ArticlePDF Available

# Eternal 5D data storage via ultrafast-laser writing in glass

Authors:

## Abstract and Figures

Securely storing large amounts of information over relatively short timescales of 100 years, comparable to the span of the human memory, is a challenging problem. Conventional optical data storage technology used in CDs and DVDs has reached capacities of hundreds of gigabits per square inch, but its lifetime is limited to a decade. DNA based data storage can hold hundreds of terabytes per gram, but the durability is limited. The major challenge is the lack of appropriate combination of storage technology and medium possessing the advantages of both high capacity and long lifetime. The recording and retrieval of the digital data with a nearly unlimited lifetime was implemented by femtosecond laser nanostructuring of fused quartz. The storage allows unprecedented properties including hundreds of terabytes per disc data capacity, thermal stability up to 1000 °C, and virtually unlimited lifetime at room temperature opening a new era of eternal data archiving.
Content may be subject to copyright.
10.1117/2.1201603.006365
Eternal 5D data storage via
ultrafast-laser writing in glass
Peter Kazansky, Ausra Cerkauskaite, Martynas Beresna,
Rokas Drevinskas, Aabid Patel, Jingyu Zhang, and
Mindaugas Gecevicius
Information storage based on the introduction of nanostructures into
fused quartz using a femtosecond laser could ensure all that we have
learned will not be forgotten.
Compared with paper or clay, digital data storage is not very
durable. As such, securely storing large amounts of informa-
tion over even the relatively short timescale of 100 years—
comparable to the human memory span—is a challenging
problem.1Conventional optical-data-storage technology of the
type employed in CDs and DVDs has reached capacities of hun-
dreds of gigabits per square inch. However, the lifetime of this
media is limited to a decade as a result of unavoidable degrada-
tion suffered by the data layer. More futuristic DNA-based data
storage is capable of holding hundreds of terabytes (Tb) of data
per gram, but its durability is limited.2
The concept of storing data optically in the bulk of non-
photosensitive transparent materials (such as fused quartz,
which is renowned for its high chemical stability and resis-
tance) via femtosecond-laser (fs-laser) writing was ﬁrst pro-
posed and demonstrated in 1996.3, 4 This method allows for
high-capacity optical recording by multiplexing new degrees of
freedom (e.g., intensity, polarization, and wavelength). This de-
velopment in data storage is based on the introduction of gold or
silver nanoparticles, which are embedded within the material.5
The plasmonic properties of these nanoparticles can then
be exploited.6, 7 More recently, polarization-multiplexed writ-
ing has been demonstrated by using self-assembled nanograt-
ings, which are produced via ultrafast-laser writing in fused
quartz.8, 9 These nanogratings, which comprise 20nm-thick lam-
ina structures embedded within the material,10–12 are resistant
to high temperatures.13 Despite several attempts to explain the
physics of this peculiar self-organization process, the formation
of the nanostructures remains a mystery.14,15
Based on this behavior, we have developed a method of
data storage that makes use of three spatial and two optical
Figure 1. 5D optical data storage, written in fused quartz using a fem-
tosecond laser. Three spatial dimensions and two optical ones (the slow-
axis orientation and the retardance) are exploited. Each voxel contains
a self-assembled nanograting that is oriented in a direction perpendic-
ular to the light polarization. The distance between two adjacent spots
is 3.7m and the distance between each layer is 20m. E: Electric ﬁeld
of light wave. Arrow: Polarization direction.
dimensions.16 On the macroscopic scale, the self-assembled
nanostructures behave as uniaxial optical crystals with negative
birefringence. The alignment of the nanogratings gives rise to
optical anisotropy (a form of birefringence) of the same order of
magnitude as positive birefringence in crystalline quartz.
In conventional optical storage such as DVDs, data is stored
by burning tiny pits in one or more layers of the plastic disc,
thereby making use of three spatial dimensions. We have also
exploited two additional (optical) dimensions. When the data-
recording femtosecond laser marks the glass, it makes a pit with
a nanograting. This nanograting produces birefringence that is
characterized by two additional parameters. The slow-axis ori-
entation introduces a fourth dimension, and the strength of
retardance—deﬁned as a product of the birefringence and the
length of the structure—forms a ﬁfth dimension. These two pa-
rameters are controlled during recording by the polarization and
dimensions to the three spatial coordinates, we achieve 5D opti-
cal data storage: see Figure 1.
