Waveguides, planar lasers

When the gain medium incorporating nanoparticles is deposited onto glass substrates defining a planar asymmetric slab waveguide, multimode laser emission can appear without the need of the presence of any resonant substructure. 

As an alternative to planar waveguiding structures we report here the fabrication of crystal cored fibres in which it is possible to maintain uniform guide dimensions over long lengths. These fibres with organic crystal core material having large second order non-linearity could be used for miniaturization of visible laser sources and realization of parametric amplifiers for optical communications. 

Figure 830 (a) Output optical field of silica planar waveguide excited by He-Ne laser, (b) Top view of the silica planar waveguide excited by He-Ne laser. Three Si3N4 microlenses are embedded to obtain the collimated beam and focalized beam. 

FIG. 14.26 Photograph of the near IR. laser light being coupled into the azopotymer-based planar waveguide by an SRG on the left and propagated to the right. 

The various laser spectra shown in Fig. 12.5 (a) demonstrate that the laser wavelength can be tuned over a spectral range of A Las = 44 nm from 604 nm for a 120-nm thick film to 648 nm for a 435-nm thick film, respectively. The resulting peak positions of the laser emission are plotted versus the film thickness in Fig. 12.5 (b). Along with the measured laser wavelengths a curve based on the simulation of a planar waveguide structure is shown. The experimental data points correspond very well to the calculated curve for increased film thicknesses. 

Many basic experiments in passive and active devices are performed without integrated planar light sources so that coupling of externally generated laser light into planar waveguides is required. This can be done with various types of couplers. Some are shown in Fig. 47. 

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