Novel slab-coupled optical waveguide laser structures for advancing performance scalability

Modeling, waveguide modifications, and cavity modifications were developed to significantly improve the performance of 1.06 mum tapered slab-coupled optical waveguide lasers (SCOWLs), and to demonstrate a 1.06 mum folded cavity SCOWL device suitable for creating a high power 2-dimensional SCOWL array technology. Improvement of individual device performance was accomplished by designing 5-mm-cavity-length GaAs-based SCOWLs with adiabatically tapered ridge waveguides. A tailored current-injection profile was used to selectively pump the adiabatically expanding TE00 mode with gain over higher order modes, achieving a single optical mode of dimensions 15.9 pm by 3.5 microm and maintaining a stable lateral M2 beam quality between 1.2 and 1.6 across all drive currents. The ~4x increase in mode size led to a maximum efficiency of >50% and a record breaking maximum CW power of 2.5 W, a 38% output power improvement over conventional 4-mum ridge control devices. A dynamic finite difference beam propagation method amplifier model was developed to simulate advanced modal behavior in flared semiconductor optical amplifiers by overlapping the diode laser rate equations. A 2-D SCOWL array technology was attempted for the first time by evolving the conventional edge-emitting SCOWL into a surface-emitter (SE-SCOWL) by etching a 45° turning mirror through the waveguide to direct the optical beam out of plane for surface-normal emission. The addition of a 90° etched back facet produced an all-etched-facet surface-emitter uniquely capable of 2-D scalability without stacking arrays of cleaved-facet edge-emitting diode lasers. The surface-emitting GaAs-based SCOWL achieved a diffraction limited beam, maximum output power of 1 W, slope efficiency of 0.63 W/A, and a maximum power conversion efficiency of 34%. This achievement represents the first single-mode surface-emitting diode laser with comparable power and efficiency to its edge-emitting counterpart. A wavelength beam combining demonstration of a 15-element 1-D SE-SCOWL array achieved a spectrally diverse single-mode output beam and 8.31 W of output power with a slope efficiency of 0.4 W/A, paving the way for future scaling to large, full-wafer, combinable 2-D diode laser arrays.