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Electrical conductivity, FTIR spectroscopy and electro-optic effect in a novel nonconjugated conductive polymer, poly(β-pinene), have been recently reported. The conductivity increases by more than ten orders of magnitude upon doping with iodine. The double bonds decrease upon doping due to charge-transfer and formation of radical cations. In this report, electron paramagnetic resonance (EPR) spectroscopic measurements of poly(β-pinene) before and after iodine doping are discussed. The results show that the EPR signal increases in proportion to the doping level consistent with the formation of radical cations upon doping. Hyperfine splitting has been observed at high doping levels due to reduction in distance between the radical cation and the iodine anion. Such splitting was not observed for a doped conjugated polymer since in that case the radical is delocalized.

The response of a pressure cell with copper diaphragm of different dimensions for the measurement of pressure using a fused multimode fiber optic coupler is presented. As the pressure varies, the deflection of the diaphragm varies and it modulates the intensity of the reflected light entering into the multimode fused coupler. The sensor is operated in back slope of its characteristic displacement curve and it enabled to sense larger range of pressures. The effect of variation of diameter and thickness of the diaphragm is also studied. The experimental results show that the sensitivity, linearity of the sensor is good and it may finds application in monitoring pressure in industries.

The structural, optical and optoelectronic properties of nano structured cadmium sulphide thin films were studied using X‐ray diffraction, optical absorption, photosensitivity and I‐V measurements. Optical studies revealed the band gap of CdS films with particle size ∼26 nm to be around 2.5±0.04 eV. The observed band gap in conjunction with the photosensitivity and n‐type conductivity make them good candidates as the window layers in solar cell applications.

Monolithic optical sensor with readout electronics are needed in optical communication, medical imaging and scintillator based gamma spectroscopy system. This paper presents the design of three different CMOS photodiode test structures and two readout channels in a commercial CMOS technology catering to the need of nuclear instrumentation. The three photodiode structures each of 1 mm2 with readout electronics are fabricated in 0.35 um, 4 metal, double poly, N‐well CMOS process. These photodiode structures are based on available P‐N junction of standard CMOS process i.e. N‐well/P‐substrate, P+/N‐well/P‐substrate and inter‐digitized P+/N‐well/P‐substrate. The comparisons of typical characteristics among three fabricated photo sensors are reported in terms of spectral sensitivity, dark current and junction capacitance. Among the three photodiode structures N‐well/P‐substrate photodiode shows higher spectral sensitivity compared to the other two photodiode structures. The inter‐digitized P+/N‐well/P‐substrate...

The R9Dy(VO4)7 [R = Sr and Ba] phosphors has been successfully synthesized by high temperature solid state reaction and characterized by XRD as well as photoluminescence measurements. The characteristic of Dy3+ emission was observed in R9Dy(VO4)7 [R = Sr and Ba] phosphors. Photoluminescence (PL) emission results shows the blue and yellow sharp bands at 480 nm and 575 nm for R9Dy(VO4)7 [R = Sr and Ba] phosphor s respectively at the excitation wavelength of 348 nm which is NUV excitation. Thus these phosphors may be applicable for the NUV excited solid state lighting devices as well as white LEDs.

Ca3Al2O6:Eu3+ phosphor has been synthesized by combustion method. The phosphors were characterized using X‐ray diffraction and photoluminescence (PL) techniques. The prepared phosphors were excited by 395 nm, the PL emission observed at 616 and 594nm and intensity of 616 nm (5D0→7F2) was almost equal to 594 nm (5D0→7F1). The photoluminescence spectrum of Ca3Al2O6:Eu3+ phosphor showed the emission intensity of phosphor increased with increasing the concentration of europium. The investigated prepared phosphors are suitable for a NUV excited LED.

