Abstract: A nozzle structure for discharging printing material onto a substrate is presented. The nozzle structure comprises a tubular member having a distal part that faces the printing plane when in operation and defining an elongated inner cavity along the tubular member for placement a filament printing material. The tubular member comprises light input ports on the proximal part thereof for directing light toward inner surfaces thereof. The tubular member has an elongated tube portion and a distal tip portion at the distal part thereof, configured and operable as a light guide trapping and guiding the input light along the tubular member in a general direction toward the distal part, thereby continuously transferring light field to distal regions of the elongated inner cavity. The distal tip portion is configured to allow the trapped light to escape towards the printing plane, thereby heating a location on the printing plane facing the nozzle.