Vortex beams have wide applications in optical tweezers, optical communications and so on. Long period fiber gratings, mode selective couplers, few mode fiber Bragg gratings or specially designed fibers are often used to generate vortex beams from fiber lasers. New methods of mode selection in fiber lasers are always attractive. When transverse modes propagate along a multimode fiber, the polarization state of each mode rotates differently due to birefringence. In this paper, a linear cavity fiber laser and a ring cavity fiber laser using a polarization rotation technique are proposed to select the output laser mode. Three waveplates and a polarizing beam splitter (PBS) are used as a mode loss controller inside the laser cavity. By rotating the waveplates inside the cavity, different laser modes can be selected and achieved from the laser cavity by the PBS. Experimentally, the fundamental LP₀₁ mode, the LP₁₁ mode, the LP₂₁ mode and vortex beams with 1 topological charges were achieved.

涡旋光束在光镊，光通信等方面有着广泛的应用。长周期光纤光栅，模式选择耦合器，很少模式的光纤布拉格光栅或专门设计的光纤通常用于从光纤激光器产生涡旋光束。光纤激光器中模式选择的新方法总是很有吸引力。当横向模沿着多模光纤传播时，由于双折射，每个模的偏振态会不同地旋转。本文提出了一种利用偏振旋转技术的线性腔光纤激光器和环形腔光纤激光器来选择输出激光模式。三个波片和一个偏振分束器（PBS）被用作激光腔内部的模式损耗控制器。通过旋转腔体内的波片，PBS可以从激光腔中选择并实现不同的激光模式。实验上，基本LP_实现了01模式，LP ₁₁模式，LP ₂₁模式和具有1个拓扑电荷的涡旋光束。