Patent ID: 7266139

Claim:
An optical semiconductor device module comprising: an optical semiconductor device emitting light and having a light-emitting end face optically coupled to an optical fiber; a stem on which said optical semiconductor device is mounted; a cap fixed to said stem, said cap having a light transmissive hole between the optical fiber and said optical semiconductor device; and a ball lens fixed in said light transmissive hole, wherein said ball lens has a light-entrance surface opposite and facing said optical semiconductor device and through which light emitted from said optical semiconductor device enters said ball lens and a light-exit surface opposite the light-entrance surface and through which the light exits said ball lens, said ball lens has a refractive index of at least 1.9 and a diameter between 1.5 mm and 2.5 mm, and minimum distance between the light-entrance surface of said ball lens and the light-emitting end face of said optical semiconductor device is at least 0.2 mm.