Leandro L. Soares

Reflecting polarizing beam splitter

We propose and experimentally demonstrate the use of metal-covered lamellar relief gratings as a polarizing beam splitter operating at a single wavelength near Littrow incidence. We report the characteristics of a grating produced by holography and reactive ion etching that was calculated for operation as beam splitter at lambda = 633 nm (for a He-Ne laser).

Metallized photoresist grating as a polarizing beam splitter

We propose and demonstrate the use of a simple holographic relief photoresist grating covered with an aluminum film as a reflecting polarizing beam splitter. The polarizing effects were achieved as a result of the nonsinusoidal profile of the grating. The best parameters of the gratings for optimizing the polarizing-beam-splitting properties were found by the introduction of the experimental profiles in diffraction calculation software. Theoretical and experimental results are presented, confirming the feasibility of the element.

Measurement of optical constants of thin a-C:H films

Abstract Amorphous hydrogenated carbon films (a-C:H) are very interesting materials for optical applications. They are transparent in the near IR part of the spectrum and its refractive index and absorption coefficient may be changed with the deposition parameters. In this paper we measure the optical constants of a-C:H films, deposited by plasma enhanced chemical vapor deposition as a function of the radio frequency power. The measurements were performed by the method of Abeles in λ=633 nm and by the approximation of Lambert–Beer in the transmission measurements using a spectrophotometer. Both methods do not require the use of thick films that are difficult to deposit due to the intrinsic stress of these films. The measurements were compared with that obtained by the fringe peaks in transmission measurements of a thick film. Our results showed that it is possible, in our system, to deposit homogeneous and uniform films with any refractive index chosen between 1.8 and 2.2 at λ=633 nm .

Fabrication of dielectric hollow submicrometric pipes

A simple technique to obtain an array of hollow submicrometric titanium oxide pipes is described. Initially, a submicrometric structure is formed in a positive photoresist by holographic exposure, followed by the deposition of the titanium oxide film and the removal of the photoresist by an appropriate solvent. These structures may be useful as waveguides for x-ray and neutron capillary optics.

Diffractive structures holographically recorded in amorphous hydrogenated carbon (a-C:H) films.

We propose and demonstrate the direct recording of submicrometer relief gratings in amorphous hydrogenated carbon (a -C:H) films by reactive ion etching (RIE) for use as diffractive optical components. The high refractive index of this film and its transparency in the IR make such structures promising candidates for IR-transmission diffractive optical components. The structures are holographically recorded in photoresist and then transferred to a thin aluminum layer that is used as a mask for RIE of the a -C:H films. The diffraction measurements of the structures recorded in these films demonstrated the feasibility of using the materials as diffractive optical components.

Recording of relief structures in amorphous hydrogenated carbon (a-C:H) films for infrared diffractive optics

Abstract We demonstrate the recording of diffractive structures in amorphous hydrogenated carbon (a-C:H) films using holographic exposures and reactive ion etching (RIE). The a-C:H (diamond-like) films are a very promising material in which to record relief optical structures because they ally the properties of hardness and optical quality of the coatings. The high refractive index of the material and its transparency in the infrared (IR) part of the spectrum make such structures also very interesting for recording IR transmission diffractive optical components. Such structures were holographically recorded in photoresist, and then transferred to a thin aluminium layer, which was used as a mask for the RIE of the a-C:H films. The recorded structures were analysed by scanning electron microscopy and by diffraction measurements. The good accordance between the measurements and the calculated diffraction curves demonstrates the feasibility of the material for recording diffractive optical components.

Noise reduction in the recording of holographic masks in photoresist

The lithography of gratings or structures using photoresist holographic masks is very critical, in particular when high selectivity etching processes were employed. In this paper we study the effect of the mask profile and of the phase perturbations during the holographic exposure in the noise of the photoresist masks. It is shown that the use of appropriate conditions of development and exposure may reduce significantly this noise allowing the recording of high aspect ratio structures and the use of selective deposition techniques.