Michael Manevich

Fabrication and testing of microlens arrays for the IR based on chalcogenide glassy resists

Abstract A new technique of microlens fabrication using inorganic chalcogenide photoresists is presented. High refractive index that is characteristic of chalcogenide photoresist films and correspondingly, the optical power of the microlenses, can be increased by means of silver photodoping of the ready-made microlens array. Unique properties of chalcogenide photoresists create new possibilities for the development of microoptical components for the IR. Microlens arrays on the base of AsS and AsSe photoresists were fabricated and tested.

Photoalignment of Liquid Crystals on Chalcogenide Glassy Films

First observation of photoaligning of nematic liquid crystals (LC) on inorganic films, namely on a chalcogenide glassy films is reported. We found that irradiation of chalcogenide surfaces by visible laser beam of low-power (∼ 30 mW) results in efficient reorientation of the director in the irradiated areas. The anchoring energy associated with the light-induced easy orientation axis is of the order 10−6 J ∗ m−2 that is typical for standard organic polymer photoaligning materials. The surprise is that the direction of the reorientation depended on the time of the exposure. For short exposures director reoriented toward the polarization of light and longer exposures resulted in the reorientation away from the light polarization. The effect of light-induced alignment was used for recording of the surface-mediated electrically controlled holograms in the LC cell.

Mechanically tunable microlasers based on highly viscous chiral liquid crystals

Chiral composition is designed for highly viscous lasing microemitters. The composition forms cholesteric liquid crystal and after doping with pyrromethene 597 was used as an active lasing media in stretchable aluminized silicone cavities. Optical pumping of the system led to lasing at the wavelengths defined by a degree of cavity deformation. Lasing thresholds were lower in aluminized cavity than in transparent cavity. A simple model allowing to predict the shift of lasing wavelength as a function of deformation is developed.

Fabrication of microlens array for the IR by lithographic processes using an inorganic chalcogenide photoresist

Micro-optical elements, particularly microlenses, are finding growing application in different fields of modern optoelectronics. One of the most promising methods of microlens fabrication is based on photolithographic processes. Organic photoresists were used in the earlier development of microlens arrays. A new technique of microlens fabrication using inorganic chalcogenide photoresists is presented. Such photoresists have many advantages, such as very high resolution, photosensitivity in wide spectral range, high values of refractive index, transparency in the IR range, and the ability to be used as positive or negative resists depending on the developer used. These unique properties create new possibilities for the development of microlens arrays in the IR.

Microlens arrays based on chalcogenide glass resists using the proximity microlithography method

A simple microlens array fabrication process based on chalcogenide glass As-Se and As-S photoresists is described. Specific properties of chalcogenide photoresists important for microlenses preparation and the parameters of fabricated spherical and cylindrical microlens arrays are measured and discussed.

Deformable Viscoelastic Cholesteric Films with Nanoparticles

Large spectral shifts of the selective reflection band and color changes are achieved in highly viscous mixture of cholesteric polymers and low molar mass liquid crystals filled with nanoparticles and subject to mechanical deformations. The color of the material changes instantaneously during deformation; the time for the color to be completely restored increased with the viscosity of the polymer mixture. The viscosity increases with increasing concentration of polymer or nanoparticles. These properties of the material were explored in building a highly sensitive mechanical sensor.

Development of I.R. micro-electro-optical devices: new methods and new results

Different methods of fabrication of micro-optical devices for the Infra-Red (I.R.) such as micro-lens, micro-prism, micro-mirror arrays and Fresnel lenses based on the use of chalcogenide photoresists are described. In chalcogenide photoresists, two photoinduced phenomena are observed: photoinduced structural transformations and photoinduced diffusion of some metals, primarily, silver, and both phenomena enabled the development of new types of I.R micro-optical devices. The use of a new three-component As-S-Se photoresist and a new efficient amine-based selective developer allows for the realization of soft contrast characteristics of the photolithographic process with a Xe-source of light. Recent progress in the development of devices using photostructural transformations based on these two innovations will be described. Devices using the photoinduced silver diffusion are based on the different dissolution rate (in selective etchants) of the non-doped and silver-doped chalcogenide films. Parameters and characteristics of several micro-optical devices made using this effect are compared and discussed.

Development of transparent microlens in negative photoresist for solar application

The use of a microlens on top of a photovoltaic solar cell working at high light concentration and the need for a very low absorption photoresist in the whole solar spectrum are explained. A process has been developed in a negative photoresist with adequate properties. The optical properties of the fabricated microlenses are described.