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Athermally photoreduced graphene oxides for three-dimensional holographic images
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The emerging graphene-based material, an atomic layer of aromatic carbon atoms with exceptional electronic and optical properties, has offered unprecedented prospects for developing flat two-dimensional displaying systems. Here, we show that reduced graphene oxide enabled write-once holograms for wide-angle and full-colour three-dimensional images. This is achieved through the discovery of subwavelength-scale multilevel optical index modulation of athermally reduced graphene oxides by a single femtosecond pulsed beam. This new feature allows for static three-dimensional holographic images with a wide viewing angle up to 52 degrees. In addition, the spectrally flat optical index modulation in reduced graphene oxides enables wavelength-multiplexed holograms for full-colour images. The large and polarization-insensitive phase modulation over π in reduced graphene oxide composites enables to restore vectorial wavefronts of polarization discernible images through the vectorial diffraction of a reconstruction beam. Therefore, our technique can be leveraged to achieve compact and versatile holographic components for controlling light.
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... [208] Li et al. have developed multimode optical recording and the generation of full-color 3D images in GO-dispersed polymers based on hologram-encoded refractive-index modulation by a focused fs-laser beam, as shown in Figure 8d. [206,207] This method utilizes fs-laser two-photon reduction, which induces a substantial refractive-index modulation ranging from 10 −2 to 10 −1 . Simultaneously, there was a decrease in fluorescence intensity, enhancing both information security and storage capacity, allowing to reach up to 290 GB per disc. ...
... Adapted under the terms of the CC-BY license. [207] Copyright 2015, Springer Nature. ...
Ultrafast laser processing has emerged as a versatile technique for modifying materials and introducing novel functionalities. Over the past decade, this method has demonstrated remarkable advantages in the manipulation of 2D layered materials, including synthesis, structuring, functionalization, and local patterning. Unlike continuous‐wave and long‐pulsed optical methods, ultrafast lasers offer a solution for thermal heating issues. Nonlinear interactions between ultrafast laser pulses and the atomic lattice of 2D materials substantially influence their chemical and physical properties. This paper highlights the transformative role of ultrafast laser pulses in maskless green technology, enabling subtractive, and additive processes that unveil ways for advanced devices. Utilizing the synergetic effect between the energy states within the atomic layers and ultrafast laser irradiation, it is feasible to achieve unprecedented resolutions down to several nanometers. Recent advancements are discussed in functionalization, doping, atomic reconstruction, phase transformation, and 2D and 3D micro‐ and nanopatterning. A forward‐looking perspective on a wide array of applications of 2D materials, along with device fabrication featuring novel physical and chemical properties through direct ultrafast laser writing, is also provided.
... In addition, k also changes from ~0.0097 to ~0.3557 -an increase of over 36-fold. The broad variation ranges for both n, k are critical for engineering and manipulation of the phase and amplitude response of many GO devices, such as optical lenses and holographic displays [31,42]. ...
Efficient heat management and control in optical devices, facilitated by advanced thermo-optic materials, is critical for many applications such as photovoltaics, thermal emitters, mode-locked lasers, and optical switches. Here, we investigate the thermo-optic properties of 2D graphene oxide (GO) films by precisely integrating them onto microring resonators (MRRs) with control over the film thicknesses and lengths. We characterize the refractive index, extinction coefficient, thermo-optic coefficient, and thermal conductivity of for the GO films with different layer numbers and degrees of reduction, including reversible reduction and enhanced optical bistability induced by photo-thermal effects. Experimental results show that the thermo-optic properties of 2D GO films vary widely with the degree of reduction, with significant polarization anisotropy, enabling efficient polarization sensitive devices. The versatile thermo-optic response of 2D GO substantially expands the scope of functionalities and devices that can be engineered, making it promising for a diverse range of thermo-optic applications.
Graphene-based nanomaterials (GBNMs) are versatile due to their large surface area, great mechanical, chemical strength, and excellent electrical properties. The versatility of graphene has increased its applicability therefore several synthesis methods to produce high quality graphene simpler, faster, and cost-effectively are actively explored. The conventional synthesis methods however employ toxic chemicals, high temperatures, and lengthy synthesis times. On the other hand, the gamma (γ) irradiation approach is facile, occurs under ambient conditions and produces graphene composites of high purity. Noteworthy, this technique enables the user to control the synthesis time and total dose, hence minimising the aggregation of the nanomaterial, the main drawback hindering the commercial production of GBNMs. γ-radiolysis synthesized GBNMs exhibit superior optical and electrical properties and hence improved supercapacitance, catalytic, and sensing abilities. Although other reviews addressed the γ-ray synthesis of metallic nanomaterials, polymers, as well as usage of a variety of radiation techniques to fabricate graphene composites, this review focuses solely on the synthesis and modifications of GBNMs via the γ-synthesis technique. Properties of graphene and conventional methods used to reduce graphene oxide (GO) to graphene as well as their shortcomings are highlighted. This is followed by detailing the γ-radiation synthesis technique, its advantages over the conventional methods and the principles thereof. Effects of γ-irradiation and the conditions required for the structural modification of graphene to obtain different graphene composites are detailed. The influence of operational parameters on the fabricated graphene-based composites are discussed followed by summaries of recent developments in the applicability of γ-irradiated GBNMs in catalysis, energy, sensing, and biomedical fields. In addition, this paper presents insights into the challenges posed and provides future research directions and prospects in the field of γ-irradiated GBNMs.
