Holography Laboratory

In our optics lab, we work mainly with holography. We perform precise optical alignments and set up interferometric configurations for micrometric metrology. Our goal is to capture and analyze wavefront information to measure surface deformations or displacements with high accuracy.

Optical Surfaces Testing

The method involved placing the lens in contact with a reference flat surface and observing interference fringes under monochromatic green light. The pattern of fringes revealed deviations from flatness or curvature, allowing us to assess the lens surface quality with micrometric precision.

Simulating DOE

The calculation of a DOE using the Gerchberg–Saxton algorithm involves an iterative Fourier transform process to design a phase-only hologram. Starting from a target intensity pattern in the image plane, the algorithm alternates between the spatial and frequency domains. The kinoform reconstruct the desired image when illuminated with coherent light.

Laguerre Beams

Programming Laguerre-Gaussian beams involves generating optical fields with specific orbital angular momentum. These beams are characterized by their doughnut-shaped intensity profiles and helical phase fronts. In practice, we simulate the complex amplitude of LG modes using mathematical expressions involving Laguerre polynomials and phase terms, which can then be encoded onto spatial light modulators (SLMs) or used to design computer-generated holograms for beam shaping.

Time Average Holography

Time-average holography is an optical technique used to visualize and measure vibrations of an object. During the exposure of the hologram, the object vibrates, and the interference pattern recorded contains averaged phase information over time. When the hologram is reconstructed, it reveals characteristic fringe patterns that correspond to the amplitude of vibration at each point on the object’s surface, allowing for precise modal analysis.

Dichromated Gelatin Holograms

Dichromated gelatin holograms use a light-sensitive layer made of gelatin and dichromate salts to record 3D light patterns. This material offers high resolution and clarity, producing detailed and bright images.

Holography Lab

In holography, diffusers are used to scatter light uniformly across the object or the recording medium. This helps to reduce speckle noise, improve the illumination of extended objects, and enhance the overall quality and contrast of the hologram.

Hologram

Classical holography records the interference between a reference beam and light scattered from an object to capture its full 3D information. When illuminated, the hologram reconstructs a realistic image with depth and parallax.

Michelson Interferometer

The Michelson interferometer splits a beam of light into two paths using a beam splitter, reflects them with mirrors, and then recombines them to produce interference. By analyzing the resulting fringes, it is possible to measure small distances, optical path differences, or changes in refractive index with high precision.

Mirror Optical Testing

Interferometric Holography

Interferometric holography consists of subtracting two wavefronts originating from an object that has undergone a slight perturbation, in this case, a small displacement. The resulting fringes are useful for quantifying the displacement at the wavelength scale.

CGH of a 3D point of Clouds

This program, developed in Python reads a three-dimensional object to generate a hologram.
The object can be modeled in any 3D software that allows saving the file in .obj format. The program reads the coordinates of each point of the object and generates a wavefront.

Depth map of 3D object

This algorithm uses AI to calculate a depth map of a single image. This is useful for creating a computer generated hologram with depth perception.

Laguerre Beam Self-Healing

Laguerre-Gaussian beams exhibit a limited form of self-healing, meaning they can partially reconstruct their intensity profile after encountering an obstruction. While they do not possess the strict non-diffractive and full self-reconstructing properties of Bessel beams, their structured phase and ring-like intensity distribution allow for some degree of recovery during propagation.

Dot matrix holograms

Dot matrix holograms are created by recording tiny diffraction gratings at each point, each with specific tilt and period. These micro-gratings diffract light to produce shifting colors and dynamic visual effects as the viewing angle changes. This technique is widely used in security features and decorative optics.

Interferometric Holography

In holographic interferometry, we can compare two holograms of a piezoelectric device operating under different sound volumes. When the object vibrates differently between the two recordings, interference fringes appear on its surface. These fringes represent the displacement field caused by the sound-induced deformation, allowing us to visualize and quantify how the piezoelectric element responds to acoustic excitation.

Self Healing in Bessel Beams

Self-healing in Bessel beams refers to the ability of these non-diffracting optical beams to reconstruct their original intensity profile after encountering obstacles. When partially obstructed, the beam automatically regenerates its characteristic structure within a short propagation distance beyond the obstacle.

White light diffraction

Unlike monochromatic diffraction, where a single wavelength produces well-defined patterns, white-light diffraction involves multiple wavelengths simultaneously, resulting in complex and colorful interference effects.

3D CGH Video

From a computed point cloud, the optical field of a pyramid was calculated. Using rotation matrices, computer-generated holograms were created to produce an animation of the three-dimensional object in rotation.

Cube Diffraction points

This program reads the coordinates of the points and assigns a spherical wave to each of them. The diffracted field is the superposition of all these waves.