Multifocus dichromated gelatin hololens

On-axis beam extinction through diffraction design and analysis

To optimize the functions of the surface-relief diffractive optical elements for optical limiters and other applications, we present a systematic design and analysis with numerical illustrations of the transmission properties of different surface-relief phase gratings and Fabry-Perot elements. The spectral response and the tolerance of fabrication errors have been included. An analysis shows that the blazed grating and the echelon grating, a multilevel element as a substitute of the blazed grating, can make the on-axis transmittance very low (less than 1% with one grating) over the broad visible band with a large tolerance of fabrication errors. The results are highly significant for the design of optical-limiting devices.

Optimal design of dual-wavelength multiple beam splitters

Dual-wavelength multiple beam splitters (DWMBS's) are designed to split a dual-wavelength beam into two beam arrays, one for each of the two wavelengths. These two beam arrays may have either the same dimension and structure or different dimensions and structures, depending on applications. We present results of our computer simulations for a 1 x 5 DWMBS that exhibits one-dimensional diffraction efficiency and uniformity of 83.8% and 98.4%, respectively, for a wavelength of 514.5 nm and of 85.1% and 99.0%, respectively, for a wavelength of 632.8 nm.

Modified-signed-digit optical computing by using fan-out elements

We present a novel three-step modified-signed-digit optical computing system based on the discrete correlation of space-coded input matrices that are multiply imaged by using optical fan-out elements. The advantages of our method over other approaches include a larger throughput, more flexible operation, and an easier optical implementation.

Modified signed-digit trinary arithmetic by using optical symbolic substitution

Carry-free addition and borrow-free subtraction of modified signed-digit trinary numbers with optical symbolic substitution are presented. The proposed two-step and three-step algorithms can be easily implemented by using phase-only holograms, optical content-addressable memories, a multichannel correlator, or a polarization-encoded optical shadow-casting system.

Multiple imaging phase-encoded optical elements written as programmable spatial light modulators

We report a multiple imaging capability of replicated binary Fresnel phase-encoded lenses written on programmable spatial light modulators (SLMs). These lenses produce a large number (up to 9 x 9) of equally intense replica images from either an external object or from a pattern which is encoded onto the SLM along with the phase-encoded lens. Theoretical details and experimental results using the magnetooptic spatial light modulator are presented.

Fabrication of space invariant fanout components in dichromated gelatin

Efficient and compact space invariant fanout holographic optical elements have been fabricated by combining the flexibility in design of computer-generated holograms with the versatility of conventional interferometric holography in dichromated gelatin. Effects of K-ratio variation and the phase distortion in the reconstruction fidelity are discussed. In addition, various preprocessing and postprocessing techniques have been employed to increase the optical damage threshold of these components to well over 100 W cm(-2).

Comparison of models for multiplexed holograms

Three models for multiplexed transmission gratings are compared. The underlying assumptions for each model are changed to allow an examination of the effects of generating higher diffraction orders and coupling between diffraction orders on the efficiency and SNR of these gratings. The influence of grating thickness, grating number, and object beam angle is also examined.

Methylene blue sensitized dichromated gelatin holograms: a study of their storage life and reprocessibility

The results of an experimental investigation on the storage life and reprocessibility of methylene blue sensitized dichromated gelatin (MBDCG) holograms are reported. The major conclusions of the investigation are: (i) Storage of MBDCG holograms in normal laboratory conditions for long periods is possible and it diminishes somewhat their diffraction efficiency. (ii) The results on short time storage and long time storage are almost similar, thus indicating that the diffraction efficiency can be stabilized through storage in a relatively short period of time. (iii) The deterioration in the diffraction efficiency on storage is less [D(eta) < 20%] for gratings of low/medium initial efficiency (eta < 70%) and it is more for gratings of high initial efficiency. (iv) About 65-95% restoration of the diffraction efficiency can be accomplished through reprocessing. (v) The restoration of diffraction efficiency is almost perfect [R(eta) > 80%] for gratings of low/medium initial efficiency (eta <75%) whereas it is rather imperfect for gratings having high initial efficiency.

Simplified dichromated gelatin hologram recording process

A simplified method for making dichromated gelatin (DCG) holographic optical elements (HOE) has been discovered. The method is much less tedious and it requires a period of processing time comparable with that for processing a silver halide hologram. HOE characteristics including diffraction efficiency (DE), linearity, and spectral sensitivity have been quantitatively investigated. The quality of the holographic grating is very high. Ninety percent or higher diffraction efficiency has been achieved in simple plane gratings made by this process.

Optical matrix-matrix multiplication method demonstrated by the use of a multifocus hololens

A method of optical matrix-matrix multiplication is presented. The feasibility of the method is also experimentally demonstrated by the use of a dichromated-gelatin multifocus holographic lens (hololens). With the specific values of matrices chosen, the average percentage error between the theoretical and experimental data of the elements of the output matrix of the multiplication of some specific pairs of 3 x 3 matrices is 0.4%, which corresponds to an 8-bit accuracy.