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.

最初预测了在施加了静电电场的固体晶格中电子的Bloch振荡（BOs）。由于电子的碰撞散射和势垒隧穿，固体中BO的观察仍然具有挑战性。然而，已经在各种晶格系统中实验证明了光子，声子和冷原子的电子BO的相似性。最近，通过使用光学微谐振器提出并研究了频率维度上的BO，这提供了一种控制光频率的独特方法。然而，有限的谐振器寿命和固有损耗阻碍了实际观察到的效果。在这里，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性地演示了BO。我们表明，调制周期和光纤环路往返时间之间的失谐充当有效矢量电位，因此具有恒定的有效力，可以在调制诱导的频率晶格中产生BOs。通过色散傅里叶变换，可以将脉冲频谱映射到时间维度，并可以精确测量其瞬态演变。这项研究为实现综合尺寸的BO提供了一种有前途的方法，并可能在光纤通信系统的频率操纵中找到应用。并可以精确测量其瞬态演变。这项研究为实现综合尺寸的BO提供了一种有前途的方法，并可能在光纤通信系统的频率操纵中找到应用。并可以精确测量其瞬态演变。这项研究为实现综合尺寸的BO提供了一种有前途的方法，并可能在光纤通信系统的频率操纵中找到应用。