Photonic Transmitter Research Articles

Electrospun hexagonal boron nitride/CNT reinforced nanocomposite fiber mats for cosmic radiation shielding

AbstractA novel methodology is introduced to asses the efficacy of cosmic radiation shielding through the fabrication of electrospun nanocomposite fiber mats reinforced with hexagonal boron nitride (h‐BN) and carbon nanotubes (CNTs). These mats were fabricated using various h‐BN particles synthesized with 1 M boric acid and four distinct 1 M nitrogen sources to produce polyethylene oxide (PEO) nanofibers via the electrospinning method at 15 kV, a 43.0 μL/min pumping rate, and a 20 cm distance with a maximum thickness of 10 μm. High neutron shielding capability nanocomposite fibers denoted BN‐F4 (spun with h‐BN [melamine]/CNT powders in a 5 wt% PEO solution) and BN‐F5 (spun with h‐BN [urea]/CNT powders in a 5 wt% PEO solution) were produced. By calculating the theoretical photon transmittance and evaluating the neutron shielding efficiency with an Am‐Be neutron source and a BF3 neutron detector, the cosmic radiation shielding capability of nanocomposite mats was discussed. BN‐F4 and BN‐F5 exhibited neutron shielding properties of 7.124% and 6.37% for 3.82 and 1.87 g/mL, respectively. This research establishes a new benchmark in the fabrication of flexible, ultrathin, and lightweight radiation shielding materials and enhances the practicality of nanocomposites reinforced with h‐BN and CNTs by incorporating synthesizing and characterizing steps.Highlights In the study, hexagonal boron nitride production was carried out with four different nitrogen sources and which one showed better structural and morphological properties was supported by analysis. Additionally, an optimization study of nanofibers by electrospinning by adding CNT and h‐BN particles with PEO polymer is included. It is thought that the production of h‐BN and nanofiber work as a radiation shielding feature for use in space studies will be innovative and contribute to the deficiency in the literature.

An intelligent threshold selection method to improve orbital angular momentum-encoded quantum key distribution under turbulence

High-dimensional quantum key distribution (HD-QKD) encoded by orbital angular momentum (OAM) presents significant advantages in terms of information capacity. However, perturbations caused by free-space atmospheric turbulence decrease the performance of the system by introducing random fluctuations in the transmittance of OAM photons. Currently, the theoretical performance analysis of OAM-encoded QKD systems exists a gap when concerning the statistical distribution under the free-space link. In this article, we analyzed the security of QKD systems by combining probability distribution of transmission coefficient (PDTC) of OAM with decoy-state BB84 method. To address the problem that the invalid key rate is calculated in the part transmittance interval of the post-processing process, an intelligent threshold method based on neural network is proposed to improve OAM-encoded QKD, which aims to conserve computing resources and enhance system efficiency. Our findings reveal that the ratio of root mean square (RMS) OAM-beam radius to Fried constant plays a crucial role in ensuring secure key generation. Meanwhile, the training error of neural network is at the magnitude around 10−3, indicating the ability to predict optimization parameters quickly and accurately. Our work contributes to the advancement of parameter optimization and prediction for free-space OAM-encoded HD-QKD systems. Furthermore, it provides valuable theoretical insights to support the development of free-space experimental setups.

Low-Light Sparse Polarization Demosaicing Network (LLSPD-Net): Polarization Image Demosaicing Based on Stokes Vector Completion in Low-Light Environment.

Polarization imaging has achieved a wide range of applications in military and civilian fields such as camouflage detection and autonomous driving. However, when the imaging environment involves a low-light condition, the number of photons is low and the photon transmittance of the conventional Division-of-Focal-Plane (DoFP) structure is small. Therefore, the traditional demosaicing methods are often used to deal with the serious noise and distortion generated by polarization demosaicing in low-light environment. Based on the aforementioned issues, this paper proposes a model called Low-Light Sparse Polarization Demosaicing Network (LLSPD-Net) for simulating a sparse polarization sensor acquisition of polarization images in low-light environments. The model consists of two parts: an intensity image enhancement network and a Stokes vector complementation network. In this work, the intensity image enhancement network is used to enhance low-light images and obtain high-quality RGB images, while the Stokes vector is used to complement the network. We discard the traditional idea of polarization intensity image interpolation and instead design a polarization demosaicing method with Stokes vector complementation. By using the enhanced intensity image as a guide, the completion of the Stokes vector is achieved. In addition, to train our network, we collected a dataset of paired color polarization images that includes both low-light and regular-light conditions. A comparison with state-of-the-art methods on both self-constructed and publicly available datasets reveals that our model outperforms traditional low-light image enhancement demosaicing methods in both qualitative and quantitative experiments.

