication but has shorter range comparatively. Underwater Optical Wireless Communication (OWC) is mainly affected by the absorption and scattering of the optical signal. In coastal waters, both inherent and apparent optical properties (IOPs and AOPs) are influenced by a wide array of physical, biological and chemical processes leading to optical variability. The scattering effect has two effects: the attenuation of the signal and the Inter‐Symbol Interference (ISI) of the signal. However, the Inter‐Symbol Interference is ignored in the present paper. Therefore, in order to have an efficient underwater OWC link it is necessary to model the channel efficiently. In this paper, the underwater optical channel is modeled using Monte‐Carlo method. The Monte Carlo approach provides the most general and most flexible technique for numerically solving the equations of Radiative transfer. The attenuation co‐efficient of the light signal is studied as a function of the absorption (a) and scattering (b) coefficients. It has been observed that for pure sea water and for less chlorophyll conditions blue wavelength is less absorbed whereas for chlorophyll rich environment red wavelength signal is absorbed less comparative to blue and green wavelength.

Dye‐sensitized solar cells (DSSCs) also known as Gratzel cells, have attracted the interests of researchers to a great extent because of its cost effective and easy manufacturing process without involving highly sophisticated lithographic technique and high cost raw materials as usually seen in conventional solar cell. Based on simple photo‐electrochemical process, it has got immense potential in converting solar energy to electrical power in remote and desert area where the supply of conventional power is not possible. The overall peak power‐production efficiency of dye‐sensitized solar cells has been reported around 11 percent, so they are best suited to low‐density applications and the price‐to‐performance ratio obtained through these solar cells is superior to others. DSSCs have ability to absorb even diffused sunlight and therefore work in cloudy whether as well without much impact over the efficiency. The present communication deals with a review of our work on DSSCs wherein we have used cost effective natural dyes/pigments as a sensitizer of nc‐TiO2 and discussed about various key factors affecting the conversion efficiency of DSSC.

Honeycomb structured porous materials from complex polymers are formed using water droplet templating method. In the present work microporous films were prepared from styrene butadiene rubber (SBR) using emulsion technique. The pore sizes can be easily tuned by changing the concentration and the humidity condition. The pore size is characterized by optical microscope and Scanning electron microscope (SEM). These films can be used for various applications in optoelectronics, photonics, catalysis, tissue engineering, bioanalytical purposes etc.

Glassy carbon substrate, multi‐walled carbon nanotubes and double stranded DNA was coated layer by layer to form an electrode. The electrode was exposed to benzene solution for 5 minutes. The layer by layer coated carbon electrode forms a viable platform for the immobilization of DNA that effectively promotes electron transfer between the DNA and electrode. The electrochemical impedance spectroscopy and cyclic voltammetry measurements was taken before and after the exposure. The effects of adsorption potential, DNA concentration and quantity of carbon nanotubes used for DNA immobilization were investigated on the voltammetric behavior of DNA. These findings could be used to design a biosensor with linear response to benzene.