Abstract: An optical wavelength selection device containing an optical beam source, a device for collimating the optical beam to produce a collimated optical beam, a diffraction grating assembly for diffracting the collimated optical beam to produce a collimated optical diffracted beam, a device for modifying the polarization state of the collimated optical beam, and a lens assembly for focusing the collimated optical diffracted beam. The device for modifying the polarization state of the collimated optical beam is located within the diffraction grating assembly in one embodiment and before the diffraction grating assembly in another embodiment.

Abstract: An optical wavelength selection apparatus containing a surface-relief transmission diffraction grating, a collimating lens for collimating a beam incident to the diffraction grating, and a focusing lens for focusing the beams diffracted by the diffraction grating. The diffraction grating, after having been subjected to a test condition of 85 degrees centigrade and a relative humidity of 85 percent for at least 500 hours, has diffraction efficiency performance within 6 percent of that achieved before being subjected to these test conditions.

Abstract: A surface-relief transmission diffraction grating which, after having been subjected to a test condition of 85 degrees centigrade and a relative humidity of 85 percent for at least 500 hours, has diffraction efficiency performance within 6 percent of that achieved before being subjected to these test conditions.