A device for producing white light includes a light conversion module and a light source. The light conversion module includes undoped metal oxide powder comprising particles having a size of less than 50 nm. The light source generates excitation light having a wavelength in the near infrared region. The excitation light is directed towards the undoped metal oxide powder, the undoped metal oxide powder is excited with the excitation light, and the excited undoped metal oxide powder emits white light having a continuous spectral distribution in the range of 440 nm to 900 nm.