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The image on the cover for Chinese Optics Letters Volume 19, Issue 11, summarizes the PAI techniques, imaging systems, and their biomedical applications in microrobots tracking in vitro and in vivo. From a robotic tracking perspective, some insight into the future of PAI technology in clinical applications is also provided.The image is based on original research by Dengfeng Li et al. presented in their paper "Review of photoacoustic imaging for microrobots tracking in vivo [Invited]", Chinese Optics Letters 19 (11), 111701 (2021).

The image on the cover for Photonics Research Volume 9, Issue 11, proposes a device that could be used for both display and visible light communication (VLC) applications. The semipolar blue &mu;LED array fabricated in this study shows a negligible wavelength shift, indicating a significant reduction in the quantum confined Stark effect. The image is based on original research by Tingzhu Wu et al. presented in their paper "Highly stable full-color display device with VLC application potential using semipolar &mu;LEDs and all-inorganic encapsulated perovskite nanocrystal", Photonics Research 9 (11), 11002132 (2021).

The image on the cover for Advanced Photonics Volume 3 Issue 5 depicts a novel spintronic-metasurface terahertz emitter, developed by researchers from Fudan University. Composed of alternating magnetic heterostructures, the emitter allows efficient, flexible generation and manipulation of chiral terahertz waves. Terahertz radiation is generated by exciting the emitter with laser pulses under an oriented external magnetic field. Transverse anisotropic confinement of the laser-induced charge currents imposed by the metasurface structure leads to chiralterahertz-wave emission.The image is based on original research presented in the report by Changqin Liu, Shunjia Wang, Sheng Zhang, and Qingnan Cai, et al., “Active spintronic-metasurface terahertz emitters with tunable chirality,” Adv. Photonics 3(5), 056002 (2021), doi: 10.1117/1.AP.3.5.056002.

The image on the cover of High Power Laser Science and Engineering Volume 9, Issue 3, presents an all-optical scheme to generate a high-energy &gamma;-photon beam with large beam angular momentum (BAM), small divergence, and high brilliance.The image is based on original research by Hao Zhang et al. presented in their paper "Efficient bright &gamma;-ray vortex emission from a laser-illuminated light-fan-in-channel target", High Power Laser Science and Engineering 9 (3), 03000e43 (2021).

The image on the cover for Chinese Optics Letters Volume 19, Issue 10, reviews the important parameters including the refractive index detection range, resonance wavelength, and spectral sensitivity responsible for the sensing properties of PCF-SPR sensors.The image is based on original research by Chao Liu et al. presented in their paper "Overview of refractive index sensors comprising photonic crystal fibers based on the surface plasmon resonance effect [Invited]", Chinese Optics Letters 19 (10), 102202 (2021).

Spotlight on Optics
Parity-time (PT) symmetry, as a physical concept, describes the special and temporal symmetry of the physical quantity. Recent year, it has been discovered that PT symmetry can be easily observed in the photonics system. Exceptional point (EP) is a particular point in the PT symmetric system, at which the eigenvalues and eigenvectors degenerate. Plenty of counterintuitive phenomena have been observed around EP. Specially, owing to the non-Hermiticity induced nonadiabatic transitions, chiral mode switching was achieved by encircling the exceptional point (EEP) in a PT symmetric system.
Photonics Research
• Jan. 21, 2022
• Vol. 10, Issue 1 (2022)
Editors' Picks
Optical tweezers (OTs) provide a powerful tool for trapping, guiding, and assembly of biological nanoparticles and cells, thus playing a unique role in biomedical and photonics areas. Particularly, OTs have been widely used to explore the structure, mechanism, and interaction of cells due to their ability of non-contact and high-resolution manipulation.
Photonics Research
• Jan. 20, 2022
• Vol. 10, Issue 1 (2022)
Editors' Picks
Topological states of matter are one of the most important research fields in condensed physics and have been deeply studied over the last 10 years. Before the discovery of topological states, researchers believed that almost all states of matter could be characterized by symmetry or local order parameters, and the phase transition of matters was accompanied by symmetry breaking.
• Jan. 19, 2022
• Vol. 10, Issue 1 (2022)
AP Highlights
Real-time, in-situ sensing and tracking of cell development and maturation is achieved using a label-free nano-optical device
• Jan. 19, 2022
• Vol. 4, Issue 1 (2022)
News
Original manuscripts are sought to the special issue on "Future Control Systems and Machine Learning at High Power Laser Facilities" of High Power Laser Science and Engineering (HPL),
High Power Laser Science and Engineering
• Jan. 18, 2022
• Vol. , Issue (2022)
Ultra-power-efficient heterogeneous III–V/Si MOSCAP (de-)interleavers for DWDM optical links

We discuss the design and demonstration of various III–V/Si asymmetric Mach–Zehnder interferometer (AMZI) and ring-assisted AMZI (de-)interleavers operati

