Direct UV patterning of waveguide devices in As2Se3 thin films

Abstract

Photodarkening of thermally evaporated amorphous As2Se3 chalcogenide thin films was generated by a UV mercury light source in a standard mask aligner. The refractive index modification of the chalcogenide glass was determined by applying Swanepoel’s method. Index changes of +0.04 were obtained for 500 s exposure. Using these photoinduced index changes, waveguides with losses of approximately 1 dB/cm at 980 nm were fabricated. Another set of waveguides was fabricated by UV exposure and subsequent selective etching to form rib structures. Those waveguides exhibited loss of approximately 2 dB/cm at 980 nm. Silver photodoping of As2Se3 was also performed on a mask aligner with index increases on the order of 0.3 obtained. Due to the rapid and large photomodification obtainable with standard photolithographic equipment, these processes are promising for integrated optic device fabrication.

Low loss waveguides and embedded Bragg gratings in As2Se3 chalcogenide glass

“…We have also embedded first-order Bragg gratings on these waveguides using a He-Ne laser. As 2 Se 3 is an interesting alloy because it is commercially available, exhibits large photo-induced index changes [7][8][9], and has the highest reported (amongst the chalcogenide glasses) third order nonlinearity at 1550 nm wavelength [10].…”

Development of chalcogenide glass photoresists for gray scale lithography

“…Diffractive optical elements (DOE) (gratings, lenses, filters, beam couplers, etc. ), holographic relief images, 3D-microphotolithographic patterns can be successfully developed in ChG media using mask, holographic exposure or direct writing laser lithography followed by wet [5][6][7][8][9][10] or dry etching [11,12]. Furthermore, the selectivity of such photoresists can be greatly enhanced by photodiffusion of silver into ChG film [8,13,14].…”

Direct laser writing of relief diffraction gratings into a bulk chalcogenide glass

“…Therefore, micropatterning and nanopatterning of chalcogenide glass or thin-film optical devices play an important role for further enhancement of functionalities and applications. Micropatterning of chalcogenide glasses can be realized by a variety of techniques, such as traditional mask-based, multiphoton or direct UV lithography [6][7][8], holography [9,10], nanoimprint lithography employing hard or soft stamps [11][12][13], ink-printing [14], or direct laser writing (DLW) [15][16][17][18]. DLW has been already demonstrated as an effective method for fabrication of chalcogenide-based threedimensional (3D) photonic crystals [16], and optical waveguides in thin films [17], under surface "buried" multimode waveguides [18] or low-loss 3D mid-IR optical waveguides [19] in Ga-La-S glasses.…”