博士后用英语简写怎么说

"博士后" is a term used to refer to someone who has completed a doctoral degree and is continuing to work in a research capacity, typically as a postdoctoral researcher. In English, "博士后" can be abbreviated as "postdoc" or "postdoctoral researcher."
For example, you could say "I am a postdoc working in the Department of Chemistry" or "I am a postdoctoral researcher studying biochemistry."
Note that "博士后" is a specific term that refers to a specific stage of academic training, and it is not the same as simply being a researcher or holding a PhD.