Wavelength tunable infrared light source based on semiconductor-integrated liquid crystal filter.

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.