In a hair styling device (20), a light emitting diode (33) is configured to deliver optical energy to hair, wherein an energy fluence of the optical energy is between 0.5 and 9 J/cm 2 , and more preferably between 1 and 5 J/cm 2 . An output wavelength of the optical energy may be between 400 and 900 nm, preferably between 400 and 650 nm, and more preferably between 450 and 550 nm. The light emitting diode (33) may be pulse-driven, and a pulse width of the optical energy is between 50 and 300 ms, preferably shorter than or equal to 200 ms, and more preferably between 100 and 200 ms. The hair styling device (20) may comprise an optical shield (32) configured to block stray light during light exposure of the hair. An inner surface of the optical shield (32) may be reflective and/or may have a parabolic shape. The optical shield (32) may be movable between an open position in which a lock of hair can be placed in the hair styling device (20) while the optical energy is not applied, and a closed position in which light is prevented from escaping the hair styling device (20) while the optical energy is applied to the hair.