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Miniaturized lasers with multicolor output and high spectral purity are indispensable for various ultracompact photonic devices. Here, we propose an optically reconfigurable Forster resonance energ...

Semiconductor nanostructures with low dimensionality like quantum dots and quantum dashes are one of the best attractive and heuristic solutions for achieving high performance photonic devices. When one or more spatial dimensions of the nanocrystal approach the de Broglie wavelength, nanoscale size effects create a spatial quantization of carriers leading to a complete discretization of energy levels along with additional quantum phenomena like entangled-photon generation or squeezed states of light among others. This article reviews our recent findings and prospects on nanostructure based light emitters where active region is made with quantum-dot and quantum-dash nanostructures. Many applications ranging from silicon-based integrated technologies to quantum information systems rely on the utilization of such laser sources. Here, we link the material and fundamental properties with the device physics. For this purpose, spectral linewidth, polarization anisotropy, optical nonlinearities as well as microwave, dynamic and nonlinear properties are closely examined. The paper focuses on photonic devices grown on native substrates (InP and GaAs) as well as those heterogeneously and epitaxially grown on silicon substrate. This research pipelines the most exciting recent innovation developed around light emitters using nanostructures as gain media and highlights the importance of nanotechnologies on industry and society especially for shaping the future information and communication society., Quantum dot are one of the best practical examples of nanotechnologies. Owing to the discrete energy levels, quantum dot lasers output unique features like thermal stability, feedback insensitivity and spectral purity.

We designed, simulated, and experimentally demonstrated components for a microwave-frequency digital-to-analog converter based on single flux quantum (SFQ) circuits and an amplifier based on superconducting-quantum-interference-device (SQUID) stacks. These are key components for a self-calibrated programmable waveform reference for communications metrology capable of synthesizing high-frequency signals with quantum-based output accuracy. The amplifier is an SFQ voltage multiplier circuit that consists of a network of SFQ-splitters and SQUID transformers that provides output signals consisting of quantized pulses. The circuits were fabricated using our Nb/Nb $_{x}$ Si $_{1-x}$ /Nb Josephson-junction (JJ) fabrication process, which produces self-shunted JJs with Nb-doped silicon barriers. In order to demonstrate quantum-based reproducibility, stability and performance at 4 K, we synthesized single-tone and multitone waveforms at gigahertz frequencies and demonstrated their operation over a range of synthesizer output and experimental bias parameters. We also propose circuit designs for achieving higher synthesis frequencies and higher output power with improved power accuracy and spectral purity, and discuss the potential limitations of these circuits.

X-ray metrology, including the metrological calibration of X-ray detectors, optical elements and sources, is important for many frontier science, such as X-ray astronomy, EUV-lithography, plasma physics. Among many types of X-ray sources, synchrotron-radiation is considered perfect for X-ray metrology, mainly due to that arbitrarily X-rays specifications can be tailored to meet the demands of metrological calibration of X-ray detectors and optical elements. As a consequence, many metrology beamlines around the world are built, upgrading or to be constructed, including the metrology sector to be constructed at High Energy Photon Source (HEPS). One reasonable way to access good metrological data is using a stable X-ray beam, which means that beam position as well as flux should be as constant as possible and the beamline configuration should be simple and robust to reduce the uncertainty from beamline itself. In addition, the spectral purity of monochromatic X-rays is another crucial factor for X-ray metrology, which means stray X-rays and harmonic X-rays must be as low as possible. Many measures are taken to satisfy these requirements. An optical design of the metrology sector optimized for synchrotron-radiation-based- metrology is described here. The metrology sector, ranging from 50 eV to 20 keV, will be set up to meet the growing needs of X-ray metrology in China. All beamlines’ configurations are simple and easy to use, with an acceptable ratio of high-order harmonics and stray X-rays, which can be under 1% in the entire energy range.

A novel photonics-assisted method for frequency up/down-conversion based on an integrated dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) with tunable optoelectronic oscillator (OEO) and phase shift is presented. The local oscillator (LO) signal with high spectral purity and low phase noise is generated by an OEO loop in one of the sub-DPMZMs. The frequency can be adjusted by an electrical bandpass filter (EBPF). The radio frequency (RF) signal is injected into another sub-DPMZM. The carrier-suppressed single-sideband (CS-SSB) modulation of both the LO and RF signals is achieved. The phase of the converted signal can be tuned by an integrated dual-channel phase modulator (DPM). Frequency up/down-conversion can be switched by tuning a single bias voltage of the DP-DPMZM. Multiple functions, including tunable LO signal generation, up/down-conversion and phase shifting, can be realized. Moreover, dispersion-induced power fading is well compensated due to CS-SSB modulation. In the experiments, the tunable LO signal from 5 to 18 GHz, with a sidemode suppression ratio as high as 46.1 dB and a phase noise level of −104.5 dBc/Hz @ 10 kHz at 10 GHz, is generated successfully. The spur suppression ratios of the up/down-converted signals are 32.6 dB and 35.6 dB, respectively. The up/down conversion performance for RF carrying 16 quadrature amplitude modulation (16-QAM) signal is also investigated. The phase shifting of dual-channel converted signals can be varied continuously and independently in the range of 0–360°, and the phase deviation is ±1.8°. The proposed compact link is characterized by function multiplexing and inherent dispersion compensation.

