Realization of refractive microoptics through grayscale lithographic patterning of photosensitive hybrid glass

Abstract

Refractive microlenses with more than 50 microm sag are fabricated using grayscale lithography. Mechanical assembly features are made simultaneously alongside the microlenses to facilitate high precision assembly of miniature optical systems. The microlens elements are formed using lithographic patterning of photosensitive hybrid sol-gel glass requiring no etch transfer to the substrate material. Grayscale lithography enables the straightforward patterning of aspheric lenses and arbitrary surfaces within the material depth. Lessons learned in the design of a grayscale photomask are described. Characterization of the fabricated lens elements is reported including lens shape, surface quality, and image quality of a complete assembled imaging system.

Ultrahigh luminescence extraction via the monolithic integration of a light emitting active region with a semiconductor hemisphere

“…Polymer based micro lenses are fabricated using reflow, hot/UV embossing, gray scale lithography, microjet technique, excimer laser ablation, and direct laser write techniques. [20][21][22][23][24][25][26] Although high aspect ratio lenses are possible, the refractive indices are typically not matched to the light emitting material. On the other hand, semiconductor based micro lenses are typically fabricated using focused ion beam or pattern transfer from photoresist to semiconductor by wet or dry etching.…”

Replication of optical microlens array using photoresist coated molds

“…Various techniques for fabricating microlens arrays using direct and/or replication processes have been studied, investigated, demonstrated, and commercially used. Among them are photoresist reflow [9], laser ablation [10,11], etched glass mold [12], grayscale lithography [13,14]. However, most of these methods are either too expensive for mass production or not easily accessible because of the complexity and high cost of the equipment and the processes.…”

Fabrication of Polydimethylsiloxane Microlenses Utilizing Hydrogel Shrinkage and a Single Molding Step

“…Due to this demand, different techniques to fabricate microlenses have emerged, including ink-jet printing [2], greyscale lithography [3], and photoresist thermal reflow [1]. The ink-jet printing method uses expensive equipment that requires very precise alignment in order to produce uniform arrays, while greyscale lithography faces difficulty in fitting the desired microlens shape into the different shades of grey [4,5].…”