We r eport the fabrication o f optical w aveguides in PMMA bulk material using direct excimer laser irradiation. Due to the radiation at 248 nm the refractive index is locally enhanced and thus channel waveguides are defined. The guiding properties are experimentally investigated by coupling visible and infrared light to the waveguides and analysing their near field patterns at the channel output. A comparison with numerical field simulations yield a clear singlemode behavior in the 1550 nm range and a calculated insertion loss of less than 0.3 dB to a standard singlemode fiber. The modal analysis indicates a c hannel w aveguide with an e xponentially decaying index profile in vertical direction. Our results suggest that the index difference as well as the channel depth can be varied independently by choosing the appropriate exposure parameters.

Optical fibers play an important role in general, and in particular in the field of sensors. As part of a sensor system quite often fibers are coupled by a ball lens. For efficient usage, the fiber ball lens systems (FBLS) have to be optimized. The present work presents analytic expressions for design parameters of such systems. FBLS comprise sections of a single-mode optical fiber, a coreless fiber (CLF) and a ball lens. Their geometric dimensions have to be optimized for their use in different application in optical metrology. The derived expressions facilitate the optimum parameter choice which usually is done by expensive numerical simulations. For comparison and validation of the results by experiments, FBLS with different ball lens radii and CLF sections have been prepared by a fusion splicer technique. Their characteristics were investigated in the optical spectral ranges at 630nm and 1550nm. Experimental methods comprising far-field, near-field, reflection /transmission measurements with optical fibers validate the theoretical considerations. To our knowledge this is the first time that simple analytic approaches have been applied to the fabrication of FBLS. This facilitates and quickens their general design for different applications in optical metrology significantly.

Optical waveguides were generated in Polymethylmethacrylate using “direct” laser and contact mask structuring. Excimer laser radiation (248 nm) produced a local refractive index increase thereby achieving light guiding in waveguides with widths from 2 to 15 $\mu$m. The near field output images were analyzed using visible and infrared laser light. The mode fields of single mode structures were evaluated to elaborate numerically the parameters of the index profile. An index increase up to 0.01 could be achieved using laser pulses at fluences below $0.15$ ${\textrm{J/cm}^{2}}$. Thus it was possible to design interference couplers of 5 $\mu$m waveguides width for the visible (635 nm to 670 nm) as well as for the infrared range at 1550 nm. The coupling properties as a function of the waveguide separation and the wavelength is investigated and found compatible with numerical simulations for the structure design. The presented approach allows for designing and fabricating single mode couplers in an efficient and simple manner.