Optical electric-field sensor based on angular optical bias using single ß-BaB₂O₄ crystal

A novel optical electric-field sensor is proposed and demonstrated in experiment by use of a single beta barium borate (ß-BaB₂O ₄, BBO) crystal. The optical sensing unit is only composed of one BBO crystal and two polarizers. An optical phase bias of 0.5p is provided by using natural birefringence in the BBO crystal itself. A small angle (e.g., 0.6 ^°) between the sensing light beam and principal axis of the crystal is required in order to produce the above optical bias. Thus the BBO crystal is used as the electric-field-sensing element and quarter waveplate. The ac electric field in the range of (1.4-703.2) kV/mhas been measured with measurement sensitivity of 1.39 mV(kV/m) and nonlinear error of 0.6%. Compared with lithium niobate crystal used as an electric-field sensor, main advantages of the BBO crystal include higher measurement sensitivity, compact configuration, and no ferroelectric ringing effect.