High-Resolution Refractive Index and Micro-Raman Spectroscopy of Planar Waveguides in KGd(WO $_{4}$) $_{2}$ Formed by Swift Heavy Ion Irradiation

We report on the characterization of planar waveguides formed in the Raman-active crystal KGd(WO
₄
)
₂
using swift carbon, fluorine, and oxygen ion irradiation. The characterization of the waveguiding regions was performed using high-resolution microreflectivity and micro-Raman spectroscopy. The high-resolution microreflectivity measurement fully characterizes the refractive index profile of the barrier formed by amorphization of the crystal and detects other index variations not detected by the m-line technique. Raman spectroscopy measurements reveal details of the Raman properties of the crystal in the waveguiding region in relation to the rest of the sample for the different ion irradiations. Both of these measurement techniques are shown to be important for use of KGd(WO
₄
)
₂
in integrated Raman-active devices.