Surface engineering of Sio2-Zro2 films for augmenting power conversion efficiency performance of silicon solar cells

Improving solar cell performance hinges significantly on the application of anti-reflective surface coatings. A wide variety of coating techniques, including blade coating, spin coating, dip coating, and others were employed. The present research investigation employed various coating materials, namely SiO2 (Silicon dioxide), ZrO2 (Zirconium dioxide), and SiO2–ZrO2 blends, to apply a protective layer onto polycrystalline silicon solar cells using the sputter coating process. The efficiency of these solar cells with multilayer coating was assessed through diverse characterization methods. The uniform thin films were obtained using a 45-min coating process using an input voltage source of 17 kV, which was confirmed through analyses conducted using FESEM and AFM techniques. The UV–Vis spectroscopy and current-voltage source metre were employed to examine the light absorption and transmittance of bare and coated silicon solar cells. When compared to alternative solar cells, the solar cell coated with a combination of SiO2 and ZrO2 demonstrated uniform deposition and a low light reflectance of only 6 %. SiO2–ZrO2 gains a highest power conversion efficiency (PCE) of 17.6 % under controlled light source. This superior performance was due to the increase in photon transmittance in to the depletion region. Furthermore, the electrical resistivity of the SiO2–ZrO2 blend coated solar cell was measured using the four-probe method was found to be 2.89 × 10−3 Ω-cm, which was lower than that of other solar cells. From the experimental results, it was clear that SiO2 - ZrO2 blend-coated solar cells outperformed both other coated and uncoated solar cells. Consequently, SiO2–ZrO2 blends emerged as superior anti-reflective materials for achieving peak performance.

An approach for designing energy-efficient integrated silicon photonics transmitters

An approach for designing energy-efficient integrated silicon photonics transmitters

PAPR Reduction and Nonlinearity Mitigation of Optical Digital Subcarrier Multiplexing Systems With a Silicon Photonics Transmitter

PAPR Reduction and Nonlinearity Mitigation of Optical Digital Subcarrier Multiplexing Systems With a Silicon Photonics Transmitter

An integrated CMOS–silicon photonics transmitter with a 112 gigabaud transmission and picojoule per bit energy efficiency

The widening application of advanced digital infrastructure requires the development of communications technologies with increased data transmission rates. However, ensuring that this can be achieved in an energy-efficient way is challenging. Here we report an integrated complementary metal–oxide–semiconductor/silicon-photonics-based transmitter in which a switching current is applied to the passive-equalization-network-guided silicon Mach–Zehnder modulator, rather than driving a standard Mach–Zehnder modulator with a traditional voltage swing. This approach allows the total electrical energy to be selectively distributed to different frequency components by choosing an appropriate inductance and near-end termination impedance values. With the approach, we achieve 112 gigabaud—112 gigabits per second on–off keying and 224 gigabit per second pulse-amplitude modulation with four levels—transmission with energy efficiencies below picojoules per bit, and without the need for signal-shaping functions in the data source. We also investigate the bit error rate for different electrical and optical power conditions at 100 gigabaud, including the electrical power consumption of the driver amplifier.

Medium-Energy Proton Detector Onboard the FY-4B Satellite

This work introduces the instrument design of the medium-energy proton detector (MEPD, detection range: 30 keV–5 MeV) mounted on the Chinese Fengyun-4B (FY-4B) satellite. Compared to a similar detector on the Fengyun-3E (FY-3E) satellite, this instrument has undergone significant changes due to the different orbital radiation environment and solar lighting conditions. Based on the calculation of the radiation model AP8, the geometrical factor is reduced to 0.002 cm2sr, while that of the MEPD on the FY-3E satellite is 0.005 cm2sr. Another difference is that the sensors in some directions are exposed to direct sunlight for 80 min every day on this orbit, depending on the attitude angle of the satellite, which is much worse than that on the FY-3E satellite. According to the calculation results of transmittance of photons through different materials, a 100 nm thickness nickel film is added in front of the sensors to eliminate light pollution completely. The test using a solar simulator shows that the measure is effective and the detector has no error count when the solar irradiance coefficient is 1.0. In addition, the Geant4 software is applied to simulate the particle transportation process under complete machine condition to check the contamination of electrons in the sensors in all directions after magnetic deflection. The data obtained in orbit show that the instrument works properly, and the data are in good agreement with the AP8 model. The observations of the MEPD on board the FY-4B satellite can provide important support for the safety of spacecraft and theoretical research related to space weather.

