ACS Photonics最新文献

Narrowband photodetectors (NPDs) are essential for surveillance, photometry, and remote sensing. However, few studies have demonstrated multiple narrowband detection abilities within a single PD, particularly in the ultraviolet (UV) and near-infrared (NIR) regions, which are not directly recognized by the human eyes. In this work, we present a method for UV and NIR dual-band photodetection on the same device through integrating tandem-like perovskite/organic bulk-heterojunction (P-OBHJ) with a translucent microcavity. By leveraging the self-doping effect of perovskites, we fabricated p-type MAPbI₃ films with the unbalanced electron–hole transport, enabling complete visible-light depletion upon bottom illumination. Meanwhile, NIR light passes through the entire perovskite layer to reach the OBHJ layers, ultimately resulting in a narrowband response to NIR light. Upon top illumination, the semitransparent microcavity selectively transmits only UV light, achieving narrowband UV detection. As a result, the optimized device exhibits the responsivity of 0.21 and 0.03 A/W with the corresponding shot-noise-limited specific detectivity reaching 4 × 10¹² and 6 × 10¹¹ Jones, at the peak wavelengths of 810 and 330 nm, respectively. Last, we showcase prototype applications of the dual-band PDs as heartbeat and solar UV intensity monitors, providing a novel strategy for the development of multifunctional NPD.

A multichannel lithium-niobate-on-insulator (LNOI) photonic filter for dense wavelength-division multiplexing (DWDM) is proposed and realized for the first time by introducing high-order 1 × 2 Fabry–Perot (FP) cavity filters in cascade. These 1 × 2 FP cavity filters are developed with a high-order FP cavity consisting of three multimode waveguide gratings (MWGs) and a mode (de) multiplexer for achieving flat-top spectral responses. Such an MWG-based LNOI photonic filter is circulator-free and convenient to be cascaded for working with multiple channels. In addition, there are no bends introduced in the cavities, which enables an extensive free spectral range (FSR) owing to the ultracompactness of the cavity. As an example, a 6-channel LNOI photonic filter is designed and fabricated for DWDM with a channel spacing of 3.2 nm. It shows that the measured 3 dB bandwidth is ∼1.4 nm, and the extinction ratio is up to 38 dB, while the excess loss is ∼0.5 dB, and the interchannel crosstalk is <−25 dB. Besides, an 8 nm × 1.6 nm LNOI DWDM filter is also developed, exhibiting an excess loss of ∼0.5 dB and interchannel crosstalk of <−18 dB. The present devices show great potential as a promising option for realizing future high-capacity optical interconnects.

Spectrometers are important analytical instruments in research fields involving light and matter, and their miniaturization is critical for portable and on-chip applications. Spectrometers based on computational reconstruction of spectra are among the most promising technologies for footprint reduction. Of the various reconstruction methods, those that require programming of the light source are particularly challenging to realize. In this work, by exploiting the gradient-composition characteristic of a single GeSn strip grown using the rapid melting growth method, near-infrared microscale light-emitting diodes (μ-LEDs) with different peak wavelengths were fabricated. The spectra of the GeSn μ-LEDs, which are integrated on a Si substrate, can be programmed in the range of 1.6 to 2.4 μm to realize a prototype reconstructive spectrometer by controlling the injection current of the individual LEDs. In this way, as an example, the absorption spectrum of water was successfully reconstructed simply by programming the spectra of the light source. These results provide a completely new technological roadmap for the miniaturization of spectrometers.

Plasmonic nanoparticles exhibit strong optical scattering and absorption due to enhanced coupling to incident electromagnetic waves, while their efficient photothermal heating enables effective conversion of electromagnetic to mechanical energy. In this work, we put forward a theoretical framework for acoustoplasmonics, where plasmonic nanoparticles control the acoustic wavefront with light. We model the coupled optical, thermoelastic and acoustic mechanisms for gold nanospheres (AuNSs) and nanoellipsoids (AuNEs), and find that each physical mechanism entails a distinct toolbox of parameters, which can be tailored for effective acoustoplasmonic design. Simple analytical studies are performed for AuNSs, both validating numerical models and enabling quasi-analytical wavefront shaping under long laser pulse durations. AuNEs introduce optical anisotropy, and we numerically demonstrate that the polarization-dependent optical absorption in AuNEs can lead to selective photoexcitation and subsequently polarization-tunable acoustic wave generation. Moreover, we investigate the varying acoustoplasmonic frequency regimes, where optical resonance arises due to electromagnetic frequency, while acoustic resonance relates to laser pulse duration. We demonstrate proof-of-concept acoustoplasmonic metasurface designs using these mechanisms for tunable acoustic wavefront shaping in the form of lensing and beam steering. We suggest that future acoustoplasmonic systems, optimized using the physical mechanisms discussed here, will find use in a variety of applications, including miniaturized ultrasonic imaging and high-frequency signal processing.

Silicon nitride (Si₃N₄) photonic integrated circuits (PICs) have emerged as a versatile platform for a wide range of applications, such as nonlinear optics, narrow-line-width lasers, and quantum photonics. While thin-film Si₃N₄ processes have been extensively developed, many nonlinear and quantum optics applications require the use of thick Si₃N₄ films with engineered dispersion, high mode confinement, and low optical loss. However, high tensile stress in thick Si₃N₄ films often leads to cracking, making the fabrication challenging to meet these requirements. In this work, we present a robust and reliable fabrication method for ultralow-loss, dispersion-engineered Si₃N₄ PICs using amorphous silicon (a-Si) hardmask etching. This approach enables smooth etching of thick Si₃N₄ waveguides while ensuring the long-term storage of crack-free Si₃N₄ wafers. We achieve intrinsic quality factors (Q_i) as high as 25.6 × 10⁶, corresponding to a propagation loss of 1.6 dB/m. The introduction of a-Si hardmask etching along with novel crack-isolation trench designs and fabrication strategies offers notable advantages including high etching selectivity, long-term wafer storage, high yield, and full compatibility with existing well-developed silicon-based semiconductor processes. We demonstrate frequency comb generation in the fabricated microring resonators, showcasing the platform’s potential for applications in optical communication, nonlinear optics, metrology, and spectroscopy. This stable and efficient fabrication method offers high performance with significantly reduced fabrication complexity, representing a remarkable advancement toward mass production of Si₃N₄ PICs for a wide spectrum of applications.