Current Issue : April-June Volume : 2025 Issue Number : 2 Articles : 5 Articles
With the ever-growing demand for high-speed optical communications, microwave photonics, and quantum key distribution systems, compact electro-optic (EO) modulators with high extinction ratios, large bandwidth, and high tuning efficiency are urgently pursued. However, most integrated lithium–niobate (LN) modulators cannot achieve these high performances simultaneously. In this paper, we propose an improved theoretical model of a chip-scale electro-optic (EO) microring modulator (EO-MRM) based on X-cut lithium–niobate-on-insulator (LNOI) with a hybrid architecture consisting of a 180-degree Euler bend in the coupling region, double-layer metal electrode structure, and ground–signal–signal–ground (G-S-S-G) electrode configuration, which can realize highly comprehensive performance and a compact footprint. After parameter optimization, the designed EO-MRM exhibited an extinction ratio of 38 dB. Compared to the structure without Euler bends, the increase was 35 dB. It also had a modulation bandwidth of 29 GHz and a tunability of 8.24 pm/V when the straight waveguide length was 100 μm. At the same time, the proposed device footprint was 1.92 × 104 μm2. The proposed MRM model provides an efficient solution to high-speed optical communication systems and microwave photonics, which is helpful for the fabrication of high-performance and multifunctional photonic integrated devices....
High-order harmonic generation (HHG) in semiconductor thin films from ultrashort mid-infrared laser drivers holds the potential for the realization of integrated sources of extreme ultraviolet light. Here, we demonstrate solid-state HHG in zinc oxide thin films synthesized by the radiofrequency reactive magnetron sputtering process directly on the cleaved facets of optical fibers. Harmonics 3 to 13 of the radiation from a fiber-based laser system delivering 500 kW, 96 fs pulses at 3130 nm are produced in the thin film and guided along the fiber. A proper choice of the laser wavelength and fiber material allows for filtering out the mid-IR pump laser and achieving the HHG mode selection. The possibility to nanostructure the fiber exit by, e.g., focused ion beam milling paves the way to an increased control over the HHG spatial mode....
Optical Fiber Displacement Sensors (OFDSs) provide several advantages over conventional sensors, including their compact size, flexibility, and immunity to electromagnetic interference. These features make OFDSs ideal for use in confined spaces, such as turbines, where direct laser access is impossible. A critical aspect of OFDS performance is the geometry of the fiber bundle, which influences key parameters such as sensitivity, range, and dead zones. In this work, we present a streamlined design methodology for azimuthally symmetric OFDSs to improve the linear range of these sensors. The most effective configuration we propose is the pentafurcated bundle, which consists of a central transmitting fiber surrounded by four concentric rings of fibers with different radii. Our experimental results show that the pentafurcated designs increase both the range—up to 10.5 mm—and the sensitivity of the sensor—2mm−1—while minimizing the dead zone of the sensor (2.5 mm), allowing accurate measurements even at very short distances...
This work discusses the behavior of transverse energy fluxes of the fundamental core mode of a holey fibers and a photonic band gap fibers when the polarization state of this mode changes. The behavior of the transverse component of the Poynting vector of the fundamental core mode is considered for both linear and elliptical polarization. It is demonstrated that despite the difference in the distribution of the Poynting vector stream lines in the cross section of the fibers for the two polarizations, the leakage loss level is maintained constant due to the forward and reverse energy flows in the radial direction. Differences in the level of leakage losses in different micro structured fibers arise from the vortex structure of the Poynting vector of the fundamental core mode....
A Hz level narrow linewidth all-optical microwave oscillator based on the torsional radial acoustic modes (TR2,m) of a single-mode fiber (SMF) is proposed and validated. The all-optical microwave oscillator consists of a 20 km SMF main ring cavity and a 5 km SMF sub ring cavity. The main ring cavity provides forward stimulated Brillouin scattering gain and utilizes a nonlinear polarization rotation effect to achieve TR2,7 mode locking. By combining the sub ring cavity with the main ring cavity and utilizing the Vernier effect, the TR2,7 mode microwave photonic single longitudinal mode (SLM) output can be ensured. Meanwhile, the 6.281 Hz narrow linewidth of the TR2,7 mode is achieved by reducing the intrinsic linewidth of the passive resonant cavity. The acoustic mode suppression ratio and side mode suppression ratio of the TR2,7 mode were 43 dB and 54 dB, respectively. The power and frequency fluctuations of within 40 min were approximately ±0.49 dB and ±0.187 kHz, indicating good stability. At a frequency offset of 10 kHz, the TR2,7 mode had a low phase noise value of −110 dBc/Hz. This solution can be used in various fields, such as high-precision radar detection, long-distance optical communication, and high-performance fiber optic sensing....
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