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Sepsis can lead to cardiac arrhythmias, of which the most common is atrial fibrillation (AF). Sepsis is associated with up to a six-fold higher risk of developing AF, where it occurs most commonly in the first 3 days of hospital admission. In many patients, AF detected during sepsis is the first documented episode of AF, either as an unmasking of sub-clinical AF or as a newly developed arrhythmia. In the short term, sepsis that is complicated by AF leads to longer hospital stays and an increased risk of inpatient mortality. Sepsis-driven AF can also increase an individual's risk of inpatient stroke by nearly 3-fold, compared to sepsis patients without AF. In the long-term, it is estimated that up to 50% of patients have recurrent episodes of AF within 1-year of their episode of sepsis. The common perception that once the precipitating illness is treated or sinus rhythm is restored the risk of stroke is removed is incorrect. For clinicians, there is a paucity of evidence on how to reduce an individual's risk of stroke after developing AF during sepsis, including whether to start anticoagulation. This is pertinent when considering that more patients are surviving episodes of sepsis and are left with post-sepsis sequalae such as AF. This review provides a summary on the literature available surrounding sepsis-driven AF, focusing on AF recurrence and ischaemic stroke risk. Using this, pragmatic advice to clinicians on how to better detect and reduce an individual's stroke risk after developing AF during sepsis is discussed. more...

Introduction The Covid-19 pandemic has put a considerable strain on procedural waiting lists, with the majority of elective outpatient work cancelled during the pandemic. With the vaccination programme and reducing infection levels, attention is turning to addressing these waiting lists. One procedure that was affected was the removal of implantable loop recorders (ILRs). Manufacturers recommend that ILRs are removed at the point of battery depletion (usually 3-4 years), if they have not already been removed due to a positive finding or patient preference. There is little evidence in the literature regarding late complications with ILRs, and we therefore wished to examine what patients’ thoughts would be about keeping the ILR in for a longer period of time. Methods Patients awaiting ILR explantation and those who had undergone explantation, were identified. A retrospective review of the notes was used to get demographic and clinical data. Both groups of patients were contacted, and a questionnaire used to gain an understanding of patients’ experience and expectations. Results Prior to the Covid-19 pandemic, 60 patients who had undergone ILR explantation were identified. A total of 22 responded to our questionnaire (table 1). The majority (86%) were happy to have their ILR removed, although a smaller majority (59%) would also have been happy to have had the device kept in, were it felt to be safe. Very few patients felt a tangible difference as a result of having the ILR removed (14%) and no patients were worried about the waiting time prior to Covid-19. Of 77 patients currently awaiting explant, 30 responded to our questionnaire (table 1), with 70% not being concerned by the wait for removal. This is likely aided by the fact that 80% of patients had no day to day symptoms as a result of the ILR. Half of the patients however, would be concerned about not having the ILR removed, predominantly due to mild discomfort or concerns regarding the presence of a battery. Across both groups (n=52) only 8 patients were concerned about the risk of coming into the hospital for the procedure, with patients commenting that the stringent regulations that hospitals had employed combined with the vaccination programme, gave them significant confidence in attending for outpatient procedures. Conclusions This study found that if patients are reassured about the safety of keeping an implantable loop recorder in, and do not suffer any discomfort or symptoms as a result of the device, they are happy both to wait longer for device removal, or even not have it removed at all. In the context of the current pandemic, more thought should perhaps be given to patient guided removal times, especially in cases of removals performed for battery depletion. Conflict of Interest Nil more...

Novel photovoltaic cells involving a nonconjugated conductive polymer have been fabricated using titanium dioxide/doped styrene-butadiene-rubber/carbon on ITO coated PET substrates. Photocurrents and photo-voltages for different intensities of light (emission at 300–700 nm) have been measured. These cells have shown significantly higher photocurrents and photo-voltages compared to previous reports. A photocurrent density of about 0.25 mA/cm2 and a photo-voltage of 0.74 V have been measured for a light intensity of ∼4 mW/cm2. more...

