Preparation Of Specific Grating Based On Photosensitive Material

Light field control technology that controls the intensity,polarization,and phase of electromagnetic waves in various frequency bands is a hot spot in optical research today.Dammann grating is a typical light field control device.Through the combination of liquid crystal patterned photoalignment technology and the common nematic liquid crystal E7,an electrically tunable liquid crystal Dammann grating can be produced.Liquid crystal is a photoelectric material with dielectric anisotropy and optical anisotropy for visible light waves,and photoalignment has become the current mainstream liquid crystal alignment technology.Liquid crystal photoalignment is not only widely used in liquid crystal displays,but also in non-display optical applications.The patterned liquid crystal photoalignment technology can prepare a multi-region,non-uniform liquid crystal alignment layer,and the liquid crystal molecules on the alignment layer will be aligned along the alignment of the alignment layer in the different regions in different regions.The difference in the orientation of liquid crystal molecules will change the refractive index of the region and the effect on the polarization state of the incident light.Using this feature,a liquid crystal grating can be fabricated.In the past,most of the methods for preparing Dammann gratings were based on periodic alignment substrates and non-alignment substrates or through special liquid crystals to form patterned alignment structures.In this paper,the patterned alignment layer prepared by mask exposure technology.In this paper,liquid crystal Dammann gratings are prepared through a variety of different substrate combinations.First,tunable Dammann gratings were fabricated and tested using two periodic orientation substrates,and their performance was evaluated.The experimental results show that for the prepared Dammann grating,the diffraction efficiency is 76.8% and the uniformity is 0.11.By applying voltage 10V(1KHz)to the Dammann grating,the switching time from the on state to the off state is 70 us,and from the off state to on state is 3.4ms.The designed Dammann grating has the advantages ofelectrically tunable,low-cost,fast switching,polarization independence.In order to compare the methods of preparing Dammann gratings,two other schemes for manufacturing Dammann gratings are proposed.One is to prepare a liquid crystal Dammann grating by a combination of a periodic patterned alignment substrate and a surface alignment substrate.The principle of applying a specific voltage to change the refractive index of extraordinary light to change the effective phase difference is to prepare a Dammann grating.For the performance of the Dammann grating,the diffraction efficiency is72.2% and the uniformity is 0.115.By applying a voltage of 11V(1KHz)to the Dammann grating,the switching time from the on state to the off state is 532 us,and the applied voltage1.7V(1KHz)returns from the off state to the on state is 4.8ms.The manufactured liquid crystal Dammann grating also has the advantages of being electrically tunable,low-cost,fast switching and polarization independent.One is to prepare a liquid crystal Dammann grating by a combination of a periodic patterned alignment substrate and a vertical alignment substrate,and also to apply a voltage to change the effective phase difference to prepare a Dammann grating.For the performance of the Dammann grating,diffraction efficiency is 71.7%,uniformity is 0.114.By applying a voltage of 10.5V(1KHz)to the Dammann grating,the switching time from the diffractive state to the non-diffractive state is 619 us,and the applied voltage 1.4V(1KHz)returns from the non-diffractive state to the diffracted state is 5.3ms.The liquid crystal Dammann grating also has the advantages of being electrically tunable,low cost,fast switching and polarization independent.By comparison,the first method performs best,and the second and third methods are almost the same.If conditions permit,priority can be given to selecting the first method for preparing liquid crystal Dammann gratings.Compared with the previous methods,this method has the advantages that the material is made of ordinary liquid crystal,the performance is improved,and the polarization is independent.