  Recently, the coexistence of parity-time (PT) symmetric laser and absorber
has gained tremendous research attention. While the PT symmetric absorber has
been observed in microwave metamaterials, the experimental demonstration of PT
symmetric laser is still absent. Here we experimentally study PT-symmetric
laser absorber in stripe waveguide. Using the concept of PT symmetry to exploit
the light amplification and absorption, PT-symmetric laser absorbers have been
successfully obtained. Different from the single-mode PT symmetric lasers, the
PT-symmetric stripe lasers have been experimentally confirmed by comparing the
relative wavelength positions and mode spacing under different pumping
conditions. When the waveguide is half pumped, the mode spacing is doubled and
the lasing wavelengths shift to the center of every two initial lasing modes.
All these observations are consistent with the theoretical predictions and
confirm the PT-symmetry breaking well.
