Indian star Rohan Bopanna and his Dutch partner Timea Babos registered a straight-sets victory to enter the semi-finals of the mixed doubles category at the Australian Open tennis tournament here on Wednesday.The fifth seeded Indo-Dutch combination beat the unseeded pair of Colombia's Juan Sebastian Cabal and American Abigail Spears in a quarter-final contest which lasted for an hour and 15 minutes.Bopanna and Babos will meet the winner of the quarter-final clash between Spain's María José Martínez Sánchez and Brazilian Marcelo Demoliner and Australians Storm Sanders and Marc Polmans for a place in the final.