In the past people can not get proper material which has high enough eo coefficient, so we seldom heard about VOAs based on eo material.

过去由于受材料的限制，无法找到足够高电光系数的透光材料，所以基于电光材料制造的光器件鲜有耳闻。

youdao

In the past people can not get proper material which has high enough eo coefficient, so we seldom heard about VOAs based on eo material.

过去由于受材料的限制，无法找到足够高电光系数的透光材料，所以基于电光材料制造的光器件鲜有耳闻。

youdao