4.3. Manganese Oxide-Based Compounds 1291 4.3.1. MnO2-Type Compounds 1291 4.3.2. Ternary Lithiated LixMnOy Compounds 1293 4.4. Vanadium Pentoxide V2O5 1298 4.4.1. V2O5 Structure 1298 4.4.2. LixV2O5 Bulk Phases 1300 4.4.3. LixV2O5 Crystallized Thin Films 1303 4.5. Titanium Oxide-Based Compounds 1305 4.5.1. Lithium Titanate Li4Ti5O12 1306 4.5.2. TiO2 Anatase 1308 5. Phospho-olivine LiFePO4 Compound 1312 6. General Conclusion 1314 7. Acknowledgments 1315 8. References 1315

Raman Microspectrometry Applied to the Study of Electrode Materials for Lithium Batteries

LiCoO2: formation, structure, lithium and oxygen nonstoichiometry, electrochemical behaviour and transport properties

Single-photon detectors (SPDs) are the most sensitive instruments for light detection. In the near-infrared range, SPDs based on III–V compound semiconductor avalanche photodiodes have been extensively used during the past two decades for diverse applications due to their advantages in practicality including small size, low cost and easy operation. In the past decade, the rapid developments and increasing demands in quantum information science have served as key drivers to improve the device performance of single-photon avalanche diodes and to invent new avalanche quenching techniques. This Review aims to introduce the technology advances of InGaAs/InP single-photon detector systems in the telecom wavelengths and the relevant quantum communication applications, and particularly to highlight recent emerging techniques such as high-frequency gating at GHz rates and free-running operation using negative-feedback avalanche diodes. Future perspectives of both the devices and quenching techniques are summarized. Recent progress in single-photon detectors for quantum communication based on III–V compound semiconductor avalanche photodiodes is reviewed. Specifically, Jun Zhang and Jian-Wei Pan at the University of Science and Technology of China and their colleagues in the USA and Switzerland introduce technological advances for InGaAs/InP single-photon detector systems in the telecommunication band along with their associated applications in quantum communication. III–V single-photon avalanche diodes are the most practical tools available for detecting ultraweak near-infrared light. The scientists overview important parameters for evaluating the performance of detector systems based on single-photon avalanche diodes and describe the experimental characterization of these parameters. They also consider emerging techniques, including high-frequency gating at gigahertz rates and free-running operation using negative-feedback avalanche diodes. Finally, the future prospects of these devices are considered.

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Advances in InGaAs/InP single-photon detector systems for quantum communication

Electrode materials for lithium secondary batteries prepared by sol-gel methods

The aggressive consumption of fossil fuels has resulted in the uncontrolled release of greenhouse gases such as carbon dioxide and methane into the atmosphere, trapping heat and causing havoc to the environment. With this in mind, the development of sustainable energy is imperative. Renewable energy will fail to reach the anticipated impact unless more efficient way to store and use electricity is found. Therefore, high-performance energy-storage devices with high energy and power density are required for renewable energy sustainability and storage security. Electrochemical batteries have been long considered as one of the most qualified candidates for providing reliable energy storage. Taking into account the safety, power density, cost, longevity and efficiency, rechargeable lithium-ion batteries (LIBs) are the most successful electrochemical storage systems available. The extensive Lithium-ion batteries (LIBs) have become one of the most prevailing techniques for rechargeable batteries. Lithium transition metal oxides are prevalent cathode materials currently, but they face great challenges due to unsatisfactory energy density, chemical/electrochemical instability, and elemental scarcity concerns. Surface/subsurface is the interface where lithium ions cross between the electrolyte and the cathode materials. Its properties and complicated nature are unambiguously regarded as a crucial controlling factor for the overall performance. Tremendous efforts have been made in the exploration of surface modification methods with remarkable progress hitherto. The purpose of this work is to review these surface behaviors in order to understand their fundamental origins and provide a summary of various surface modification methods that can be used to address impeding issues. Finally, a rational method of surface modification is proposed for use in cathode materials.