Optical frequency combs (OFC) have revolutionized the field of optics ranging from metrology to radio-frequency photonics. One of the main advantages of an OFC is its spectral purity and broadband phase coherence. An increase in comb linewidth corresponds to elevated phase noise and system performance degradation that mandates larger processing complexity. A specialized processing scheme relying on Vernier OFC pair seeded by a single laser has highly correlated tones over the entire processing band. Recognizing this fact, this report describes a low complexity joint phase noise compensation scheme for orthogonal frequency division multiplexing (OFDM) receiver assisted by dual combs. 4-QAM modulated OFDM signals with 60 subcarriers were demodulated using a dual-comb OFDM receiver. The experiment measured the error vector magnitude (EVM) to validate the receiver performance. The new joint phase noise compensation algorithm can effectively suppress phase noise for high order tones without pilot channels and was shown to be robust under variable SNR levels.

Second harmonic generation (SHG) and frequency mixing of electrical signals are fundamental for a wide range of radiofrequency applications. Recently, ferroelectric field-effect transistors (FeFETs), made from ferroelectric hafnium oxide (HfO2), have demonstrated promising SHG capabilities because of their unique symmetric transfer curves. In this paper, we illustrate how this symmetry is highly sensitive to material properties by varying the thickness of the ferroelectric layer and the doping of the silicon substrate. We show that the SHG conversion gain and the spectral purity are greatly increased (up to 96%) by precisely tuning the ferroelectric polarization reversal and the quantum tunneling currents. Based on this, we propose and experimentally demonstrate the generation of the difference and of the sum of two input frequencies (frequency mixing) with a single FeFET, which we attribute to the inherently strong quadratic component of the symmetric transfer characteristics. Because of the reversible and continuous ferroelectric switching in HfO2, our approach allows for an electrical control of the energy distribution of spectral components, thus opening up new and very promising paths for frequency manipulations with simple ferroelectric devices.

This brief presents a 16-electrode electrical impedance tomography (EIT) system for hand gesture recognition. The hardware of the system is based on integrated circuits including a 12-bit high spectral purity current-steering DAC implemented in $0.18~\mu \text{m}$ CMOS technology, a current driver and an instrumentation amplifier in $0.35~\mu \text{m}$ CMOS technology. Both 2D and 3D EIT electrode arrangements were tested for hand gesture recognition. It is shown that using machine learning algorithms, eight hand gestures can be distinguished from the measured bio-impedance data with an accuracy of 97.9% when the electrodes are placed on a single wristband, and an accuracy of 99.5% with the same number of electrodes distributed on two wristbands for 3D EIT measurement. In particular 3D EIT demonstrated significant superiority in its ability to discriminate between gestures with similar muscle contractions.

Introduction . When developing and validating methods of impurity determination, it is important to test the spectral peak purity (SPP) of the main substances using diode array detectors (DAD). Text . It is emphasized that the task of testing SPP is to detect invisible coeluting impurities under the peak of the main substance, and not the control the absolute purity of the peak. SPP testing reduces the risk of getting non enough specific methods. In this regard, we considered the main criteria and key points for assessing the spectral purity of peaks when using computer programs of Agilent's, Shimadzu's, and Waters's chromatographs. Conclusion . Recommendations are given, which should be taken into account for the correct assessment of spectral purity of peaks during development of chromatographic methods and validation of their specificity.

Miniaturized lasers with high spectral purity and wide wavelength tunability are crucial for various photonic applications. Here we propose a strategy to realize broadband-tunable single-mode lasing based on a photoisomerization-activated intramolecular charge-transfer (ICT) process in coupled polymer microdisk cavities. The photoisomerizable molecules doped in the polymer microdisks can be quantitatively transformed into a kind of laser dye with strong ICT character by photoexcitation. The gain region was tailored over a wide range through the self-modulation of the optically activated ICT isomers. Meanwhile, the resonant modes shifted with the photoisomerization because of a change in the effective refractive index of the polymer microdisk cavity. Based on the synergetic modulation of the optical gain and microcavity, we realized the broadband tuning of the single-mode laser. These results offer a promising route to fabricate broadband-tunable microlasers towards practical photonic integrations.

