The resilience of quantum two-photon interference against optical loss and background sets it apart from classical single-photon interference for the purpose of sensing. However, achieving fast measurements at the nanometer scale with two-photon interference is challenging, as attaining high resolution typically requires either ultra-broadband photons or many probe photons. To realize nanometer-scale measurements in a matter of seconds or less, we greatly increase the per-photon information content via highly non-degenerate energy entanglement. Our fast measurements thereby enable us to probe time-varying signals at the nanometer scale. To further develop our capabilities, we have drawn on single-photon imaging techniques to implement a robust protocol for reconstructing periodic signals from our relatively sparse detection data, complete with amplitude and frequency information. With this analysis regimen, we have successfully extracted complex multi-frequency signals as well as kHz-range acoustic vibrations. We review our method and present the results of an example measurement to illustrate our capabilities.
This work reports on the quantum mechanical based approach to establish electronic band structure modeling of ternary-based type-II superlattices using a modified sp3s* empirical tight binding method. The study shows that using a virtual crystal approximation with a bowing of the s-on-site tight-binding energy is relevant to model superlattices including ternary layers and solving the Hamiltonian. Additionally, a theoretical explanation of atomic segregation as a crucial parameter during the growth was considered. The quantum mechanical based simulation results show agreement with experimentally measured band gap of InAs/InA(s1-x)Sb(x) and InAs/AlAs(1-x)Sbx/InAs/InAs1-xSbx superlattices and their variants. The model can be used to explain experimental results for superlattices grown at different growth conditions, especially the bandgaps, within some growth uncertainties.
Lung tumor segmentation in thoracic CT scans is vital for radiomics analysis and treatment assessment, but is hindered by heterogeneous tumor morphology, ambiguous boundaries, and inaccuracy and labor-intensiveness of manual segmentation. Existing methods, including traditional machine learning and deep learning methods, often suffer from over-/under-segmentation or poor robustness. In this study, we propose an improved Segment Anything Model (called Tumor-SAM) for semi-automatic lung tumor segmentation, integrating U-Net for multi-scale feature extraction and a novel ellipse prompt. Tumor-SAM first detects lung ROI to reduce interference from the surrounding tissue. Then, we design an ellipse prompt defined by center, axes, and rotation that captures tumor shape/location better than points, boxes, or circles. The architecture of Tumor-SAM includes a U-Net-based image encoder (replacing ViT), prompt encoder with positional encoding, multi-head attention fusion, and mask decoder. Our method achieved an average Dice index of 0.84±0.13 and an average Hausdorff distance of 7.25±6.24 mm on 164 testing scans, demonstrating good lung tumor segmentation accuracy.
Compact, stable and narrow-linewidth laser sources in the visible spectral range are essential for various quantum and precision measurement applications. Wavelength between 630 nm to 520 nm are particularly interesting for research and development of diode lasers, because these wavelengths are usually not easily attainable by diode based systems. However, realizing miniaturized diode lasers in this wavelength regime that simultaneously offer high spectral purity, good beam quality and sufficient output power remains challenging. In this work, we investigate and compare miniaturized visible diode lasers emitting at 619 nm that employ a fiber Bragg-grating (FBG) and volume Bragg-grating (VBG) for spectral stabilization. We design and fabricated both device variants and characterize their electro-optical, spectral and beamquality performance. The FBG-stabilized device achieved peak power of 5 mW, whereas the VBG-stabilized device emits up to 40 mW at 150 mA. The emission linewidth remains below 5 MHz and the beam quality factor M2 approximately 1.8. Compared with the FBG device, the VBG-stabilized design exhibits a reduced threshold current and a significantly improved emission power. These results demonstrate that compact, wavelength stabilized visible diode laser modules at 619 nm can meet key requirements of quantum technologies. This technology platform is suitable for other wavelengths below 630 nm.
We report a comparative investigation of the optical properties of Dy3+ doped low-phonon crystals and glasses for potential applications in visible and mid-infrared solid-state laser development. All samples were excited at 450 nm for visible emissions in the 480 - 800 nm spectral region and at 910 nm for mid- infrared emissions spanning 2100 - 5000 nm. Direct optical excitation in the blue resulted in dominant yellow emission bands centered near 575 - 585 nm originating from the F-4(9/2) -> H-6(13/2) transition. In addition, weaker emission features were observed in the blue (similar to 480 nm) and red (similar to 670 - 750 nm) spectral regions corresponding to the F-4(9/2) -> H-6(15/2), F-4(9/2) -> H-6(11/2), and F-4(9/2) -> H-6(9/2) transitions. Among the investigated hosts, Dy3+:KPb2Cl5 exhibited the strongest and most spectrally distinct yellow emission, while Dy3+:InF3 also demonstrated well-defined visible emission features. In contrast, Dy3+:BaF2 and Dy3+: Ga2Ge5S13 displayed broadened emission bands accompanied by increased background contributions. The peak emission cross sections for the yellow F-4(9/2) -> H-6(13/2) transition were determined to be 0.8 x 10(-20) cm(2) for Dy3+:KPb2Cl5 and 0.1 x 10(-20) cm2 for Dy3+:InF3. Fluorescence lifetime measurements of the 4F9/ 2 excited state revealed millisecond-scale decay in Dy3+:KPb2Cl5 and Dy3+:InF3, while significantly faster decay times (< 5 mu s) were observed in Dy3+:BaF2 and Dy3+:Ga2Ge5S13. Mid-infrared emission from the H-6(11/2) -> H-6(13/2) transition was observed in the 3 - 5 mu m spectral region under near-infrared excitation, exhibiting millisecond-scale lifetimes in both crystalline and glass hosts. The observed differences in spectral characteristics and decay dynamics are attributed to host-dependent phonon energy and local structural environment.