Differential scanning calorimetry (DSC) has been used to measure the thermal properties of the nonconjugated conductive polymer, poly(s-pinene) before and after doping with iodine. The measurements have been made over the temperature range of −50°C to 110°C. The glass transition temperature of undoped poly(s-pinene) has been determined to be about 77°C. The specific heat increased by about 16% upon doping, from about 2.03 J/g-°C in the undoped state to about 2.35 J/g-°C in the doped state. The observed increase in specific heat capacity upon doping, along with the reported electrical, linear optical and exceptionally large nonlinear optical characteristics in the doped state, have been attributed to the nanometallic-like structures formed in this polymer upon doping. more...

Novel photovoltaic cells involving a nonconjugated conductive polymer have been fabricated using titanium dioxide/doped poly(β-pinene)/carbon on ITO glass-substrates. Photocurrents and photo-voltages for different intensities of light (emission at 300-700 nm) have been measured. Use of iodine-doped nonconjugated conductive polymer (poly(β-pinene)) film has led to significant enhancement of photocurrent compared to previous reports involving undoped polymer in a different device-structure. A photocurrent density of about 0.03 mA/cm2 and a photo-voltage of 0.65 V have been measured for a light intensity of ∼5 mW/cm2. These cells being the first generation of its kind the results are promising for applications. more...

The quadratic electro-optic effect in the nonconjugated conductive polymer iodine-doped poly( β -pinene), measured at longer wavelengths including 1.55 μm, is reported. The field-induced birefringence technique was used. A modulation depth of 0.1% was observed in a 1 μm thick sample for an applied field of 1 V/μm at 1.55 μm. The corresponding Kerr coefficient obtained is 1.6×10 −10 m/V 2 . The Kerr coefficients measured at 790–810 nm are also very large. This exceptionally large (largest known) optical nonlinearity has been attributed to the subnanometer size metallic quantum dots formed in this polymer upon doping with iodine and the optimized film quality recently achieved. more...

Organic single-crystal films involving a combination of a molecular salt (DAST) and a laser dye (IR-125) have been grown on quartz substrates using the modified shear method. Polarized optical microscopy, polarization-dependent optical absorption, x-ray diffraction and electro-optic effect have been measured to characterize the film. The dipole axis of DAST is oriented close to parallel to the substrate. The IR-125 molecule appears to be oriented close to perpendicular to the dipole axis of DAST. The optical gap of the film is about 1.4 eV. The electro-optic coefficient ( r 11 ) as measured by the field-induced birefringence is ∼300 pm/V at 633 nm. Such films are promising for various photonic applications. more...

Recently, new additions to nonconjugated conductive polymers have been made that include: poly(β-pinene), poly(ethylenepyrrolediyl) derivative and polynorbornene. These polymers have different double-bond number fractions per repeat compared to previously reported nonconjugated conductive polymers. Upon doping with electron acceptor (e.g. iodine) the conductivities increase more than ten orders of magnitude to levels consistent with their double-bond number fractions. Radical cations that are formed upon doping have dimensions less than a nanometer leading to unexpectedly large nonlinear optical effects. The measured Kerr coefficient of doped polyisoprene is ∼1.6 × 10-10 m/V2 at 633 nm. For doped poly(β-pinene) the Kerr coefficient is ∼1.2 × 10-10 m/V2 and for poly(ethylenepyrrolediyl) derivative it is ∼1.2 × 10-9m/V2. Exceptionally large two-photon absorption coefficient (∼2.6 cm/MW at 810 nm) has been measured for doped poly(β-pinene). The mechanism of the nonlinear optical effect has been explained usi... more...

We report electrical and optical properties of a novel nonconjugated conductive polymer, polynorbornene which has an isolated double bond in the repeat. Electrical conductivity of this polymer increases by twelve orders of magnitude to about 0.01 S/cm upon doping with iodine. Optical absorption measurements of the polymer film have been made at different dopant concentrations. For a lightly doped polymer, two absorption peaks: one corresponding to cation radicals and the other corresponding to charge transfer between the double bond and the dopant were observed at 4.20 eV (295 nm) and 3.13 eV (396 nm) respectively. FTIR spectroscopic measurements have shown reduction in the intensities of the C═C stretching and ═C─H bending vibration bands upon doping indicating formation of radical cations. Photoluminescence studies have shown an emission band with a major peak at ∼422 nm when excited at 280 nm. The peaks in the photoluminescence spectrum are consistent with the vibration bands observed in the FTIR spectrum. more...

