Optical Information Recording Research Articles

Spatially Resolved Organic Whispering-Gallery-Mode Hetero-Microrings for High-Security Photonic Barcodes.

Whispering-gallery-mode (WGM) microcavities featuring distinguishable sharp peaks in a broadband exhibit enormous advantages in the field of miniaturized photonic barcodes. However, such kind of barcodes developed hitherto are primarily based on microcavities wherein multiple gain medias were blended into a single matrix, thus resulting in the limited and indistinguishable coding elements. Here, a surface tension assisted heterogeneous assembly strategy is proposed to construct the spatially resolved WGM hetero-microrings with multiple spatial colors along its circular direction. Through precisely regulating the charge-transfer (CT) strength, full-color microrings covering the entire visible range were effectively acquired, which exhibit a series of sharp and recognizable peaks and allow for the effective construction of high-quality photonic barcodes. Notably, the spatially resolved WGM hetero-microrings with multiple coding elements were finally acquired through heterogeneous nucleation and growth controlled by the directional diffusion between the hetero-emulsion droplets, thus remarkably promoting the security strength and coding capacity of the barcodes. The results would be useful to fabricate new types of organic hierarchical hybrid WGM heterostructures for optical information recording and security labels.

Spatially Resolved Organic Whispering‐Gallery‐Mode Hetero‐Microrings for High‐Security Photonic Barcodes

AbstractWhispering‐gallery‐mode (WGM) microcavities featuring distinguishable sharp peaks in a broadband exhibit enormous advantages in the field of miniaturized photonic barcodes. However, such kind of barcodes developed hitherto are primarily based on microcavities wherein multiple gain medias were blended into a single matrix, thus resulting in the limited and indistinguishable coding elements. Here, a surface tension assisted heterogeneous assembly strategy is proposed to construct the spatially resolved WGM hetero‐microrings with multiple spatial colors along its circular direction. Through precisely regulating the charge‐transfer (CT) strength, full‐color microrings covering the entire visible range were effectively acquired, which exhibit a series of sharp and recognizable peaks and allow for the effective construction of high‐quality photonic barcodes. Notably, the spatially resolved WGM hetero‐microrings with multiple coding elements were finally acquired through heterogeneous nucleation and growth controlled by the directional diffusion between the hetero‐emulsion droplets, thus remarkably promoting the security strength and coding capacity of the barcodes. The results would be useful to fabricate new types of organic hierarchical hybrid WGM heterostructures for optical information recording and security labels.

Study of Optical Information Recording Mechanism Based on Localized Surface Plasmon Resonance with Au Nanoparticles Array Deposited Media and Ridge-Type Nanoaperture

To verify the possibility of multiple localized surface plasmon resonance based optical recording mechanism, the present study has demonstrated that an Au nanoparticles array deposited with media combined with a ridge-type nanoaperture can amplify the |E|2 intensity of the incident optical light transmitted into the media under specific conditions. Using a numerical Finite-Difference Time-Domain method, we found that the optical intensity amplification first occurred in the near-field region while penetrating the ridge-type nanoaperture, then the second optical amplification phenomenon was induced between the metal nanoparticles, and eventually, the excitation effect was transferred to the inside of the media. In a system consisting of a Gold (Au) NPs deposited media and nanoaperture, various parameters to increase the |E|2 intensity in the near-field region were studied. For an Au nanoparticle size (Cube) = 5 nm × 5 nm × 5 nm, an inter-particle space = 10 nm, and a gap (between nanoaperture and media) = 5 nm, the |E|2 intensity of a ridge-type nanoaperture with an Au nanoparticles array was found to be ~47% higher than the |E|2 intensity of a ridge-type nanoaperture without an Au nanoparticles array.

7-Dialkylamino-3-[1,5-diaryl(3-pyrazolinyl)]coumarins: two-photon absorption in solution and in polymer film

Cross section of the two-photon absorption in 7-dialkylamino-3-(3-pyrazolinyl)coumarins in acetone and polymethylmethacrylate films has been found to be dependent on the substrate and medium nature. 7-Dialkylamino-3-[1,5-diaryl(3-pyrazolinyl)]coumarins are shown to be effective in the photosensitive media with excitation at 1060 nm for optical recording of information.

Photolysis of 3-(1-acyl-5-aryl-3-pyrazolinyl)coumarins-Effective Fluorescence Decay.

Photophysical characteristics of new 3-(1-acyl-5-aryl-3-pyrazolinyl)coumarins have been measured. These coumarin derivatives are found to be effective fluorophores and show high values of quantum yields of fluorescence both in nonpolar and in polar solvents. The 3-(1-acyl-5-aryl-3-pyrazolinyl)coumarins turned to be photosensitive compounds and undergo photolysis under irradiation in the range of 310-465nm. Photolysis is suggested to include retro-cyclization and retro-condensation steps. The process is accompanied by a sharp drop of fluorescence that can be of interest for the creation of new media in optical recording of information.

