Efraim Goldenberg

Ray model for transmission of metallic-dielectric hollow bent cylindrical waveguides.

The problem of transmitting CO(2) laser radiation through metallic or metallic with inner dielectric coating (metallic-dielectric) bent hollow cylindrical waveguides is investigated using a ray model. Computer calculations of transmission as a function of the geometrical dimensions of the waveguide are performed. The coupling of laser radiation at the entrance of the waveguide is also taken into account. The theoretical calculated transmission is compared with previously published experimental data and good agreement is obtained for a large range of curvatures. The devised ray model contributes to a better understanding of the role of the dielectric layer in the metallic-dielectric waveguide, increasing the transmission of the radiation. The calculation of the transmission as a function of the radius of the cross section of the waveguide shows that, for a best metallic-dielectric waveguide, an optimal cross-sectional diameter appears where the transmitted energy is maximum. The method presented will be of value as a tool in the design of hollow cylindrical waveguides.

Optical characteristics of the compound PLZT

We present a summary of measured characteristics of lanthanum-doped lead zirconium titanate (PLZT) compound in its mechanical housing. It is expected that the PLZT device will be used as the main component in an ultrafast electro-optic switch. We have performed several experiments to measure and calculate the following characteristics: optical power transmission, thermodynamic effects, switching speed, and dc drift phenomenon.

Infrared Chalcogenide Tube Waveguides

Chalcogenide hollow fibers were made from As-Se, As-Se-Te or Ge-Sb-Se cylindrical raw material. Theoretical investigation had shown that by using metallic cladding, losses due to bendings could be reduced. The optimum conditions for minimum loss were calculated for the ratio between TE and TM modes. Experimentally, fibers were drawn with an attenuation of 8 dB/m. It was shown that by using plastic for cladding, fibers with less fragility and high elasticity were achieved.

Ultrafast all-optical switching

We present innovative concepts related to the realization of ultrafast optical switches to be used for obtaining all-optical switching. We review the construction and the achievements of Civcom Incorporated during its research and development stages of constructing its ultrafast switch. Experimental measurements are exhibited.

Improved Metallic Tube Infrared Waveguides With Inside Dielectric Coating

Hollow fibers were made of plastic materials with both metallic and dielectric inside coating. Previous theoretical investigation had shown that by the use of optimal metallic and dielectric layers, low attenuation could be achieved, even for bent fibers. Experimentally, the attenuation of 2 dB/m was measured for a 3 mm diameter flexible plastic waveguide.

Use Of Metallic And Dielectric Films For Hollow Fibers

The problem of transmission of CO2 laser radiation through hollow fibers and waveguides was studied theoretically and confirmed experimentally. The transmission of the laser radiation through metal and metal-dielectric tubes was measured and compared with the theoretical data based on a ray model solution. This makes possible the investigation of the transmission of the CO2 radiation through waveguides when the internal wall is covered with a metal or a metal-dielectric film. It was shown theoretically and proved experimentally that the transmission of the CO2 radiation is possible even through bent waveguides.

Hollow Plastic Waveguides Internally Coated With Metal And Dielectric Films

The CO2 laser radiation (λ=10.6) is very useful in many fields especially in medicine. For this application plastic hollow waveguides are very suitable, since they are flexible and nontoxic. Such plastic tubes were devised and the obtained results are given in this paper. The transmission of infrared radiation was made possible by covering the inside with metallic films. To achieve high transmission, even when the waveguides were bent, an inside dielectric film was added over the metallic one. Theoretical and experimental investigation of the energy transmission and the output power distribution was done. The theoretical results were obtained based on a ray model calculation. Experimental results have shown an attenuation of about 1.5 dB/m for a straight waveguide and a transmitted power up to 14 watts for 55 cm length and 3.5 mm inner diameter of the waveguide. For a bent waveguide (radius of bending 15 cm) attenuation of 5-6 dB/m and maximum of 6 watts was achieved.

From computer-generated holograms toward partially coherent optical signal processors

Optical signal processing has its roots in the experiments of Lord Rayleigh, Abbe and Porter that were the first that dealt with the spectrum of an image. This historical path of revolution has been followed years later by the extraordinary work of A. W. Lohmann in the optical data processing during the last 40 years. The new innovations and the future possibilities that are to be opened up in the new millennium show his dominant signature. Some recent projects that enlighten the future ofthe optical signal processing field are described in this presentation. The invention of the computer generated holograms (CGH) was a giant leap for the optical signal processing field. Filters and holograms that previously were generated by direct holographic recording means, have been all of a sudden replaced by synthetic functions designed and realized by digital computers. It was the first interface between digital computers and optical systems. Such an approach led to the design of opto-electronic systems that operate in perfect synergy where each element is utilized for what it does best. Along the years, the field of computer-generated holography has been expanded to what is known as: diffractive optical elements. Techniques like kinoforms, binary optics, on-axis CGH, etc. have been developed for addressing the growing application list ofsuch elements. CGHs highly affected the optical signal-processing field. For example, various new processing techniques were created and applied for invariant pattern recognition (Circular Harmonics (CH), Synthetic Discriminate Filters (SDF) etc). The next innovation wave reached the shores of the optical data processing community in the 80s when A. W. Lohmann presented the optical interconnections as the next challenge of optical data processing. Many configurations were discussed, investigated and applied for optical processing (perfect shuffle, omega net, cross over etc.). In the 90s A. W. Lohmann was a key player in a new revolution in optical processing where optics was used as a transformation tool. New transformations were invented and realized by optical means as for instance Fractional Fourier Transform, Wigner distribution, Fractional Hubert and Hartley Transforms etc. Those were applied for various signal-processing applications and used also in digital processing. In the new millenium optics adapts itself to the binary mode of operation that is common in computer systems. This trend becomes feasible also due to the impressive progress in the opto-electrical interface devices such as the spatial light modulators, light sources such as VCSELs and detectors such as photo-diodes. These new achievements permit also the operation of opto-electronic systems at extremely high rates. It is evident that in the next years of the millenium optical data processing field will continue to grow, develop and replace additional processing modules in the digital computation world. Without much doubt those will be accompanied and innovated by the scientific assistance foundation and guidance of A. W. Lohmann. In this paper we will focus on optical processing of partially coherent light. This field is mostly interesting and relevant since it includes both the aspects of data processing and the optical design skills that insure its promising industrial future.

Infrared Plastic Waveguides for Surgical Applications

For successful use of the IR lasers in medicine a good type of waveguide is essential to be devised. The known IR transparent materials, from which fibers might be drawn (1–3) have several disadvantages such as: sensitivity to light, chemicals and humidity, or high toxicity and limited flexibility. In this paper we present a new type of hollow fiber made of plastic tubes which were covered, on the inside walls, with metallic or metallic and dielectric films. The metallic and dielectric films were obtained by depositing successively a metal film followed by a dielectric one. These hollow plastic waveguides are good waveguides and do not suffer from the above shown disadvantages.