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. more...

Electrical conductivity in a novel nonconjugated conductive polymer, poly(β-pinene), has been measured as a function of molar concentration of iodine. The conductivity increases about 10 orders of magnitude to a maximum value ˜8 × 10−3 S/cm. The molar concentration of iodine, corresponding to saturation, is ˜0.85. The optical absorption measurements after light doping have shown two peaks: one at 4.0 eV and the other at 3.1 eV. The first peak is due to the radical cation, and the second due to the charge-transfer between the double bond and the dopant. As observed in other nonconjugated conductive polymers, the second peak becomes broader and undergoes a red shift, upon higher doping. The FTIR spectroscopic studies have shown that the CC stretching vibration at 1610 cm−1 and the CH bending vibration band at 728 cm−1 decrease upon doping, because of decrease of double bonds. Photoluminescence studies of poly(β-pinene) show a maximum value at 360 nm for excitation at 280 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3695–3698, 2005 more...

Thin films of 1,4-trans-polyisoprene have been prepared on various substrates from toluene solution and characterized using Fourier transform infrared (FTIR) spectroscopy, optical absorption spectroscopy and X-ray diffraction before and after doping with iodine. The optical absorption spectrum at low doping shows two peaks: one at 4.2 eV and the other at 3.2 eV. X-ray diffraction indicates an increase of (111) and (122) peak intensities upon doping. Quadratic electro-optic measurements have been made using field-induced birefringence. The Kerr coefficients as measured (3.5×10−10 m/V 2 at 633 nm and 2.5×10−10 m/V 2 at 1.55 μm) are exceptionally large, and they have been attributed to the subnanometer-size metallic domains formed upon doping and charge transfer. more...

Conjugation is not a prerequisite for a polymer to be conductive. A polymer must have at least one double bond in the repeat to become conductive. Interaction with a dopant (e.g., electron acceptor) causes transfer of an electron from the double bond to the dopant creating a hole at the double bond site. Electrical conduction occurs via intersite hopping of holes. Various spectroscopic methods (FTIR, optical absorption, solid-state 13C NMR, etc.) along with electrical measurements have been used to elucidate the mechanism of conduction in specific nonconjugated conductive polymers. Examples of these polymers include 1,4-polyisoprene which has one double bond and three single bonds in the repeat. The conductivity of polyisoprene increases 100 billion times upon doping with iodine to a maximum value of 10 S/m. Polyisoprene (natural rubber) is used nonconjugated conductive polymers have a wide range of applications in antistatics, various sensors and optoelectronics. more...

Single-crystal thin films of 4-aminobenzophenone have been prepared by a modification of the shear method, and the significant elements of the second-order optical polarizability tensor have been measured by the transverse second-harmonic generation (SHG) technique. Films with thickness less than the coherence length allowed measurements without significant effects due to phase-mismatch. Detailed SHG experiments with different polarization conditions were performed to determine the d coefficients. The magnitudes of the d coefficients at the fundamental wavelength of 1064 nm were found to be d23=7.3±0.4 pm/V and d22=0.73±0.04 pm/V. Directions for both type-I and type-II phase-matched propagation parallel to the film were identified. The results showed that guided-wave phase-matched SHG (type I and type II) should be possible using the films. more...

A correlation between the line-width in super-resolved fluorescence microscopy and nonlinear optical theory used for polydiacetylene crystal-film is discussed.

Photoluminescence of two thienylpyrrole polymers, one containing three thiophene and one pyrrole rings in the repeat, and the other having four thiophene and one pyrrole rings in the repeat, were studied. The photoluminescence peaks were observed to shift with the change of the excitation frequencies. The shift in the peak position had a nearly linear dependence on the shift in the excitation frequency. This result showed that using different excitation frequencies optical gaps corresponding to different conjugation lengths were accessed, and, thus, the corresponding photoluminescence peaks were observed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 461–464, 1999 more...

