The integrated electro-optic modulator plays an important role in the broadband wireless communication and phase-coded radar etc. The electro-optic modulator using a lithium niobite (LN) ridge waveguide is easy to be integrated and has excellent electro-optic response. However, its fabrication and coupling still face great challenge. In this paper, an intensity modulator (IM) based on heterogeneous platform with LN and silicon nitride (Si3N4) is designed. The optical mode field distribution is simulated as the waveguide size changes. The parameters such as the width and height of loadinged strip are optimized to ensure that the light power is highly concentrated in the LN layer (over 90%). The propagation loss of the IM with different Y-junction shapes is analyzed. In addition, the influence of different electrode parameters on half-wave voltage is discussed systematically. The results demonstrate that the designed IM has a low half wave voltage of 2.1V, characteristic impedance of 53Ω and propagation loss of -0.2dB. The proposed IM has the advantages of convenient fabrication and coupling, which provides an alternative modulation unit for multi-level or large-scale modulation integrated chips.
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