Advanced Photonics Research最新文献

In this article, a waveform-selective antenna that integrates the functions of waveform selectivity, electromagnetic (EM) shielding, and EM wave radiation has been proposed. By integrating different nonlinear circuits and selecting appropriate component values, the antenna can achieve high reflection of either a pulse wave (PW) or a continuous wave (CW) at the same frequency, while allowing the other waveform to transmit with minimal interference. When exposed to pulse waves (PWs) of varying pulse widths, the antenna can adaptively process them by adjusting the values of its capacitive or inductive components. The proposed design introduces an additional degree of freedom for manipulating EM waves in the terahertz (THz) band, that is, the ability to select the time-domain waveform. Combining functional integration with a compact size, the waveform-selective antenna holds significant potential for a range of applications, including detection, EM shielding, and THz communications.

Single-crystal diamond needles (SCDNs) have emerged as promising candidates for optical and quantum sensing applications due to their unique shape, high-quality crystalline structure, and availability for relatively simple mass production. In this study, morphology modification and luminescence features of SCDNs subjected to high-temperature oxidation in air at 650 °C and 700 °C are investigated. Significant morphological changes, including sharpening, length reduction, and surface feature formation, are revealed as a result of oxidation with scanning electron microscopy observations. The morphology modifications are dependent on oxidation temperature. Gradual sharpening and formation of surface protrusions with (100) and (111) surfaces during oxidation at 650 °C significantly accelerate at oxidation temperature increase to 700 °C. Observed formation of the surface protrusions is explained by local variation in resistance to oxidation at diamond needle surface. Furthermore, photon correlation measurements reveal that oxidation duration may be optimized allowing obtaining of SCDNs with single nitrogen-vacancy centers situated in their tips, and confirming the viability of these diamonds for quantum sensing. This findings highlight the superior optical properties and structural integrity of SCDNs, making them highly suitable for single-photon emission and other quantum technological applications.

The investigation of spin waves provides fundamental insights into magnetic materials and is essential for advancing spintronic and magnonic technologies. The Transient Grating (TG) technique, a four-wave mixing method, has been widely used to study collective excitations at controlled wave vectors on the micron to nanometer scale. This study presents an all-optical TG approach for exciting standing dipolar spin waves with a controlled in-plane wave vector in a ferrimagnetic Co₇₈Gd₂₂ thin film, with potential applicability to a broad range of materials. Spin waves with a wavelength of 2.5 μm are excited by the interference of two coherent laser pulses on the sample surface and probed through the diffraction of a third laser pulse. Polarization analysis separates magnetic and thermoelastic signals and enables time-resolved measurements of the spin-wave dynamics.

The investigation of spin waves provides fundamental insights into magnetic materials and is essential for advancing spintronic and magnonic technologies. The Transient Grating (TG) technique, a four-wave mixing method, has been widely used to study collective excitations at controlled wave vectors on the micron to nanometer scale. This study presents an all-optical TG approach for exciting standing dipolar spin waves with a controlled in-plane wave vector in a ferrimagnetic Co₇₈Gd₂₂ thin film, with potential applicability to a broad range of materials. Spin waves with a wavelength of 2.5 μm are excited by the interference of two coherent laser pulses on the sample surface and probed through the diffraction of a third laser pulse. Polarization analysis separates magnetic and thermoelastic signals and enables time-resolved measurements of the spin-wave dynamics.

Single-Crystal Diamond Needles

In their Research Article (10.1002/adpr.202500302), Sergei Malykhin, Polina Kuzhir, and co-workers investigate the morphological evolution of single-crystal diamond needles through oxidation in air at 650–700 °C. Electron microscopy reveals temperature- and time-dependent sharpening, length reduction, and surface changes. Measurements of the second-order correlation function show that optimized oxidation enables obtaining single nitrogen-vacancy centers at needle tips for single-photon probes.

Raman Amplification

Raman amplification is a powerful method for selectively enhancing optical signals within specific spectral bands. In their Research Article (10.1002/adpr.202500164), Zhenxu Bai, Zhiwei Lu, and co-workers propose an adaptive Raman amplification scheme, employing diamond as the Raman gain medium, which alternates between Raman and energy-level gain stages to efficiently recycle residual pump energy. Through self-synchronizing and delay-tolerant pump recovery, it provides a robust and highly efficient strategy for high-power nonlinear optical amplification.

Here, we demonstrate that applying an external magnetic field to break time-reversal symmetry (TRS) induces topological phase transitions and topologically protected unidirectional edge state propagation in photonic crystals. We investigate nonreciprocal propagation in a square array of indium antimonide (InSb) rods embedded in air at terahertz frequencies. In photonic crystals, a modest external magnetic field applied to semiconductor rods creates gyroelectric (magneto-optical) anisotropy. This anisotropy breaks the TRS, which lifts the degeneracy at the Dirac-like point, opening a new nontrivial bandgap. The resulting edge modes supported by photonic crystals exhibit nonreciprocal propagation and remain immune to backscattering, even when encountering large obstacles, 90° sharp bends, and structural defects. The propagation direction of this state is determined by the magnetic field. A novel design approach for nonreciprocal terahertz topological devices is proposed, leveraging the strong correlation between the unidirectional edge mode properties and the Voigt effect. These findings offer promising potential for developing and fabricating advanced nonreciprocal terahertz topological devices.

Methods for high resolution phase trimming of silicon Mach–Zehnder interferometers via the electrical annealing of amorphized waveguide sections are presented. A high resolution of phase change is necessary to accurately trim the performance of individual devices to correct fabrication errors and when scaling to large programmable photonic circuits. On-chip microheaters positioned above amorphous waveguide sections are driven by short voltage pulses, causing a degree of recrystallization, controllably changing the material's refractive index. An average resolution of phase change per voltage pulse of 0.0007π is demonstrated if an adaptive method is employed, where the voltage step between successive pulses is set to be dependent on the average phase change brought about by the previous three voltage pulses.

Methods for high resolution phase trimming of silicon Mach–Zehnder interferometers via the electrical annealing of amorphized waveguide sections are presented. A high resolution of phase change is necessary to accurately trim the performance of individual devices to correct fabrication errors and when scaling to large programmable photonic circuits. On-chip microheaters positioned above amorphous waveguide sections are driven by short voltage pulses, causing a degree of recrystallization, controllably changing the material's refractive index. An average resolution of phase change per voltage pulse of 0.0007π is demonstrated if an adaptive method is employed, where the voltage step between successive pulses is set to be dependent on the average phase change brought about by the previous three voltage pulses.

Near-infrared phosphor-converted light emitting diodes (NIR pc-LEDs) have emerged as a revolutionary photonic technology with significant applications in nondestructive inspection, biomedicine and night vision imaging. Crucially, the performance of NIR pc-LEDs depends on the luminescence properties of NIR-emitting phosphors. This review systematically summarizes the recent advances in garnet-structured NIR-emitting phosphors. The basic luminescence fundamentals and spectral characteristics of garnet-structured NIR-emitting phosphors doped with transition metal ions (Cr³⁺, Fe³⁺, and Ni²⁺) and rare-earth ions (Eu²⁺ and Yb³⁺) are examined, and the corresponding performance regulation strategies are discussed. The potential applications enabled by garnet NIR-emitting phosphors in biomedicine, component detection, plant growth and solar cells are explored. Finally, it outlines the critical challenges and opportunities of garnet NIR-emitting phosphors for next-generation photonic applications.