Reversible multiplexing for optical information recording, erasing, and reading-out in photochromic BaMgSiO4:Bi3+ luminescence ceramics

Optical data storage technology has many advantages over the traditional solid-state and magnetic storage technology, such as low cost, multi-dimensional storage, and rewritable capability. Therefore, the optical data storage technology has been in increasing demand for optical storage media. Herein, the photochromic and photoluminescence properties of BaMgSiO4:Bi3+ ceramics were investigated. The BaMgSiO4:Bi3+ ceramics showed reversible photochromism from gray to pink upon alternating the 254 nm ultraviolet light and 532 nm laser irradiation. This is caused by the electron trapping and de-trapping in the oxygen vacancies of the BaMgSiO4:Bi3+ host. This reversible behavior of photochromism was applied to fabricate different patterns on the surface of the BaMgSiO4:Bi3+ ceramics, which exhibited the reversible dual-mode optical information recording and erasing abilities. The photoluminescence reversible modulation of the BaMgSiO4:Bi3+ ceramics was obtained through the photochromic phenomenon. This modification behavior of luminescence could be applied to read-out the recording information in the BaMgSiO4:Bi3+ ceramics. The coloration and bleaching of BaMgSiO4:Bi3+ ceramics were dependent on the time of light stimulation, which facilitated multiplexing encoding. This photoluminescence and photochromism multiplexing of the BaMgSiO4:Bi3+ ceramics enhanced the optical data storage capability.

Structural modification of transparent materials with band gap by laser radiation at the absorption edge.

The problem of control over the process of structural modification of transparent materials by laser radiation is currently of great practical interest. This work proposes a novel method of controllable modification of a material structure, using laser pulses with wavelength at the material fundamental absorption edge. The method is based on the effect of thermal shift of the semiconductor absorption edge. The structure is modified by local heating of the material with laser pulses focused inside a transparent semiconductor. The laser heating process is investigated numerically and experimentally in order to determine the conditions under which the preset increase in temperature occurs in the local material area. As clarified, the heating is a threshold process and can be of two spatial structures: spot-like and line-like. The proposed method provides temperature changes in a large range, and therefore can be used for different structural modifications. It has multiple applications in practical tasks such as the optical recording of information, the formation of various photonic or other microstructures with complicated topology inside transparent materials, and the dividing of semiconductor wafers into chips.

Laser-stimulated birefringence of Ga2O3-La2S2.95Se0.05 glasses for optical recording of information

Abstract We show an opportunity to change the birefringence of Ga2O3 – La2S2.95Se0.05 glasses doped by Er3+ and La3+ ions at λ = 1150 nm wavelength of cw He-Ne laser under illumination of the femtosecond laser. The variation of the refractive indices was found during illumination by 180 fs laser with frequency about 65 MHz (at wavelength λ = 1045 nm). The laser-stimulated birefringence has been explored versus temperature. The observed laser induced and temperature dependences of the birefringence confirm a huge contribution of anharmonic phonon subsystems which is typical for chalcogenide glasses. Due to an occurrence of local space charge density asymmetry, the efficiency of birefringence is enhanced. The anisotropy effect exists only during the illumination and is diminished during 10…12 s after switching off of the photo-inducing laser treatment. There is observed also a correlation between the occurred grating patterns and the values of the birefringence.

Reversible LED controlled optical activity of a cholesteric liquid crystal layer

A thin layer of the photosensitive cholesteric liquid crystal possessing a high value of the optical activity is studied. Reversible change in the optical activity controlled by two light emission diodes (LEDs) with different emission wavelengths is applied for information recording. The behavior of this structure under exposure to UV and blue light is investigated. A smooth decrease in optical activity caused by the UV light resulting in a change in the color of the structure between crossed polarizers is obtained. The reverse process occurs under exposure to the blue light. On the basis of the obtained results, two methods of optical information recording in such a layer have been demonstrated.

