Edson José de Carvalho

Metallic submicrometer sieves fabricated by interferometric lithography and electroforming

We propose and demonstrate a low cost technique to fabricate submicrometer sieves using the association of laser interference lithography and nickel electroforming. The sieves are fabricated on glass substrates and are released from the substrate by adding a hexagonal sustaining structure, electroformed in nickel, using conventional lithography. The resulting sieves are free self-sustained membranes similar to those used in filtration devices, with typical diameters of the holes of about 250 nm and areas of about 1 cm2.

Study of the injection molding of a polarizing beam splitter

We describe the replication of a relief grating that behaves like a polarizing beam splitter by injection molding. Measurements of the grating master, nickel shim, and replica, performed by atomic force microscopy, allow establishing a limit for the injection molding technique (currently used in CD fabrication) to aspect ratios of approximately 0.15. Although this limit strongly reduces the diffraction efficiency of the elements as well as their polarizing properties, extinction ratios of approximately 10:1 were measured for the replicas in a large range of wavelengths.

Phase constraint for the waves diffracted by lossless symmetrical gratings at Littrow mount

The energy conservation of grating diffraction is analyzed in a particular condition of incidence in which two incident waves reach a symmetrical grating from the two sides of the grating normal at the first-order Littrow mounting. In such a situation the incident waves generate an interference pattern with the same period as the grating. Thus in each direction of diffraction, interference occurs between two consecutive diffractive orders of the symmetrical incident waves. By applying only energy conservation and the geometrical symmetry of the grating profile to this problem it is possible to establish a general constraint for the phases and amplitudes of the diffracted orders of the same incident wave. Experimental and theoretical results are presented confirming the obtained relations.

Nanosieves fabricated by interference lithography and electroforming

Self-sustaining Nickel membranes with periodic and regular distribution of pores, in the scale of hundred of nanometers, were produced by interference lithography and electroplating. The process consists in the recording of submicrometric 2D periodic photoresist columns, on a metal-coated glass substrate, using the double exposure of an interference fringe pattern. As the photoresist is a good electrical isolator, when the sample is immersed in a Ni electroplating bath, the array of photoresist columns impedes the Nickel deposition in the patterned areas. A nickel film is then growth among the photoresist columns with a thickness up to 80 % of the height of the columns. In order to release the submicrometric membrane from the substrate, a thick hexagonal Nickel sustaining structure is electroformed, using conventional photolithography. The dimensions of the sustaining structure can be adapted in order to fulfill the pressure requirements of the filtration system. The good uniformity of the pore sizes as well as the smooth of the surface make such devices very interesting for separation of particles by size in filtration systems.

Replication of diffractive optical elements by injection molding

In this paper we describe the replication processes of DOE carried out at the Diffractive Optics Laboratory/UNICAMP for replicating DOE. In particular we present the results obtained in the replication by injection molding of microlens array, diffraction gratings and polarizing elements. The measurements of the geometric dimensions of the DOE masters, the nickel shims and the replicated structures were accomplished by perfilometry, AFM and SEM microscopy. The optical properties of both the DOE masters and their replicas were evaluated by measuring of the diffraction efficiency as a function of the incident wavelength, for orthogonal polarizations.

Optical Properties of a Replicated Polarizing Holographic Element

We described the replication of a polarizing holographic optical element by injection molding. The optical properties of the replicated structures were evaluated by measurements of the diffraction efficiency for the two orthogonal polarizations.

Phases of the Diffracted Waves and Energy Conservation

The energy conservation is used in an experiment in which two incident waves reach the grating at the symmetrical Littrow condition, to analyze the phases of the waves diffracted by a non-absorbing relief grating.

Holographic lithography for electroforming submicrometric structures

In this paper we proposed and demonstrated the association of holographic lithography with electroforming to produce submicrometric metallic structures. To demonstrate the potential of the technique, different types of submicrometric metallic structures were generated: periodic lines, nano-tunnels and arrays of holes. Such structures can met different applications from optics to micromechanical systems.