{HEAD ~ The optical device} 1, wherein the peripheral portion is covered by {TAIL ~ the dielectric film} which has an optical thickness of an odd multiple of λ/4, wherein λ is an oscillation wavelength 
{ HEAD ~ The optical device } 1 , wherein the peripheral portion is covered by { TAIL ~ the dielectric film } which has an optical thickness of an odd multiple of λ/4 , wherein λ is an oscillation wavelength
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH