Juho Karhu (IMAGE) University of Helsinki Caption In his research, Juho Karhu utilised an optical frequency comb and an optical parametric oscillator. Credit Anu Vallinkoski Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.