Continued on next page
10.1117/2.1201603.006365 Page 2/3
We have recorded the ﬁrst digital documents (including
copies of the Universal Declaration of Human Rights, New-
ton’s Opticks, the Magna Carta, and the King James Bible) across
up to 18 layers using optimized parameters (light pulses with
energies of 0.2J and a duration of 600fs at a repetition rate
of 500kHz): see Figure 2. To test the durability of this data-
storage mechanism, we used accelerated aging measurements
(see Figure 3). These tests reveal that the decay time of the
nanogratings is 31020˙1years at room temperature (303K),
showing the unprecedentedly high stability of nanostructures
imprinted in fused quartz. Even at elevated temperatures of
462K, the extrapolated decay time is comparable to the age of
the Universe (13.8 billion years). Based on the tests, we believe
that these copies could survive the human race.9
The addition of more states of polarization and intensities—
currently limited by the resolutions of the slow axis orientation
(4:7) and the retardance (5nm)—could enable more than one
byte (8 bits, or 256 possible combinations) per modiﬁcation spot
using the same birefringence measurement system. By recording
data with a 1.4NA (numerical aperture) objective and a shorter
wavelength (250–350nm), recording a disc with a 360Tb capacity
(more than 7000 times today’s 50Gb double-layer Blu-ray capac-
We have developed an extremely durable 5D data-storage
technique based on the imprinting of nanostructures in silica
glass via femtosecond-laser writing. This technology, which we
have coined ‘Superman memory crystal,’ could be produced on
a commercial scale for organizations with large archives (e.g., na-
tional archives, museums, libraries, and private organizations).
We believe that our method will also prove attractive for the
consumer market if the cost of hardware (particularly the ex-
pensive femtosecond laser) is reduced.17 Additionally, a number
of projects (such as Time Capsule to Mars, MoonMail, and the
Google Lunar XPRIZE)18–20 could beneﬁt from the technique’s
extreme durability, which fulﬁlls a crucial requirement for stor-
Figure 2. Copies of (a) the King James Bible and (b) the Magna Carta
imprinted in glass.
Figure 3. Arrhenius plot of the nanograting decay rate. The black dots
indicate measured values and the red dots are calculated based on ﬁt-
ting results, showing the extrapolated lifetime of the stored data. The
gray shaded zone indicates the tolerance of extrapolated values. Based
on these results, the nanogratings would last for the current lifetime of
the Universe (D13:8 billion years) at a temperature (T) of 462K. The
inset shows the decay of the retardance strength over time at different
annealing temperatures (900, 1000, and 1100C).
age on the Moon or Mars. With this technology, we may have
ﬁnally achieved information immortality.21 In our future work,
we plan to improve write speeds and to develop a microscope-
free disc drive for data readout.
Author Information
Peter Kazansky, Ausra Cerkauskaite, Martynas Beresna,
Rokas Drevinskas, Aabid Patel, Jingyu Zhang, and
Mindaugas Gecevicius
Optoelectronics Research Centre
University of Southampton
Southampton, United Kingdom
References
1. M. C. Elwenspoek, Long-time data storage: relevant time scales,Challenges 2,
pp. 19–36, 2011.
2. G. M. Church, Y. Gao, and S. Kosuri, Next-generation digital information storage in
DNA,Science (337), p. 1628, 2012.
3. E. N. Glezer, M. Milosavljevic, L. Huang, R. J. Finlay, T.-H. Her, J. P. Callan, and
E. Mazur, Three-dimensional optical storage inside transparent materials,Opt. Lett. 21,
pp. 2023–2025, 1996.
4. M. Watanabe, S. Juodkazis, H. B. Sun, S. Matsuo, H. Misawa, M. Miwa, and
R. Kaneko, Transmission and photoluminescence images of three-dimensional memory in
vitreous silica,Appl. Phys. Lett. 74, pp. 3957–3559, 1999.
Continued on next page
10.1117/2.1201603.006365 Page 3/3
5. P. Zijlstra, J. W. M. Chon, and M. Gu, Five-dimensional optical recording mediated
by surface plasmons in gold nanorods,Nature 459, pp. 410–413, 2009.
