Mario Perez-Cortes

Dynamic diffraction ring projector by doped polymer-dispersed liquid crystal

Ring light distribution patterns emerging after illumination of a material that forms a conic beam can be obtained in diverse cases. There are some phenomena that produce such distributions without an artificially tailored or designed mask. This device is produced by intermixing and curing of conventional PDLC form by the combination of optical glue and the nematic liquid crystal E7. When the device is illuminated with a He-Ne laser, a ring diffraction pattern with a spot in the center is observed. It was observed experimentally that the radius of the projected ring decreased when we applied an external voltage to the device with the indium tin oxide electrodes. The voltage dependent variation in the radii of the rings can be understood as a change in the period of the concentric spiral following the direction of the applied field when a voltage is applied in this device.

Holographic materials composed by rosin with ammonium dichromate

We present a new material with potential application in holography. We have used a film of mixing ammonium dichromate with rosin resin diluted in isopropyl alcohol. This material can be easily elaborate in the laboratory. A phase grating in this material was recording using Argon-Ion laser at (lambda) equals 457 nm, showing good diffraction efficiency. This material is capable of high resolution when we record some diffraction gratings, observing 2,000 l/mm (grooves). A characteristic of the developed process is their simplicity, takes approximately 25 seconds.

Electro-optic modulator of polarization for the visible spectrum region

We show an electro optic linear polarizer for the visible spectrum region. The device is made of a CyberdisplayTM liquid crystal display (LCD) manufactured by Kopin Co. and a linear polarizer. The device can rotate from 0 to 70 degrees the linear polarization state of a beam. To control the polarization rotation, we displayed gray levels from 0 to 255 in a PC connected to the LCD. We present the complete characterization of our device and experimental results.

Fish gelatin and ammonium dichromate as photosensitive film

In this work we propose a phase material based on fish gelatin from Norland Products© mixed with ammonium dichromate deposited on a glass substrate. The photosensitive film has 110 mm thickness. In this material we record low frequency (264 lines/mm) holographic gratings using a λ=532 nm from an Ar laser and reconstruct the image with λ=594 nm from a He-Ne laser. The diffraction efficiency is approximately15% for the first order. The material no requires developing process and is very easy to make. Experimental results are shown.

Characterization of a PDLC mixed with crystal violet dye

We show the optical characterization of a Polymer Dispersed Liquid Crystal which was made mixing Norland Optical Adhesive No. 65®, nematic liquid crystal and crystal violet dye, deposited between two glass substrates with indium tin oxide (ITO) as electrodes. In this device, we recorded low frequency (104 lines/mm) holographic gratings made with the interference of two beams from an Ar laser at 515 nm in emission line. We measured the diffraction efficiency of the gratings obtaining 2% when the grating was read with a beam from a He-Ne laser at 612 nm.

Refraction indexes of the polyester film 3M PP2500

In this work we describe an experimental technique to measure the refraction index of the 3M PP2500 film which has good behavior as quarter wave retarder plate for λ=633 nm. This technique is achieved when two perpendicular linearly polarized beam from a Wollaston prism are incident on the thickness of the film. The beams were incident parallel to the fast axis to measure the ordinary refraction index and parallel to the slow axis to measure the extraordinary refraction index. Some experimental results are shown.

Ronchi retarder gratings as polarization modulators

We show Ronchi grating made of cellophane; this device has the particularity of modulate the polarization state of an arbitrary polarizes source. The grating period can be designed to obtain two linear perpendicular polarization states, horizontal and vertical, or circular, right and left if the source has linear or circular polarization state respectively. With this grating, we can modulate or demodulate images for stereoscopic applications.

Imaging polarimetry for phase change measurements of the cellophane film

It is well known that cellophane film has good behavior as half wave retarder for wide spectrum, so, in this work, we present imaging polarimetry method to measure the phase change introduced by a cellophane film at several wavelengths in the visible range. The method is achieved when we introduce the cellophane film in a simple optical arrangement composed by linear polarizers. The phase change of the film is obtained as function of the light intensities at the output of the system.

Birefringence measurement of the cellophane film

In this work we describe an experimental technique to measure the birefringence of the cellophane film that has good behavior as half wave retarder. This technique is achieved when the film is placed in a polariscope that consists of a light source and properly arranged polarizing elements and a system of fringes is observed. Using Jones formalism for the system the birefringence appears in the phase term of harmonic functions. Some experimental results are shown.

Interferometric measurement of refraction index of dye-doped photopolymer

Holographic interferometer is used with a dye-doped photopolymer on one of its arms, the sample is radiated simultaneously with two wavelengths, and measuring the pattern fringe displacement we can calculate the refraction index changes. The photopolymer we use is a mix of Norland Optical Adhesive No. 65 and Crystal Violet dye deposited between two glass plates making a cell of 220 microns thickness. The sample is radiated with a beam from an Ar-ion laser at 515 nm; in the interferometer we employed a He-Ne laser at 633 nm in emission line. We show some experimental results.