ASIAN JOURNAL OF PHYSICS

 

Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 145-152

 

Optimization of Efficiency in a 1D Grating Structure at 1310nm Wavelength for Application in Optical Interconnect

 

G Palai¹, *S K Tripathy², N Muduli³, S K Patnaik²

¹Gandhi Institute for Technological Advancement, Bhubaneswar

²National Institute of Science and Technology, Berharmpur

³Gandhi Engineering College, Bhubaneswar

²National Institute of Science and Technology, Berharmpur

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This paper optimizes the diffraction efficiency of 1D silicon-a silicon grating structure at wavelength 1310 nm. Optimization is made with respect to absorption and transmission losses using plane wave expansion (PWE) method. The simulation results showed the efficiency of 1D grating structure is more than 99% for 1 µm-1 µm, 1 µm-4 µm, 4 µm-1 µm and 10 µm-1 µm thickness of silicon-a silicon layer at 1310 nm. 

Keywords: 1 D grating, PWE, Reflectance, SOI

Total Ref : 12

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 153-158

Fluctuations induced conductivity in YBYBa₂Cu₃O_7-d  + x CoFe₂O₄ composites

M Sahoo^a, B Bhol^a, D Behera^a,*

^aDepartment of physics, National institute of technology, Rourkela-769008, India

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Fluctuations on the electrical conductivity of polycrystalline YBa₂Cu₃O_7-d  + x CoFe₂O₄(x = 0.0, 0.1, 0.2, and 0.3 wt.%) superconductors were investigated from the resistivity vs. temperature(R-T) data. Attempts have been made to identify the optimum inclusion of ferromagnetic CoFe2O4 particles in YBa₂Cu₃O_7-d δ (YBCO) superconductor. With the increase of CoFe₂O₄ addition, it is found that the superconducting transition temperatures (Tc) determined from standard four-probe method and magnetization vs. temperature (M-T) studies, were decreased and dropped sharply with higher wt.% addition of CoFe₂O₄. M-T graphs shows that the composites satisfy Meissner effect. Excess conductivity fluctuation analysis using Aslamazov-Larkin (AL) model fitting reveals transition of two dominant regions (2D and 3D) above Tc. The decrease in 2D-3D crossover temperature (TLD) (Lawerence-Doniach temperature) in the mean field region has been observed as a consequent dominance of 3D region with increase in wt.% of CoFe₂O₄ in the composite.

Total Ref : 18

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 159-164

Dynamic study of phonon excitation spectrum in some heavy fermion systems

 

J Sahoo^1*, N Shadangi² and P Nayak³

¹Regional office of vocational Education, Sambalpur

²Padmashree Krutartha Acharya College of Engineering, Bargarh

³School of Physics, Jyoti Vihar, Sambalpur

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The phonon excitation spectrum of some Heavy Fermion (HF) systems in the presence of electron-phonon interaction is studied in the dynamic limit (ω¹i H*0). The renormalized excitation phonon frequencies (ώ=ω/ω0) are evaluated through Periodic Anderson Model (PAM) in presence of electron –Phonon interaction using Zubarev type double time temperature dependent Green function .The calculated renormalized phonon energy is analyzed through the plots of (ώ=ω/ω0) against temperature for different system parameters like effective coupling strength ‘g’, the position of f-level‘d’ and the onsite coulomb interaction ‘U’. The observed behaviour is analyzed and found to agree with the general features of HF systems found in experiments

Total Ref : 18    

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 165-170

Dielectric anomaly in Na₂Pb₂Dy₂W₂Ti₄Nb₄O₃₀ ceramic

 

L Biswal^1,3, Piyush R Das^2,*, and Banarji Behera³

¹Department of Physics, SOT, KIIT University, Bhubaneswar - 751 024, Odisha, India

²Department of Physics, ITER, S. O. A. University, Odisha, Bhubaneswar - 751 030, India

³School of Physics, Sambalpur University, Jyoti Vihar, Burla-768 019, Odisha, India

 

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A new polycrystalline ceramic Na₂Pb₂Dy₂W₂Ti₄Nb₄O₃₀ was prepared by high temperature solid state reaction technique. Preliminary X-ray diffraction (XRD) study showed the formation of single-phase compound in an orthorhombic structure. Surface morphology of the compound was studied by scanning electron microscopy (SEM). The frequency and temperature dependence of dielectric properties (er and tand) of the compound was investigated in the frequency range of 102 to 106 Hz and temperature range 300K to 800 K. The ceramic compound showed non-relaxor type diffused dielectric anomaly at 577K. Ferroelectric property of the compound was confirmed with polarization (hysteresis) study. Using modified Curie-Weiss law around transition temperature, the order and type of transition has been suggested.