СИНТЕЗ ТА ФОТОВОЛЬТАЇЧНІ ВЛАСТИВОСТІ СИМЕТРИЧНИХ БІС-АЗОМЕТИНІВ З АКЦЕПТОРНИМИ ЗАМІСНИКАМИ У 4,4'-ПОЛОЖЕННІ

Two new symmetric azomethine dyes capable of photoinduced isomerization were synthesized by condensing symmetric bis-aldehyde (obtained by the reaction of epichlorohydrin with 4-oxybenzaldehyde) with 4-nitroaniline and 4-chloroaniline, respectively. The yield of the target products decreases with the transition from nitro-substituted azomethine to chlorine-substituted. This is due to the greater basicity of the starting amines with nitro-substitution when increasing the acceptor force of the substituent complicates the course of the reaction. Azomethines are characterized by absorption with a maximum at 400–410 nm, which makes them sensitive to radiation with a blue component of the spectrum. The photoelectric properties of azomethines upon irradiation were investigated by the method of measuring the surface potential with the help of a Kelvin dynamic probe. The maximum value of the electric potential of the photosensitive films free surface during irradiation with white LED at I = 60 W/m2 is about 270 mV in the case of azomethine with a nitro group in the 4,4' position and about 125 mV in the case of azomethine with chlorine as a substituent. That is, the magnitude of the electric potential of the free surface decreases approximately twice during the transition from nitro substituent to chlorine. This may be explained by the fact that the photoinduced changes in azomethine with a higher acceptor substituent flow more quickly and with greater efficiency. But at the same time, the reverse changes when turning off the light are just as fast. For chlorine substituted azomethine samples, the reverse process proceeds rather slowly, which may indicate greater stability over time of the photochemically modified form in case of chlorine substitution compared to the nitro-substituted analogue. Thus, the synthesized azomethines can be used in the development of new photovoltaic media and recording media for optical information recording.

Cr3+-doped Mg4Ga4Ge3O16 near-infrared phosphor membrane for optical information storage and recording

A new near-infrared phosphor Mg4Ga4Ge3O16: Cr3+ with multi-photo-functionalities has been developed. Such phosphors can act as luminescent down-shifting materials converting UV and visible photons into NIR light (600–850 nm). UV irradiation induced strong NIR long persistent luminescence (LPL) can persist for more than 10 h. With the prolonged decay time, the extinguished NIR LPL can be rejuvenated by external photo stimulus including not only 980 nm light but also visible light. Such NIR photostimulated persistent luminescence (PSPL) presents separated write-in and read-out wavelength ranges. Meanwhile, photochromism (PC), that the material surface undergoes reversible change between white/pale green and ronbrown when triggered alternatively by UV and visible irradiation/heating, was also observed. Several recycle measurements demonstrate the robust fatigue resistance of PC property. Owning to the multi-photo-functionalities of Mg4Ga4Ge3O16: Cr3+, the fabrication of flexible phosphor membranes endows their application for optical information storage and repeatable optical recording. The electron motion in traps was studied by thermoluminescence (TL) and the color center formation was verified with electron spin resonance (ESR) spectra, based on which an energy level diagram was proposed for the illustration of the multifunctional mechanism. The revealing of multi-photo-functional mechanism and fabrication of flexible phosphor membranes may promote the development of a universal design principle for further study.

Highly sensitive switching of solid-state luminescence by controlling intersystem crossing

The development of intelligent materials, in particular those showing the highly sensitive mechanoresponsive luminescence (MRL), is desirable but challenging. Here we report a design strategy for constructing high performance On–Off MRL materials by introducing nitrophenyl groups to molecules with aggregation-induced emission (AIE) characteristic. The on–off methodology employed is based on the control of the intersystem crossing (ISC) process. Experimental and theoretical investigations reveal that the nitrophenyl group effectively opens the nonradiative ISC channel to impart the high sensitivity and contrast On–Off behavior. On the other hand, the twisted AIE luminogen core endows enhanced reversibility and reduces the pressure required for the luminescence switching. Thin films can be readily fabricated from the designed materials to allow versatile applications in optical information recording and haptic sensing. The proposed design strategy thus provides a big step to expand the scope of the unique On–Off MRL family.

Photothermoplastic recording media and its application in the holographic method of determination of the refractive index of liquid objects.

The photothermoplastic medium based on the films of photosensitive polymeric composites with semiconductor properties is developed for application in optical information recording and storage, in holographic interferometry, as well as for medical purposes. This medium was used in the modified holographic device for determination of changes of the refractive index of homogeneous and inhomogeneous liquid objects. The technique and holographic equipment were modified by employing the specially developed and produced transparent cuvette of special shape and the phase shifting interferometry method. Experimentally demonstrated precision of the measurements is not less than 10-5.

Effect of nanosecond UV laser irradiation on luminescence and absorption in silver- and copper-containing phosphate glasses

Experimental evidence is presented that nanosecond UV laser irradiation of silver- and copper-containing barium phosphate glasses leads to luminescence quenching in the visible range. Subsequent heat treatment induces an absorption in the range 350 – 500 nm. These effects are due to the ionisation and fragmentation of subnanometre molecular clusters by laser radiation and subsequent (heat treatment-induced) formation of nanoparticles possessing plasmon resonance. Our numerical modelling results demonstrate the feasibility of producing stable AgnCum hybrid molecular clusters in glass. Local modification of the optical properties of glass by laser light can be used for optical information recording.

