Giant amplification of modes in parity-time symmetric waveguides

The combination of the interference with the amplification of modes in a waveguide with gain and losses can result in a giant amplification of the propagating beam, which propagates without distortion of its average amplitude. An increase of the gain-loss gradient by only a few times results in a magnification of the beam by a several orders of magnitude. -- Highlights: ► We report giant beam amplification in parity-time symmetric optical waveguides. ► The amplification is due to interference of gain-guided modes. ► Flexible control both by parameters of the waveguide and of the input beam.