6. A. Royon, K. Bourhis, M. Bellec, G. Papon, B. Bousquet, Y. Deshayes, T. Cardinal,
and L. Canioni, Silver clusters embedded in glass as a perennial high capacity optical
recording medium,Adv. Mater. 22, pp. 5282–5286, 2010.
7. A. Podlipensky, A. Abdolvand, G. Seifert, and H. Graener, Femtosecond laser as-
sisted production of dichroitic 3D structures in composite glass containing Ag nanoparti-
cles,Appl. Phys. A. 80, pp. 1647–1652, 2005.
8. Y. Shimotsuma, M. Sakakura, P. G. Kazansky, M. Beresna, J. Qiu, K. Miura,
and K. Hirao, Ultrafast manipulation of self-assembled form birefringence in glass,Adv.
Mater. 22, pp. 4039–4043, 2010.
9. J. Zhang, M. Geceviˇ
cius, M. Beresna, and P. G. Kazansky, Seemingly unlimited
lifetime data storage in nanostructured glass,Phys. Rev. Lett. 112, p. 033901, 2014.
10. P. G. Kazansky, H. Inouye, T. Mitsuyu, K. Miura, J. Qiu, K. Hirao, and F. Star-
rost, Anomalous anisotropic light scattering in Ge-doped silica glass,Phys. Rev. Lett. 82,
pp. 2199–2202, 1999.
11. Y. Shimotsuma, P. G. Kazansky, J. Qiu, and K. Hirao, Self-organized nanogratings
in glass irradiated by ultrashort light pulses,Phys. Rev. Lett. 91, p. 247705, 2003.
12. R. S. Taylor, C. Hnatovsky, E. Simova, P. P. Rajeev, D. M. Rayner, and P. B.
Corkum, Femtosecond laser erasing and rewriting of self-organized planar nanocracks in
fused silica glass,Opt. Lett. 32, pp. 2888–2890, 2007.
13. E. Bricchi and P. G. Kazansky, Extraordinary stability of anisotropic femtosecond
direct-written structures embedded in silica glass,Appl. Phys. Lett. 88, p. 111119, 2006.
14. S. Richter, C. Miese, S. D ¨
oring, F. Zimmermann, M. J. Withford, A.
T¨
unnermann, and S. Nolte, Laser induced nanogratings beyond fused silica—periodic
nanostructures in borosilicate glasses and ULETM,Opt. Mater. Express 3, pp. 1161–
1166, 2013.
15. M. Lancry, B. Poumellec, J. Canning, K. Cook, J.-C. Poulin, and F. Brisset, Ultra-
fast nanoporous silica formation driven by femtosecond laser irradiation,Laser Photon.
Rev. 7, pp. 953–962, 2013.
16. J. Zhang, A. Cerkauskaite, R. Drevinskas, A. Patel, M. Beresna, and P. Kazansky,
Eternal 5D data storage by ultrafast laser writing in glass
Presented at SPIE Photonics West, 2016.
17. http://longnow.org/about/ The Long Now Foundation. Accessed 3 March
2016.
18. http://www.timecapsuletomars.com/ Time Capsule to Mars. Accessed 1
March 2016.
19. https://www.astrobotic.com/moon-mail MoonMail. Accessed 1 March 2016.
20. http://lunar.xprize.org/ Google Lunar XPRIZE. Accessed 1 March 2016.
21. http://singularityhub.com/2016/02/25/have-we-ﬁnally-achieved-
information-immortality/ Have we ﬁnally achieved information immortality? Accessed
1 March 2016.
c
2016 SPIE
... This describes a situation of high individual and population exposure, and since there are few of manufacturers of HDD's, information storage can also be noted to illustrate centralisation at multi-nation level. Several technologies allowing long-term storage have been proposed (Kazansky et al., 2016, Longnow Foundation, 2017; Permanent Archival Solution, 2020, Nanoarchival™ technology) but these are currently expensive and lack the integration to allow them to truly offer changes to population exposure. ...
... A criterion of E 1 < 1 could in principle be achieved by massive redundancy, but in practice the use of identical operating systems and software make it likely that residual exposure will remain. Technologies such as the 5D glass storage approach (Kazansky et al., 2016) or proposals by the Longnow Foundation, 2017; or organisations such as "Nanoarchival™ technology" avoid the reliance upon proprietary data retrieval systems and provide very long life -but still lack a mature and decentralised data-writing approach, and a mature and decentralised approach for reading stored data back into a machine-readable form. The advances needed in order to achieve a durable, low-exposure storage medium are immature but are technologically achievable. ...
