Pranas Narmontas

Holograms recording with pulsed laser on diazonaphthoquinone-novolac-based photoresists and their nanocomposites

Abstract. Direct write digital holography technique (DWDH) using a single 440-nm pulsed laser exposure has been proposed to record master holograms on commercially available positive-tone photoresist systems based on a mixture of diazonaphthoquinone and novolac resin (DNQ-novolac) of different thicknesses. The DNQ-novolac nanocomposite doped with copper nanoparticles (CuNPs) films was also used. The method for numerical evaluation of hologram quality based on reflected beam diffraction intensity measurements was proposed and verified. It was found that all investigated photoresist nanocomposites were sensitive enough to record holographic structures at low single pulse laser exposures (from 3.3 to 18.0  mJ/cm2). Moreover, doping DNQ-novolac nanocomposite with CuNPs s increases its sensitivity to pulsed laser exposure by more than 30%. The potential of single pulsed laser exposures to record high quality master holograms on commercially available and metal nanoparticles doped photoresists with at least five times lower exposures values as compared to the continuous-wave laser exposures usually used to expose photoresist materials in holographic applications, opens the possibility to use pulsed lasers for quick master-originals origination for embossed holograms applying a DWDH technique or analog methods.

Master-holograms recorded with pulsed laser on photoresist

Direct write digital holography technique (DWDH) using single pulsed exposures of 440nm pulsed laser has been applied to record master holograms on commercially available photoresists (ma-P1200 and Shipley 1800 series) of different thickness. Method for numerical evaluation of hologram quality, based on diffraction intensity measurement (reflected beam), was proposed and verified. It was found that all investigated photoresists: ma-P1205, ma-P1225 and S1805, were sensitive enough to record holographic structures at low single pulse laser exposures from the range 3.3 ÷ 19.5 mJ/cm2 . Best quality holograms with well – structured holopixels (hogels) were observed on 0.67 μm thick ma- P1205 photoresist exposed to 11.4 mJ/cm2 and on 0.65 μm thick S1805 photoresits exposed to 13 mJ/cm2, where corresponding measured diffraction intensity had its maximum value. In the case of thicker photoresists (ma-P1225, 3.33 μm), comparable quality of the hogel structure was found in the interval 9.8 – 13 mJ/cm2. Investigation has shown a potential of single pulsed laser exposures to record good quality master holograms on commercially available photoresists applying at least 5 times lower exposures values as compared to CW laser exposures usually used to expose photoresist materials in holographic applications. That opens a possibility to use pulsed lasers for quick origination of master-originals for embossed holograms applying DWDH technique or analogue methods.

Synthesis and Characterization of Silver-Poly(Methylmethacrylate) Nanocomposite

Silver nanoparticles and polymethylmethacrylate (PMMA) nanocomposite was prepared in situ by photo-induced thermal reduction method. The interfacial interaction of Ag nanoparticles and PMMA polymer is investigated using Fourier transform infrared spectroscopy (FTIR). Optical properties of Ag/PMMA films were characterized by UV-Vis and FTIR absorption spectroscopy. Effects of the UV and heat-treatment time on the formation of silver nanoparticles in PMMA matric matrix were studied in detail. These investigations proposed new nanocomposite structures. They can be defined as plasmonic materials with improved optical properties. Ag/PMMA structures may found a number of technological applications: in optical devices, various plasmonic sensors or even in nanomedicine.

The influence of sublayer material on surface properties of electrodeposited nickel with periodical structures

Surface topography, hardness and microstructure of nickel coatings electrodeposited on Si master with a periodical structure have been studied depending on vacuum deposited sublayer material (Ni, Cu or Ag). It is shown that the quality of replication of silicon master in a nickel shim electrodeposited simultaneously on different sublayers is dependent on the material used. All types of the analyzed coatings enabled transfer of lateral dimensions and showed good replication quality of the tested periodical structures (2 μm period), while the structure replicated using the coatings deposited on the Ni sublayer exhibited the worst roughness. The hardness of the electrodeposited layers was found to be dependent on the sublayer material used as well as on the side of deposit. Despite the fact that the backside of nickel shim had the same hardness for all the sublayers used, it was found that the hardness of the working surface with periodical structure (the side that has been in contact with the vacuum deposited layer) is dependent on the sublayer material: the Ni and Cu sublayers increased the hardness of Ni coating, while for the nickel shim deposited on Ag sublayer the hardness was reduced.