High power laser with integrated lens using focused ion beam etching

Control of the optical mode in high power lasers is essential for a range of high brightness optical pumping applications. The inclusion of a lens within the cavity of a semiconductor laser is desirable not only to increase the proportion of light coupled back into the optical waveguide for improved efficiency, but also in the reduction of the divergence in the far field emission for higher brightness operation. In this work, a collimating lens is introduced at the output facet of a tapered waveguide laser to compensate for the divergence of the optical mode. This in turn is shown to enhance the laser efficiency while simultaneously reducing the far field divergence. Tapered waveguide lasers are considered in this work which operate at a wavelength of 980 nm with a well defined single lobed far field and up to 54 % wall plug efficiency. The lens has been formed by focused ion beam etching to leave a parabolic region of higher refractive index near the output facet. The lens design is computer generated and transferred to the laser using focused ion beam etching running under custom software.