Article
Full-text available
The nature and level of individuals' exposure to technological systems has been explored previously and is briefly restated here. This paper demonstrates how the concept of technological exposure can be extended to generic needs of individuals, and further to the needs of populations of individuals and even as far as “existential threats” to humanity. Technological categories that incur high levels of population exposure are explored, and categories are described. A theoretical basis for reducing population exposure is developed from the basic concepts of technological exposure. Technological developments that potentially enable less centralised societies having lower levels of population exposure, are considered for practicality and effectiveness as are the factors that could allow and cause transition to a less technologically centralised model. Some conclusions regarding practicality, triggers, and issues arising from a decentralised society are considered and include the key conclusion that a higher level of decentralisation and exposure reduction is both desirable and possible.
... Sur la figure b), la zone grise correspond à la zone extérieure, non fondue. Figure modifiée de[Fernandez et al. (2018)].La génération de tels nanoréseaux est proposée pour le stockage optique de données sur de très longues durées en 5D (trois dimensions spatiales, une dimension de polarisation et une dimension de retardance)[Kazansky et al. (2016)].(iii) CristallisationComme mentionné précédemment, l'irradiation laser femtoseconde dans un verre peut entraîner la génération de chaleur dépassant sa température de fusion. ...
... C'est ce que l'on appelle communément la photo-structuration intrinsèque. Par ce biais, plusieurs groupes de recherches tentent de développer de nouvelles technologies comme la miniaturisation de laboratoires dans/sur une fibre optique[Haque et al. (2014);Vaiano et al. (2016)] ou encore le stockage optique pérenne de données numériques[Kazansky et al. (2016)]. Toutefois, une voie distincte peut être employée. ...
Thesis
Full-text available
La recherche de nouvelles de technologies de rupture pour le développement de systèmes photoniques performants, compacts et à moindre consommation énergétique représente un défi majeur dans le domaine des matériaux. A cette problématique, l’inscription laser directe dans les matériaux vitreux transparents est une approche à fort potentiel. En effet, par modification multi-échelle (du nanoscopique au macroscopique) en trois dimensions, une multitude de fonctionnalités peut être incrémentée par cette technique tout-optique. Une approche novatrice repose sur l’irradiation laser femtoseconde de verres non conventionnels, dont la photosensibilité a été améliorée en amont, dès la conception du verre. Ainsi, dans un verre comportant des ions argent, l’inscription laser directe permet le déploiement de nombreuses fonctionnalités reposant sur la photochimie induite de l’argent, sans pour autant affecter la qualité optique de la matrice vitreuse. Une telle photostructuration permet notamment dans les verres phosphates de générer de nouvelles espèces moléculaires correspondant à des agrégats d’argent. Sur des échelles sub-microniques et en trois dimensions, la formation contrôlée de ces espèces permet la création maîtrisée de plusieurs propriétés optiques à très fort contraste optique : fluorescence, variation d’indice de réfraction, génération de seconde et troisième harmonique, voire développement de nanoparticules métalliques plasmoniques.Les travaux exposés dans cette thèse traitent d’aspects théoriques et technologiques en science des verres, s’articulant autour de la photochimie de l’argent. Premièrement, dans un système vitreux phosphate P2O5 – Ga2O3 – Na2O dopé à l’argent (GPN:Ag), une étude détaillée portant sur les relations structure-propriété a été réalisée. Grâce à cette étude, une corrélation entre la structure vitreuse, l’environnement de l’argent et la photosensibilité des verres a pu être mise en évidence. Deuxièmement, deux compositions du système vitreux GPN:Ag, respectivement de faible et forte photosensibilité, ont été soumises à l’implémentation de deux fonctionnalités : l’inscription laser de structures résilientes aux rayons X et le fibrage de ces verres. L’apport de ces fonctionnalités atteste des fortes potentialités et valeurs ajoutées de cette famille de verre GPN:Ag pour l’élaboration de capteurs intégrés et/ou fibrés de rayons X. Parallèlement, l’étude réalisée entre deux verres