Low phase noise microwave signal generation with microcombs (Invited)
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摘要: 低相位噪声微波信号在通信、雷达、时频计量、深空探测等领域中不可或缺,光子学微波信号产生近年来发展快速,有望在载波频率、调谐性、相噪、可集成、功耗等多个方面突破传统电子学微波信号产生瓶颈。早期的光生微波系统复杂,激光器以及相关稳定设备体积庞大,难以在实验室以外的场所应用。近年来,基于微谐振腔的光学频率梳的迅速发展,凭借其低损耗、小体积、强稳定的优势,基于微腔光梳的微波光子学应用吸引了研究者们的广泛关注,其中基于微腔光梳的光生微波系统得到深入研究。文中将综述国内外近10年来基于微腔光梳的低相噪微波信号产生发展状况,并对基于微腔光梳的光生微波系统在未来应用中的主要挑战与发展趋势作以展望。Abstract: Microwave signals with low phase noise are indispensable in wireless communication, radar, time and frequency metrology, and deep astronomy. Photonic microwave signal generation approaches are promising. They can break through the bottleneck of classical microwave signal generation methods in many aspects, such as carrier frequency, tunability, phase noise, integrability, and power consumption. The early systems of photonic microwave signal generation were complex, the lasers and related equipment were bulky, which restricted their application outside of the laboratories. In recent years, optical frequency combs based on microcavities develop rapidly. With the advantages of microcombs such as low loss, small size, and ultrahigh stability, the application of microwave photonics based on microcombs has attracted extensive attention of researchers and the systems of photonic microwave signal generation have been intensively studied. In this paper, we reviewed the topic of low phase noise photonic microwave generation with microcombs and prospected the challenges and development trend in the future application of the systems of photonic microwave signal based on microcombs at the end.
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图 2 基于微腔光频梳拍频的微波信号产生。(a)~(d)分别基于氟化镁微腔的光频梳微波信号发生器、基于布里渊辅助稳定的光频梳微波信号发生器、芯片级微波信号发生器、基于二氧化硅微盘腔的光频梳微波信号发生器。图(a)中五条曲线分别为:(1)光电探测器后无窄带滤波器时的微波信号相位噪声(红线),(2)光电探测器后有窄带滤波器时的相位噪声(蓝线),(3)、(4)分别是振荡器热折射噪声理论极限与量子噪声理论极限,(5)相位噪声仪底噪
Figure 2. Microwave signal generation based on beat signals of microcombs. (a)-(d) Frequency comb microwave signal generator based on
$ {\mathrm{M}\mathrm{g}}_{2}\mathrm{F} $ microresonator, microcomb microwave signal generator based on Brillouin assisted stabilization, chip-scale microwave signal generator, frequency comb microwave signal generator based on silica disk microresonator respectively. The five lines in Fig.(a), phase noise of microwave signal without and with(red line, (1)) and with(blue line, (2)) a narrow-band filter-placed after the photodetector. Curves(3) and (4) describe theoretically found fundamental thermorefractive and quantum noise of the oscillator, sensitivity of phase noise analyzer is described by curve(5)3 基于微腔光频梳分频的微波信号产生。(a)和(c)、(b)和(d)、(e)和(g)、(f)和(h)分别为基于布里渊斯托克斯光分频的毫米波振荡器、基于光纤延迟线干涉仪的定时抖动测量装置、基于光纤光子稳定方法的微波信号合成器、基于微腔光频梳转移振荡器的微波合成器。图(d)中的三条曲线分别为:(i)测量的微波信号的时间抖动,(ii)预计的孤子相对强度噪声耦合的时间抖动,(iii)计算的量子限时间抖动。图(h)中的蓝色曲线和绿色曲线分别为通过克尔传输振荡器和克尔梳重频获得的微波信号的14.09 GHz信号绝对单边带相位噪声,红色曲线是通过超稳激光相位噪声计算得到的微波信号理论极限
3. Microwave signal generation based on the microcomb division frequency. (a) and (c), (b) and (d), (e) and (g), (f) and (h) Millimetre wave oscillator based on Brillouin Stokes division frequency, measurement device of timing jitter based on optical fiber delay line interferometer, microwave signal generator based on optical fiber photonic stabilisation method, microwave generator using a microcomb-based transfer oscillator. The three lines in Fig.(b), measured timing jitter[curve(i)], projected timing jitter from soliton relative intensity noise [curve (ii)] and computed quantum limit of timing jitter [curve (iii)]. The lines in Fig.(d), absolute single-sideband (SSB) phase noise of the 14.09 GHz signal via the Kerr comb transfer oscillator (blue line) and obtained directly from the Kerr comb repetition rate (green line). The red line is the limit inferred from the optical phase noise of the ultra-stable laser
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