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Microwave/mm-wave photonics and its applications for radars and radio astronomy
Femtosecond mode-locked lasers and optical frequency combs can be a useful optical source for various microwave photonic applications by coherently linking optical frequencies and microwave frequencies. We have pioneered ultralow-noise frequency comb-based microwave photonics field. We have established several important microwave photonic methodologies including sub-fs-resolution, long-term stable timing detection and synchronization between optical pulse train and microwave signals [1,2,3], ultralow-noise microwave synthesis [4,5,6], and remote transfer of microwave phase over long fiber links [7,8].
Using these microwave photonic methods, we tackled timing and synchronization issues between mode-locked lasers and microwave sources in ultrafast quantum science facilities such as ultrafast electron diffraction (UED) apparatus, with successful installation and operation at the Max-Planck Institute of Quantum Optics (Garching, Germany) [9] and the Korea Atomic Energy Research Institute (Daejeon, Korea) [10]. Recently, we achieved long-term sub-10-fs laser-electron synchronization for MeV-level electron pulses for the first time by combining laser-microwave synchronization and THz streaking [11].
Currently we are focusing on developing innovative applications of microwave/mm-wave photonic technology. First, we are working with Hanwha Systems and ADD to apply photonic techniques, such as optical sampling, data conversion, and chirped microwave signal synthesis and detection, to enhance the performance of radar systems. In addition, we are working with KRISS, KASI and KISTI to greatly enhance the performance of radio astronomy facilities based on Very Long Baseline Interferometer (VLBI). Specifically, we are working on the generation of optical atomic clock-referenced, synchronized microwave/mm-wave signals and phase-calibrating flat RF-comb signals at multiple VLBI antenna sites. This technological advancement will not only greatly improve the VLBI performance for imaging new cosmic radio sources, including black holes, but also facilitate intercontinental comparison of optical atomic clocks, which is necessary for redefining the second in the coming decade.
Related Publications
[1] K. Jung and J. Kim, "Subfemtosecond synchronization of microwave oscillators with mode-locked Er-fiber lasers," Opt. Lett. 37, 2958 (2012)
[2] C. Jeon, Y. Na, B. Lee, and J. Kim, "Simple-structured, subfemtosecond-resolution optical-microwave phase detector," Opt. Lett. 43, 3997-4000 (2018)
[3] C. Ahn, Y. Na, M. Hyun, J. Bae, and J. Kim, "Synchronization of an optical frequency comb and a microwave oscillator with 53 zs/Hz1/2 resolution and 10-20-level stability," Photonics Research 10, 365-372 (2022)
[4] K. Jung, J. Shin, and J. Kim, "Ultralow phase noise microwave generation from mode-locked Er-fiber lasers with subfemtosecond integrated timing jitter," IEEE Photonics J. 5, 5500906 (2013)
[5] J. Wei, D. Kwon, S. Zhang, S. Pan, and J. Kim, "All-fiber-photonics-based ultralow-noise agile frequency synthesizer for X-band radars," Photon. Res. 6, 12-17 (2018)
[6] D. Kwon, D. Jeong, I. Jeon, H. Lee, and J. Kim, "Ultrastable microwave and soliton-pulse generation from fibre-photonic-stabilized microcombs," Nature Communications 13, 381 (2022)
[7] J. Kim, J. A. Cox, J. Chen, and F. X. Kaertner, "Drift-free femtosecond timing synchronization of remote optical and microwave sources," Nature Photon. 2, 733 (2008)
[8] K. Jung, J. Shin, J. Kang, S. Hunziker, C. K. Min, and J. Kim, "Frequency comb-based microwave transfer over fiber with 7x10-19 instability using fiber-loop optical-microwave phase detectors," Opt. Lett. 39, 1577 (2014)
[9] M. Walbran, A. Gliserin, K. Jung, J. Kim, and P. Baum, "5-fs laser-electron synchronization for pump-probe crystallography and diffraction," Phys. Rev. Appl. 4, 044013 (2015)
[10] H. Kim, N. Vinokurov, I. Baek, K. Oang, M. Kim, Y. Kim, K. Jang, K. Lee, S. Park, S. Park, J. Shin, J. Kim, F. Rotermund, S. Cho, T. Feurer, and Y. Jeong, "Towards jitter-free ultrafast electron diffraction technology," Nature Photon. 14, 245-249 (2020)
[11] J. Shin, H. Kim, S. Park, H. Bark, I. Baek, K. Oang, K. Jang, K. Lee, F. Rotermund, Y. Jeong, and J. Kim, "Sub-10-fs timing for ultrafast electron diffraction with THz-driven streak camera," Laser Photon. Rev. 15, 2000326 (2021)
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