Physics at γγ and eγ Colliders

New developments in linear collider and laser technology should soon make it possible to construct a Photon Linear Collider, where high energy photon beams, produced by Compton backscattering laser photons off linac electrons, are brought into collision with electron beams or with other photon beams. High luminosities, along with control over both the energy distribution and polarization of the photon beams, will give such a facility the potential for a very interesting physics program. In particular, a Photon Linear Collider offers a unique environment for the study of Higgs bosons and discovery of new particles such as excited electron states, supersymmetric particles, heavy charged particle pairs, or any particles with appreciable two-photon couplings. Precision electroweak tests also benefit from such a machine, allowing a test of the three-gauge-boson WWγ vertex. The Photon Linear Collider would serve as an excellent laboratory for Quantum Chromodynamics studies involving photon structure functions, jet and hadron production, and resonance production.