Holographic Data Storage Technology- The future of Data Storage

In the present times technological advancement has grown at rapid rate. Today most of the people are using smart devices which comprises of various kinds of technologies. One of the most important factor in using technology is to store digital data. Presently most of the work are done using digital devices such as computers and mobiles and people need to store their data in devices but the device has limited amount of storage. So need arises to store more amount of data using less space. For this purpose we need to invent storage technologies which helps people to store more amount of data. In order to meet demands of greater storage there are various storage technologies such as different types of ROM, optical storage discs, USB flash drives which uses different technologies to store data. This paper focuses on Holographic data storage technology which helps people to store large amount of data

Photopolymer characterization for diffractive and holographic applications

The work was supported by the “Ministerio de Economía y Competitividad” of Spain under projects FIS2011-29803-C02-01 and FIS2011-29803-C02-02 and by the “Generalitat Valenciana” of Spain under projects PROMETEO/2011/021 and ISIC/2012/013

Investigation of the Sensitivity to Humidity of an Acrylamide-based Photopolymer Containing N-phenylglycine as a Photoinitiator

Sensitivity of holographic recording materials to the relative humidity (RH) of the environment often restricts their use in fabrication of holographic optical elements and other applications. It is important to develop materials with little or no sensitivity to humidity. In this paper the humidity response of transmission gratings recorded in an acrylamide-based photopolymer containing N-phenylglycine (NPG) as a photoinitiator is studied at RH = 20 – 90 %. The hologram is found to be completely insensitive to humidity at RH below 70 % and its diffraction efficiency remains constant. A decrease in diffraction efficiency is observed at RH = 80 – 90 % but this decrease is fully reversible, demonstrating quantitatively the NPG photopolymer’s excellent resistance to humidity

Non-Print Information Resources and The Preservation Approaches Recommendation in Tanzanian Academic Libraries

 Background: Non-print information resources are increasingly becoming more important as vital learning materials in higher learning institutions. Academic libraries therefore, have to acquire, process, organize and preserve them for current and future use. Purpose: This paper aims to assess the factors affecting the non-print information resources and their recommended preservation approaches in academic libraries.  Method: The study adopted a convergent parallel mixed approach which collects and analyses data to produce integrated findings by using both qualitative and quantitative techniques in a single study. Data was collected by means of questionnaire and in-depth interview. Result: The study revealed that dust, loss of data on disc and hard disc, loss of data due to server failure, high heat, and excessive light, fading of disc surface, high humidity, fungus on disc surface, atmospheric pollutants and virus attack were factors affecting non-print information resources. It was also revealed that highly recommended preservation approaches were good cleanliness of library where information resources are kept, educating library users on how to handle and use information resources, migrating information resources from obsolete storage media to modern storage media, technology preservation and refreshing. Conclusion: The study concludes that library staff need to adopt recommended preservation approaches to safeguard the important information in academic libraries but also system librarians in academic libraries need to be employed to assist in trouble shooting issues.  Keywords: Non-Print Information Resources; Information Resources; Information Resources Preservation; Preservation Approaches; Academic Library   Abstrak  Latar Belakang: Sumber informasi non-cetak sekarang ini menjadi semakin penting sebagai bahan pembelajaran vital di perguruan tinggi. Oleh karena itu, perpustakaan akademik harus memperoleh, memproses, mengatur, dan melestarikannya untuk penggunaan saat ini dan masa depan. Tujuan: Makalah ini bertujuan untuk menilai faktor-faktor yang mempengaruhi sumber informasi non-cetak dan pendekatan pelestarian yang direkomendasikan di perpustakaan akademik. Metode: Studi ini mengadopsi pendekatan campuran paralel konvergen yang mengumpulkan dan menganalisis data untuk menghasilkan temuan yang terintegrasi dengan menggunakan teknik kualitatif dan kuantitatif dalam satu studi. Pengumpulan data dilakukan dengan kuesioner dan wawancara mendalam. Temuan: Hasil penelitian menunjukkan bahwa debu, hilangnya data pada disk/hard disk, hilangnya data karena kegagalan server, panas yang tinggi, dan cahaya yang berlebihan, memudarnya permukaan disk, kelembaban tinggi, jamur pada permukaan disk, polutan atmosfer dan serangan virus adalah faktor yang mempengaruhi sumber informasi non-cetak. Diungkapkan juga bahwa pendekatan pelestarian yang sangat direkomendasikan adalah kebersihan perpustakaan tempat sumber informasi disimpan, mendidik pengguna perpustakaan tentang cara menangani dan menggunakan sumber informasi, migrasi sumber informasi dari media penyimpanan usang ke media penyimpanan modern, pelestarian teknologi dan penyegaran koleksi. Kesimpulan: Studi ini menyimpulkan bahwa staf perpustakaan perlu mengadopsi pendekatan pelestarian yang direkomendasikan untuk melindungi informasi penting di perpustakaan akademik, tetapi juga pustakawan di perpustakaan akademik perlu dioptimalkan untuk membantu memecahkan masalah yang ada.  Kata kunci: Sumber Informasi Non-Cetak; Sumber Daya Informasi; Pelestarian Sumber Daya Informasi; Pendekatan Pelestarian; Perpustakaan Akademik&nbsp

