Yao Yu-Hsin, Wang Chun-Ta, Chen Rui-Ren, Jau Hung-Chang, Chiu Yi-Jen, Lin Tsung-Hsien
Department of Photonics, National Sun Yat Sen University, Kaohsiung, Taiwan.
Opt Express. 2012 Sep 24;20(20):22872-7. doi: 10.1364/OE.20.022872.
This work proposes an electrically tunable infrared light source based on a new compact structure, i.e., an AlGaInAs semiconductor multiple quantum well (MQW) integrated with a liquid crystal Fabry-Pérot filter. The AlGaInAs MQW is used as a luminance layer that emits broadband light. By sandwiching the AlGaInAs and LC material with two conducting mirrors, the active light source with an optical filter can be tuned with a wide wavelength range. The filter filled with nematic liquid crystal enables continuous tuning of emission along the extraordinary mode and provides a 58 nm tuning range with a bias of 14 V. The simulation results of wavelength and tunability are consistent with the experimental results. Cholesteric liquid crystal with a planar texture is also used to examine the properties of the tunable light source. Under an electric field, all the helical liquid crystal molecules tend to be aligned parallel to the field. The variation of the refractive index is normal to the substrate surface, and the polarization-independent tuning range is 41 nm. The wide tuning range and the polarization properties observed when NLC and CLC are respectively incorporated into the AlGaInAs based Fabry-Pérot cavity suggest that this integration scheme has potential for applying to optical communication system.
这项工作基于一种新型紧凑结构提出了一种电可调红外光源，即一种集成了液晶法布里 - 珀罗滤波器的AlGaInAs半导体多量子阱（MQW）。AlGaInAs多量子阱用作发射宽带光的发光层。通过用两个导电镜夹着AlGaInAs和液晶材料，可以在很宽的波长范围内调谐带有光学滤波器的有源光源。填充向列型液晶的滤波器能够沿异常模式实现发射的连续调谐，并在14V偏压下提供58nm的调谐范围。波长和可调谐性的模拟结果与实验结果一致。具有平面纹理的胆甾型液晶也用于研究可调光源的特性。在电场作用下，所有螺旋状液晶分子都倾向于与电场平行排列。折射率的变化垂直于衬底表面，且偏振无关调谐范围为41nm。当分别将向列型液晶和胆甾型液晶纳入基于AlGaInAs的法布里 - 珀罗腔时所观察到的宽调谐范围和偏振特性表明，这种集成方案有应用于光通信系统的潜力。
