Opportunities for searches for axion-like particles (ALPs) coupling to
photons in e+e− collisions at the Future Circular
Collider (FCC-ee) and International Linear Collider (ILC) are investigated. We
perform a study of the photon-fusion production of ALPs decaying into two
photons, e+e−⟶γγe+a(γγ)e−, over the light-by-light
continuum background, for the planned FCC-ee and ILC center-of-mass energies
and integrated luminosities. An analysis of the feasibility measurements is
presented using parametrized simulations for two types of detectors. Upper
limits at 95% confidence level (CL) on the cross section for ALP production,
σ(γγ→a→γγ), and on the ALP-photon coupling
are obtained over the ma≈0.1--1000 GeV ALP mass range, and compared
to current and future collider searches. Production cross sections down to
σ(γγ→a→γγ)≈1 fb (1 ab) will be
probed at ma≈1 (300) GeV, corresponding to constraints on the
axion-photon coupling as low as gaγγ≈2⋅10−3 TeV−1