We report the results of optical absorption, quadratic electro-optic and electroabsorption measurements in a novel nano-optical material based on the nonconjugated conductive polymer, poly(ethylenepyrrolediyl) derivative. Two peaks at about 310 and 420 nm have been observed in the optical absorption spectrum of the polymer at a low doping level of iodine. The Kerr constant as determined at 633 nm, which is close to resonance, is about 1.2×10−9 m/V 2 which is about 495 times that of nitrobenzene. This exceptionally large Kerr coefficient has been attributed to the special structure and quantum confinement of this electronic system within a subnanometer domain. more...

In this letter, we report results of electroabsorption and resonant electro-optic measurements in single-crystal film of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST). The electroabsorption measurement was made by recording the changes in transmission through the film as an ac field was applied along the dipole axis. The electro-optic measurement was made using the field-induced birefringence method. The measurements were made in the absorptive domain, at 633 and 488nm. The modulation (ΔT∕T) due to electroabsorption decreased as the angle between the incident polarization and the dipole axis was increased. The observed electroabsorption is due to the imaginary part of the electro-optic coefficient. The real part of the electro-optic coefficient (r11) as measured at 633nm is 770pm∕V. The imaginary parts of the electro-optic coefficients at 633 and 488nm are 104 and 259pm∕V, respectively. more...

We have made off-resonant nonlinear optical measurements of PTS polydiacetylene in a Fabry-Perot cavity. The measurement was made by a pump-probe technique using 90 ps pulses at 1.06 μm wavelength. The change in transmission at specific bias points on the F-P fringe, was measured as a function of time delay between the pump and probe. Large (-50%) changes in transmission with a pulse-with-limted response time, were observed at low optical intensities. The magnitude of n2 as measured (-10−5 cm2/MW) and the negative sign are consistent with our Z-scan measurement of PTS at this wavelength. The results of the measurement on the F-P cavity clearly demonstrate possibilities of applications of PTS in ultrafast (sub-picosecond) all-optical switching and logic operations using this device geometry. This is the first time that all-optical switching with time resolution has been demonstrated for an organic material. more...

Lead Selenide multilayer thin films were prepared by thermal evaporation technique by successive coatings of Lead and Selenium metals. The temperature of the substrates varied from low to high during the deposition. The optical characterization of the prepared films carried out using UV‐Vis‐NIR spectroscopy and Photoluminescence spectroscopy. The absorption edge towards shorter wavelength (300 nm) may be the quantum size effect at the interfaces of Lead and selenium layers. The films on low substrate temperature have the many linear regions in the optical band gap graph. The calculated band gap is larger than the bulk band gap value of the PbSe material. The room temperature Photoluminescence spectrum was studied under the excitation wavelength of 300 nm. The hot luminescence tail was observed at low temperature substrate. The Effective mass approximation and quantum mechanical models were used to study the quantum size effect of the prepared films and discussed in this paper. more...

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. more...

At suitable conditions, sub‐micron sized colloidal particles self assemble into crystalline arrays (known as colloidal crystals) with lattice constants in the visible range. These crystals exhibit Bragg diffraction of visible light, as certain frequencies cannot propagate through, hence can serve as photonic crystals. Highly diffracting photonic crystals (PCs) can be prepared through colloidal route by self‐assembly of monodisperse particles. However size polydispersity (SPD) is inherent to all colloidal suspensions: hard‐sphere, charge stabilized and stimuli responsive microgels. Disorder introduced by temperature and SPD have important implications on optical properties of these crystals. First and second‐type disorder in these crystals are known to arise from thermal motion and SPD, respectively. In the case of photonic crystals prepared through hard‐sphere or charge stabilized suspensions, the SPD should be less than 11% and is not tunable. Thermo‐responsive microgels particles in aqueous medium are k... more...

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. more...