phosphates à l’argent avec ou sans ions co-mobiles (sodium, fluor) a permis de mieux appréhender la propriété de réinscription laser, corrélée à la gestion du réservoir d’ions argent. Par approche tout-optique, des périodicités spatiales de 200 à 300 nm ont ainsi pu être obtenues dans une composition GPN:Ag spécialement élaborée. La maîtrise conjointe de la synthèse de verres spéciaux et de la structuration laser, a conduit à la première démonstration de réseaux de Bragg intégrés à des guides d’onde, uniquement sous-tendus par la photochimie de l’argent sous irradiation laser. Troisièmement, un nouveau système vitreux d’oxydes lourds Ga2O3 – Ge2O – K2O (GGK), compatible avec la photochimie de l’argent, a été considéré. Ce système vitreux est très intéressant car il possède une fenêtre de transmission étendue jusque dans l’infrarouge moyen. Par frittage flash de poudre de verre GGK, des pastilles transparentes amorphes et vitrocéramisées de phase non-centrosymétrique KGaGeO4 ont pu être obtenues. Conjointement, l’introduction d’argent dans le verre GGK étant délicate, une étude substituant des ions potassium par du baryum a mis en évidence la stabilisation de l’argent dans la matrice vitreuse. En perfectionnant les rapports cationiques de ces verres GGK avec du baryum, un verre accueillant la photochimie de l’argent a pu être élaboré et photostructuré par laser. Ce nouveau verre ouvre alors le large potentiel de structuration laser à l’argent pour la gamme de longueur d’onde d’intérêt entre 3 et 5 µm.
... These make it promising for a variety of applications in the fields of smart windows [6], photocatalysis [7], photonic crystals, sensors, non-emissive displays, information storage media, optical signal processing and so on. These molecular property changes can be applied to various photonic devices, such as erasable optical memory media and photo optical switch components [8,9]. Big data storage is one of the great challenges to be overcome nowadays in the mass communication in which the photochromic effect plays the fundamental rule. ...
... Big data storage is one of the great challenges to be overcome nowadays in the mass communication in which the photochromic effect plays the fundamental rule. Recently, P. Kazansky et al. have demonstrated a very stable at high temperature glass to a 5D optical data storage based on the photochromic effect [8]. ...
Article
The effect of silver ions on the photochromic properties of tungsten phosphate glass is investigated. All samples when excited at 377 nm exhibit ∼430 nm luminescence attributed to the charge transfer mechanism within the WO42−tungstate anions. The broad absorption band extending from ultraviolet to the visible region, between 500 and 1400 nm, of the NaPO3-WO3 (PW) base matrix due to the small-polarons(Wx5+W1−x6+O3) transferring charges between neighboring tungsten ions according to the following photon absorptionWA5++WB6++hvs→WA6++WB5+. The dual oxidation state of the antimony, Sb³⁺ and Sb⁵⁺, incorporated into the matrix at the (50−x)NaPO3−50WO3−xSb2O3(x=0…20mol%) (PWS) ratio acts as a reducing element of the W⁵⁺ ions leading to the suppression of polarons as UV-VIS absorption centers. These results are confirmed by EPR measurements with scanned magnetic field between 2500 and 4500G. The most intense effect is observed for nominal doping aboveAgNO3≥10mol%. The temporal dynamics of luminescence at ∼430 nm as a function of UV exposure time shows that both,Wx5+W1−x6+O3 for PW glasses as well as Ag⁺ for PWSA glasses act as traps for the charge generated by the excitedWO42− anions. Photodarkening due to continuous exposure to UV radiation reduces the pump transmission by ∼12% of its initial value for PW and PWSA glasses. This is attributed to F-center formation (Ag⁺) which acts traps to the photoexcited electrons. This is attributed to oxidation of silver ions (Ag⁺) becoming metallic silver (Ag⁰). The effect when compared to PWS glass was observed to be reduced by only 2% over the same interval under the same pumping conditions.
... In [12], Ono et al. utilized a single SLM, two QWPs, and four HWPs to generate a vector hologram beam, where the SLM controlled the polarization distribution in the cross-section of the two writing beams. An efficient polarization method based on a single SLM was developed by a University of Southampton group [13][14][15][16][17]. They utilized an LCOS SLM and a rotation-free half-wave plate matrix (HPM) to obtain the data pattern generation and the writing beam's polarization state control. ...
