A diffractive optical element according to the present invention includes: a lens body 11 with a blazed grating 13 on an aspheric surface 11a thereof; and an optical adjustment layer 15 that covers the diffraction grating 13. A plurality of propellant cells are positioned within the pressure chamber. As the musician moves the slide across the strings as the instrument, such as a guitar, is played, a visual effect is created by the movement of the light.