Thin films of Zn0.95Mn0.05O (ZMO) and Al or Bi (1 weight %) incorporated ZMO thin films (viz. Al: Zn0.95Mn0.05O (AZMO) and Bi: Zn0.95Mn0.05O (BZMO)) were grown on Al2O3 substrate by pulsed laser deposition (PLD). X‐ray diffraction studies indicate that all the deposited thin films were highly c‐axis oriented and showed single phase formation with wurtzite structure. Incorporation of 1 wt. % Al leads to reduction of the extensive strain (in AZMO) when compared to the ZMO thin film. However in case of BZMO, compressive strain is observed. Raman studies indicate that the wurtzite structure of the host material is preserved albeit incorporation of 1 wt. % highly mismatched Al or Bi ions. The optical transmission spectra (in the range 350 to 700 nm) of the AZMO and BZMO thin films show significant changes compared to ZMO thin film. The otherwise spin forbidden d‐d transitions of Mn2+ in the tetrahedral symmetry give rise to a strong absorption in the visible region for the ZMO thin film. This absorption band, ... more...

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... more...

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. more...

Atmospheric effects can deteriorate the intensity of the received signal and increases the bit error rate (BER). However, the use of error correcting codes in FSO system can mitigate the effect of turbulence and helps in improving the system performance. In this paper, performance of FSO link without and with coding is investigated for coherent (sub‐carrier BPSK and QPSK) and non‐coherent (OOK) modulation schemes. It has been observed that LPDC codes offer considerable performance advantage over convolution codes in terms of coding gain for varying strength of turbulence in the atmosphere. For example, convolution code with viterbi decoding yields coding gain of about 1 dB while LDPC codes shows the improvement of about 4.5 dB at a turbulence level of 0.2 and BER = 10−4 for different modulation schemes. more...

The Compton scattering measurement on intermetallic alloy Ti3Al is reported in this work. The measurement is made using 59.54 keV gamma‐rays from Am241 source. Theoretical calculation of Compton profile is also performed employing CRYSTAL code within the framework of density functional theory to compare with the measurement. The theoretical profile of the alloy is also synthesized following the superposition model taking the published Compton profiles of elemental solids from the APW method. The experimental study of charge transfer in the alloys has also been done by performing the experimental Compton profile measurements on Ti and Al following the superposition model and charge transfer from Al to Ti is clearly seen on the alloy formation. more...

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. more...

Transparent ZnO/PMMA (Poly methyl methacrylate) nanocomposites with high‐UV shielding efficiency were reported in this paper. The zinc oxide (ZnO) nanoparticles were synthesized chemically via the homogeneous precipitation method using different concentration of capping agent (2‐Mercaptoethanol). The structural properties of the as‐prepared ZnO nanoparticles were characterized by X‐ray diffractometer (XRD) and transmission electron microscopy (TEM) measurements. The transparent ZnO/PMMA nanocomposites were subsequently prepared by dispersing as‐prepared ZnO nanoparticles in PMMA via solution mixing and then solution casting method. The optical properties of ZnO/PMMA nanocomposites, namely visible light transparency and UV light shielding efficiency, were studied using an ultraviolet–visible (UV–Vis) spectrophotometer. The optical properties of the as‐obtained nanocomposites were shown to depend on ZnO particle size. The nanocomposite containing small sizes ZnO nanoparticles with an average particle size of (∼10 nm) possessed the most optimal optical properties, namely high‐visible light transparency and high‐UV light shielding efficiency, which are desirable for many important applications. more...

Phthalocyanines and their derivatives have been extensively studied as organic semiconductors since the first report of organic field effect transistors (OFETs) in 1986. An extended conjugated π system, unique optical and electrical properties along with high thermal stability render them ideal organic semiconductor materials as active layer for OFTs. In this study, Silicon Phthalocyanine dichloride thin films are prepared on glass substrates kept at different temperatures by vacuum deposition method. Using spectrometric techniques, the optical constants of the prepared thin films are measured, From the UV‐Visible absorption studies it is found that the transitions in these materials are direct band‐ band type. The temperature dependent conductivity studies on the prepared thin films yield activation energy and its variation with respect to the deposition temperature is also studied in this work. more...

