What is the ruling on joking and laughing with non-Muslim colleagues at a mixed-gender university, what are the limits of interaction with them, and is repentance required for that?

Islam has erected an impenetrable barrier between a man and an unrelated woman, as a preventative measure and to block the path for Satan. One of Satan's greatest weapons is the temptation of a man by a woman. A woman's conversation with an unrelated man is permissible out of necessity, provided there is no softness in her speech, as Allah Almighty says: "So do not be soft in speech [to men], lest he in whose heart is disease should covet." If speech can be a temptation, then smiling and laughter are an even greater and more severe temptation. The Permanent Committee for Issuing Fatwas has issued a ruling prohibiting a woman from smiling at an unrelated man or uncovering her face to him, due to the evil that this leads to. Accordingly, it is not permissible for a woman to be expansive in her speech, or to prolong conversations with colleagues without necessity, or to smile and laugh with them.