Design and Fabrication of Volume Holographic Optical Couplers for a Range of Non-Normal Incidence Angles

A theoretical model has previously been developed to calculate the holographic recording beam angles required in air (at any recording wavelength) to produce a Volume Holographic Optical Element (VHOE) for operation as a coupler for different input and output angles. In this paper, the experimental study is extended to further validate the VHOE coupler design and fabrication approach for additional incident beam angles, comparing -40° -45° and -50° (in air). The output angle for each VHOE is +45° within the medium and the coupler operational wavelength is 633nm. Holographic recording in Bayfol HX 200 photopolymer at 532nm is used to fabricate the VHOE couplers. The experimental Bragg curves for each VHOE coupler obtained at 633 nm demonstrate agreement of the measured angles to within ±1.5° (in air) with the expected values

Modelling and Design of Holographic Optical Elements for Beam-Coupling Applications for a Range of Incident Beam Angles

Theoretical modelling has been used to calculate the holographic recording beam angles required in air (at any recording wavelength) to produce a Volume Holographic Optical Element (VHOE) for any defined input and output beam angles. The approach is used to facilitate the design and fabrication of diffractive coupling elements through a holographic process that avoids the use of coupling prisms during recording and will help in the design of recording arrangements that better suit the mass production of low-cost elements, especially those designed for non-normal incidence. In this study, the recording angles needed for a range of recording wavelengths were explored for VHOE couplers designed for input angles (in air) ranging from 0◦ to −55◦ . Then, in order to validate the model, holographic recording in Bayfol HX 200 photopolymer at 532 nm was used to fabricate photopolymer VHOE couplers for 633 nm light (−45◦ input angle in air). Bragg curves obtained experimentally for different probe wavelengths (403 nm, 532 nm and 633 nm) confirm the recording of the desired grating structures to a precision of ±1 ◦ , and coupling is demonstrated at 633 nm with a diffraction efficiency of up to 72%. Furthermore, the model is used to identify the origins of some weaker spurious gratings observed alongside the expected ones

Non-Print Information Resources and The Preservation Approaches Recommendation in Tanzanian Academic Libraries.

Background: Non-print information resources are increasingly becoming more important as vital learning materials in higher learning institutions. Academic libraries therefore, have to acquire, process, organize and preserve them for current and future use. Purpose: This paper aims to assess the factors affecting the non-print information resources and their recommended preservation approaches in academic libraries. Method: The study adopted a convergent parallel mixed approach which collects and analyses data to produce integrated findings by using both qualitative and quantitative techniques in a single study. Data was collected by means of questionnaire and in-depth interview. Result: The study revealed that dust, loss of data on disc and hard disc, loss of data due to server failure, high heat, and excessive light, fading of disc surface, high humidity, fungus on disc surface, atmospheric pollutants and virus attack were factors affecting non-print information resources. It was also revealed that highly recommended preservation approaches were good cleanliness of library where information resources are kept, educating library users on how to handle and use information resources, migrating information resources from obsolete storage media to modern storage media, technology preservation and refreshing. Conclusion: The study concludes that library staff need to adopt recommended preservation approaches to safeguard the important information in academic libraries but also system librarians in academic libraries need to be employed to assist in trouble shooting issues. Keywords: Non-Print Information Resources; Information Resources; Information Resources Preservation; Preservation Approaches; Academic Librar

