School of Physics, University of Hyderabad, Hyderabad, 500046, India.
Sci Rep. 2017 May 24;7(1):2395. doi: 10.1038/s41598-017-02613-3.
The more than a century old Sagnac interferometer is put to first of its kind use to generate an achromatic single-charge vortex equivalent to a Laguerre-Gaussian beam possessing orbital angular momentum (OAM). The interference of counter-propagating polychromatic Gaussian beams of beam waist ω with correlated linear phase (ϕ ≥ 0.025 λ) and lateral shear (y ≥ 0.05 ω) in orthogonal directions is shown to create a vortex phase distribution around the null interference. Using a wavelength-tunable continuous-wave laser the entire range of visible wavelengths is shown to satisfy the condition for vortex generation to achieve a highly stable white-light vortex with excellent propagation integrity. The application capablitiy of the proposed scheme is demonstrated by generating ultrashort optical vortex pulses, its nonlinear frequency conversion and transforming them to vector pulses. We believe that our scheme for generating robust achromatic vortex (implemented with only mirrors and a beam-splitter) pulses in the femtosecond regime, with no conceivable spectral-temporal range and peak-power limitations, can have significant advantages for a variety of applications.
一个多世纪历史的萨格纳克干涉仪首次被用于产生无色单电荷旋涡等效于具有轨道角动量（OAM）的拉盖尔-高斯光束。在正交方向上，具有相关线性相位（(\phi\geq0.025\lambda)）和横向剪切（(y\geq0.05\omega)）的反传播多色高斯光束的干涉被证明可以在零干涉处创建一个旋涡相位分布。使用波长可调谐连续波激光，整个可见波长范围都满足了产生旋涡的条件，从而实现了具有极好传播完整性的高度稳定的白光旋涡。通过产生超短光学旋涡脉冲、其非线性频率转换以及将它们转换为矢量脉冲，展示了所提出方案的应用能力。我们相信，我们在飞秒范围内生成稳健的无色旋涡（仅使用镜子和分束器实现）脉冲的方案，不存在可以想象的光谱-时间范围和峰值功率限制，对于各种应用都具有显著的优势。