Keywords: Ceramics; Sintering; Dielectric Properties; Hysteresis

Total Ref : 24

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 171-174

Analysis of grains grown on pond-ash treated soils

 

K C Patra^a,b, N R Mahapatra^c,d, P  Nayak^a, and Tapash R. Rautray^d,e*

^aDepartment. of Physics, Sambalpur University, Jyoti Vihar, Sambalpur - 768 019, Odisha, India

^bInstitute of Physics, Sachivalaya Marg, Bhubaneswar - 751005, Odisha, India

^cDepartment of Physics, Silicon Institute of Technology, Patia, Bhubaneswar, Odisha, India

^dCentre of Excellence in Theoretical and Math Sciences, SOA University, Bhubaneswar - 751030, Odisha, India

^eCentre for Functional Biomaterials and Tissue Engineering, Saheed Nagar, Bhubaneswar - 751007, Odisha, India

____________________________________________________________________________________________________________________________________ Elements namely Mn, Fe, Cu, Zn, Mo and Pb were determined in the current study by using Energy dispersive X-ray fluorescence (EDXRF) technique. The increase in yield of the rice grains using pond ash was 16% and 22% produced at Malud and Dhenkanal (in Orissa, India) respectively as compared to their control values. The concentration of trace elements in rice grains was well below the critical levels in the plants for human consumption.

Total Ref : 17

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 175-178

Competence of 4H-SiC IMPATT diode for terahertz application

J Pradhan¹, S K  Swain¹, G N Dash¹ and S R Pattanaik²

¹School of Physics, Sambalpur University, Jyoti Vihar, Sambalpur-768 019, Odisha, India

²Apex Institute of Technology and Management, Bhubaneswar -752 101, Odisha, India 

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The competence of 4H-SiC material for being used as a base material for possible terahertz application was examined following our computer simulation method. The computed power density value of 8.3 × 1011 W/m2 with a DC-to-RF conversion efficiency of 11% at the operating frequency of 1.0 THz are note worthy. A significant negative conductance value of 9.7×108 Sm–2 and a noise measure of 56dB are also computed at the frequency of 1.0 THz using a small signal model for sub-mm-wave or terahertz applications. The results speak about the potential of SiC material for terahertz application.

Keywords: Terahertz, IMPATT, 4H-SiC

Total Ref : 20

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 179-186

Synthesis and characterization of Na₂Pb₂Y₂W₂Ti₄Ta₄O₃₀ ferroelectric ceramic

 

S Behera¹, Piyush R Das^2*, P Nayak³ and R N P Choudhary²

²Department of Physics, Hi-tech College Engineering, Bhubaneswar- 751 025, India

²Department of Physics, Institute of Technical Education & Research, Siksha OAnusandhan
University, Bhubaneswar-751015, Odisha, India 

³School of Physics, Sambalpur University, Jyoti Vihar, Burla – 768019 

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In the present work, sample of composition Na₂Pb₂Y₂W₂Ti₄Ta₄O₃₀ (NYT) was prepared by a high-temperature solid-state reaction technique. X-ray diffraction (XRD) analysis reveals the formation of single-phase compound with an orthorhombic structure at room temperature. Surface morphology of the compound was studied by scanning electron microscope (SEM). Temperature dependence of dielectric constant indicates the presence of two dielectric anomalies at 408K and 586K, which may be attributed to the ferroelastic-ferroelectric and ferroelectric-paraelectric transitions respectively as suggested by hysteresis loop at room temperature. Complex impedance spectroscopy analysis has been carried out as a function of frequency at different temperatures to establish the correlation between microstructure and electrical properties of the material. The frequency dependence of ac conductivity obeys the Jonscher's universal power law. The values and nature of temperature variation of dc conductivity exhibit the NTCR behavior of the material like a semiconductor.

Keywords: Electronic material; Ferroelectricity; XRD; Electrical conductivity.

Total Ref : 34 

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 187-192

Study of interface sheet charge density of AlGaAs/InGaAs/GaAs-based pseudomorphic HEMT

 

T R Lenka, Sudhakar Das, Rasmita Ku Nayak, G N Dash and A K Panda

National Institute of Science and Technology, Palur Hills, Berhampur-761 008, Odisha, India

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In this paper a new AlGaAs/InGaAs/GaAs based pseudomorphic heterostructure device is proposed and various subbands are calculated by solving 1D Schrodinger and Poisson's equation self-consistently in the heterostructure by applying suitable boundary conditions. The interface sheet charge density (ns) for each subband is calculated from the various eigenvalues by numerical approach. The conduction band profile followed by the formation of 2DEG and electric field as a function of distance (Ao) are also discussed. The 2DEG density and electric field at the heterointerface are measured to be 1.092 ´ 1012 cm–2 and 2 ´ 105 V/cm respectively. The dependency of interface charge density on doping density of barrier layer and thickness of spacer is also discussed.

Index Terms: 2DEG, HEMT, Heterostructure, MBE, Pseudomorphic, Subband

Total Ref : 9

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Asian Journal of Physics                                                                                                        Vol. 21, No 2 (2012) 193-200

Impedance-Spectroscopy Analysis of (Bi_0.5Na_0.5)TiO₃ –SrTiO₃ Lead-Free  Ceramic Systems

B Parija^1,2 & S Panigrahi^1*

¹Department of Physics, NIT, Rourkela-769008, India

²Department of Physics, P C E, Rourkela-76002, India

Keywords: Impedance Spectroscopy; Electrical Modulus; Relaxations; Conductivity

Total Ref : 28 

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