Article
Full-text available
In this paper, we propose and experimentally demonstrate a parallel coding and two-beam combining approach for the simultaneous implementation of dynamically generating holographic patterns at their arbitrary linear polarization states. Two orthogonal input beams are parallelly and independently encoded with the same target image information but there is different amplitude information by using two-phase computer-generated holograms (CGH) on two Liquid-Crystal-on-Silicon-Spatial-Light Modulators (LCOS SLMs). Two modulated beams are then considered as two polarization components and are spatially superposed to form the target polarization state. The final linear vector beam is created by the spatial superposition of the two base beams, capable of controlling the vector angle through the phase depth of the phase-only CGHs. Meanwhile, the combined holographic patterns can be freely encoded by the holograms of two vector components. Thus, this allows us to tailor the optical fields endowed with arbitrary holographic patterns and the linear polarization states at the same time. This method provides a more promising approach for laser data writing generation systems in the next-generation optical data storage technology in transparent materials.
... According to the periods of the LIPSS, the ripples can be separated into high spatial frequency LIPSS (HSFL, Λ < 0.5λ) and low spatial frequency LIPSS (LSFL, 0.5λ < Λ < λ) [11]. LIPSS technology has become a flexible technique for the fabrication of functionalized surface, such as colored structure, super-hydrophobicity surface, surface-enhanced Raman spectroscopy, and optical data storage [12][13][14][15]. ...
Article
Full-text available
The formation dynamics of periodic ripples induced by two 800 nm femtosecond laser pulses on Al film are studied using a pump-probe imaging technique. The results shows that the first femtosecond laser pulse only induced random nanostructures on the surface of the Al film. Periodic ripples appear near these nanostructures after the second femtosecond pulse irradiation. The surface-plasmon-polariton (SPP) model combined with the Drude-Lorentz model is used to explain the formation of periodic ripples structure on the surface of the smooth Al film after the second femtosecond laser irradiation. The dynamics of electron and lattice temperatures after femtosecond laser irradiation on the Al surface is calculated by a two-temperature model, and the influences of the electron and lattice temperatures are taken account on electron scattering frequencies. Single-photon absorption and the localization of hot electrons are also considered in the Drude-Lorentz model. The simulated results show that the period of the periodic ripples predicted by the SPP model accords well with experimental results. It demonstrates that the SPP are excited by the second femtosecond laser pulse irradiating the nanostructure formed by the first femtosecond laser pulse, are the main reason for the formation of the periodic ripples.
... One type of such media relies on fluorescent dyes on polymer films or the rotaxane molecular architecture [90,91]. Another type relies on creating nano-structures to obtain an etched crystalline quartz or even a thin diamond layer [92,93]. ...
Article
Full-text available
About fifty times more data has been created than there are stars in the observable universe. Current trends in data creation and consumption mean that the devices and storage media we use will require more physical space. Novel data storage media such as DNA are considered a viable alternative. Yet, the introduction of new storage technologies should be accompanied by an evaluation of user requirements. To assess such needs, we designed and conducted a survey to rank different storage properties adapted for visualization. That is, accessibility, capacity, usage, mutability, lifespan, addressability, and typology. Withal, we reported different storage devices over time while ranking them by their properties. Our results indicated a timeline of three distinct periods: magnetic, optical and electronic, and alternative media. Moreover, by investigating user interfaces across different operating systems, we observed a predominant presence of bar charts and tree maps for the usage of a medium and its file directory hierarchy, respectively. Taken together with the results of our survey, this allowed us to create a customized user interface that includes data visualizations that can be toggled for both user groups: Experts and Public.
... Generation of volume subwavelength structures using ultrafast laser pulses is a field which has attracted considerable attention. In this field, generation of three-dimensional birefringence in the bulk of isotropic transparent materials such as glass has found various applications such as 5-D optical memories [1], optical wave plates [2,3], polarization converters [4], polarization-sensitive holograms [5], polarization-sensitive waveguides [6], Fresnel zone plates [7], and nanofluidics channels for lab-on-chip devices [8]. ...
