Patent ID: 7259904

Claim:
An apparatus, comprising: a photonic device package having: an erbium doped fiber amplifier (EDFA), the EDFA configured to emit a quasi-monochromatic light beam having a centroid wavelength and sub-wavelengths towards a first edge of a substrate; the substrate having: said first edge, said first edge having refractive index perturbations disposed therein or thereon; the substrate further having: a second edge having a reflective inner surface, the refractive index perturbations on said first edge configured to direct the centroid wavelength in the light beam and the sub-wavelengths in the light beam to the reflective inner surface at the second edge of the substrate; and a third edge being arranged at a predetermined angle with said second edge, said predetermined angle being less than the angle of total-internal reflection of the substrate, wherein the reflective inner surface at the second edge of the substrate is configured to reflect the centroid wavelength and the sub-wavelengths in the light beam to the third edge of the substrate, the third edge of the substrate configured to direct the centroid wavelength and the sub-wavelengths in the light beam to free space; and a position sensitive detector operatively coupled to receive the light beam from free space, the position sensitive detector further operatively coupled to determine the centroid wavelength of the light beam based on a position of the light beam incident on the detector.