Sub-THz wireless transmission based on graphene-integrated optoelectronic mixer

Optoelectronics is a valuable solution to scale up wireless links frequency to sub-THz in the next generation antenna systems and networks. Here, we propose a low-power consumption, small footprint building block for 6 G and 5 G new radio wireless transmission allowing broadband capacity (e.g., 10–100 Gb/s per link and beyond). We demonstrate a wireless datalink based on graphene, reaching setup limited sub-THz carrier frequency and multi-Gbit/s data rate. Our device consists of a graphene-based integrated optoelectronic mixer capable of mixing an optically generated reference oscillator approaching 100 GHz, with a baseband electrical signal. We report >96 GHz optoelectronic bandwidth and −44 dB upconversion efficiency with a footprint significantly smaller than those of state-of-the-art photonic transmitters (i.e., <0.1 mm2). These results are enabled by an integrated-photonic technology based on wafer-scale high-mobility graphene and pave the way towards the development of optoelectronics-based arrayed-antennas for millimeter-wave technology.

Highly reliable integrated W-band transmitter based on an on-chip dual-mode DFB laser and cascaded microring modulators

We propose an integrated W-band transmitter enabled by an integrated dual-mode distributed feedback (DFB) laser and cascaded silicon photonic microring modulators for next-generation wireless communication. 10 Gb/s error-free intensity modulation and direct detection W-band transmission are achieved in experiments by using the dual-mode DFB laser and two free-running lasers. Moreover, we conduct an experiment of dual-carrier modulation based on cascaded microring modulators, achieving 3 dB signal-to-noise ratio improvement and better signaling integrity for wireless communication. The proposed photonic integrated W-band transmitter will be a viable solution for a high-speed and low-power wireless communication system.

Radiation Shielding Properties of Synthetic Ca-Al2O3 Polymer Based Composites

The optical and radiation shielding capabilities of Ca-Al2O3polymer-based composites were explored by combining synthesized aluminum oxide (Al2O3) with calcium (Ca) obtained from different shells. The obtained powders were dispersed into polymeric materials in a ratio of 2:1 via the melt-mixing process and then cast in a 10cm x10cm mold with a thickness of 10 mm and allowed to set at ambient temperature. The X-ray transmission through the composite samples was investigated using a well-collimated point source, and a linear attenuation coefficient was estimated. X-ray fluorescence results revealed calcium contents of 32 %, 37 %, and 34 % for snail shells, seashells, and periwinkle shells, respectively. The X-ray diffraction result confirmed the Al2O3polymorphs at approximately 32oand 57oand the aluminum phase at 46o. The X-ray photon transmittance of the composites is quite low at 40 keV to 60 keV and comparatively higher at 100 keV to 200 keV. For Ca-Al2O3polymer-based composites with calcium contents sourced from seashells, periwinkle shells, and snail shells, the maximum linear attenuation coefficients were 1.0 cm-1,0.79 cm-1, and 0.65 cm-1, respectively. The half-value layer (HVL) and relaxation length of all the samples under investigation decreased abruptly at 40 keV and 60 keV and grew linearly as the energy increased from 100 keV to 200 keV. A Ca-Al2O3polymer-based composite with calcium contents sourced from seashells was found to have higher x-ray attenuating characteristics than other composites.