Article
Full-text available
We show spectacular and different effect of the sequential and simultaneous writing of two perpendicularly polarized ultrashort laser pulse trains on profile and magnitude of induced optical retardation inside fused silica glass. Clear birefringence was observed in the region exposed to linearly polarized pulse train radiation. It found out that the induced birefringence is erasable. It means that, when the sample is irradiated again with pulse train having perpendicular polarization, the induced birefringence is vanished and can be totally erased by optimizing the pulse energy. However, in a simultaneous writing approach, a contradictory result was observed. When the glass substrates were simultaneously (i.e. with an accuracy better than the pulse duration) exposed to two beams with perpendicular polarization the induced birefringence not only remained but also enhanced. Discussion and study on the results of interaction of polarized single ultrashort laser pulse and sequential laser beams (which spatially overlapped) having different polarizations and also change of energy ratio of simultaneously writing pulse trains helps us to analyze different results of the simultaneous interaction of two orthogonally polarized ultrashort laser pulse trains with transparent material. Our results provide pieces of evidence for further understanding the physical mechanism of creation of the birefringence using ultrashort laser pulses. Additionally, they provide the ability to manipulate the transient electron dynamics to control the profile and tailor of the induced birefringence.
... Since interactions with material surfaces can be optimized, it has become an increasingly important part of laser applications. For example laser annealing 1 , photo litographics 2,3,4 optical data storage / processing 5,6 and direct laser structuring can benefit from beam shaping. In most cases the optimization stems from a better usage of the beam's power. ...
Article
Quantitative phase imaging and holography allow highly sensitive detection of phase changes, for example of surface non-uniformities or refractive index (RI) structures in the volume of a sample. For many applications, wide field-of-view (FoV) and high phase sensitivity are required. Lens-free interferometric microscopy can operate over a wide FoV and volume, but with the drawbacks of low axial resolution and poor optical sectioning, which comes with increased noise from out-of-focus planes. In this work, we propose and demonstrate a novel implementation of lens-free phase imaging with phase-shifting interferometry and multi-angle illumination that enhances axial resolution and image quality, enabling ultra-high phase sensitivity with optical path difference (OPD) background root-mean-square (RMS) noise of 0.2 nm, while operating over a wide FoV (>10 mm²). As a prototypical application, we demonstrate imaging of 10 nm thin transparent glass structures, and of 3D laser-written structures of RI modifications in glass over a large volume (>10 mm³), where the location of features along the z-axis can be determined with 3x higher accuracy compared to an on-axis illumination. The technology is particularly suitable for large-scale analysis and characterization of structures on the surface or embedded in transparent materials.
Conference Paper
Full-text available
Securely storing large amounts of information over relatively short timescales of 100 years, comparable to the span of the human memory, is a challenging problem. Conventional optical data storage technology used in CDs and DVDs has reached capacities of hundreds of gigabits per square inch, but its lifetime is limited to a decade. DNA based data storage can hold hundreds of terabytes per gram, but the durability is limited. The major challenge is the lack of appropriate combination of storage technology and medium possessing the advantages of both high capacity and long lifetime. The recording and retrieval of the digital data with a nearly unlimited lifetime was implemented by femtosecond laser nanostructuring of fused quartz. The storage allows unprecedented properties including hundreds of terabytes per disc data capacity, thermal stability up to 1000 °C, and virtually unlimited lifetime at room temperature opening a new era of eternal data archiving.
Article
Full-text available
We demonstrate recording and retrieval of the digital document with a nearly unlimited lifetime. The recording process of multiplexed digital data was implemented by femtosecond laser nanostructuring of fused quartz. The storage allows unprecedented parameters including hundreds of terabytes per disc data capacity, thermal stability up to $1000\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, and virtually unlimited lifetime at room temperature. We anticipate that this demonstration will open a new era of eternal data archiving.
Article
Full-text available
Digital information is accumulating at an astounding rate, straining our ability to store and archive it. DNA is among the most dense and stable information media known. The development of new technologies in both DNA synthesis and sequencing make DNA an increasingly feasible digital storage medium. We developed a strategy to encode arbitrary digital information in DNA, wrote a 5.27-megabit book using DNA microchips, and read the book by using next-generation DNA sequencing.
Article
Full-text available
Dynamic processes relevant for long-time storage of information about human kind are discussed, ranging from biological and geological processes to the lifecycle of stars and the expansion of the universe. Major results are that life will end ultimately and the remaining time that the earth is habitable for complex life is about half a billion years. A system retrieved within the next million years will be read by beings very closely related to Homo sapiens. During this time the surface of the earth will change making it risky to place a small number of large memory systems on earth; the option to place it on the moon might be more favorable. For much longer timescales both options do not seem feasible because of geological processes on the earth and the flux of small meteorites to the moon.
