Color compensation for multi-view video coding based on diversity of cameras

A novel color compensation method for multi-view video coding (MVC) is proposed, which efficiently exploits the inter-view dependencies between views with the existence of color mismatch caused by the diversity of cameras. A color compensation model is developed in RGB channels and then extended to YCbCr channels for practical use. A modified inter-view reference picture is constructed based on the color compensation model, which is more similar to the coding picture than the original inter-view reference picture. Moreover, the color compensation factors can be derived in both encoder and decoder, therefore no additional data need to be transmitted to the decoder. The experimental results show that the proposed method improves the coding efficiency of MVC and maintains good subjective quality.

Atom-referenced and stabilized soliton microcomb

For the applications of the frequency comb in microresonators,it is essential to obtain a fully frequency-stabilized microcomb laser source.In this study,we present a system for generating a fully atom-referenced stabilized soliton microcomb.The pump light around 1560.48 nm is locked to an ultra-low-expansion(ULE)cavity.This pump light is then frequency-doubled and referenced to the atomic transition of87Rb.The repetition rate of the soliton microcomb is injection-locked to an atomic-clockstabilized radio frequency(RF)source,leading to mHz stabilization at 1 s.As a result,all comb lines have been frequencystabilized based on the atomic reference and the ULE cavity,achieving a very high precision of approximately 18 Hz at 1 s,corresponding to the frequency stability of 9.5×10^(-14).Our approach provides a fully stabilized microcomb experiment scheme with no requirement of f-2f technique,which could be easily implemented and generalized to various photonic platforms,thus paving the way towards the ultraprecise optical sources for high precision spectroscopy.

Programmable meta-holography dynamics enabled by grating-modulation

Towards next-generation intelligent display devices, it is urgent to find a cheap and convenient dynamic optical control method. Conventional gratings are widely used as cheap diffractive elements due to their effective optical control capabilities. However, they are limited within multi-function or complex optical modulation due to the lack of accurate control of the amplitude/phase at pixel-level. Here, a metasurface-assisted grating-modulation system is originally proposed to achieve switchable multi-fold meta-holographic dynamics. By incorporating metasurfaces with traditional gratings and tuning their relative coupling positions, the modulation system gains the optical modulation capability to realize complex optical functionalities. Specifically, by varying the grating periods/positions relative to the metasurface, 2–8 holographic image channels are programmed to be dynamically exhibited and switched. The proposed metasurface-assisted grating-modulation approach enjoys cost-effective convenience, strong encoding freedom, and facile operation, which promises programmable optical displays,optical sensors, optical information encryption/storage, etc.

Realization of quantum ground state in an optomechanical crystal cavity

Ground-state cooling of the mechanical degree of freedom is a fundamental requirement for quantum state transfer between relevant optical and mechanical systems.Here,we fabricate optomechanical crystal cavities with co-localized mechanical and optical modes on a monolithic chip.The typical linewidth of the optical modes at telecom wavelength is as low as 0.95 GHz,and the mechanical resonant frequency is around 5 GHz,which means the optomechanical system can be operated in the resolved sideband regime.With the statistics of the asymmetry in the scattering rates of red and blue detuning driving processes,we initialize and characterize the mechanical system in its quantum ground-state of motion,with a mean thermal phonon occupancy nth=0.018±0.0034,corresponding to a mode temperature of 57.3 m K.It is a general platform for quantum state transfer between relevant optical and mechanical systems,as well as the quantum entanglement between these systems.

Soliton microcomb-assisted microring photonic thermometer with ultra-high resolution and broad range

Whispering gallery mode resonators(WGMRs)have proven their advantages in terms of sensitivity and precision in various sensing applications.However,when high precision is pursued,the WGMR demands a high-quality factor usually at the cost of its free spectral range(FSR)and corresponding measurement range.In this article,we propose a high-resolution and wide-range temperature sensor based on chip-scale WGMRs,which utilizes a Si_(3)N_(4)ring resonator as the sensing element and a Mg F_(2)-based microcomb as a broadband frequency reference.By measuring the beatnote signal of the WGM and microcomb,the ultra-high resolution of 58 micro-Kelvin(μK)was obtained.To ensure high resolution and broad range simultaneously,we propose an ambiguity-resolving method based on the gradient of feedback voltage and combine it with a frequency-locking technique.In a proof-of-concept experiment,a wide measurement range of 45 K was demonstrated.Our soliton comb-assisted temperature measurement method offers high-resolution and wide-range capabilities,with promising advancements in various sensing applications.

A mechanically tuned Kerr comb in a dispersion-engineered silica microbubble resonator

This paper discusses the developement and investigation of a silica microbubble resonator(MBR) that is optimized to cancel mode dispersion with material dispersion, at a wavelength of approximately 1550 nm and maintain a quality factor of an optical mode as large as 5.4 × 10~7. Benefitting from the near-zero dispersion and high quality factor, a primary optical comb is generated in the MBR using cascaded four-wave mixing processes, which span over 300 nm with several tens of teeth. Furthermore, the frequency comb could be gradually tuned by mechanically stretching the MBR. This tunable Kerr comb has multiple potential applications in precision measurements and sensing applications, such as molecular spectroscopy and ranging.

