Surface holograms for sensing application

Surface holograms, in which the interference pattern is inscribed on the surface rather than in the volume of the material, can be formed using various approaches. One method involves formation of surface relief structures... [ view full abstract ]

Surface holograms, in which the interference pattern is inscribed on the surface rather than in the volume of the material, can be formed using various approaches. One method involves formation of surface relief structures upon exposure of a photoresist to a patterned light (using holographic recording or exposure through a mask).This approach requires wet processing in order to develop the surface profile. In mass production, the photoresist structures are copied to create a master which is used in embossing. Another method of surface hologram fabrication consists of holographic patterning of material using high power pulsed laser which ablates locally material from the surface.^[1] This technique is a very flexible patterning method that can be easily applied to a range of materials. Moreover, provided that the material being patterned is sensitive to chemical or physical stimuli, the surface hologram can act as a sensor. Exposure of the hologram to the stimulus induces changes to the refractive index modulation resulting in the change of the diffraction efficiency, which constitutes the working principle behind such surface hologram based sensor (Fig. 1). To maximise the efficiency of the sensor, the characteristics of both of the holographic grating and of the sensing material must be optimised. The approach to the fabrication of this novel type of sensors using high power laser holographic ablation method will be discussed. The advantages and challenges of the technique being used will be presented. The experimental data will be compared with theoretical predictions concerning holographic structures diffraction efficiency.

[1] Q. Zhao, A. K. Yetisen, C. J. Anthony, W. R. Fowler, S. H. Yun, H. Butt, Appl. Phys. Lett. 106, 041115 (2015).