The third‐order nonlinear optical properties of a charge‐transfer organic compound ethyl 2‐[(2E)‐2‐(4‐hydroxy‐3‐methoxybenzylidene) hydrazino]‐5‐nitrobenzoate were investigated by employing Degenerate Four Wave Mixing (DFWM) and Optical Kerr Gate (OKG) techniques. The study enables to compare the χ(3) values obtained on different time scales of the laser pulses and to understand the origin of nonlinear response of the samples.

We present our results from the measurements of Supereonlinuum emission (SCE) resulting from the propagation ol” tightly foe used 40 femtosecond laser pulses through distilled water. The e fleet of linearly polarized (LP) and circularly polarized (CP) light pulses on the SCE: in different external focal geometries (f/6 & f/12) is studied in detail. A considerable shift in the minimum wavelength of SCF under tighter focusing limit is observed.

Rb lamp is a very critical component of the Rb atomic clock’s Physics Package. The Rb lamp’s performance is very sensitive to temperature and its stability. In this paper we discuss the behaviors of Rb Lamp with temperature. The Rb lamp exciter power and temperature of Rb bulb are very important parameters in controlling the performance of the Rb Lamp. It is observed that at temperatures beyond 110° C, the lamp mode changes from the ring to red mode resulting in abnormal broadening of emission lines and self reversal. The results of our studies on spectral analysis of Rb lamp under various operating conditions are reported in the paper.

Se100−xPbx (x = 0.1,5 & 10) chalcogenide glasses are prepared by conventional melt quenching. Chalcogenide glasses containing Pb are very important material for tunable radiations in the mid infrared region. DSC thermo grams of these glasses are taken at different heating rates. Activation energy of crystallization is calculated using Matusita and Kissinger methods. Hruby’s constant and the value of (Tc‐Tg) are also calculated. Using these values the stability of the system is discussed.

In this paper, synthesis of Eu2+ activated BaCaP207 pyrophosphate based phosphor by using modified combustion synthesis has been reported and studied for its X‐ray diffraction pattern (XRD).Photoluminescence (PL) properties under near ultraviolet (n‐UV) excitation . The BaCaP207:Eu2+ exhibits unique color: a blue band centered at 455 nm originating from Eu2+ when excited at 354 nm, which is suitable for solid state lighting and near ultra violet light emitting diodes (n‐UV LED).Surface morphology has been also studied by scanning electron microscope and the room temperature FTIR spectrum for studying the nature of the chemical bonds, and their molecular environment was investigated.CIE(Commission Internationalede L’Eclairage) chromaticity coordinates values are estimated from emission spectra of BaCaP207:Eu2+ for the prepared sample

Zinc sulfide (ZnS) thin films were deposited on glass substrates by radio—frequency (RF) magnetron sputtering technique at pressure of 10−6 torr. The deposition parameters were optimized and the films were annealed in air atmosphere (300°C for 1hr). The obtained (as‐deposited and annealed) thin films were characterized for structural and optical properties. The thickness of the films was calculated by ellipsometry. XRD patterns revealed that the films were crystalline in nature with hexagonal structure. The morphological characteristic was carried out by optical microscopy. The optical absorption studies in the wavelength range 300‐900 nm show that energy band gap of the film was found to be decreased with the annealing temperature.

We have recently developed a simple method based on variational principle for the scalar analytical approach to study the propagation characteristics of MOFs. The model retains required azimuthal variation of field unlike Effective index method (EIM). We have analyzed, based on this model, the splice loss between two MOFs and that between an MOF and a conventional step‐index fiber (SMF‐28). As expected, the splicing between two MOFs depends on the relative orientation of air‐holes. For typical fibers, this loss could be as high as 0.23 dB.