Copper 2, 9, 16, 23‐tetra‐tert‐butyl‐29H, 31H‐phthalocyanine (CuTTBPc) thin films have been prepared by vacuum sublimation technique. The films were annealed at 50 to 250°c for 1 hr. The optical, electrical and morphological properties have been investigated as a function of different annealing temperature. The optical measurements have been carried out in the ultraviolet and visible region. The analysis of the spectral behaviour of the absorption coefficient in the absorption region near fundamental edge reveals direct transitions. The energy band gap is investigated. The d.c electrical conductivity is carried out as a function of temperature to investigate the electronic structure of CuTTBPc thin films and to understand the conduction mechanism. The morphology of the films are studied using Scanning Electron Microscopy (SEM). more...

Since last two decades free‐space optical communication (FSO) has become more and more interesting as an alternative to radio frequency communication. This paper gives an overview of the power budget of an FSO system, designer has to consider while designing an FSO link. In this paper we have calculated the power needed for the transmission of a signal in free space. The received power and distance graph shows that more power needed when the link distances increases; also power and Bit Rate graph obtained at a distance 500 meter. In order to evaluate the power vs. Bit Rate graph we consider a link of distance 500 meter, optical window 1550 nm and three different atmospheric condition 10 dB/Km, 40 dB/Km and 60 dB/Km. The VCSEL laser is used for direct line of sight communication and at the receiver side the APD is used for power reception. The NRZ–OOK modulation format is used for laser beam modulation. more...

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. more...

CuO nanoparticles were successfully prepared by a chemical method which has been widely studied as photothermal and photo conductive materials. The samples were characterized by X‐ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV‐Visible spectroscopy and Photoluminescence Spectroscopy. The SEM image showed that the prepared product consists of spherical nanoparticles with narrow size distribution. The average crystallite size of CuO nanoparticles calculated from XRD pattern was 8 nm. The UV‐Visible absorption spectrum of CuO nanoparticles shows a strong blue shift compared to that of bulk. The band gap energy was calculated from the absorption spectra. Due to the high surface to volume ratio, CuO nanoparticles have high density of surface defects, interstitials and oxygen vacancies. Photo luminescence spectroscopy has been employed in order to explore the optical emission properties of CuO nanoparticles. The emission at 535 nm corresponds to the band edge emission and that at 600 nm is due to the oxygen vacancy. In addition to these two peaks there shows an additional peak at 657 nm which indicates the oxidation state of Cu. more...

We study the effect of carrier envelope offset (CEO) phase of a few cycle pulse on the dynamics of two‐level systems in the domain of extreme nonlinear optics. Strong dependence of polarization on the CEO phase is observed. Intensity of different high harmonics and their interference is clearly seen to be dependent on the CEO phase of the optical pulses. Our results show that the final state of the atomic system, just after the few cycle optical pulse has passed through the system, depends very strongly on the CEO phase of the pulse. more...

Single crystals of Calcium Barium tartrate (CBT) were grown by controlled diffusion in silica gel at ambient temperature. The structural characterization of the grown crystals was carried out by Powder X‐ray diffraction analysis. The functional groups present in the crystals were identified using Fourier Transform Infrared spectral analysis. The UV‐Vis‐NIR transmission spectrum was recorded to study the optical transparency of the grown crystals. more...

We report the experimental demonstration of tunable stop gap in the visible wavelength region by changing the angle of incidence of light. The width and peak reflectance of the stop gap do not change till an angle of incidence of 45°. For angle of incidence greater than 45°, new diffraction resonances appear in the reflectance spectra. At 55° incidence, the stop band split into to two peaks with equal reflected intensity. This multiple Bragg diffraction is in good agreement with the theoretical calculations. more...