We discuss the design and demonstration of various III–V/Si asymmetric Mach–Zehnder interferometer (AMZI) and ring-assisted AMZI (de-)interleavers operating at O-band wavelengths with 65 GHz channel spacing. The wafer-bonded III–V/Si metal-oxide-semiconductor capacitor (MOSCAP) structure facilitates ultra-low-power phase tuning on a heterogeneous platform that allows for complete monolithic transceiver photonic integration. The second- and third-order MOSCAP AMZI (de-)interleavers exhibit cross-talk (XT) levels down to $-22$ dB and $-32 dB$ with tuning powers of 83.0 nW and 53.0 nW, respectively. The one-, two-, and three-ring-assisted MOSCAP AMZI (de-)interleavers have XT levels down to $-27$ dB, $-22$ dB, and $-20 dB$ for tuning powers of 10.0 nW, 7220.0 nW, and 33.6 nW, respectively. The leakage current density is measured to be in the range of $1.6–27 μA/cm2$. To the best of our knowledge, we have demonstrated for the first time, athermal III–V/Si MOSCAP (de-)interleavers with the lowest XT and reconfiguration power consumption on a silicon platform.show less

• Jan.22，2022
• Photonics Research,Vol. 10, Issue 2
• 02000A22 (2022)
Four-wave mixing in graphdiyne-microfiber based on synchronized dual-wavelength pulses

We demonstrate four-wave mixing (FWM) in the graphdiyne (GDY) microfiber based on the synchronized dual-wavelength pump pulses that are transformed from a

We demonstrate four-wave mixing (FWM) in the graphdiyne (GDY) microfiber based on the synchronized dual-wavelength pump pulses that are transformed from a mode-locked fiber laser. Benefiting from the large nonlinear refractive index of GDY and the synchronized pump pulses, a maximum conversion efficiency of -39.05 dB can be achieved in GDY with only an average pump power of 6.9 mW, greatly alleviating the possible damage compared to previous investigations employing the continuous-wave pump. In addition, our proposal can be applied to measure the effective nonlinear coefficient $γ$ of the GDY-microfiber, which could be extended as a practical measurement tool for $γ$ of nanomaterials-based devices.show less

• Jan.22，2022
• Photonics Research,Vol. 10, Issue 2
• 02000503 (2022)
Single-shot three-input phase retrieval for quantitative back focal plane measurement

This paper presents quantitative measurements facilitated with a new optical system that implements a single-shot three-input phase retrieval algorithm. T

This paper presents quantitative measurements facilitated with a new optical system that implements a single-shot three-input phase retrieval algorithm. The new system allows simultaneous acquisition of three distinct input patterns, thus eliminating the requirement for mechanical movement and reducing any registration errors and microphonics. We demonstrate the application of the system for measurement and separation of two distinct attenuation measurements of surface waves, namely, absorption and coupling loss. This is achieved by retrieving the phase in the back focal plane and performing a series of virtual optics computations. This overcomes the need to use a complicated series of hardware manipulations with a spatial light modulator. This gives a far more accurate and faster measurement with a simpler optical system. We also demonstrate that phase measurements allow us to implement different measurement methods to acquire the excitation angle for surface plasmons. Depending on the noise statistics different methods have superior performance, so the best method under particular conditions can be selected. Since the measurements are only weakly correlated, they may also be combined for improved noise performance. The results presented here offer a template for a wider class of measurements in the back focal plane including ellipsometry.show less

• Jan.22，2022
• Photonics Research,Vol. 10, Issue 2
• 02000491 (2022)
All-fiber spatiotemporal mode-locking lasers with large modal dispersion

It is a challenging problem to balance the modal walk-off (modal dispersion) between multiple transverse modes and chromatic dispersion in long step-index

It is a challenging problem to balance the modal walk-off (modal dispersion) between multiple transverse modes and chromatic dispersion in long step-index multimode fibers (MMFs). By properly designing the oscillator, we have overcome the difficulty and successfully obtained an all-fiber spatiotemporal mode-locked laser based on step-index MMFs with large modal dispersion for the first time, to our knowledge. Various proofs of spatiotemporal mode-locking (STML) such as spatial, spectral, and temporal properties, are measured and characterized. This laser works at a fundamental frequency of 28.7 MHz, and achieves a pulse laser with single pulse energy of 8 nJ, pulse width of 20.1 ps, and signal-to-noise ratio of $∼70 dB$. In addition, we observe a dynamic evolution of the transverse mode energy during the STML establishment process that has never been reported before.show less

• Jan.22，2022
• Photonics Research,Vol. 10, Issue 2
• 02000483 (2022)

Light field imaging has shown significance in research fields for its high-temporal-resolution 3D imaging ability. However, in scenes of light field imaging through scattering, such as

