Optica

Specially shaped deep-hole components, such as gun barrels, long shaft sleeves, and complex tubing, are widely used in aerospace and heavy machinery manufacturing. Their large length-to-diameter ratios, non-circular internal cross sections, and severely confined inspection space make it difficult for conventional contact measurement to simultaneously satisfy efficiency and full-field coverage requirements, while existing optical methods suffer from long-stroke error accumulation.

In digital holographic microscopy (DHM), the reconstructed wrapped phase is often severely affected by background aberrations arising from optical path imperfections, device inaccuracies, and environmental disturbances. Existing aberration compensation methods generally rely on phase unwrapping procedures, which are prone to error propagation and instability under complex aberration conditions.

The widespread pollution of water environments by microplastics (MPs) is a critical global issue. The identification of MPs remains challenging, primarily due to their limited texture and color information. To address this issue, this Letter proposes a learning-based approach that incorporates what we believe to be a novel geometric polarization characterization of MPs with quantum neural networks (QNNs). Our method comprises three stages.

A novel, to the best of our knowledge, millijoule-class femtosecond optical parametric amplification-based source is implemented as a seeder in the high-repetition-rate HF-PW laser of ELI ALPS. High energy seeding results in a bandwidth corresponding to a sub-19 fs transform limit, significant gain reduction in the Ti:Sa amplifier chain, and an extremely low amplified spontaneous emission relative intensity of 2 × 10−14 with 10 J compressed energy.

Lensless imaging is attractive for its compact and low-cost design. However, high-accuracy and robust phase retrieval from a single pattern remains challenging and critically relies on accurate priors. Here, we propose a parallel consensus optimization termed PaCO to achieve robust and high-accuracy lensless imaging. PaCO decomposes the ill-posed problem into parallel subproblems with a distributed computational architecture.

We propose an environment-coupled dynamic model to analyze the mode splitting of orbital angular momentum (OAM) beams propagating in complex environments and suppress the mode splitting through pre-compensated OAM. The feasibility of the model in analyzing mode splitting and splitting suppression was demonstrated through spatial light modulators, generated turbulence, and water flow experiments.

By taking advantage of the unique structure of Ba3W2O9, a positioning restriction is applied to precisely control doped Mn to form isolated Mn4+ ions or Mn4+−Mn4+ ion pairs, thereby achieving the dual emission centers. The optimized phosphor (Ba3W1.97O9:0.03Mn4+) boasts excellent performances of a broadband near-infrared emission with the full width at half maximum of 170 nm, internal quantum efficiency of 74%, and external quantum efficiency of 43%.

The RGB (de)multiplexer is a key component in laser display systems and demands advanced design solutions that achieve high efficiency within a small form factor. Here, a CMOS-compatible silicon nitride (SiN) visible light photonic integrated circuits (PICs) platform is employed to successfully demonstrate an ultracompact RGB (de)multiplexer, featuring a footprint as small as 86 × 2.3 µm2.

We demonstrate an LSTM-assisted optical frequency domain reflectometry (OFDR) method for differential modal group delay (DMGD) characterization of short few-mode fibers. Sparse phase-domain resampling is first applied to compensate for laser sweep nonlinearity with a low sampling rate. Then, the resampled beat signal is extrapolated by an LSTM network to improve the resolution. In a 5-m single-mode fiber, the distance resolution is improved from 4.95 mm to 0.44 mm with a 20.74-GHz sweep bandwidth.

We report a high-power, high-repetition-rate picosecond optical parametric oscillator (OPO) based on cadmium silicon phosphide CdSiP${}_{2}$ (CSP) nonlinear crystal, synchronously pumped by a Yb-fiber laser at ~78 MHz, delivering record idler average power in the deep-infrared (deep-IR). The OPO generates 243 mW at 6249 nm, maintaining >150 mW across nearly 75% of the idler tuning range from 6199 to 6760 nm, along with simultaneous signal tuning from 1262 to 1284 nm.