High-resolution direct-write multiphoton photolithography in poly(methylmethacrylate) films

Abstract

Multiphoton photolithography in poly(methylmethacrylate) films is demonstrated. High-resolution structures of arbitrary geometry with edge sharpnesses as small as 120nm are produced using femtosecond pulses of 870nm light focused to a diffraction-limited spot in the films. The power dependence of etching and tests of different polymers prove that the process is nonlinear and involves excitation of the polymer’s chromophores. Atomic force microscopy images show that the vast majority of polymer is removed during etching. It is concluded that the etching mechanism involves depolymerization and thermal evaporation of the polymer. Application of this method in the fabrication of electrochemical microelectrodes is demonstrated.

Fabrication and Characterization of Polymer/Liquid Crystal Composite Diffractive Optics by Multiphoton Methods

“…[24] The work described herein demonstrates the fabrication, testing, and characterization of electrically switchable polymer/LC composite diffraction gratings prepared by using this same method.…”

“…This system has been described previously in detail. [24,26,27] A high numerical aperture (NA) objective (NA= 1.3) was employed to achieve a diffraction-limited focused spot of ca. 560 nm 1/e 2 diameter in the sample, and hence, to obtain the intensities necessary for etching.…”

“…A sharp transition from no apparent etching to complete removal of the PMMA is observed between 17 and 20 mW, indicating the process is highly nonlinear. As shown previously, through an analysis of structures etched at different powers, [24] the etching process most likely involves three-or four-photon absorption of the incident 870 nm light by the PMMA chromophores. Other poly- …”

“…[15] A number of research groups have recently demonstrated that high-resolution structures can be prepared in polymer films by multiphoton-induced photolithography. [16][17][18][19][20][21][22][23][24] The resulting materials have a variety of potential applications, [16][17][18][20][21][22][23][24] including in electrically switchable diffractive optics. [19] Multiphoton photolithography has a distinct advantage over most other lithographic methods in that preparing three-dimensional structures is relatively straightforward.…”

“…In this paper, direct-write multiphoton-induced photolithography [24] is employed to prepare polymer/LC composites for use as electrically switchable diffraction gratings. High-resolution polymeric structures and surface-relief gratings with spacings as small as 1 lm are obtained by multiphoton etching of poly(methyl methacrylate) (PMMA) films.…”