A nurses' aide used his mobile phone to film his co-worker performing a sexual act on him in a nursing home bathroom then used the video to extort money from her, a court has been told.

Brisbane District Court was told today that Christopher Morgan, 34, of Mount Gravatt in Brisbane's south, demanded $10,000 from his lover so he could repay loan sharks who had threatened to break his bones.

Fearing the affair would be revealed to her partner of 16 years, the 28-year-old woman paid the money.

The court was told Morgan then demanded a further $2,000 to cover interest owed to the loan sharks and a six-month supply of steroid tablets.

The woman, a nurse at the Algester Lodge Nursing Home in Brisbane's south, eventually went to the police.

The court was told he initially denied making the threats, but later confessed and said he had committed the offence out of desperation.

The court was told Morgan started making the threats in June, just one week after they began a physical relationship.

Senior Judge Tony Skoien said the woman had "contributed to her own vulnerability" but Morgan had preyed on this weakness.

He sentenced Morgan to three years' jail with a non-parole period of a year.