Lithium tetraborate, Li2B4O7 films on glass substrate were prepared by chemical solution decomposition (CSD) method. The spin coated film (2000 rpm, 20 sec) was preheated (200 °C, 20 min) and then annealed at different temperatures (450°–600 °C) to form polycrystalline Li2B4O7 film. By X‐ray diffraction (XRD), the prominent planes are found to be (100), (113), (302) and (403). The result shows that the main component of the film is Li2B4O7 crystalline phase. A slow XRD scan was used to calculate the crystallite size (D) and the average crystallite size was found to be 178 nm. The lower cut off wavelength at 325 nm with 75% transparency was measured by the UV‐Vis spectra and the spectral dependence of the optical constants (extinction coefficient (K), reflectance(R)) was estimated. The optical energy band gap was found to be 3.62 eV. The nonlinear optical properties were studied by Z‐scan experiment using a Q‐switched, Nd: YAG laser (532 nm, 7 ns). The nonlinear absorption coefficient (NLA) β was found to ...

1% Eu3+ doped KGd(WO4)2 (KGW) was synthesized through Pechini sol‐gel process and crystallized by subsequent annealing at high temperature. Potassium nitrate, gadolinium nitrate and ammonium para tungstate precursors were mixed with citric acid and ethylene glycol to synthesis the polymerizable complex gel. The gel was heated to 250 °C for decomposition of polymer, which after the brownish white powder was used to synthesis the pure form of 1% Eu:KGW. The pre‐fired powder was further heated at high temperature/s (550, 600, 650 and 700 °C) for calcination. The properties of heat treated samples were characterized by powder XRD, FT‐IR, Raman, FESEM and fluorescence analysis to understand the crystallinity, organic liberation, tungstate ribbon formation, surface morphology and emission nature, respectively. Phase evaluation from the amorphous pre‐fired sample to well crystalline KGW powder formation was confirmed with powder XRD analysis. Powders calcined at 600 °C show the appearance of monoclinic phase of ...

Storage and retrieval of object information from hologram using partial object as input is reported. This method uses holographic associative memory principles combined with digital image processing techniques. The inclusion of digital image processing helps in eliminating the iterations which are otherwise mandatory when using neural network principles for object information retrieval. The implementation method is explained and simulation results are presented. The reconstructed images agree well with the object chosen.

Single crystals of Pure and Glycine sodium nitrate (GSN) doped Potassium dihydrogen Phosphate (KDP) were grown from aqueous solution by slow evaporation technique. The cell parameters of the grown pure and GSN doped KDP crystals were estimated by Single X‐ray diffraction studies. The functional groups present in the grown crystals were ascertained using FTIR spectral analysis. The UV‐Vis‐NIR transmission spectra reveals that the semiorganic dopant has increased the optical transparency of the KDP crystals.

The absorption coefficients of aqueous potassium permanganate (KMnO4) solution at 638.8 nm for various concentrations are determined using a simple experimental set up. The setup consists of He‐Ne laser source (Red, 638.8 nm, 10 mW), a glass jar in which the KMnO4 sample is taken, a mirror strip inclined at 45° to direct the laser beam towards the bottom of the glass jar, a traveling microscope to adjust the position of light dependent resistor (LDR) and a digital multimeter to measure the resistance.

In the present research work, we have deposited Copper Indium diselenide (CuInSe2) thin films on to well cleaned glass substrates in a vacuum 10−5 Torr. The as‐deposited films were annealed in air at different temperatures. Optical absorption spectra of CuInSe2 thin films were investigated using optical absorption spectroscopy. Direct energy band gap values for CuInSe2 thin films were derived from the variation of (αhν)2 with energy (hν). The structural and morphological properties of thin films (as‐deposited & annealed) were characterized by X‐ray diffraction (XRD) analysis and optical microscopy. After annealing, the XRD pattern reveals that the films are polycrystalline in nature. The optical micrograph shows that the as‐deposited films have a uniform surface morphology with homogeneity distribution of crystallites.

