Chengmingyue Li

Athermally photoreduced graphene oxides for three-dimensional holographic images

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.

Holographic kinetics for mixed volume gratings in gold nanoparticles doped photopolymer

A holographic kinetic model is proposed to quantitatively represent the dynamics of mixed volume gratings in a bulk gold nanoparticles (NPs) doped photopolymer. Due to the polymerization-driven multicomponent diffusion, the volume refractive index grating is induced by the periodic spatial distribution of photoproduct while the absorption grating is formed by the periodic spatial distribution of gold NPs. By simulating this model with the characterization of time varying absorption modulation, it is capable to describe the behavior of gold NPs in both the polymerization and the multicomponent diffusion process. The temporal evolution of refractive index modulation and absorption modulation can be extracted, respectively, from a diffraction efficiency curve by fitting the model. The established model could be an effective method for understanding the photophysical and photochemical mechanism of holographic nanocomposite.

Improvement of volume holographic performance by plasmon-induced holographic absorption grating

We report on the enhanced holographic performance by employing a strong volume holographic absorption grating induced by localized surface plasmon resonance effect in a bulk gold nanoparticles doped photopolymer. The contributions of plasmon-induced volume holographic absorption grating is characterized through the Kogelniks coupled wave model and demonstrated experimentally by using two-beam interference technology. At the 0.05 vol. % concentration of the gold nanoparticles in the bulk photopolymer, 101.8% increase in the diffraction efficiency and more than four times suppression of the first side lobe in angular selectivity have been achieved.

Exciton-plasmon coupling mediated photorefractivity in gold-nanoparticle- and quantum-dot-dispersed polymers

In this paper, we report on the enhanced photorefractivity induced by the exciton-plasmon coupling in type-II CdSe/CdTe quantum-dot (QD) and gold-nanoparticle (NP)-doped polymeric nanocomposites (NCs). The new NCs exhibit a nearly 110% increase in the refractive-index grating construction speed and a 100% enhancement in the two-beam coupling gain coefficient compared with those of QD-sensitized samples at moderate biases. These features are achieved by the exciton-plasmon coupling between QDs and Au NPs, which leads to not only an enhanced charge separation process but also a reduced recombination probability of free carriers during the charge transport.

Experimental realization of a multiplexed quantum memory with 225 individually accessible memory cells

To realize long-distance quantum communication and quantum network, it is required to have multiplexed quantum memory with many memory cells. Each memory cell needs to be individually addressable and independently accessible. Here we report an experiment that realizes a multiplexed DLCZ-type quantum memory with 225 individually accessible memory cells in a macroscopic atomic ensemble. As a key element for quantum repeaters, we demonstrate that entanglement with flying optical qubits can be stored into any neighboring memory cells and read out after a programmable time with high fidelity. Experimental realization of a multiplexed quantum memory with many individually accessible memory cells and programmable control of its addressing and readout makes an important step for its application in quantum information technology.

Hybrid polarization-angle multiplexing for volume holography in gold nanoparticle-doped photopolymer.

We report on volume holographic hybrid polarization-angle multiplexing in a gold nanoparticle-doped photopolymer. When doping the gold nanoparticles, the linear photoinduced birefringence of the phenanthrenequinone-doped poly (methyl methacrylate) (PQ/PMMA) photopolymer could be increased by nearly 38%. The data pages could be recorded with the orthogonal circular polarization multiplexing, and the reconstructed images have a symbol-error rate of 3.81% and 4.46% for left circular polarization and right circular polarization state, respectively. Two biological image sets multiplexed both with the angle interval of 0.1° and with orthogonal circular polarization are reconstructed separately and simultaneously.

Dynamic microscale temperature gradient in a gold nanorod solution measured by diffraction-limited nanothermometry

We quantify the dynamic microscale temperature gradient in a gold nanorod solution using quantum-dot-based microscopic fluorescence nanothermometry. By incorporating CdSe quantum dots into the solution as a nanothermometer, precise temperature mapping with diffraction-limited spatial resolution and sub-degree temperature resolution is achieved. The acquired data on heat generation and dissipation show an excellent agreement with theoretical simulations. This work reveals an effective approach for noninvasive temperature regulation with localized nanoheaters in microfluidic environment.

Polarized, phase-encoded and 2D angular multiplexed volume holographic correlator

The volume holographic correlator (VHC) is a highly parallel processor. For an angularly multiplexed VHC, the processing speed is limited by the ratio of the maximum angle range and the minimum angle interval of the reference beam. Limited by the angle scanning range of the reference beam, the pure angular multiplexing in the reference beam of the VHC can only establish thousands of parallel correlation channels, which is far from the high parallelism demand for real-time applications. In this paper, the maximum multiplexing number of the VHC system is increased. The polarized and phase-encoded multiplexing methods are introduced into the object beam, with the angular multiplexing method in the reference beam. The mutual orthogonality of the polarization multiplexing, phase-encoded multiplexing and angular multiplexing methods are verified with experiment. This shows that the number of parallel channels can be increased with the object beam both polarized and phase-encoded multiplexed and with the reference beam still angularly multiplexed in the VHC. The optical setup is established and the feasibility of the proposed hybrid multiplexing method is experimentally verified. The two multiplexing methods extended to the object beam make it possible to establish more parallel correlation channels in the VHC. Although millions of parallel correlation channels can be realized with the proposed multiplexing method in theory, the paper presents some principal experimental results.

Plasmon-active mixed gratings in volume holographic polymeric nanocomposites

The plasmon-active mixed gratings were demonstrated and characterized in a volume holographic polymer nanocomposite. The counter-diffusion physical mechanism between the polymeric component and nanoparticles related to the holographic mixed gratings was analyzed. By dispersing gold nanoparticles in the bulk holographic polymer, a plasmon-active strong absorption grating was introduced into the polymeric refractive-index gratings. The nanocomposites with several volume ratios of doped gold nanoparticles were fabricated. Holographic angular selectivity curves of saturated diffraction efficiencies were measured for the prepared samples. Significantly suppression of side lobes with the improved diffraction efficiency was observed in the gold nanoparticles doped photopolymer. It is found that the noticeable holographic-apodization phenomenon is caused by the plasmon-active strong absorption grating.

Crosstalk analysis of multilayer collinear volume holographic data storage

An optical model to describe the reconstructed image of the collinear holographic data storage system is presented. The 2-D shape of the recording spot in the medium is simulated. The system structure parameters that influence the signal-to-noise ratio (SNR) of the reconstructed image are investigated in order to choose proper optical components to improve data storage density of the system. The role of the random binary phase mask (RBPM) utilized in the multilayer collinear holographic system is investigated. It is proved that the inter-layer crosstalk can be effectively suppressed by using different RBPMs. Different layers of data pages can be recorded with the SNR increased by a factor of six at least and the shift selectivity along z-axis can also be improved significantly.