  We present squeezed light that is robust against spatial mode mismatch (beam
displacement, tilt, and beam-size difference), which is generated from a
self-imaging optical parametric oscillator below the threshold. We investigate
the quantum properties of the generated light when the oscillator is detuned
from the ideal self-imaging condition for stable operation. We find that the
generated light is more robust to mode mismatch than single-mode squeezed light
having the same squeezing level, and it even outperforms the single-mode
infinitely squeezed light as the strength of mode mismatch increases.