Semiconducting chalcogen glasses have extensive application in device technology due to its threshold switching and memory. The major drawback of these glasses is the thermal instability leading to crystallization which can be rectified to certain extent by suitable doping. The thermal studies of the semiconducting chalcogen glass Ge15Te80 with Ag as dopant is reported and discussed. The heating rate dependence of the glass transition temperature (Tg) of the system is analyzed and an empirical equation is developed regarding the same. The crystallization kinetics of the glass is studied using different kinetic equations based on the formal theory of transformation kinetics developed by Johnson, Mehl and Avrami(JMA). The activation enthalpies for glass transition (Eg), crystallization (Ec) and onset crystallization (Eoc) are evaluated using the available data by non isothermal techniques. The compositional dependence of Tg of the chalcogen system Ge15Te(85−x) Agx(x = 5,7.5,10,12.5,17.5,18.5,20,21.5) is als...

RGB emission is observed from titania/PVP hybrid material codoped with RE ions (Eu3+ and Tb3+), were prepared by the non hydrolytic sol‐gel method. Down conversion of light is used for the generation of white light which involves the conversion of UV into visible light by the involvement of phosphors. These activated phosphors with two rare earth ions in the hybrid host represent an efficient way to produce white light emission with CIE chromaticity coordinates of x = 0.291 and y = 0.338, which shows it is a potential phosphor for applications in white UV‐LED and field emission display devices.

The invention of the laser, with its precise wavelength and beam divergence characteristics, coupled with the techniques like q‐switching, mode locking to produce ultra‐short pulses has been influencing the era of space technology. Space agencies worldwide are equipping satellites with laser transmitters in the hope of achieving crucial and vital tasks. Though, both laser technology and space operations have matured substantially in the recent decades, offering synergistic possibilities of using lasers from space‐based platforms, development of a reliable laser sources meeting the space mission types and constraints is still the current quest. This paper especially focuses on the conceptualization and engineering design aspects of developing a miniaturized diode pumped, passive q‐switch Er: Glass laser capable of delivering pulses of energy 3 mJ, pulse width of 7 ns at a repetition rate of 1 Hz and operating wavelength of 1535 nm. This paper sheds the light also on the selected resonator configurations, p...

Transparent indium tin oxides (ITO) electrodes were patterned using flash lamp pumped Q‐switched Nd: YAG laser ablation technique. The Optical microscopy, atomic force microscopy and energy dispersive x‐ray spectrum along with scanning electron microscope analysis shows the depth and width of the ablated area and the elements available in the ablated area. In‐plane switching liquid crystal display were constructed using the patterned indium tin oxide and its switching characteristics are investigated.

Radiation effects in Poly (ethylene maleic anhydride) (MANPE) have been investigated by Electron spin resonance (ESR), Fourier transform infrared (FTIR) and Differential scanning calorimeter (DSC) techniques. The ESR spectra of MNAPE under conditions like radiation dose and temperature have been recorded on irradiation. Alkyl group formed in MANPE which abstract oxygen and convert to peroxy radical on increase of radiation dose. More number of chain cleavages occur producing more number of free radicals which resulted increase in intensities of ESR spectrum. With the increase of temperature the free radical formed in MANPE may react with themselves or with other radical, resulting in the decay of ESR signals at high temperature. The FTIR spectra of irradiated MANPE possess absorption bands at 3500‐3000cm−1 and 1700cm−1 positions indicating the presence of OH and C = O groups. The DSC data suggests that on irradiation the melting point slightly increases due to the formation of network structure.

Robust methods for the chemically selective deposition of metals, semiconductors, biomolecules and other substances are developed and applied in the construction of complex two‐and three‐dimensional structures. This work has important applications in molecular and organic electronics, sensing, biotechnology and photonics. These methods are easily parallelized, afford precise nanoscale placement and are compatible with photolithography. Two examples are discussed in detail: the electroless deposition of Cu and the chemical bath deposition (CBD) of CdSe on functionalized self‐assembled monolayers (SAMs).

Laser break down and subsequent plasma formation in liquids, in particular in water is of considerable interest due to its potential application in biomedical applications and also in the generation of micro/nano particle formation. There are two mechanisms which can lead to plasma formation: direct ionization of the medium by multiphoton absorption or avalanche ionization via inverse bremsstrahlung absorption. Spectroscopic investigation was performed in the early stage of breakdown of water at and beyond breakdown threshold and subsequent formation of shock waves and cavitation bubble is studied using shadow graphic and interferometric technique.

Silver (Ag) nanoparticles were prepared in Poly Vinyl Pyrrolidone (PVP) by laser ablation with 1064 nm and 532 nm wavelengths. Particles were characterized by using an electron microscope. The mean diameter of particles is found to be decrease with decrease in ablation wavelength. Third order nonlinearities of Ag/PVP nanocomposite films were studied by Z‐scan technique with 7 ns Nd: YAG laser pulses at 532 nm. Third order susceptibility (χ(3)) is measured with an emphasis on particle size dependence. Open aperture Z scan measurement indicated that composite films exhibited reverse saturable absorption.

Good quality single crystals of metal complexes of thiourea with II group transition metals (Zn, Cd) as central atom and III period element (Cl) were grown from aqueous solution by slow evaporation method. Their structural, optical, thermal and dielectric properties were investigated and reported in detail. Metal complexes show a bathochromic shift in the absorption edge and a blue shift in the optical band gap value. An improved photopyroelectric measurement technique was employed to study the thermal properties of the metal complexes. Dielectric measurements were made as a function of frequency (50 Hz–5 MHz) and temperature (303–423 K) ranges. Laser Damage threshold and powder SHG efficiency of the samples were found using Nd: YAG (1064 nm, 10 ns, 10 Hz) laser. The low power optical limiting properties have been investigated using a 532 nm second harmonics of diode pumped Nd:YAG laser (1064 nm, 50 mW). The role of II group metal ions (Zn and Cd) in tuning the properties of the metal complexes in (100) has been discussed in detail. Cadmium was found to be more efficient than zinc for short wavelength laser generation and low power optical limiting applications.

Holographic recording materials based on photopolymerising systems have contributed significantly to the recent growth of holography. Of the available materials for holography, photopolymer is proved to be highly versatile due to its rapid dry processing, low cost, high optical quality and resolution, low diffusivity, easy preparation techniques, high diffraction efficiency, transparency in the visible spectral region etc. However, availability of commercial grade photopolymer material is very limited due to its strategic importance. On the other side, there are a set of research grade materials widely available. But, a major obstacle for the wider use of such materials is the short shelf life and storage life. The paper presents the shelf life and storage life studies of a laboratory made polymeric mixture which is sensitive to blue wave length. The material yielded stable quality and efficiency for over three months.

Mixed alkali effect in oxide based glasses is one of the current research activity and studies on the behavior of spectroscopic parameters in these systems are quite important to understand the basic nature of this phenomenon. EPR studies of mixed alkali glasses Li2O–K2O–ZnO–B2O3 doped with Fe3+ and Mn2+ were carried out at room temperature. The EPR spectra show typical resonances of d5 system (Fe3+ and Mn2+) in all the measured glass specimens. Evaluated hyperfine constant, number of paramagnetic centers and paramagnetic susceptibility values show deviation from the linearity with the progressive substitution of the Li ion with K in glass network.

In this paper we describe a point scanning optical microscope where the illumination beam can be programmably controlled in real time using a liquid crystal spatial light modulator (LCSLM). With an appropriate pattern displayed on the LCSLM, the device can be made to act as a binary diffraction hologram. In the proposed microscope the illumination beam is in fact the +1 order beam diffracted from the binary hologram. By displaying a sequence of binary holograms it is possible to make a beam scanning, similar to a conventional scanning microscope. Here we use a computer generated holography technique to compute the binary holograms which facilitate complete control of the amplitude and phase profile of the illumination beam. In a number of microscopy applications using reflected light, the reflectivity of the sample plane may differ from region to region. Therefore if a single illumination beam intensity is used for the whole sample plane, then the regions with less reflectivity will be imaged with poor signal to noise ratio. In our proposed microscope the sample plane is first imaged to determine the regions of weak reflectivity. Holograms are then computed to make the illumination beam adapt to the reflectivity variations in the given sample plane. The image obtained with the modified set of holograms have superior signal to noise ratio all over, relative to a conventional point scanning microscope with a fixed intensity illumination beam. In this paper we present some preliminary results using the proposed setup.

