Abstract

The astigmatism and asymmetrical divergence of gain-guided diode laser beams are major disadvantages in many uses. These characteristics are caused by asymmetry in the two traverse beam profiles: in the plane of the active junction confinement is effected by the electric current profile, whereas perpendicular to the junction the beam is trapped within the much narrower waveguide dimension. A holographic correcting and collimating element for such diodes is desirable for its low mass-production costs and small dimensions. Unfortunately, efficient holograms cannot be recorded directly with the infrared wavelengths of diode lasers. Large aberrations and reduced efficiencies are expected if the hologram would be recorded at shorter wavelengths. Previously¹ we presented a method for recording high-efficiency low-aberration collimators for spherical light sources with large recording/readout wavelength shifts. Here we generalize that method for astigmatic light sources. We record with nonspherical waves to compensate for wavelength shift aberrations and correct for the source’s astigmatism. Suitable wavefronts are derived from spherical holograms by a judicious choice of their readout and recording geometries.

© 1991 Optical Society of America