A two step process has been developed for the fabrication of diffraction limited concave microlens arrays. The process is based on the photoresist filling of melted holes obtained by a preliminary photolithography step. The quality of these microlenses has been tested in a Mach-Zehnder interferometer. The method allows the fabrication of concave microlens arrays with diffraction limited optical performance. Concave microlenses with diameters ranging between 30 µm to 230 µm and numerical apertures up to 0.25 have been demonstrated. As an example, we present the realization of diffusers obtained with random sizes and locations of concave shapes.

We show the miniaturization and parallelization of a scanning standing wave spectrometer with a long term goal of creating a compact imaging spectrometer. In our standing wave integrated Fourier transform spectrometer, light is injected with micro-lenses into several optical polymer waveguides. A piezo actuated mirror located at the waveguide end-facet can shift the interferogram to increase its sampling frequency. The spatial distribution of the standing wave intensity inside the waveguide is partially scattered out of the plane by a periodic metallic grating and recorded by a CCD camera. We present spectra acquisition for six adjacent waveguides simultaneously at a wavelength of 632.8 nm.

Abstract:We present a comparison of three different technologies for the fabrication of microoptical elements with arbitrary surfaces. We used direct laser writing, binary mask lithography in combination with reactive ion etching, and graytone lithography.

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Various fabrication methods have been investigated to manufacture refractive and diffractive micro-optical elements [1]. The structure of the elements is generated by holographic recording, optical lithography and direct writing (e-beam, laser beam). The pattern is then transferred into quartz by reactive ion etching (RIE), or replicated into plastic for low-cost mass production. Of special interest is the fabrication of hybrid elements, which combine the unique properties of diffractive optics (fan-out, high dispersion) with those of refractive optics (high numerical aperture, low dispersion). Therefore, we have studied different concepts for the manufacturing of hybrid (refractive/diffractive) elements and we present here some first results.