Fiber optic sensor based on cladding modification method for detecting various gas emissions such as ammonia methanol, and ethanol is proposed. The Ce doped ZnO annealed at 500 and 1200 °C are used as a gas sensing material. The spectral characteristics of the gas sensor are studied for different concentrations (0–500 ppm) of gases. The sensor exhibits a linear variation in the output light intensity with the concentration. The gas sensitivity and selectivity of the sensor is discussed briefly.

In the present work Aluminum doped Zinc Oxide (AZO) thin films have been deposited on glass substrates from room temperature to 300°C by direct current (d.c) magnetron sputtering. The effects of substrate temperature on the crystallization behavior and optical properties of the films have been studied. The optical transmittance of aluminum zinc oxide films are obviously influenced by the substrate temperature. Optical constants such as absorption coefficient (α), extinction coefficient (k), optical band gap (Eg) and Urbach’s energy (EU) are evaluated from the transmission spectra. Optical absorption edge of aluminum zinc oxide films has a significant blue shift to the region of higher photon energy. The optical band gap of the Aluminium zinc oxide thin films is found to be in the range of 3.2‐3.3 eV.

We present our experimental results from the measurements of Supercontinuum emission (SCE) from air resulting from propagation of tightly focused femtosecond (40 fs) laser pulses. The effect of linearly polarized (LP) and circularly polarized (CP) light pulses on the SCE in two different external focal geometries (f/6, f/15) is presented. A considerable shift in the minimum wavelength of SCE is observed with external tighter focusing.

Solar energy is the most potential alternative source of energy. One way to effectively tap this potential source is application of concentrating systems cascaded with high efficiency Photovoltaic cells. In the design of a photovoltaic system, the primary goal is to maximize the efficiency of conversion and to minimize the light coupling losses. Wavelength selective and focusing properties of Holographic Optical Elements can be used to design concentrators that enhance the power yield from photovoltaic systems and reduce cost per Watt. The paper discusses our initial efforts and the preliminary studies on optimization of design parameters of phase holograms in Light Logics photopolymer HoloMer 6A, to achieve high efficiency PV concentrating systems. Spectral and angular responses of the optimized elements and diffraction efficiencies were measured at different wavelengths. The best efficiency achieved was 70%.

Nanocomposite films of an organic dye‐polymer (Indigo Carmine‐PVA) system were fabricated and their optical limiting behaviour was investigated under excitation with 532 nm laser pulses of 5 ns temporal width using the open aperture Z‐scan technique. The samples displayed optical limiting behavior under the experimental conditions. The Atomic Force Microscopic (AFM) analysis of the surface topography revealed homogeneous distribution of nanoclustered aggregates grown within the polymer matrix and an average roughness of ∼2.02 nm for the surface. The estimated values of the effective nonlinear absorption coefficient, βeff (∼10−7–10−8 cm/W) marked up to the highest reported ones in literature in the nanosecond regime. The results indicate that these nanocomposite films are potential materials for optical limiting devices used for the protection of human eyes and other delicate optical sensors from laser induced optical damage.

The effect of temperature and silicon content on the switching characteristics of the chalcogenide As40Te60−xSix(2≤x≤17) glass system is investigated. Switching voltages is found to decrease linearly with an increase in temperature. The compositional dependence of switching voltage is found to exhibits a minimum at x = 13 (〈r〉 = 2.66) corresponding to chemical threshold. The variation of the composition with activation energy for switching also exhibits the same effect.