Light field imaging has shown significance in research fields for its high-temporal-resolution 3D imaging ability. However, in scenes of light field imaging through scattering, such as biological imaging in vivo and imaging in fog, the quality of 3D reconstruction will be severely reduced due to the scattering of the light field information. In this paper, we propose a deep learning-based method of scattering removal of light field imaging. In this method, a neural network, trained by simulation samples which are generated by light field imaging forward models with and without scattering, is utilized to remove the effect of scattering on light field captured experimentally. With the deblurred light field and the scattering-free forward model, 3D reconstruction with high resolution and high contrast can be realized. We demonstrate the proposed method by using it to realize high-quality 3D reconstruction through a single scattering layer experimentally.show less

• Jan.22，2022
• Chinese Optics Letters,Vol. 20, Issue 4
• (2022)

A single-frequency 1645 nm pulsed laser with frequency stability close to 100 kHz was demonstrated. The laser oscillator is injection-seeded by a single-frequency narrow linewidth Er:YA

A single-frequency 1645 nm pulsed laser with frequency stability close to 100 kHz was demonstrated. The laser oscillator is injection-seeded by a single-frequency narrow linewidth Er:YAG nonplanar ring oscillator and frequency stabilized by modified Pound–Drever–Hall method. The pulse repetition rate can be set from 100 to 500 Hz with the frequency stability from 82.72 kHz to 134.44 kHz and pulse energy from 9.84 mJ to 19.55 mJ. To our knowledge this is the best frequency stability of single-frequency pulsed laser with injection-seeded. show less

• Jan.22，2022
• Chinese Optics Letters,Vol. 20, Issue 4
• (2022)

We demonstrate a novel approach to achieve wavelength-tunable ultrashort pulses from an all-fiber mode-locked laser with a saturable absorber based on nonlinear Kerr beam clean-up effec

We demonstrate a novel approach to achieve wavelength-tunable ultrashort pulses from an all-fiber mode-locked laser with a saturable absorber based on nonlinear Kerr beam clean-up effect. This saturable absorber was formed by a single-mode fiber spliced to a graded-index multimode fiber, and its tunable band-pass filter effect is described by a numerical model. By adjusting the bending condition of graded-index multimode fiber, the laser could produce dissipative soliton pulses with their central wavelength tunable from1040 nm to 1063 nm. The pulse duration of output laser could be compressed externally to 791 fs, and the signal to noise ratio of its radio frequency spectrum was measured to be 75.5 dB. show less

• Jan.22，2022
• Chinese Optics Letters,Vol. 20, Issue 4
• (2022)

The linewidth of BaGa4Se7 optical parametric oscillator (BGSe OPO) was narrowed for the first time by inserting a Fabry-Perot (FP) etalon into an L-shaped cavity. When a 15 mm long BGSe

The linewidth of BaGa4Se7 optical parametric oscillator (BGSe OPO) was narrowed for the first time by inserting a Fabry-Perot (FP) etalon into an L-shaped cavity. When a 15 mm long BGSe(56.3°, 0°) was pumped by a 1064 nm laser, the peak wavelength was ~3529 nm and the linewidth was 4.53 nm (3.64 cm-1) under type I phase matching. After inserting a 350 µm thick FP etalon, the linewidth was decreased to 1.27-2.05 nm. When the tilt angle of the etalon was 2.34°, the linewidth was 2.05 nm (1.65 cm-1) and the peak wavelength was still ~3529 nm. When the tilt angle of the etalon was 3.90°, the peak wavelength was 3534.9 nm and the linewidth was 1.27 nm (1.02 cm-1), which was the narrowest linewidth of BGSe OPO, to the best of our knowledge. The beam quality was improved after inserting the FP etalon, too.show less

• Jan.22，2022
• Chinese Optics Letters,Vol. 20, Issue 4
• (2022)
Xi'an, ChinaAug 7-10, 2022
Hangzhou, ChinaJuly 14-16, 2022
The image on the cover for Chinese Optics Letters Volume 19, Issue 11, summarizes the PAI techniques, imaging systems, and their biomedical applications in microrobots tracking in vitro and in vivo. From a robotic tracking perspective, some insight into the future of PAI technology in clinical applications is also provided.The image is based on original research by Dengfeng Li et al. presented in their paper "Review of photoacoustic imaging for microrobots tracking in vivo [Invited]", Chinese Optics Letters 19 (11), 111701 (2021).
• Journal
• 19th Nov，2021
The image on the cover for Photonics Research Volume 9, Issue 11, proposes a device that could be used for both display and visible light communication (VLC) applications. The semipolar blue &mu;LED array fabricated in this study shows a negligible wavelength shift, indicating a significant reduction in the quantum confined Stark effect. The image is based on original research by Tingzhu Wu et al. presented in their paper "Highly stable full-color display device with VLC application potential using semipolar &mu;LEDs and all-inorganic encapsulated perovskite nanocrystal", Photonics Research 9 (11), 11002132 (2021).
• Journal
• 19th Nov，2021