A TE/TM Polarization-independent Frequency Upconversion Based on PC

Frequency conversion like second-harmonic generation and sum-/difference frequency generation plays a vital role in many applications. Currently, almost all nonlinear devices based on the second-order nonlinearity operate in the polarization-sensitive mode which has greatly restricted their applications. Therefore, it is desirable to obtain a polarization-independent operation for frequency conversions. In this work, we propose and experimentally demonstrate a paradigm of TE/TM polarization-independent frequency upconversion by leveraging the PC and second-order nonlinearity. i.e., sum frequency generation, in the periodically-poled lithium niobate-on-insulator (LNOI) ridge waveguide. With a proper transverse electric field, the fundamental waves of TE and TM mode can be frequency-up converted with an equal efficiency in the frequency converter. Also, by taking the advantages of the LNOI ridge waveguide, the applied voltage is as low as 14.1V in the device. The conversion efficiencies for TE and TM polarized inputs are balanced from 0:1 to 0.3:0.3. The TE/TM polarization-independent operation can be accessed at different wavelengths via a temperature tuning. The proposed method could be used in all-optical wavelength conversion and upconversion detection technologies.