Raman spectra of KTP crystal in an in situ electric field

Raman spectra of the KTP single crystal are recorded in electric fields (dc and ac) applied along the polar axis c. Spectra with the laser beam focused near the cathode end, anode end and the centre of the crystal are recorded. The cathode end of the crystal develops a spot ‘grey track’ where the laser beam is focused after a lapse of 5 h from the application of a dc electric field of 38 V/cm. The spectra recorded at the cathode end after the application of field show variations in intensity of bands. A new band appears at 177 cm⁻¹. Changes in band intensities are explained on the basis of changes in polarizability of the crystal due to the movement of K⁺ ions along the polar axis. K⁺ ions accumulate at the cathode end, where the ‘Grey track’ formation occurs. The intensity enhancement observed for almost all bands in the ac field is attributed to the improvement of crystalline quality.