This paper reports the design of a new type of Mach‐Zehnder Interferometer (MZI) by using two concatenated fourth order Gaussian Apodized‐linear chirped long period gratings (LPGs) which have a flat‐band of 22.6 nm with top flatness around 0.5 dB and Full Width Half Maxima (FWHM) of 52 nm in the transmission spectrum. The designed MZI finds applications in Wavelength Division Multiplexing (WDM) channel isolation filter. The parameters of LPG have been optimized by using advanced OptiGrating 4.2 software. Also it is compared with two other designed MZIs configurations.

Transparent conducting aluminum doped zinc oxide (AZO) films were deposited on glass substrates by radio (RF) frequency magnetron sputtering employing zinc oxide and aluminum targets. The targets are fixed coaxially in one cathode, by using a center hollow aluminum disc. Gas pressure was kept constant and the sputter power was varied. The nature of AZO film was found to be polycrystalline with hexagonal structure and a preferred orientation along c‐axis. The Al content in the films is determined using EDXA analysis and it is found to vary with the applied power. Surface morphology of the films was found to be uniform and has fine grained structure. Electrical resistivity of the deposited films was found to be as low as 26×10−4 Ω‐cm for the film deposited at 250 W. The average transparencies up to 85% in the visible region were obtained for all the films. Optical band gap of the films show a slight blue shift as indicated by the (αhν)2 v/s hν plots. In the present investigation we have controlled Al conten...

The nonlinear optical (NLO) properties of covalently linked Graphene‐(Sn, OH) porphyrin composite materials were investigated using Z‐scan technique at 532 nm with picosecond laser pulses. We have observed enhanced figure of merit values for composites in comparison with individual graphene, copper and zinc porphyrin. The enhanced figure of merit values for graphene‐porphyrin composite material should be attributed to two‐photon absorption and excited state absorption. We also observed different behavior, reverse saturable absorption to saturable absorption and back to reverse saturable absorption in composite molecules leading to better ultrafast nonlinear optical switching applications.

YAG:Ce is an important phosphor having applications in various fields ranging from solid state lighting to scintillation detectors. YAG phosphors doped with activators are mainly synthesized by solid state reaction techniques that require high sintering temperatures (above 1500°C) to eliminate YAM and YAP phases. Though several soft chemical routes have been explored for synthesis of YAG, most of these methods are complex and phase pure materials are not obtained in one step, but prolonged annealing at temperatures around 1000 C or above becomes necessary. One step combustion synthesis of YAG:Ce3+ and related phosphors carried out at 500 C furnace temperature is reported here. Activation with Ce3+ could be achieved during the synthesis without taking recourse to any post‐combustion thermal treatment. LEDs prepared from the combustion synthesized YAG:Ce3+, exhibited properties comparable to those produced from the commercial phosphor.

In the present work, compact and an all‐fiber modal interferometer has been fabricated using SMF‐PMPCF‐SMF structure. By introducing the fine core‐offset between SMF and PMPCF at lead in splice, cladding modes of the PMPCF has been excited leading to interference between core and cladding modes of PMPCF at the lead out splice between PMPCF and SMF. Temperature and strain response of the interferometer has been studied where we found significant temperature sensitivity with very low strain sensitivity.

This study reveals the preparation of conical pores in polyethylene terephthalate (PET) by track etching. The polymer membrane is etched from one side by keeping between the clamps of conductivity cell followed by irradiation with swift heavy ion of 197Au. Electrical stopping supports chemical stopping. During etching process current is measured as a function of time till a sharp increase ‐breakthrough‐observed. After etching membranes are thoroughly washed with stopping solution and water. Resultant films are characterized using Optical microscope and field emission scanning electron microscopy. Polymer films with uniform pores can be a cheaper templating material in the fields of photonic crystals and micro‐ electronics.

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.

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...

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.

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 ...

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.

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.

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.