Spontaneous optical emission properties of laser-produced plasma during laser damage events at input and exit surfaces of fused silica were retrieved and compared. We show that plasma at the input surface is much larger in size and exhibits significantly higher electron number density and excitation temperature, even when smaller laser energy was used. This effect was attributed to the stronger laser-plasma coupling at the input surface. In addition, a strong continuum background containing

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... e peaks at 1.3 eV, 1.9 eV, and 2.2 eV was observed at the exit surface, and possible origins for this effect are also discussed.