以液晶為夾層之光纖耦合器及光源波長與耦合率之關係

Abstract

本實驗用不同的介電異向差（Δε＞0及Δε＜0）的低折射係數液晶取代一般的折射油，作為研磨式光纖耦合器的夾層。對不同的液晶材料，分別採用平行排列和垂直排列二種方式。藉由外加電壓改變液晶的有效折射係數，來控制耦合比例。 實驗中，以1.3μm的半導體雷射為光源，利用其有一較寬波段的波長範圍，量測在不同的外加電壓下，不同的波長之耦合率比例。實驗結果顯示較長波長的耦合率比例之極大值，所需外加的電壓為較大。

We use 1.3μm semiconductor Laser diode as light source and low-refractive index liquid crystals with positive and negative dielectric anisotropy(Δε＞0 andΔε＜0), respectively, as intermediate layer of the optical fiber coupler. By applying voltage, we can change the effective refractive index of the liquid crystal to tune the light coupling ratio. In this experiment, we measure the coupling ratio between the coupled and uncoupled fiber output power under different wavelength when varying the applied voltage. The results show that coupling ratio are better for longer wavelength with higher voltage.