Whispering gallery mode microspheres have garnered considerable attention due to their applications in signal processing and telecommunications. Unique properties such as high quality factor and small mode volume of whispering-gallery mode microspheres make them suitable for laser applications with a low pumping power requirement and narrow emission linewidth. Tellurite glass is a promising material for making microlasers because of its high transparency range, high refractive index, and it has been proven as a good host for rare earth ions leading to powerful and broad stimulated emission cross section. We reported lasing in Er3+ doped tellurite glass microspheres fabricated using the plasma torch method. 15Na2O25WO360TeO2 doped with 0.5 mol% Er3+ is used for the fabrication of microspheres. Laser light from the pump is coupled to the microsphere through a half and a full tapered fiber. An optical spectrum analyzer receives the counter propagating light from the microsphere. A pump laser of 980 nm is used to achieve the laser emission at 1570 nm.
To efficiently sense small gas concentrations using a whispering gallery mode resonator a xerogel coating can be applied onto the surface of the resonator. In this way, gas molecules can enter into the xerogel layer where they can interact with the electric filed of the whispering gallery modes. Here we present some results on ammonia gas detection using a silica microsphere coated with a sol-gel porous silica xerogel. The frequency shift of an isolated whispering gallery mode was measured in dependence on the ammonia gas concentration in the testing chamber and efficient gas sensing was observed. We discuss the observed results and elaborate how the proposed systems sensitivity can be tailored in respect to the geometrical parameters of the system including the sphere radius and the coating thickness.
Microresonators are very suitable for sensing application and investigation of nonlinear effects, due to their enormous quality factor and small mode volume. These properties can be extended to the mid-infrared spectral range by creating microresonators from chalcogenide glasses, which are transparent in the mid-infrared and have large third-order optical nonlinearity. We present the analysis of the nonlinear effects observation in chalcogenide microspheres created by inert gas heating.
Optical microresonators are a very promising component for use in optoelectronics. They have very high quality factors and low mode volumes which makes them suitable for many applications such as lasing, sensing or non-linear optics. We will present our work on microspheres coated with sol-gel Er3+ activated 70SiO2 - 30HfO2. In particular the lasing properties of such microspheres will be presented. Different coating thicknesses will be employed and the peak lasing power will be discussed in respect to the coating thickness. The lasing peaks will be identified in respect to the radial and azimuthal numbers of the whispering gallery modes and the assignments will be discussed in terms of mode selectivity.
Highly non-linear chalcogenide glasses are considered as a prospective material for frequency comb generation in optical microresonators. Using of a 2D microresonator for tailoring the normal material dispersion of chalcogenide glass is analyzed by evaluation of the group velocity dispersion coefficient in near- and mid- infrared. This is done for both approximate and accurate modal resonances of the whispering gallery modes of a 2D circular chalcogenide resonators. The results show that the using of a chalcogenide resonator extends the spectral range of normal dispersion regime to longer wavelengths.
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