3D holography capable of reproducing all necessary visual cues is considered the most promising route to present photorealistic 3D images. Three elements involving computer‐generated hologram (CGH) algorithms, hologram carriers, and optical systems are prerequisites to create high‐quality holographic displays for photorealistic 3D holography. Especially, the hologram carrier directly determines the holographic display capability and the design of high space‐bandwidth‐product (SBP) optical systems. Currently, two categories of hologram carriers, i.e., spatial light modulators (SLM) and metasurfaces, are regarded as promising candidates for photorealistic 3D holography. However, most of their SBP capability still cannot match the amount of information generated by the CGH. To address this issue, tremendous efforts are made to improve the capability of hologram carriers. Here, the main hologram carriers (from SLM to metasurfaces) that are widely utilized in holography systems to achieve high SBP capability (high resolution, wide viewing angles, and large sizes) are reviewed. The purpose of this review is to identify the key challenges and future directions of SLM‐based and metasurface‐based holography for photorealistic 3D holographic images.
The degree of freedom of orbital angular momentum of light has been used as a new information carrier in optical holographic information processing technology. However, current research on orbital angular momentum holography mainly focuses on two-dimensional orbital angular momentum holography, where the reconstructed two-dimensional holographic image is located in a certain plane in three-dimensional space. How to further implement three-dimensional spatial orbital angular momentum holographic technology and use it to increase the information capacity of holographic communication is still a blank. Here, we implement three-dimensional spatial orbital angular momentum holographic technology based on the degrees of freedom of orbital angular momentum and the positional degrees of freedom of reconstructed two-dimensional images in three-dimensional space. In other words, in the three-dimensional spatial orbital angular momentum holography, the acquisition of the target object image requires not only the correct orbital angular momentum state used for decoding, but also the correct spatial position where the object's image is detected. In addition, we further investigate the three-dimensional spatial orbit angular momentum holographic multiplexing technology and points out that this multiplexing technology can be used for information encryption. Compared with traditional two-dimensional orbital angular momentum holography, three-dimensional spatial orbital angular momentum holography uses an additional degree of freedom. Therefore, the encryption scheme based on three-dimensional spatial orbital angular momentum holographic technology can further improve the security level of information. Our simulation results and experimental results have verified the feasibility of three-dimensional spatial orbit angular momentum holographic technology and three-dimensional spatial orbit angular momentum holographic encryption technology.
Vectorial holography through a strongly scattering medium can facilitate various applications in optics and photonics. However, the realization of vectorial holography with arbitrary distribution of optical intensity is still limited because of experimental noise during the calibration of vectorial transmission matrix (TM) and reconstruction noise during the retrieval of input wavefront for a given holographic target. Herein, we propose and experimentally demonstrate the vectorial holography with arbitrary distribution of optical intensity over a multimode fiber (MMF) using the Tikhonov regularization. By optimizing the noise factor, the performance of vectorial holography over an MMF is improved compared with the conjugate transpose and inverse TM methods. Our results might shed new light on the optical communication and detection mediated by MMFs.
We report on the direct experimental determination of the temperature increment caused by laser irradiation in a optical recording media constituted by a polymeric film in which gold nanorods have been incorporated. The incorporation of CdSe quantum dots in the recording media allowed for single beam thermal reading of the on-focus temperature from a simple analysis of the two-photon excited fluorescence of quantum dots. Experimental results have been compared with numerical simulations revealing an excellent agreement and opening a promising avenue for further understanding and optimization of optical writing processes and media. (C) 2014 AIP Publishing LLC.
