We experimentally generate an orbital-angular-momentum (OAM) beam with a tunable mode order over a range of wavelengths utilizing an integrated broadband pixel-array OAM emitter. The emitter is composed of a 3-to-4 coupler, four phase controllers, and a mode convertor. An optical input is split into four waveguides by the coupler. Subsequently, the four waveguide fields are coherently combined and transformed into a free-space OAM beam by the mode convertor. By tuning the phase delay ${\boldsymbol \Delta}{\boldsymbol \varphi}$ between the four waveguides using the integrated phase controllers, the OAM order of the generated beam could be changed. Our results show that (a) a single OAM beam with a tunable OAM order ($\ell = - 1$ or $\ell = + 1$) is generated with the intermodal power coupling of ${\lt}\,{-} {11}\;{\rm dB}$, and (b) in a wavelength range of 6.4 nm, a free-space link of a single 50 Gbaud quadrature-phase-shift-keying (QPSK) channel carried by the tunable OAM beam is achieved with a bit error rate below the forward-error-correction threshold. As proof of concept, a 400 Gbit/s OAM-multiplexed and WDM QPSK link is demonstrated with a ${\sim}{1 - }$dB OSNR penalty compared with a single-beam link.

中文翻译：

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演示使用集成宽带像素阵列结构在一定波长范围内生成具有可调模式阶数的 100 Gbit/s 轨道角动量光束

我们利用集成的宽带像素阵列 OAM 发射器，通过实验在一定波长范围内生成具有可调模式阶数的轨道角动量 (OAM) 光束。发射器由一个 3 对 4 耦合器、四个相位控制器和一个模式转换器组成。光输入被耦合器分成四个波导。随后，四个波导场相干组合并通过模式转换器转换为自由空间 OAM 光束。通过使用集成相位控制器调整四个波导之间的相位延迟${\boldsymbol \Delta}{\boldsymbol \varphi}$，可以改变生成光束的 OAM 顺序。我们的结果表明 (a) 具有可调 OAM 阶数 ( $\ell = - 1$或$\ell = + 1$) 是通过模间功率耦合${\lt}\,{-} {11}\;{\rm dB}$和 (b) 在 6.4 nm 的波长范围内产生的，a 的自由空间链路由可调谐 OAM 波束承载的单个 50 Gbaud 正交相移键控 (QPSK) 通道以低于前向纠错阈值的误码率实现。作为概念证明，与单波束链路相比，400 Gbit/s OAM 复用和 WDM QPSK 链路的OSNR 损失为${\sim}{1 - }$ dB。