Effect of electron beam irradiation dose on luminescence and optical absorption of LiF crystals

Abstract It is shown experimentally that local electron irradiation of LiF crystals by focused electron beam with relatively low electrons energy ( E = 50 keV) and doses of Q = 10–100 mC/cm 2 results in the formation of Li nanoparticles and luminescent centers in near-surface layer less than 30 μm thick. The formation of spherical Li nanoparticles is confirmed by computer simulation in dipole quasistatic approximation. When electron irradiation dose increases from 10 mC/cm 2 up to 35 mC/cm 2 the amplitude of plasmon absorption band of Li nanoparticles increases by 6 times and luminescence intensity increases by 30–40 times. Local Li nanoparticles and luminescent centers formation in LiF crystals by focused electron beam may be promising in integrated optics for fabrication of non-linear optical elements, elements with metamaterial properties, submicrometer two-color light sources and for multilevel optical information recording.

Photoinduced formation of the laser dye coumarin 6 from its dihydro derivatives

The dihydro form of the laser dye Coumarin 6 and its acylated derivatives undergo photoinduced transformations with Coumarin 6 formation. The reactions go easily both in organic solvents and in polymer films with a high increase of fluorescence. Irreversibility of the reaction provides potential use of the new photosensitive media for optical information recording and sensing technologies.

Formation of metal nanoparticles in MgF2, CaF2 and BaF2 crystals under the electron beam irradiation

It is shown experimentally that electron beam action with electrons energies of 50 and 70keV on MgF2, CaF2 and BaF2 crystals results in local formation in the crystal near-surface layer of Mg, Ca or Ba nanoparticles which possess plasmon resonance. In the case of MgF2 spheroidal nanoparticles are formed, in the cases of CaF2 and BaF2 – spherical. The formation of metal nanoparticles is confirmed by computer simulation in dipole quasistatic approximation. The dependence of absorption via electron irradiation dose is non-linear. It is caused by the increase of nanoparticles concentration and by the increase of nanoparticles sizes during irradiation. In the irradiated zones of MgF2 crystals, for irradiation doses less than 80mC/cm2, the intense luminescence in a visible range appears. The practical application of fabricated composite materials for multilevel optical information recording is discussed.

Multilevel optical information recording in silver-containing photosensitive glasses by UV laser pulses

It is experimentally shown that silver-containing silicate photosensitive glasses can be used for multilevel optical information recording using UV nanosecond laser pulses. Information can be recorded by the creation of luminescent centers, which are neutral silver molecular clusters, or silver nanoparticles with plasmon resonance using additional thermal treatment. It is shown that silver nanoparticles formed in glass have spheroidal shapes and have dielectric shells. Multilevel optical information recording can be performed by modulation of luminescence or absorption intensity varying UV laser irradiation dose. The effect of dopants (Ce, Sb, and Cl) on the recording process is shown. The described methods allow to record optical information in octal and hexadecimal number systems.

Multicolour laser recording of optical information in silicate glasses with europium, silver and cerium ions

We have shown experimentally that the effect of cw UV radiation and pulsed UV radiation from a nanosecond laser as well as thermal treatment of glasses with europium, silver and cerium ions (photosensitizer) allow the local formation of the areas in glass, having different luminescence colour or the areas of different colouration. These effects are caused by a change in the charge state of molecular clusters and the formation of silver nanoparticles possessing plasmon resonance in glass. This allows recording of multicolour optical information by means of a focused beam from a UV laser, both near the glass surface and within its volume. We have revealed the influence of chlorine on the formation and properties of silver nanoparticles in glass in the course of thermal treatment following the laser impact.

Laser induced birefringence in La–Ga–S–O–Gd glass polymer nanocomposites

In this work, we demonstrate a possibility to use La–Ga–S–O–Gd glass polymer nanocomposites as effective materials for photo-induced birefringence. Here we chose PVA as a photopolymer matrix. The photo-induced effects were studied using 8 ns Nd: YAG laser generating bicolor coherent light beams with wavelengths 1064, and 532 nm. The detection of the photo-induced birefringence was carried out using cw He–Ne laser at 1150 nm. The optimal concentration of the nanoglass favoring maximal changes of refractive indices is established. The photo-induced laser power density was changed up to 0.9 GW/cm2. The photo-induced beams were incident at angles varying within the 32° and 52° with respect to the nanocomposite planes. The polarizations of the beams did not play principal role. We discovered an appearance of maximal birefringence equal to about 0.078. The effect is strongly dependent on the nanoparticle sizes and is completely reversible after switching off the laser treatment within several milliseconds. Such features are useful for the recording of optical information and production of gratings with desirable periods.