Geometric-phase-induced arbitrary polarization and orbital angular momentum generation in helically twisted birefringent photonic crystal fiber
Geometric-phase-induced arbitrary polarization and orbital angular momentum generation in helically twisted birefringent photonic crystal fiber
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DOI：
10.1364/prj.393255
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发表时间：
2020-08-01
影响因子：
7.6
通讯作者：
Saitoh, Kunimasa
中科院分区：
文献类型：
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作者：
Fujisawa, Takeshi;Saitoh, Kunimasa
分析了螺旋扭曲双折射光子晶体光纤 (TB-PCF) 中光的偏振态和轨道角动量 (OAM) 态的演变。结果表明，当 PCF 发射通常的线偏振 (LP) 模式时，会周期性地激发圆偏振 (CP) 分量（斯托克斯参数的 S-3）。激发源自 TB-PCF 中的几何相位。对于固定扭转率，S-3 激励较大，线性双折射较大。如果线性双折射足够大，除了 S-3 激励之外，还可以看到 CP 滤波行为。从几何相位符号的分析考虑，提出了扭转周期反转的TB-PCF在庞加莱球上产生任意偏振态。接下来，显示了高阶 LP 模式输入的多模式 TB-PCF 中的 OAM 状态生成。通过观察 TB-PCF 与 LP01 模式混合的远场干涉图样，可以看到与 OAM 状态相关的涡旋。与单模情况类似，通过使用周期性扭转反转，可以有效生成 OAM。这些结果表明，通过简单地将光纤的 LP 模式发射到 TB-PCF 中，可以生成任意偏振和 OAM 状态，从而形成一种操纵光空间状态的新机制。 (C) 2020中国激光出版社
The evolutions of polarization and orbital angular momentum (OAM) states of light in helically twisted birefringent photonic crystal fibers (TB-PCFs) are analyzed. It is shown that a circular polarization (CP) component (S-3 of a Stokes parameter) is periodically excited when usual linearly polarized (LP) modes of PCF are launched. The excitation originates from a geometric phase in TB-PCFs. The S-3 excitation is larger for larger linear birefringence for a fixed twisting rate. If the linear birefringence is large enough, a CP filtering behavior can be seen in addition to the S-3 excitation. From the analytical consideration of the sign of the geometric phase, the TB-PCF with periodical inversion of twisting is proposed to generate arbitrary polarization state on the Poincare sphere. Next, an OAM state generation in multimode TB-PCFs is shown for higher-order LP mode input. By observing a far-field interference pattern from TB-PCF mixed with LP01 mode, a vortex associated with the OAM state can be seen. Similar to the single-mode case, by using periodical twisting inversion, efficient OAM generation is possible. These results indicate that by simply launching fiber's LP mode into TB-PCF, arbitrary polarization and OAM states can be generated, leading to a novel mechanism for the manipulation of the spatial state of light. (C) 2020 Chinese Laser Press