Optics letters最新文献

Nontraditional glasses obtained from containerless processing techniques such as aerodynamic levitation melting have attracted much attention in recent decades for their unique structural motifs and optical properties. Herein, we report what we believe is the first demonstration of lasing from any glass produced by levitation melting. Spectroscopic properties are studied in detail, and the host is seen to have a high active ion solubility, with a quenching concentration of 6.7 × 10²⁰ ions/cm³. Laser experiments were carried out with a 1 mm thick glass disk of composition 0.5 Nd₂O₃-16.5 La₂O₃-83 TiO₂ glass. Slope efficiency with respect to absorbed power reaches 40%, and beam quality is good with an average M² = 1.88. Notably, the inhomogeneous broadening driven by the unconventional glass network's structural diversity enables a wide continuous tuning range spanning 1058-1121 nm. These outcomes provide impetus to continue research into spectroscopic and lasing properties of nontraditional glass gain media.

We report a femtosecond laser direct writing (LDW) method for localized in-situ fabrication of highly crystalline metal-organic framework-5 (MOF-5) microstructures directly from a precursor solution. Confined photothermal reactions induced by tightly focused pulses enable site-selective crystallization without pre- or post-processing. Structural and spectroscopic analyses confirm the formation of MOF-5 without thermal degradation. This substrate-compatible and straightforward approach provides a new route for spatially controlled synthesis of MOFs, facilitating their direct integration into micro-optical and sensing devices.

We report a high-performance erbium-doped tantalum pentoxide (Er³⁺: Ta₂O₅) large-mode-area (LMA) waveguide amplifier fabricated by direct etching of the gain medium. The device achieves strong optical confinement and high pump-signal overlap (>98.6%) while maintaining propagation loss of 0.7 dB/cm after annealing. Under 140 mW total pump power at 980 nm, the 2.75-cm-long amplifier delivers a maximum on-chip signal enhancement of 38.1 dB at 1530 nm and 24.1 dB at 1550 nm, corresponding to net gains of 8.6 and 9.6 dB, respectively, with gain exceeding 3 dB/cm across the C-band. Large-signal measurements show a maximum output power of 2.4 mW (1.25 dB net gain), confirming stable high-power operation enabled by the LMA design. A minimum noise figure of 5.68 dB is achieved at 1550.5 nm. This device not only overcomes the fabrication challenges associated with Er³⁺: Ta₂O₅ and validates its amplification potential, but also demonstrates excellent large-signal amplification performance, highlighting its strong potential for compact, high-output, and low-noise on-chip optical amplification in integrated photonic systems.

The spectral coherence properties of supercontinuum generation in polarization-maintaining all-normal dispersion fibers are investigated. Stochastic phase noise induced by energy fluctuations, along with spectrally resolved intensity-to-phase transfer coefficients, is quantitatively analyzed, confirming the high coherence of the generated supercontinuum. Our results show that the nonlinear process is fundamentally deterministic with ultra-low spectral phase noise yet exhibits significant intensity-to-phase coupling.

We present a simplified model for analyzing the reflection coefficients of anisotropic semiconductor thin films in terahertz magneto-optical ellipsometry. Derived from electromagnetic boundary conditions, the model is valid when the film thickness is much smaller than the wavelength. Its applicability is demonstrated through terahertz time-domain spectroscopic ellipsometry of two doped GaAs thin films under an external magnetic field. The approach allows direct extraction of sheet conductivity spectra and accurately reproduces the observed magneto-optical response, offering a non-invasive method for characterizing various thin-film materials.

We report a 100 kHz linewidth for the ¹S₀ to ³P₁ intercombination line of ⁸⁸Sr atoms at 689 nm in a microfabricated (9×14×4.4) mm³ vapor cell. This puts an upper bound on the residual gas pressure in the vapor cell of 10 mTorr. The microfabricated Sr vapor cell offers an inexpensive and scalable way to lock lasers in state-of-the-art cold-atom-based atomic clocks and quantum computing experiments. It also paves the way for compact and precise optical frequency references based on alkaline earth vapor cells.

We report the generation and shaping of ∼20 femtosecond pulses in the deep ultraviolet (DUV). Our approach combines spectral broadening in a stretched hollow-core fiber with compression and shaping via an acousto-optic modulator-based pulse shaper. The pulse shaper allows for automatic compression, useful for in-air delivery of pulses to two-dimensional (2D) spectroscopy and other time-resolved experiments. Unlike previous DUV pulse generation schemes that lack phase stability, our method enables programmable generation of phase-locked pulse-pairs with attosecond-level stability. We demonstrate pulse characterization via self-diffraction frequency-resolved optical gating and dispersion scan methods in the DUV and validate performance through a pump-probe experiment resolving electronic dynamics on attosecond timescales.

Ternary chalcopyrite is a promising "green" near-IR (NIR) photonic material with superior properties that are suitable for multiple applications. Here, we report on Cu_xIn_yS nanocrystals with NIR-II (1000-1500 nm) emissions originating from defects-mediated radiative recombination. The asymmetric PL spectrum reveals three distinct bands, suggesting multiple recombination centers linked to intrinsic defects, particularly copper vacancies (V_Cu). The defect-engineered NIR-II luminescence makes these environmentally-friendly nanocrystals highly suitable for biomedical imaging, lighting, and photovoltaics in the NIR-II window.

Wavefront correction is of great significance in a variety of fields but still faces many challenges. Here we propose an all-optical wavefront calibration routine based on a diffractive optical neural network (DONN), which consists of pre-trained multi-layer phase modulation pixel arrays. This enables real-time correction without a wavefront sensor. The optimized DONN is capable of compensating unknown wavefront distortions without task-specific retraining, and it demonstrates broad generalization. Our results promise rapid optical system calibration and establish a broadly applicable and almost all-optical wavefront correction approach with DONN-in-the-loop.

The hydroxyl (OH⁺) radical, with its distinctive 308 nm emission, provides a unique fingerprint for hydrocarbon combustion monitoring. Exploiting the low ultraviolet sky background, OH⁺-based detection achieves high accuracy without cooling but suffers from narrowband-filter blue shifts caused by light-convergence angles, degrading uniformity and reliability. We propose a differential correction method using a coordinated filter pair-308 nm target and 307 nm reference-engineered to share identical blue shifts. Images from both channels are acquired, and the background (I_off) is subtracted from the target (I_on). Because broadband background signals (mainly sky scattering) remain nearly equal after blue shift, subtraction cancels them while fully retaining the narrowband OH⁺ emission present only in the 308 nm channel. Experiments show that this approach cleanly extracts a 1 nm bandwidth 308 nm signal under ideal conditions and markedly improves the signal-to-noise ratio (SNR). The resulting dual-channel synchronized imaging and differential system provides a reliable, engineering-ready solution to mitigate filter blue shift and enhance UV spectral detection accuracy in dynamic scenarios.