Random fiber lasers (RFLs), which employ random distributed feedback (RDFB) provided by the intrinsic Rayleigh scattering (RS) along the passive fiber, have gained wide attention in the last decade. A major advantage of Raman gain based RFL is wavelength flexibility, and the so-called cascaded Raman conversion can extend the operating wavelength considerably. However, frequently used silica fibers often need multiple Raman shifts to reach the final desired wavelength due to its peak frequency shift of ∼13.2 THz. A good alternative is the phosphosilicate fiber which has a gain peak at ∼39.8 THz. Nevertheless, the simultaneous existence of silica-related and phosphorus-related gain peaks in the phosphosilicate fiber intensifies the gain competition, further limiting the power scaling and the enhancement of spectral purity, even making it difficult to reach the desired wavelength. In this article, we experimentally explored the influences of the pump wavelength and bandwidth on the lasing performance of a phosphosilicate RFL, and measured the extreme frequency shift of the phosphorus-related Raman gain peak. Besides, by the aid of a modified power balance model, we qualitatively simulated the impacts of pump spectrum and boundary condition on the laser output. The simulation agrees well with the experimental results, and may also explain the parasitic lasing in the prior reports of phosphosilicate RFLs. As a result, the extreme frequency shift of phosphosilicate RFL is measured to be ∼1 THz. And through optimizing the pump wavelength and pump bandwidth, 99.24% high spectral purity random lasing at 1237 nm with 33.1 W output power is obtained. This work may help to reveal the gain competition in phosphosilicate RFL and guide the future laser design.

Microwave synthesizers that are used to generate microwave signals for the CSF1 and CSF2 fountain clocks at the Physikalisch-Technische Bundesanstalt (PTB) are described. The synthesizers are based on a divider chain and a digital frequency synthesis and have been designed for use with an optically stabilized microwave oscillator. They have been designed in a modular fashion to assure long-term operation and low down times. The results of an in-depth examination of spectral purity, phase noise, and long-term phase stability are presented. Also, the implications of measured parameters on the fountain timing are assessed. Two methods of suppressing the frequency-shifting effect of microwave leakage fields are implemented, with one method in each synthesizer. The first method uses an interferometric switch, and the second uses a phase-coherent and phase-preserving frequency detuning scheme; their contribution to the systematic uncertainty of the fountains is assessed. The overall systematic uncertainty contribution associated with the fountain electronics is below $1 \times 10^{-17}$ for both fountain clocks.

While integrated photonics is a robust platform for quantum information processing, architectures for photonic quantum computing place stringent demands on high quality information carriers. Sources of single photons that are highly indistinguishable and pure, that are either near-deterministic or heralded with high efficiency, and that are suitable for mass-manufacture, have been elusive. Here, we demonstrate on-chip photon sources that simultaneously meet each of these requirements. Our photon sources are fabricated in silicon using mature processes, and exploit a dual-mode pump-delayed excitation scheme to engineer the emission of spectrally pure photon pairs through inter-modal spontaneous four-wave mixing in low-loss spiralled multi-mode waveguides. We simultaneously measure a spectral purity of 0.9904 ± 0.0006, a mutual indistinguishability of 0.987 ± 0.002, and >90% intrinsic heralding efficiency. We measure on-chip quantum interference with a visibility of 0.96 ± 0.02 between heralded photons from different sources., Suitability for large-scale quantum computation imposes severe requirements on single-photon sources in terms of purity, indistinguishability and heralding efficiency. Here, the authors boost all these figures of merit through a dual-mode pump-delayed four-wave mixing scheme in low-loss silicon waveguides.

We synthesize single- and multiple-tone waveforms at gigahertz frequencies from arrays of Josephson junctions and demonstrate their quantum-locked operation over a range of experimental input parameters. We first use a lumped-element circuit to synthesize 1 and 2 GHz single-tone waveforms with -71 dBm output power and in-band spurious-free dynamic range (SFDR) of -66 dBc. We then introduce a narrow-band diplexer circuit and synthesize a 1 GHz sinusoid with higher power (-49 dBm) and in-band SFDR of -79 dBc. To demonstrate the spectrally selective power- and phase-programmability of the diplexer circuit, we also synthesize multisine waveforms with total waveform power of -51 dBm. The spectral purity of the reported waveforms is limited by the room-temperature electronics rather than by the quantized pulse-based synthesis technique. This article provides direction for future circuit designs and uncovers the main factors that must be addressed to achieve higher power, higher spectral purity, and improved output power accuracy. The reported results represent significant progress towards a JAWS-based primary RF reference source that synthesizes programmable, quantum-referenced, low-distortion signals at gigahertz frequencies.