Effective Dose Transmittance of Photons of 85 Radionuclides for Shield Calculation of Radiation Facilities—Additional Data to “Data for Shield Calculation of Radiation Facilities (2015)”—

『放射線施設の遮蔽計算実務（放射線）データ集』（原子力安全技術センター）は遮蔽計算の典拠として広く利用されている。現行の2015年版のデータを補うため，近年重要性が高まっている85核種を対象に，光子の実効線量透過率，放射平衡を示す核種の使用状況を想定しての子孫核種，遮蔽材（鉛・タングステン・鉄・銅・コンクリート及び水）について計算を行った。

Multi-dimensional data transmission using inverse-designed silicon photonics and microcombs

The use of optical interconnects has burgeoned as a promising technology that can address the limits of data transfer for future high-performance silicon chips. Recent pushes to enhance optical communication have focused on developing wavelength-division multiplexing technology, and new dimensions of data transfer will be paramount to fulfill the ever-growing need for speed. Here we demonstrate an integrated multi-dimensional communication scheme that combines wavelength- and mode- multiplexing on a silicon photonic circuit. Using foundry-compatible photonic inverse design and spectrally flattened microcombs, we demonstrate a 1.12-Tb/s natively error-free data transmission throughout a silicon nanophotonic waveguide. Furthermore, we implement inverse-designed surface-normal couplers to enable multimode optical transmission between separate silicon chips throughout a multimode-matched fibre. All the inverse-designed devices comply with the process design rules for standard silicon photonic foundries. Our approach is inherently scalable to a multiplicative enhancement over the state of the art silicon photonic transmitters.

53 GBd PAM-4 fully-integrated silicon photonics transmitter with a hybrid flip-chip bonded laser

We present a fully-integrated single-lane 53 GBd PAM-4 silicon photonics (SiPh) transmitter (Tx) with a flip-chip bonded laser diode (LD). The LD is butt-coupled to a Si edge coupler including a SiO2 suspended spot-size converter. The coupled power exceeds 10 dBm with a 1 dB allowable misalignment of 2.3 µm. The RF and eye performances of the Tx are evaluated. Extinction ratio >5 dB is obtained at 3.5 Vppd voltage swing. Aided by silicon capacitors, the Tx decouples parasitic inductances leading to remarkable improvements in the eye openings and transmitter dispersion eye closure quaternary by 1.16 dB. By implementing the fully-integrated Tx with driver packaging, we successfully demonstrate 106 Gb/s real-time operation satisfying KP4-FEC threshold at -5 dBm receiver sensitivity.

Simulation of Light-Trapping Characteristics of Self-Assembled Nano-Ridges in Ternary Organic Film

The presence of self-assembled nano-ridged (SANR) structures in PTB7-Th:PC70BM:PC60BM ternary organic blend film with the specific component ratio was experimentally clarified, and the light-trapping effect of the SANR structures was demonstrated. On this basis, the light-trapping characteristics of the PTB7-Th:PC70BM:PC60BM ternary blend film with the SANR structures were investigated by using the finite-difference time-domain (FDTD) algorithm. The results showed that the SANR structures have a light-trapping effect, which can effectively reduce the transmittance and reflectance of the incident photons at the specific wavelengths and thus exhibit stronger photon absorption, especially for the photons in the wavelength range of 550–650 nm. The light-trapping effect of the SANR structures does not depend on the direction of photon incidence, and the active layer traps the photons incident from both its top and bottom. The dimensional variation of the SANR has a significant effect on the light-trapping characteristics of the active layer, and the effect caused by the height variation is overwhelmingly superior compared with that of the width variation. In addition, the higher the density of the SANR, the more significant the light-trapping effect of the active layer. This work provides a theoretical basis for the further experimental enhancement of the photon absorption capacity of the PTB7-Th:PC70BM:PC60BM active layer with SANR structures.

Design and Realization of Multi-Channel and High-Bandwidth 2.5D Transmitter Integrated With Silicon Photonic MZM

Recently, the interconnection bandwidth of the data center is rapidly increasing. To satisfy the requirement for the high-performance data center, a 4-channel 2.5D silicon photonic transmitter is proposed and the packaging structure could increase the high-density scalability of the architecture for 1.6T/3.2T co-packaging optics (CPO) module. The electrical driver and silicon photonic Mach-Zehnder modulator (MZM) are mounted to the silicon interposer by the micro-bumps. Meanwhile, the silicon interposer is mounted to the low temperature co-fired ceramic by the solder balls. The 2.5D transmitter is assembled to the motherboard by the high-speed ball grid array (BGA) connector to make it convenient to be replaced. The electrical optimization is implemented to make the insertion loss of the whole passive link within −1.55 dB under 40 GHz, which ensures the transmitter with the socket transmit the clear simulated eye diagram at 64 Gbps PAM4 rate per channel. Moreover, the thermal evaluation is performed, which includes the heat- dissipation evaluation and the thermal-induced impact on the edge light coupling. Finally, the substrates in the 2.5D transmitter are fabricated and the transmitter is realized by the improved assembly method. By the verification of the measurement, the 2.5D transmitter we proposed could work at 64 Gbps PAM4 signal transmission rate per channel with the 6pJ/bit power consumption. Regardless of the bandwidth of the electronic integrated circuit (EIC)/MZM and the BGA connector, based on the simulation electrical bandwidth, it is potential for realizing 100 Gbps PAM4 signal transmission.

