We report a novel micro-optical systems approach for gas chromatographic detection based on plasma excitation of the eluate and subsequent emission spectroscopic evaluation. Specifically, we propose a detector architecture that integrates a microhollow cathode setup and an optical collector system on a common planar microsystems platform. The collector consists of an array of identical imaging systems that surround the microplasma and couple the emitted light side-on into fibers via which it can be fed into a spectrometer. Elliptically shaped reflector profiles ensure nearly aberration-free achromatic imaging and hence a high coupling efficiency. This is confirmed by ray-tracing simulations. An experimental demonstration of the detector module is assembled. The elliptical profiles are milled out of aluminium with diamond tools on an ultraprecision machining center. Experimental tests with a He plasma prove that a higher optical coupling efficieny than with the traditional end-on signal pickup scheme can be achieved.
An integrated pulse shaper for femtosecond pulses was built and characterized. It uses far-field grating diffraction to generate the spectrum of an input pulse in the Fourier plane. The implementation of the system we present uses the concept of planar integration of free-space optical systems with a folded optical axis. The system is dispersion-free. Optical path-length differences are compensated for by using two cascaded 4f-imaging and filtering setups in the optical design. Material dispersion is avoided, since the light propagates in air and all optical elements in the system are implemented as reflective microoptical devices. Lenses were designed as concave mirrors and fabricated by ultraprecision micromachining. We present results regarding the design of the pulse shaper and its fabrication.
Self-imaging is demonstrated based on Montgomery’s theory for periodic wave fields and the use of diffractive optical elements. We review the theory of self-imaging, describe the grating design and present experimental results. The presented work aims at building an interferometer that may serve as a tapped-delay-line filter for the shaping of ultra-short light pulses.