Abstract: An electromagnetic waveguide having a large cross section portion tapering to a narrow throat is supplied with microwaves in the large portion to produce a high intensity electric field in the throat. An optical waveguide defined by the throat itself or a separate waveguide tube in or adjacent the throat is supplied with a laser medium which is pumped by the high intensity electric field to produce a lasing action. Suitable mirrors aligned with the optical waveguide complete the optical laser cavity. Alternatively several tapered waveguides in series with a common optical waveguide are excited sequentially to progressively pump the laser medium along the optical waveguide tube so that laser emission is effected without mirrors.