Frequency stabilization and tuning of breathing solitons in Si3N4 microresonators

Dissipative Kerr solitons offer broadband coherent and low-noise frequency combs and stable temporal pulse trains,having shown great potential applications in spectroscopy,communications,and metrology.Breathing solitons are a particular kind of dissipative Kerr soliton in which the pulse duration and peak intensity show periodic oscillation.Here we have investigated the breathing dissipative Kerr solitons in silicon nitride(Si3N4)microrings,while the breathing period shows uncertainties of around megahertz(MHz)order in both simulation and experiments.This instability is the main obstacle for future applications.By applying a modulated signal to the pump laser,the breathing frequency can be injection locked to the modulation frequency and tuned over tens of MHz with frequency noise significantly suppressed.Our demonstration offers an alternative knob for the control of soliton dynamics in microresonators and paves a new avenue towards practical applications of breathing solitons.

Fabrication of the high-Q Si_(3)N_(4) microresonators for soliton microcombs

The microresonator-based soliton microcomb has shown a promising future in many applications.In this work,we report the fabrication of high quality[Q]Si_(3)N_(4)microring resonators for soliton microcomb generation.By developing the fabri-cation process with crack isolation trenches and annealing,we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area.The highest intrinsic Q of the Si_(3)N_(4)microring obtained in our experiments is about 6×10^(6),corresponding to a propagation loss as low as 0.058 dBm/cm.With such a high Q film,we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power,with an optical parametric oscillation threshold of only 13.4 mW.Our Si_(3)N_(4)integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics.

Experimental demonstration of dissipative sensing in a self-interference microring resonator

The dissipative sensing based on a self-interference microring resonator composed of a microring resonator and a U-shaped feedback waveguide is demonstrated experimentally. Instead of a frequency shift induced by the phase shift of the waveguide or the microcavity, the dissipative sensing converts the phase shift to the effective external coupling rate, which leads to the change of linewidth of the optical resonance and the extinction ratio in the transmission spectrum. In our experiment, the power dissipated from a microheater on the feedback waveguide is detected by the dissipative sensing mechanism, and the sensitivity of our device can achieve0.22 d B/m W. This dissipative sensing mechanism provides another promising candidate for microcavity sensing applications.

Observation of a manifold in the chaotic phase space of an asymmetric optical microcavity

Chaotic dynamics in optical microcavities, governed dominantly by manifolds, is of great importance for both fundamental studies and photonic applications. Here, we report the experimental observation of a stable manifold characterized by energy and momentum evolution in the nearly chaotic phase space of an asymmetric optical microcavity. By controlling the radius of a fiber coupler and the coupling azimuth of the cavity, corresponding to the momentum and position of the input light, the injected light can in principle excite the system from a desired position in phase space. It is found that once the input light approaches the stable manifold, the angular momentum of the light experiences a rapid increase, and the energy is confined in the cavity for a long time.Consequently, the distribution of the stable manifold is visualized by the output power and the coupling depth to high-Q modes extracted from the transmission spectra, which is consistent with theoretical predictions by the ray model. This work opens a new path to understand the chaotic dynamics and reconstruct the complex structure in phase space, providing a new paradigm of manipulating photons in wave chaos.

Distinct expression profiles and overlapping functions of IL-4/13A and IL-4/ 13B in grass carp (Ctenopharyngodon idella)

In mammals,interleukin(IL)-4 and IL-13 are important cytokines involved in the immune response of the host defence against pathogens and play critical roles in the polarization of monocytes/macrophages(MO/Mϕs).However,in teleost fish,the role of IL-4/13 homologues in the polarization of MO/Mϕremains unknown.In this paper,we identified a second isoform of IL-4/13(CiIL-4/13A)from grass carp(Ctenopharyngodon idella)in addition to the IL-4/13 homologue previously reported and comparatively studied their expression profiles and functions.The two CiIL-4/13 transcripts were constitutively expressed in tissues but displayed distinct expression patterns.Infection with Flavobacterium columnare or grass carp reovirus II(GCRV-Ⅱ)resulted in the alteration of expression levels of both IL-4/13 isoforms.Furthermore,in the primary head kidney cells,the recombinant CiIL-4/13A and B could up-regulate the expression of IL-10,inducible nitric oxide synthase(iNOS)and M2 macrophage marker gene(KLF4,kruppel like factor 4),whilst down-regulate the expression of IL-1βand M1 macrophage marker gene(MARCO,macrophage receptor with collagenous structure).The results suggest that the CiIL-4/13A and B play similar roles in regulating inflammation and differentiation of MO/Mϕs in grass carp.