Coherent Multidimensional Off-resonant THz Spectroscopy on Semiconductors

Zum ersten Mal konnte die kohärente Erzeugung von ultrakurzen Pulsen mit Feld stärken im MV/cm Bereich mit einem Spektralbereich von 0.1-30 THz im organischen Kristall DSTMS. Kohärente mehrdimensionale Terahertzspektroskopie (CMTS) hat sich zu einer wichtigen Methode zur Untersuchung der niederenergetischen Anregungen von Halbleitern and deren kohärenter Dynamik entwickelt. Eine neuartige CMTS Methode mit drei phasenstarren, zueinander zeitverzögerten Terahertzpulsen wurde entwickelt. Sie beruht auf der kollinearen Wechselwirkung der Pulse mit der Probe, sodass verschiedene Ordnungen des nichtlinearen Signals in gleicher Richtung emittiert werden und deshalb gleichzeitig gemessen werden können. Amplitude und Phase des nichtlinearen Signals können durch elektro-optisches Abtasten vermessen werden, wodurch die zeitliche Entwicklung der kohärenten Wechselwirkungen in Echtzeit untersucht werden kann. CMTS erlaubt zusätzlich die eindeutige Zerlegung des nichtlinearen Signals in die verschiedenen nichtlinearen Ordnungen in der jeweiligen mehrdimensionalen Frequenzdomäne. Die nichtlineare, nicht-resonante Antwort zweier undotierter Halbleiter, des Ferroelektrikums Lithiumniobat (LiNbO3) und Indiumantimonids (InSb) kann mit dieser neuartigen Methode untersucht werden. In LiNbO3 wird das nichtlineare Signal durch einen Femtosekunden nichtlinearen Verschiebestrom (SC) hervorgerufen. SC wird durch die gebrochene Inversionssymmetrie des Kristalls in Verbindung mit einer ultraschnellen Dephasierung der feldinduzierten, kohärenten interband-Polarisation hervorgerufen. Die Dephasierung der interband-Polarisation erlaubt das Tunneln von Elektronen vom Valenzband in das Leitungsband. In InSb wird das kohärente Signal durch sowohl zwei-Phonen als auch zwei-Photonen interband-Anregungen erzeugt. Die impulsive Anregung einer kohärenten zwei-Phononen Polarisation wird durch das große Übergangsdipolmoment von InSb verstärkt, was zu deutlich größeren Amplituden der Polarisation als im linearem Regime führt.For the first time, the coherent generation of ultrashort MV/cm field pulses with a spectrum covering the frequency range 0.1-30 THz is demonstrated in the organic crystal DSTMS. Coherent multidimensional terahertz spectroscopy (CMTS) has become a prominent technique for, e.g., driving low-energy excitations in semiconductors and monitoring their coherent dynamics. A novel CMTS technique using three phase-locked inter-delayed THz pulses is implemented. It relies on a collinear interaction of the pulses with a sample, so that different contributions to the nonlinear signal are emitted in the same direction, and thus can be measured all at once. Phase-resolved detection by electro-optic sampling allows for measuring amplitude and absolute phase of the nonlinear signal, thereby enabling to investigate the evolution of coherent interactions between quantum excitations in real time. In CMTS, the nonlinear signal is dissected into the distinct nonlinear contributions in the corresponding multidimensional frequency domain. This novel technique is applied to study the nonlinear off-resonant response of two undoped bulk semiconductors, the wide-bandgap ferroelectric lithium niobate (LiNbO3) and the narrow-bandgap indium antimonide (InSb). In LiNbO3, the nonlinear signal is generated by a femtosecond nonlinear shift current (SC), a distinctive characteristic of the bulk photovoltaic effect. The SC stems from the lack of inversion symmetry and the ultrafast dephasing of the field-induced interband coherent polarization due to a sufficiently high decoherence rate, which enables tunneling of electrons from the valence to the conduction band. In InSb, the nonlinear signal is caused by the coherent response on both the two-phonon and two-photon interband excitations. The impulsive generation of the two-phonon coherent polarization is enhanced by the large interband transition dipole of InSb, resulting in much larger polarization amplitudes than in the regime of linear response