Development of InGaAsP/GaAs Diode Lasers for Ultrashot Pulse Generation

Abstract

The groundwork has been completed for a large new research initiative involving the development of diode lasers for moderate power ultrashort pulse generation. This thesis reports on the status of three core areas of this initiative: InGaAsP/GaAs diode laser design and characterization, split contact device testing, and thin film interference filter deposition and characterization. Two new short wavelength diode laser designs have been realized and tested. A 980 nm laser was designed, using an InGaAsP barrier/waveguide region. This showed improved far field performance and better contact isolation as compared to an existing 980 nm laser using GaAs barriers. A laser emitting at 850 nm was also designed using GaAs quantum wells surrounded by a new quaternary waveguide region. A test arrangement was developed to facilitate the measurement of IV and LI curves for split contact lasers. Numerous lasers were tested, indicating that short absorber sections and narrow gap widths are preferable for use as saturable absorbing regions in a passively mode locked diode laser. Finally, thin film silicon oxynitride interference filters have been designed, deposited, and characterized for several antireflecting and high reflectance coatings on semiconductor laser facets. A comparison ofsingle layer AR coatings accounting for the modal reflectivity was performed. A four layer high reflectance coating with a peak broadband reflectance of over 90% was deposited on a laser facet.