  Producing high-brightness and high-charge (>100 pC) electron bunches at
blowout regime requires ultrashort laser pulses with high fluence. The effects
of laser pulse heating of the copper photocathode are analyzed in this paper.
The electron and lattice temperature is calculated using an improved
two-temperature model, and an extended Dowell-Schmerge model is employed to
calculate the thermal emittance and quantum efficiency. A time-dependent growth
of the thermal emittance and the quantum efficiency is observed. For a fixed
amount of charge, the projected thermal emittance increases with decreasing
laser radius, and this effect should be taken into account in laser
optimization at blowout regime. Moreover, laser damage threshold fluence is
simulated, showing that the maximum local fluence should be less than 40
mJ/cm^2 to prevent damage to the cathode.
