2023, 50(22): 2215001
2023, 43(17): 1714009
2023, 43(14): 1415002
Integrated photonics provides a promising platform for quantum key distribution (QKD) system in terms of miniaturization, robustness, and scalability. Tremendous QKD works based on integrated photonics have been reported. Nonetheless, most current chip-based QKD implementations require additional off-chip hardware to demodulate quantum states or perform auxiliary tasks such as time synchronization and polarization basis tracking. Here, we report a demonstration of resource-efficient chip-based BB84 QKD with a silicon-based encoder and a decoder. In our scheme, the time synchronization and polarization compensation are implemented relying on the preparation and measurement of the quantum states generated by on-chip devices; thus, we need no additional hardware. The experimental tests show that our scheme is highly stable with a low intrinsic quantum bit error rate of in a 6 h continuous run. Furthermore, over a commercial fiber channel up to 150 km, the system enables the realization of secure key distribution at a rate of 866 bit/s. Our demonstration paves the way for a low-cost, wafer-scale manufactured QKD system.
2023, 11(8): 1364
Based on the 90 nm silicon photonics commercial foundry, sidewall-doped germanium–silicon photodetectors (PDs) are designed and fabricated. The large designed overlap between the optical field and electric field achieves high responsivity while retaining high-speed performance. Even including the loss due to optical fiber coupling, the PD demonstrates an external responsivity greater than 0.55 A/W for transverse magnetic (TM) polarization and 0.65 A/W for transverse electric (TE) polarization at 1530 nm. A flat responsivity spectrum of is achieved up to 1580 nm for both polarizations. Their internal responsivities can exceed 1 A/W in the optical communication bands. Furthermore, with the aid of a 200 mm wafer-level test and analysis, the overall PDs of 26 reticles have a 3 dB optoelectrical bandwidth and a dark current at a bias voltage. Finally, the eye diagram performances under TE and TM polarizations, various modulation formats, and different input wavelengths are comprehensively investigated. The clear open electrical eye diagrams up to 120, 130, 140, and 150 Gbit/s nonreturn-to-zero are experimentally attained at a photocurrent of 1 mA. To the best of our knowledge, this is the first time that single-lane direct detection of record-high-speed 200, 224, 256, and 290 Gbit/s four-level pulse amplitude modulation (PAM) and 300, 336, 384, and 408 Gbit/s eight-level PAM optical signals has been experimentally achieved.
2023, 11(6): 961
In this work, a confined-doped fiber with the core/inner-cladding diameter of 40/250 μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate gas deposition technique, and subsequently applied in a tandem-pumped fiber amplifier for high-power operation and transverse mode instability (TMI) mitigation. Notably, the impacts of the seed laser power and mode purity are preliminarily investigated through comparative experiments. It is found that the TMI threshold could be significantly affected by the seed laser mode purity. The possible mechanism behind this phenomenon is proposed and revealed through comprehensive comparative experiments and theoretical analysis. Finally, a maximum output power of 7.49 kW is obtained with the beam quality factor of approximately 1.83, which is the highest output power ever reported in a forward tandem-pumped confined-doped fiber amplifier. This work could provide a good reference and practical solution to improve the TMI threshold and realize high-power high-brightness fiber lasers.confined-doped fiber fiber laser good beam quality high power transverse mode instability mitigation
High Power Laser Science and Engineering
2022, 10(6): 06000e44
2022, 42(23): 3788/AOS2336001