Learning vocabulary: Is it better to learn the word through translations?

Suppose that you have a student that is bilingual. Take for example that the student speaks Chinese and English. Suppose that said student is very fluent in Chinese, but not so fluent in English. He/she can hold everyday conversations in English but he/she has a really hard time reading an English newspaper or magazine (i.e. Wall Street Journal and Times). Suppose that you are trying to teach English vocabulary to said student. Would you teach said student:

1. New English vocabulary using English words that he already knows, or
2. New English vocabulary by using translated Chinese?

Is there some research that is related to such scenario?