One of the most challenging tasks in the field of light‐producing pyrotechnics is the generation of saturated blue light with high spectral purity. Only copper salts in combination with chlorine seem to be high‐performing blue light emitters. However, in modern pyrotechnics the application of chlorine should be avoided. Different strategies are presented to further fine‐tune literature‐known chlorine‐free blue‐light‐emitting pyrotechnical compositions. The copper iodate as well as the copper bromate systems have been studied by using small amounts of nitrogen‐rich compounds like 1,2,4‐triazole, 5‐amino‐1H‐tetrazole or 3‐nitro‐1H‐1,2,4‐triazole. To overcome sensitivity issues, a two‐component epoxy binder system was introduced. The application of both copper(I) iodide and copper(I) bromide in the same pyrotechnical formulation were considered as blue‐light‐emitting species. Further, a quite new approach by using copper(I) nitrogen‐rich coordination compounds was investigated to give a blue flame color. All relevant formulations were characterized with respect to their dominant wavelength and spectral purity as well as impact and friction sensitivity.

The ability to organize nanoscale objects into well-defined three-dimensional (3D) arrays can translate advances in nanoscale synthesis into targeted material fabrication. Despite successes in nanoparticle assembly, most extant methods are system specific and not fully compatible with biomolecules. Here, we report a platform for creating distinct 3D ordered arrays from different nanomaterials using DNA-prescribed and valence-controlled material voxels. These material voxels consist of 3D DNA frames that integrate nano-objects within their scaffold, thus enabling the object's valence and coordination to be determined by the frame's vertices, which can bind to each other through hybridization. Such DNA material voxels define the lattice symmetry through the spatially prescribed valence decoupling the 3D assembly process from the nature of the nanocomponents, such as their intrinsic properties and shapes. We show this by assembling metallic and semiconductor nanoparticles and also protein superlattices. We support the technological potential of such an assembly approach by fabricating light-emitting 3D arrays with diffraction-limited spectral purity and 3D enzymatic arrays with increased activity.

We demonstrate noise suppression and precise phase control of a commercial 2.45GHz magnetron aiming for wireless power transfer application. The impurity of the microwave spectrum was confirmed to be due to the switching frequency of 76kHz in the power supply. With the decoupling capacitor installed to the output of the high-voltage power-supply driving the magnetron, the spectral purity of the magnetron was significantly enhanced. And we achieved extreme precision in phase-control (peak-to-peak 0.3°) for the high-power (1 kW) microwave magnetron by applying the phase locking loop to the noise-suppressed magnetron system.

This article presents a 5-GS/s 12-b passive-sampling $8\times $ -interleaved hybrid analog-to-digital converter (ADC) that achieves a low-frequency SFDR/SNDR of 75.2/62.4 dB and a Nyquist SFDR/SNDR of 65.4/58.5 dB. A significant power reduction while attaining a bandwidth in excess of 6 GHz and a high spectral purity are enabled by: 1) an on-chip terminated very fast settling buffer-less input front end; 2) an on-chip clock chain with as low as 11-fs added jitter; 3) an asynchronous three-stage pipelined-successive approximation register (SAR) sub-ADC; and 4) on-chip co-designed analog–digital calibrations deal with sub-ADC and time-interleaving (TI) artifacts to achieve the desired spectral performance levels. The 28-nm bulk CMOS prototype chip occupies a total area of 4.56 mm2 with a core area of 1.76 mm2 and consumes 158.6 mW from a 1-V supply, leading to the Nyquist figure of merits of Schreier (FoMS) and Walden (FoMW) of 160.5 dB and 46.1 fJ/conversion step, respectively.

Due to the advantages of fast frequency shifting, continuous phase shifting, fine frequency resolution, large bandwidth, and excellent spectral purity, the direct digital frequency synthesis (DDFS) technique is attracting more attention than ever before. Although the DDFS suffer from high power consumption, recent researches on the development of the low power DDFS (LP-DDFS) increases the feasibility of applying the DDFS to portable devices. To further accelerate the use of LP-DDFS, a new LP-DDFS design to significantly improve power efficiency is proposed and analyzed in this paper. In the new design, the dominant spur by truncation errors causing performance degradation has been also thoroughly considered. Since the existing dithering techniques for the truncation error problems can cause the additional performance degradation due to the side effects such as frequency offset and SNDR deterioration, an enhanced dithering technique is also proposed in this paper. The proposed technique includes a frequency compensation circuit and thus minimizes the truncation errors in the LP-DDFS with the minimal additional power consumption and SNDR degradation. Both theoretical and experimental analysis are conducted to verify the proposed design, where a prototype chip is fabricated and measured.