The 39-year-old pop star has Daisy, three, with actor Orlando Bloom, and Katy has revealed that her daughter is the inspiration behind her new single.
Katy - who is engaged to Orlando - told The Sun newspaper's Bizarre column: "It is funny how sometimes you're looking for your soulmate in a partner. It could be a dog, your mom, your best friend, your cat ... but for me it came in the form of Daisy.
"I wrote 'Lifetimes' about her. Every night before we go to sleep I say, 'I love you', and then I ask, 'Will you find me in every lifetime?' and she says, 'Yes'."
Katy is set to release her long-awaited new album, '143', in September, and she's revealed that it's a mix of dance music and "quintessential pop".
The chart-topping star shared: "I always wanted to make a dance pop record.
"One third is more dance than I have ever done before. One third is quintessential pop and then one third is rhythmic."
Katy quit her role on 'American Idol' in order to focus on her new album.
The pop star previously suggested that a female star should replace her on the show's judging panel - but she also argued that female stars face more scrutiny than their male counterparts.
The 'California Gurls' hitmaker - who previously appeared on the hit TV show alongside Lionel Richie and Luke Bryan - told E! News: "When you have an opinion, when you're bold, when you're a female, it just happens."
Jelly Roll has been tipped to replace her on the show, but Katy insists that a female voice is necessary.
She said: "That would be too many men, let's be honest.
"But we love Jelly Roll, and I'd love for him to be on this show whenever it's appropriate."