Optics letters最新文献

In contrast to the more conventional gas-filled post-compression technique, solid-state-based multi-pass cells and multiple plates allow for the robust and efficient generation of intense few-cycle pulses from ytterbium (Yb) lasers with moderate energies. In this Letter, 180-fs 200-μJ pulses at 50 kHz were efficiently compressed down to 6.9 fs 144 μJ, enhancing the peak power from 1.1 GW to 12.5 GW with a long-term power stability of 0.1%. Moreover, we generated over-1.5-octave-spanning white light (500 nm-1420 nm) by using an enhanced self-steepening effect, supporting a Fourier transform limit (FTL) pulse of 2.7 fs (0.8-cycle).

It is well-known that both the phase velocity surface and the ray velocity surface of a biaxial crystal have two layers that touch each other at only four points. However, we show that the two layers of the group velocity surface of a biaxial crystal penetrate through each other and form four inverted zones. Inside an inverted zone, the slow and fast light pulses are carried by the fast and slow modes of rays, respectively. The border of an inverted zone passes through the optic ray axis and intersects with the cone of internal conical refraction. Numerical examples of the orthorhombic crystal KNbO₃ and the monoclinic crystal Sn₂P₂S₆ are given.

Multispectral compatible camouflage has attracted widespread attention due to the rapid development of various detection technologies. This work presents a multifunctional metasurface that is compatible with laser stealth, infrared shielding, and the thermal management function. To achieve laser stealth, the metasurface is designed as a metal-insulator-metal (MIM) structure for high absorption of laser lights at 1.06 and 1.54 µm, with absorption rates of 97.7 and 95.9%, respectively. Also, the metasurface is designed to minimize the specular reflectance of a 10.6 µm laser light based on the phase cancellation principle. To achieve infrared stealth, the proposed metasurface has achieved an ultralow emissivity in the atmosphere window, with an average emissivity of 0.04 in the 3-5 µm range and 0.11 in the 8-14 µm range. Additionally, the thermal management function is achieved by using the high absorption property of the metasurface in the non-atmospheric window (5-8 µm), which further improves the stealth performance in the infrared band. This work provides a novel, to the best of our knowledge, strategy to realize multispectral compatible camouflage with the thermal management function by using a compact integrated metasurface, indicating that it has promising prospects in future high-performance compatible stealth applications.

Symmetry-protected quasi-bound states in the continuum (qBICs) in metasurfaces with broken in-plane symmetry are extensively investigated to achieve high quality-factor (Q-factor) resonances. Herein, we propose the hetero-out-of-plane (H-OP) dielectric metasurface, which is composed of Si cuboids tetramer broken out-of-plane symmetry by adding a layer of silica. Dual polarization-independent qBICs are realized. The multipolar decomposition of scattering powers and near-field distributions reveal the physical mechanism of dual qBICs modes, which are dominated by the magnetic quadrupole and the toroidal dipole. The two symmetry-protected qBICs in the H-OP metasurface have robust Q-factors and stable resonance wavelengths compared with these in the out-of-plane metasurface. Our results provide a route to achieve the high Q-factor resonator with better performance applied in many optical and optoelectronic devices.

O-band intensity modulation and direct detection (IM/DD) transmission offers a promising solution for high-speed data center interconnects (DCIs). Additionally, the introduction of bismuth-doped fiber amplifiers (BDFAs) results in less nonlinear impact and a higher link budget compared with semiconductor optical amplifiers (SOAs). However, with these key issues resolved, the system bandwidth limitation emerges as the next critical bottleneck for high-speed O-band DCI transmission that limits overall performance. In this letter, we propose an efficient pre-equalization (pre-Eq) method based on the frequency pilot tones (FPTs), utilizing detectors for both magnitude and phase responses. With a single-shot characterization, the FPT-based pre-Eq method can effectively compensate for high-frequency fading caused by bandwidth limitation. We successfully demonstrate the O-band transmission of a 100-GBaud PAM-4 signal over 40-km standard single-mode fiber (SSMF) under a 10-dB bandwidth limitation of around 30 GHz. Our results show that the FPT-based pre-Eq significantly outperforms the constant modulus algorithm (CMA)-based pre-Eq.

This publisher's note contains a correction to Opt. Lett.49, 3102 (2024)10.1364/OL.524198.

We have developed an effective one-step extrusion method to prepare a nodeless chalcogenide hollow-core anti-resonance fiber, characterized by excellent symmetry and less requirements for drawing pressure in achieving the desired wall thickness. The resulting fiber exhibits excellent uniformity, with an ultra-large effective mode area of 21970 µm² and a low overlap factor of η = 0.03%. It can withstand an input power exceeding 10 W at 4.5 µm and maintain a stable output power of 1.2 W at an input power of 5.25 W, all while preserving a high beam quality with an M² value of 1.09. The output single-mode laser remains highly stable when the translation offset of the laser coupling into the fiber is less than 100 µm. The chalcogenide hollow-core fibers with watt-level mid-infrared laser delivery power and near-diffraction-limited beam quality can be used for practical applications in industry, medicine, and defense.

The conductive polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) is considered as a flexible electrode material that can replace traditional electrodes. However, its performance optimization, practical application, and related research are primarily focused on a single band. In this study, we designed and prepared a broadband transparent electrode with a conductivity of up to 1300 S cm^-1 based on dimethyl sulfoxide (DMSO)-doped PEDOT: PSS. The as-fabricated PEDOT: PSS electrode achieved high transmittance in a wide range from a visible to terahertz band. The physical mechanism of its high conductivity and broadband transparency is studied by using a first-principle calculation. Furthermore, the transparent electrode exhibited excellent stability after 100,000 cycles of electrical cycling and 200°C of heating. Based on the transparent electrode, we fabricated a liquid crystal phase shifter with an extended operating range, showing its efficient driving performance as an electrode. The characterization and optimization of the properties of PEDOT: PSS in this work provide guidance for the application of PEDOT: PSS in broadband optical devices.

For commercially available infrared radiometers with a small volume and a light weight and without an independent cooling system for the optical structure, thermal sensitivity is a key constraint for their application to high-precision limb observations. In this research, the response law of a medium wave (3.7-4.8 µm) infrared radiometer with different thermal states is investigated, and emphasis is placed on the background gray variability caused by different thermal states. We construct a similarity model to describe the response difference. Utilizing the very small radiance of the upper atmosphere and the similarity model, we can correct the deviation caused by the thermal fluctuation of the sounder with high accuracy. The method of improving the retrieval accuracy is validated by simulating the limb-sounding scenarios with ground experiments. When the target radiance is 2.27 × 10^-7 Wcm^-2sr^-1, a temperature difference of 2.5°C causes a 918% deviation in the retrieved radiance, which can be reduced to 23% after correction with the similarity model proposed in this paper. This method can facilitate the application of portable radiometers in the field of high-precision detection.

We present a two-stage bismuth-doped fiber amplifier (BDFA) that achieves ultra-broadband amplification from 1280 to 1480 nm. The two-stage BDFA is designed to limit the reabsorption of bismuth-doped silica fiber (BDSF) by high-power pumps pulled fluorescence. A peak gain of 37.9 dB was obtained at 1340 nm for a -23 dBm input signal, with >23 dB gain from 1300 to 1470 nm. Furthermore, the gain of 40.0 and 36.1 dB was measured at small signal power for 1340 and 1430 nm, respectively, and the 3 dB saturation output power reaches 16.0 and 14.6 dBm, respectively. In addition, the basic properties and luminescence characteristic of two types of BDSFs fabricated using atomic layer deposition and modified chemical vapor deposition technique worked in the configuration were investigated.