In this article, we discuss the waveguide dimensions optimization aiming to reduce the Vπ. For that purpose, various
cover materials are investigated leading to a minimum effective core area " Aeff". The index contrast (core-cladding) at
λ= 1550 nm, is varying from 0.07 to 0.21. As a result, the Aeff decreases from 12 μm2 down to 2.3 μm2, the total
thickness of the waveguide is thus reduced and consequently the Vπ. Optimal parameters were calculated at λ= 1550 nm
for single mode inverted-rib waveguides structure. The PAS1 a new polymer is used as electro-optic material for the
core. An analytical model taking account the losses by tunnelling, allowed us to estimate the optimum distance between
electrodes to reduce the Vπ which could be about 1.6V ( 0.8 V in a push-pull configuration). Related with the bandwidth
of the modulator, permittivity measurements were carried out on core and cladding polymers as well. The process of
waveguides fabrication is described in details and several waveguides are performed. Finally, a new experimental
technique for precision measurements of the propagation losses in waveguides is presented. The principle is simple, and
the propagation losses measured is found to be independent of coupling conditions.
Both theoretical and experimental analysis of a new efficient method to measure the number and type of modes
propagating in optical fibers are presented. This consists in measuring the intensity of the near field image at the end of a
fiber while scanning the wavelength with a laser source signal. Modes are extracted from Fourier transformation of the
spectral data at each point (x,y) of the images. A novel technique which is referred to as scalar product technique is
implemented in order to reconfirm real modes and exclude spurious modes. The technique is based on the orthogonality
of different modes. A standard multimode fiber has been measured to verify the technique. Three real modes LP01, LP11, and LP02 are discovered and reconfirmed by the orthogonality with the minimum values of the scalar products. One
spurious mode, which comes from the dependence of the power of the laser source on the wavelength, is thus excluded as it is not orthogonal either to the LP11 mode or the LP02 mode.
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