Chen Hao, Yang NingNing, Qin Chengzhi, Li Wenwan, Wang Bing, Han Tianwen, Zhang Chi, Liu Weiwei, Wang Kai, Long Hua, Zhang Xinliang, Lu Peixiang
School of Physics and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China.
Light Sci Appl. 2021 Mar 5;10(1):48. doi: 10.1038/s41377-021-00494-w.
Bloch oscillations (BOs) were initially predicted for electrons in a solid lattice to which a static electric field is applied. The observation of BOs in solids remains challenging due to the collision scattering and barrier tunnelling of electrons. Nevertheless, analogies of electron BOs for photons, acoustic phonons and cold atoms have been experimentally demonstrated in various lattice systems. Recently, BOs in the frequency dimension have been proposed and studied by using an optical micro-resonator, which provides a unique approach to controlling the light frequency. However, the finite resonator lifetime and intrinsic loss hinder the effect from being observed practically. Here, we experimentally demonstrate BOs in a synthetic frequency lattice by employing a fibre-loop circuit with detuned phase modulation. We show that a detuning between the modulation period and the fibre-loop roundtrip time acts as an effective vector potential and hence a constant effective force that can yield BOs in the modulation-induced frequency lattices. With a dispersive Fourier transformation, the pulse spectrum can be mapped into the time dimension, and its transient evolution can be precisely measured. This study offers a promising approach to realising BOs in synthetic dimensions and may find applications in frequency manipulations in optical fibre communication systems.
布洛赫振荡（BOs）最初是针对施加了静电场的固体晶格中的电子所做的预测。由于电子的碰撞散射和势垒隧穿，在固体中观测布洛赫振荡仍然具有挑战性。尽管如此，电子布洛赫振荡与光子、声子和冷原子的类比已在各种晶格系统中得到实验证明。最近，通过使用光学微谐振器，人们提出并研究了频率维度上的布洛赫振荡，这为控制光频率提供了一种独特的方法。然而，有限的谐振器寿命和固有损耗阻碍了实际观测到这种效应。在此，我们通过采用具有失谐相位调制的光纤环路电路，在合成频率晶格中实验证明了布洛赫振荡。我们表明，调制周期与光纤环路往返时间之间的失谐充当有效矢量势，从而充当能在调制诱导的频率晶格中产生布洛赫振荡的恒定有效力。通过色散傅里叶变换，脉冲光谱可映射到时间维度，并且其瞬态演化能够被精确测量。这项研究为在合成维度中实现布洛赫振荡提供了一种很有前景的方法，并且可能在光纤通信系统的频率操纵中找到应用。
