Optimization of electrically tunable VCSEL with intracavity nematic liquid crystal

Light Propagation in Confined Nematic Liquid Crystals and Device Applications

Liquid crystals are interesting linear and nonlinear optical materials used to make a wide variety of devices beyond flat panel displays. Liquid crystalline materials can be used either as core or as cladding of switchable/reconfigurable waveguides with either an electrical or an optical control or both. In this paper, materials and main device structures of liquid crystals confined in different waveguide geometries are presented using different substrate materials, such as silicon, soda lime or borosilicate glass and polydimethylsiloxane. Modelling of the behaviour of liquid crystal nanometric molecular reorientation and related refractive index distribution under both low-frequency electric and intense optical fields is reported considering optical anisotropy of liquid crystals. A few examples of integrated optic devices based on waveguides using liquid crystalline materials as core for optical switching and filtering are reviewed. Reported results indicate that low-power control signals represent a significant feature of photonic devices based on light propagation in liquid crystals, with performance, which are competitive with analogous integrated optic devices based on other materials for optical communications and optical sensing systems.

Polarization-stabilized tunable VCSEL with internal-cavity sub-wavelength grating

In this paper, a tunable VCSEL with internal-cavity sub-wavelength grating structure at 850nm was demonstrated. Utilizing the birefringence and anti-reflection characteristics of the sub-wavelength grating, the tunable VCSEL with wide wavelength tuning range and stable TE polarization mode was achieved. The relationships between the parameters of sub-wavelength grating and the transmittance/effective index of two polarization modes were analyzed. The tuning efficiency, polarization mode and wavelength tuning range of the tunable VCSEL with internal-cavity sub-wavelength structure were studied. Simultaneously, the MEMS cantilever structure with 'bowknot' shape on the end of the cantilever was designed, which can effectively avoid the concentration of stress distribution and reduce the maximum stress. The results show that the wavelength tuning range is 22.7nm, the peak output power is 1.6mW at 20°C, and the polarization suppression ratio is more than 20dB.