This paper describes the design and fabrication of a microlens array in photosensitive hybrid sol-gel glass to enhance the coupling efficiency of fiber-to-fiber and fiber-to-waveguide systems. The Code V software is employed in the design and simulation of the microlens array with a theoretical coupling efficiency of as high as 0.18 dB (or 96%). The proposed technique can also be used for the fabrication of thick micro-optical elements in sol-gel materials, and it can open up great opportunities for fabrication of microlenses with a high numerical aperture and thick diffractive optical elements in future.
This paper describes a cost-effective and high-volume soft-lithography method for building microlenses in hybrid sol-gel glass. The fabrication processes comprise the following three steps, namely fabricating microlens array in photoresist as a master lenses, molding replication of the lenses in poly-dimethylsiloxane (PDMS) as elastometric molds and embossing to press the PDMS replica onto the hybrid sol-gel glass. During the embossing process, while the PDMS mold is applied, the sol-gel sample was cured by UV exposure for densification. In this work, the master microlenses were patterned in photoresist using the reflow technique, where the authors took full advantage of the matured photosensitive material and fabrication technologies as the first and transitional step. This method enables us to fabricate thick micro-optical elements in sol-gel glass and it will be suitable for a range of applications in free-space and guided wave optics.
To extend the application of self-development sol-gel glass, we report a simple method to fabricate arbitrary multilevel structures in self-development photosensitive hybrid sol-gel glass by using a high-energy beam-sensitive gray scale mask under UV radiation. Characterization results showed that the maximum depth of deformation induced by the UV light can be more than 1.3 µm, which makes it possible to fabricate diffractive optical elements with a 2 phase delay for visible light. As an example, the self-development sol-gel glass was used for fabrication of blazed gratings with excellent surface smoothness.
Computer generated holograms are used to create doughnut beams. We use negative-tone inorganic-organic hybrid SiO2: TiO2 glasses to fabricate computer-generated holograms. This sol-gel material enjoys an advantage over materials used in the conventional photoresist-based fabrication techniques in terms of a single-step etching-free process. The doughnut beams may be useful in making laser traps for precision measurements and for Bose-Einstein condensation.
In micro-optical elements design, in order to achieve an optimal performance and reduce the undesired background optical system noise, multilevel phase-only micro-optical elements and/or continuous-relief structures are required. The multilevel and continuous relief structures can be fabricated by multiple exposures through a set of binary masks, electron-beam direct writing, laser-beam direct writing and grey scale masks. For mass production of cost-effective monolithic micro-optical elements, the high-energy beam-sensitive (HEBS) glass offers an opportunity to generate a grey-scale mask for analogue 3D surface relief structures. In this paper, a negative-tone inorganic-organic hybrid SiO2/TiO2 glass is investigated for the fabrication of refractive and diffractive micro-optical elements. The sol-gel material enjoys an advantage over the conventional photoresist based fabrication techniques due to its single step etching-free process.
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