This form of sexual slavery is the slavery of unwilling people for sexual exploitation.
Forced prostitution, also known as involuntary prostitution is a classical form of this form of sexual slavery, wherein sex traffickers force victims to become prostitutes or work in the sex industry.
This various work in the sex industry includes prostitution, dancing in strip clubs, performing in pornographic films and pornography, and other forms of involuntary servitude.

IMPORTANT NOTE: Non-consensual sexual slavery starts out as non-consensual and stays that way. The victim doesn't go through mindbreak and doesn't become a willing slave at any point in the story.