An image forming apparatus includes at least one inkjet head which is disposed above a feed path of a print medium and on which plural nozzles are aligned along a primary sweeping direction perpendicular to a feed direction of the print medium fed along the feed path. Contents to be protected include foodstuffs, beverages, pharmaceuticals, cosmetics, personal care products, shampoos and the like. In an illustrative embodiment, the core is fabricated from a laser gain medium and the cladding material is a multi-oxide eutectic ceramic glaze having a refractivity slighter lower than the refractivity of the gain medium, such that the glaze layer forms a step-index refractivity interface cladding that can effectively suppress parasitic oscillations in the core gain medium. Light present in the resonator is coupled with the lights respectively propagating in the waveguides. During this discharge phase, energy in the capacitor discharges through the protection circuit of the semiconductor device.