Nanoscale oxides of transition metals, particularly manganese, are desirable for many applications in designing electric, magnetic and heterogeneous catalytic materials. Manganese oxides exist in different phases, viz. MnO, MnO2, Mn2O3, Mn2O7 and Mn3O4. Using different synthetic routes it is possible to synthesize different phases of manganese oxides. Moreover, composites of these oxides with polymer have the potential to address the needs of emerging dielectric technologies. In the present work, using manganese chloride and hydrazine hydrate, Mn3O4 and Mn2O3 nanoparticles were successfully synthesized by conventional and hydrothermal method respectively. The variation in the formation of the different phases has been discussed. The nanoparticles were well characterized by X‐ray Diffraction and using the Debye Scherrer formula, the average size of Mn3O4 and Mn2O3 nanoparticles were calculated to be 35 nm and 25 nm respectively. Using solution casting method, nanocomposites of chitosan/Mn3O4 were prepared ... more...

Effect of added brine on the structural transitions of SDS, in different compositions of gelatin has been investigated by viscosity, circular dichroism, TGA and DSC. The slow and steady growth of the normal spherical micelles to the higher order aggregates were predicted by viscosity and conductivity measurements. The large negative value for ellipticity observed from CD measurements indicated absence of any conformational change for gelatin. Other measurements were used to study the molecular packing in the micellar aggregates. The complex formed exhibits fantastic properties to be explored in the field of smart gels. more...

Multilayer structure of Tin Selenide thin films were prepared by thermal evaporation technique by successive coatings of Tin and Selenium metal powders. The number of layers varied from 3 to 11 during deposition on the glass substrate with 423 K temperature. The optical properties of the multilayer films studied using UV‐Vis spectrophotometer. The absorption edge towards blue region shows the nanocrystalline effect of the films. The optical band gap values lies in the ranges of 2.6‐3.2 eV. The structural studies reveals that the prepared films oriented at (0 0 1) plane with hexagonal structure. The crystalline size varies from 11‐22 nm on the different multilayer films and discussed in this paper. more...

In this communication we describe the design and synthesis of a new conjugated polymer (P) carrying 3,4‐dialkoxythiophene, 1,3,4 oxadiazole and pyrazole units, from its monomers through condensation polymerization method. The structure of newly synthesized polymer was established by FT‐IR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. Further, its electrochemical, linear and nonlinear optical properties of the polymer have been investigated. The optical and electrochemical band gap was found to be 2.39 eV. Z‐scan results reveal that the polymer exhibits strong optical limiting behavior due to effective three‐photon absorption (3PA). The value of 3PA coefficient was found to be 1.1×10−20 m3/W2, which is comparable to that of good optical limiting materials. The fluorescence quantum yield of the polymer in solution was determined using quinine sulfate as standard and it was found to be 42%. more...

All‐Optical network is still in adolescence to cope up with steep rise in data traffic at the backbone network. Routing of packets in optical network depends on the processing speed of the All‐Optical routers, thus there is a need to enhance optical processing to curb the delay in packet forwarding unit. In the proposed scheme, the header processing takes place on fly, therefore processing delay is at its lower limit. The objective is to propose a framework which establishes high data rate transmission with least latency in data routing from source to destination. The Routing table and optical header pulses are converted into Pulse Position (PP) format, thus reducing the complexity and in turn the processing delay. Optical pulse matching is exercised which results in multi‐output transmission. This results in ultra‐high speed packet forwarding unit. In addition, this proposed scheme includes dispersion compensation unit, which makes the data reliable. more...

Thin films of TiO2 have been deposited on well cleaned glass substrates by Sol‐Gel dip‐drive coating technique. The films have been prepared at three different pH values (3, 5, and 9) of Sol and annealed in muffle furnace at three distinct temperatures (350 °C, 450 °C, and 550 °C) for one hour and are allowed to cool to room temperature. The films were characterized by XRD, EDAX, SEM and UV‐Vis Spectrophotometer. The as deposited films were found to be amorphous in nature. The annealed films exhibit anatase in crystalline structure. The EDAX results have shown that all the films are maintained with TiO2 in composition. The XRD results reveal that they are nano‐crystalline in nature and the crystalline nature increases with annealing temperature and pH of the Sol. The transmittance and absorbance spectra have shown that the films are transparent and band gap of the films are of the order of 3 eV. The ab initio studies of TiO2 (using GGA) was performed with Vienna ab initio Simulation package and the band s... more...