Graphene has been identified as an emerging horizon for a nanoscale photonic platform because the Fermi level of intrinsic graphene can be engineered to support surface plasmons (SPs). The current solid back electrical gating and chemical doping methods cannot facilitate the demonstration of graphene SPs at the near-infrared (NIR) window because of the limited shift of the Fermi level. Here, we present the evidence for the existence of graphene SPs on a tapered graphene-silicon waveguide tip at a NIR wavelength, employing a surface carrier transfer method with molybdenum trioxides. The coupling between the graphene surface plasmons and the guiding mode in silicon waveguides allows for the observation of the concentrated field of the SPs in the tip by near-field scanning optical microscopy. Thus the hot spot from the concentrated SPs in the graphene layer can be used as a key experimental signature of graphene SPs. The NIR graphene SPs opens a new perspective for optical communications, optical sensing and imaging, and optical data storage with extreme spatial confinement, broad bandwidth and high tunability.
Benefitting from the flexibility in engineering their optical response, metamaterials have been used to achieve control over the propagation of light to an unprecedented level, leading to highly unconventional and versatile optical functionalities compared with their natural counterparts. Recently, the emerging field of metasurfaces, which consist of a monolayer of photonic artificial atoms, has offered attractive functionalities for shaping wave fronts of light by introducing an abrupt interfacial phase discontinuity. Here we realize three-dimensional holography by using metasurfaces made of subwavelength metallic nanorods with spatially varying orientations. The phase discontinuity takes place when the helicity of incident circularly polarized light is reversed. As the phase can be continuously controlled in each subwavelength unit cell by the rod orientation, metasurfaces represent a new route towards high-resolution on-axis three-dimensional holograms with a wide field of view. In addition, the undesired effect of multiple diffraction orders usually accompanying holography is eliminated.
Holography, a revolutionary 3D imaging technique, has been developed for storing and recovering the amplitude and phase of light scattered by objects. Later, single-beam computer-generated phase holography was proposed for restoring the wavefront from a given incidence. However, because the phase modulation depends on the light propagation inside the material, the thickness of phase holograms usually remains comparable to the wavelength. Here we experimentally demonstrate ultra-thin metasurface holograms that operate in the visible range whose thickness is only 30 nm (approximately 1/23 of the operational wavelength). To our knowledge, this is the thinnest hologram that can provide both amplitude and phase modulation in the visible wavelength range, which generates high-resolution low-noise images. Using this technique, not only the phase, but potentially the amplitude of the incident wave can be efficiently controlled, expanding the route to new applications of ultra-thin and surface-confined photonic devices.
Although graphene films have a strong potential to replace indium tin oxide anodes in organic light-emitting diodes (OLEDs), to date, the luminous efficiency of OLEDs with graphene anodes has been limited by a lack of efficient methods to improve the low work function and reduce the sheet resistance of graphene films to the levels required for electrodes. Here, we fabricate flexible OLEDs by modifying the graphene anode to have a high work function and low sheet resistance, and thus achieve extremely high luminous efficiencies (37.2 lm W–1 in fluorescent OLEDs, 102.7 lm W–1 in phosphorescent OLEDs), which are significantly higher than those of optimized devices with an indium tin oxide anode (24.1 lm W–1 in fluorescent OLEDs, 85.6 lm W–1 in phosphorescent OLEDs). We also fabricate flexible white OLED lighting devices using the graphene anode. These results demonstrate the great potential of graphene anodes for use in a wide variety of high-performance flexible organic optoelectronics.
Holography, with its stunning 3-D realism and its expressive potential, in the 1970s and 1980s seemed poised to become the next step in the evolution of visual display. Yet apart from certain specialized niches, display holograms are perhaps more rarely encountered in everyday life than they were 20 or 30 years ago. But the recent resurgence of interest in 3-D video for entertainment applications has underlined the limitations of left/right stereoscopic imaging and created a desire for more natural 3-D imagery in which no glasses are required and all perceptual cues to depth are provided in a consistent fashion. Could holography—whose transition from darkroom to digital has taken some years longer than that of photography—capitalize on this opportunity? In this paper, I examine digital developments in holographic printing, holographic projection, and holographic television, and explore connections between holographic imaging and areas such as integral imaging and telepresence.
Digital recording and numerical reconstruction of holograms is a new method of laser metrology: two or more Fresnel holograms, which represent different loading states of the object, are generated directly on a CCD-target and stored electronically. In contrast to speckle interferometry, no lens or other imaging device is used. The reconstruction is done from the digitally stored holograms with numerical methods. For both states, the intensity as well as the phase of the object wave can be calculated in the reconstruction process. This makes it possible to calculate the interference phase directly from the holograms, without generating an interference pattern. In this paper, applications of digital holography in the field of nondestructive testing are presented. A thin-walled pressure vessel (satellite tank) is loaded by changing the internal pressure and the resulting deformation field is measured quantitatively. Defects in the wall become visible as local peaks in the global deformation field.