Surface and Subsurface Reactions of Lithium Transition Metal Oxide Cathode Materials: An Overview of the Fundamental Origins and Remedying Approaches

Electrochemical and structural properties of HT-LiCoO2 and LT-LiCoO2 prepared by the citrate sol-gel method

A multi-wavelength optical transmitting module includes a housing, an optical output block, an optical transmitting block, and an optical multiplexer (MUX) block. The optical output block is coupled to a first coupling hole of the housing and to an optical signal connector, and includes a first lens. The optical transmitting block is coupled to a second coupling hole of the housing and to an electrical signal connector. The optical transmitting block includes a plurality of transmitting devices which respectively output light having different wavelengths and are arranged parallel to the optical output block, and a plurality of second lenses which correspond respectively to the transmitting devices. The optical multiplexer (MUX) block multiplexes optical signals of multiple wavelengths, which were output from the transmitting devices and passed through the second lenses, and transmits the multiplexed optical signals to the optical output block.

Multi-wavelength optical transmitting and receiving modules

We demonstrate a real-time 25-Gb/s PON prototype with ethernet-PON MAC/PHY, O-band transmitter, and cost-effective APD receivers. With applying parasitic inductance and capacitance reduction, the frequency response of 25-Gb/s APD ROSA with TO46-pacakge is improved to support high receiver sensitivity around −25 dBm at the BER of 10−3. The 30 dB power budget of 25 Gb/s downstream is achieved at the BER of 10−3. With long-term ethernet packet transmission, 25 Gigabit and 10 Gigabit ethernet traffics are successfully transmitted through the 20-km SMF over 14 hour’s observation window. Furthermore, QoS and bandwidth re-assignment function of the 25-Gb/s PON prototype are successfully demonstrated with respect to residential, business and mobile backhaul services in ONUs.

Real-time demonstration of QoS guaranteed 25-Gb/s PON prototype with Ethernet-PON MAC/PHY and cost-effective APD receivers for 100-Gb/s access networks.

We have developed a 4 × 25 Gb/s ROSA (receiver optical sub-assembly) module for 100G Ethernet optical transceiver. This ROSA module has very large alignment tolerance of more than ± 250 µm between the optical DMUX (demultiplexer) and four photodiodes, for the reason it has the advantage of being easily assembled. The large alignment tolerance can be attributed to the dimensional tolerant optical DMUX, which is composed of four thin film filters attached to a parallelogram-shaped optic block. Since it is important to define the fabrication specifications for the dimension of the optic block, we analyze dimensional tolerance for the optic block using three-dimensional simulation. This parallelogram-shaped optical DMUX permits length tolerance of ± 300 µm and angular tolerance of ± 0.1°. The fabricated optical DMUX is estimated to have the angular error of less than 0.09°.

Analysis of dimensional tolerance for an optical demultiplexer of a highly alignment tolerant 4 × 25 Gb/s ROSA module.

The after-pulsing effect is a common problem that needs to be overcome for high-speed single-photon detection based on gated-mode single-photon avalanche photodiodes (SPADs). This paper presents a simple and practical method for suppression of the after-pulsing probability using an auxiliary signal to discriminate quite weak avalanches. The detection efficiency and after-pulse probability of an InGaAs/InP SPAD are investigated with a 10 MHz gating for conventional and proposed methods, and a sharp decrease of after-pulse probability is demonstrated with the application of the proposed method. At a gating frequency of 100 MHz, a detection efficiency of 10.4% is achieved with an after-pulse probability of 5.6% without dead time.

Sae-Kyoung Kang

Papers

Electrochemical and structural properties of HT-LiCoO2 and LT-LiCoO2 prepared by the citrate sol-gel method

Multi-wavelength optical transmitting and receiving modules

Real-time demonstration of QoS guaranteed 25-Gb/s PON prototype with Ethernet-PON MAC/PHY and cost-effective APD receivers for 100-Gb/s access networks.

Analysis of dimensional tolerance for an optical demultiplexer of a highly alignment tolerant 4 × 25 Gb/s ROSA module.

Weak avalanche discrimination for gated-mode single-photon avalanche photodiodes.