Coherent Wireless Link at 300 GHz With 160 Gbit/s Enabled by a Photonic Transmitter

The increasing demand for high-capacity wireless communication requires data links at millimeter waves and terahertz frequencies, respectively. At those frequencies, electronic and photonic technologies compete to prove powerful transmitters and receivers. In this work, we demonstrate a wireless link at 300 GHz using a fiber-coupled PIN photodiode as the transmitter. Thus, the whole emitter side is based on components and techniques from standard fiber-optical communication, which inherently enable broadband data channels. We investigated two antenna designs with amplitude modulated and coherent data signals. Despite similar characteristics in terms of output power and carrier bandwidth, the quality of the data signals differed significantly. In addition, we found that the bit-error ratio (BER) scales non-monotonically with the optical input power of the photodiode, which is proportional to the terahertz output power. Depending on the modulation format and the symbol rate, we identified the optimal driving conditions of the photodiode. For amplitude modulation at 5 Gbit/s, we achieved error-free transmission with a BER of 7.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−13</sup> . QPSK modulation was error-free up to 64 Gbit/s. The highest line rate of 160 Gbit/s was achieved with 32QAM modulation. This corresponds to 133 Gbit/s net data rate after forward-error correction with 20% overhead. The highest spectral efficiency was achieved with 64QAM at 8 GBaud, i.e., 48 Gbit/s line rate. The presented results highlight the high bandwidth of photonic wireless THz links. Furthermore, the carefully analysis helps to improve the quality of future wireless links in the 300 GHz band.

O-Band Multimode Interference Coupler Power Combiner Using Slot-Waveguide Structures

Photonic transmitters that operate with a high data transfer rate (over 150 Gb/s) at the O-band range (1260–1360 nm) require at least 100 milliwatts of power to overcome the power losses that are caused by using high-speed modulators. A laser with higher power can probably handle this requirement; however, for the transmitter system, this solution can be problematic due to the nonlinear effects that can happen, which may lead to high noise in the transmitter system. Thus, to solve this issue, we propose a new design of a 2 × 1 multimode interference (MMI) power combiner using silicon nitride (SiN) slot waveguide structures. The MMI power combiner and the SiN slot waveguide structures were optimized using the full-vectorial beam propagation method (FV-BPM) and the finite difference time domain (FDTD) method. After combining two sources, high efficiency was obtained of 94.8–97.6% from the total power after a short coupling length of 109.81 µm over the O-band range with a low back reflection of 44.94 dB. Thus, the proposed device can be very useful for combining two O-band sources to gain a higher power level, which can be utilized to improve performances in transmitter systems.

Silicon Photonic Integrated Circuits for Soliton Based Long Haul Optical Communication

We demonstrate a silicon photonic transmitter for soliton-based communications enabling the interleaving of QPSK and APSK modulated soliton pulses overlapping in both the time and frequency domains. The nonlinear Fourier transform is used to both determine adequate soliton launch conditions and facilitate nonlinear equalization at the receiver. A spectral efficiency of 0.5 b/s/Hz per polarization is reached over a 5400 km transmission distance and constitutes, to the best of our knowledge, a record for soliton transmission over such long distances. Linear and nonlinear minimum mean square error and artificial neural network-based equalizers are also experimentally benchmarked, with artificial neural networks resulting in particularly effective equalization in this system.

Dual-polarization multiplexing amorphous Si:H grating couplers for silicon photonic transmitters in the photonic BiCMOS backend of line

In this paper, we report on polarization combining two-dimensional grating couplers (2D GCs) on amorphous Si:H, fabricated in the backend of line of a photonic BiCMOS platform. The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter, which can be implemented on bulk Si wafers. The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of − 5 dB with a wafer variation of ± 1.2 dB. Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated.Graphical