Results from the investigation of the diffusion processes in a dry acrylamide-based photopolymer system are presented. The investigation is carried out in the context of experimental work on optimization of the high spatial frequency response of the photopolymer. Tracing the transmission holographic grating dynamics at short times of exposure is utilized to measure diffusion coefficients. The results reveal that two different diffusion processes contribute with opposite sign to the refractive index modulation responsible for the diffraction grating build up.Monomer diffusion from dark to bright fringe areas increases the refractive index modulation. It is characterized with diffusion constant D 0 =1.6.10 -7 cm 2 /s. A second diffusion process takes place during the recording. It decreases the refractive index modulation and we ascribe it to diffusion of short chain polymer molecules and/or radicals from bright to dark fringe areas. The estimated diffusion coefficient for this process is D 0 = 6.35.10 -10 cm 2 /s. The presence of the second process could be responsible for poor high spatial frequency response of the investigated photopolymer 2 system. Comparison with the diffusion in photopolymer systems known for their good response at high spatial frequencies shows that both investigated diffusion processes measured here occur in a much faster time scale.

Recent research on an acrylamide-based photopolymerizable holographic recording material is presented. The recording characteristics of the material are discussed in detail in terms of sensitivity, diffraction efficiency, recording linearity, resolution limit, and sources of noise. Although the resolution is not sufficient for reflection holography, the recording characteristics are excellent for transmission gratings. The material was found to suffer no shrinkage during recording, and high-diffraction-efficiency slanted gratings were made. Finally, the suitability of this self-developing material to both double-exposure and real-time holographic interferometry is demonstrated.

A reflection hologram for visual indication of environmental humidity has been studied. The hologram is recorded in a self-developing photopolymer and changes color when exposed to a change in humidity and is fully reversible. The range of color change, reversibility, and the response time of the hologram have been studied in a controlled humidity environment. Fully reversible holograms with response times from few seconds to tens of minutes have been designed. Extremely sensitive bright visual humidity indicators, capable of dramatic color change within a few seconds of breathing on them are demonstrated.

The use of adhesive bonding in joining of materials with different characteristics is of major importance in a variety of microelectronic and photonic applications. The curing of such adhesives is also of great consequence, with the use of optical radiation for adhesive curing becoming the method of choice in various applications, especially bonding of components in microelectronics and fiber-optic assembly. This article reviews recent advances in the development of adhesives, their applications, and their curing methods using optical radiation; it also includes a brief overview of the adhesion mechanisms.

Abstract:We report the design, fabrication, and performance of monolithic, slot-antenna coupled Schottky-collector resonant tunnel diode (SRTD) oscillator arrays. A 64-element oscillator array oscillated at 650 GHz while a 16-element array produced 28 pt.W at 290 GHz. Introduction:Resonant tunnel diode (RTD) waveguide oscillators have been reported at frequencies as high as 712 GHz [1], well beyond the highest frequency transistor oscillators built to date [2]. Power levels achieved by discrete waveguide RTD oscillators are limited by constraints imposed on maximum device area for suppressing parasitic bias circuit oscillations [3]. Higher power levels can be obtained with monolithic RTD oscillators in which these constraints are eliminated by on-wafer bias stabilizers [4]. Power levels can then be further increased using quasi-optical array RTD oscillators [5]. Here, we report monolithic Schottky-collector RTD (SRTD) oscillator arrays with on-wafer Schottkydiode bias stabilizers. Different circuits operated at frequencies ranging from 100 GHz to 650 GHz. A 64-element array oscillated at 650 GHz. To our knowledge this is the highest oscillation frequency achieved by a monolithic oscillator. Additionally, a 16-element array produced 28 p,W at 290 GHz.