Article
Full-text available
Three-dimensional optical recording by laser-induced fluorescent silver clusters is demonstrated in glass. The fluorescence properties of these stable clusters can be altered, depending on the glass recording exposure conditions. A "Blu-ray"-like drive enables readout of the information inside the glass without cross-talk and photobleaching (see figure). This original recording medium can provide an answer to the societal problem of long-term high-density data storage.
Article
We report on the ultrashort pulse laser induced formation of birefringent structures in the volume of different glasses: Borofloat 33, BK7 and ULE (TM). Using polarization contrast and scanning electron microscopy we could prove that this birefringence is induced by nanogratings. We were able to identify the pulse duration as a crucial process parameter for the generation of nanogratings in these glasses. The achieved birefringence in ULE is comparable to fused silica, while borosilicate glasses show much less birefringence (only about 12%). Remarkably, the period of the nanogratings is also dependent on the type of the glass, being 250 nm for ULE and only 60 nm in case of Borofloat 33. (C) 2013 Optical Society of America
Article
A type of glass modifications occurring after femtosecond laser irradiation gives rise to strong (10−2). This form birefringence is thought to be related to index nanostructure (called nanogratings). Analyzing induced tracks in fused silica using scanning electron microscopy (SEM) with nm resolution shows that nanostructures are porous nanoplanes with an average index lower than typical silica (�n ∼ –0.20). Their origin is explained as arising from fast decomposition of the glass under localized, high-intensity femtosecond laser radiation where strong nonlinear, multiphoton-induced photoionization leads to plasma generation. Mechanistic details include Coulombic explosions characteristic of strong photoionization and the production of self-trapped exciton (STE). Rapid relaxation of these STE prevents recombination and dissociated atomic oxygen instead recombines with each other to form molecular oxygen pointed out using Raman microscopy. Some of it is dissolved in the condensed glass whilst the rest is trapped within nanovoids. A chemical recombination can only occur at 1200 ◦C for many hours. This explains the thermal stability of such a nanostructure. Precise laser translation and control of these birefringent nanoporous structures allows arbitrarily tuning and positioning within the glass, an important tool for controlling optical properties for photonic applications, catalysts, molecular sieves, composites and more.
Article
We demonstrate separate readouts of three-dimensional memory by (i) transmission imaging using a conventional optical microscope and (ii) photoluminescence (PL) of the bits created by inducing optical damage within the vitreous silica. Recording was done by tightly focused (objective ×100, numerical aperture 1.3) single shot irradiation of 120 fs duration pulses at a 400 nm wavelength. For the readout, a broadband of PL at 470–600 nm was excited by 400 nm, 120 fs irradiation with pulse energy smaller by a factor of 106 compared with that for the recording. We found an erasing of the PL after 400 °C annealing, while the readability of the bits by the transmission was sustained. This shows the potential for two-bit information recording per single bit by means of separate readout procedures. © 1999 American Institute of Physics.
Article
Three-dimensional, permanent anisotropic modifications in glass containing spherical Ag nanoparticles are demonstrated using multicolor fs laser irradiation. The method can produce dichroism by deformation of nanoparticles to oblong shapes oriented parallel to the laser polarization. Using samples with a vertical gradient of the fill factor of Ag nanoparticles in the glass substrate and an accordingly inhomogeneous broadening of the surface plasmon band, modifications in various depths can be made using different excitation wavelengths. The induced modifications are reversible: heating to ≈600C restores the spherical shape of Ag nanoparticles. This technique could be used in manufacturing of different, 3D, polarization and wavelength selective micro-devices such as polarizers, filters, gratings, display and rewriting optical 3D data storage devices.
Article
In this letter we report the different response to temperature displayed by isotropic femtosecond written structures (type I_fs), and anisotropic ones (type II_fs), which are characterized by the presence of a self-assembled subwavelength periodic structure within the irradiated volume. We observe that the anisotropic structures display an extraordinary annealing behavior, namely, their photoinduced change in refractive index increases with the annealing temperature. We explain our experimental results with a theoretical model.