Akademik Veri Yönetim Sistemi
26th Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications, California, Amerika Birleşik Devletleri, 18 - 21 Ocak 2026, cilt.13883, (Tam Metin Bildiri)
We demonstrate a novel femtosecond-scale optical gating technique based on non-degenerate two-photon absorption (2PA) directly within the photodetector, thereby integrating nonlinear gating and signal detection into a single element. This method eliminates the need for separate nonlinear crystals and complex optical alignments typically required in conventional gating approaches such as Kerr shutters or up-conversion techniques. We experimentally validate this concept through cross-correlation measurements using a bi-alkali photocathode in a photomultiplier tube (PMT). The measured cross-correlation width is ~600 fs, while the actual temporal resolution of the method is significantly better. The gating process relies on the simultaneous absorption of signal and gate photons, with photon energies carefully selected to suppress undesired linear or degenerate two-photon processes. We further extend this technique to a silicon CMOS sensor for time-resolved imaging through scattering media. Using synchronized femtosecond gate and signal pulses, we demonstrate ballistic image reconstruction of an object obscured by a turbid medium. Sub-picosecond temporal gating enables efficient separation of ballistic photons from scattered light, with enhanced contrast observed at zero delay, confirming the ultrafast gating capability. This study establishes the operational conditions, spectral requirements, and temporal performance of non-degenerate two-photon gating in conventional photodetectors. By allowing the interchangeability of gate and signal wavelengths, the technique enables detection of long-wavelength signals beyond the spectral sensitivity range of the detector using short-wavelength gating. Our approach offers a simplified architecture for ultrafast optical measurements while maintaining high temporal resolution and sensitivity, with strong potential for applications such as in-vivo biomedical imaging.