MBE growth of III-V materials with orientation-patterned structures for nonlinear optics.

摘要

There are numerous applications of nonlinear optical frequency conversion in the infrared, ranging from generation of coherent radiation for spectroscopy and military applications, to wavelength conversion in communication systems. Semiconductors such as AlxGa1-xAs and GaP have excellent properties for nonlinear frequency conversion, in particular large nonlinear coefficients and transparency throughout the mid- to far-infrared. However, due to the absence of birefringence, quasi-phasematching (QPM) has to be used for the phasematching, requiring a modulation of the sign of the nonlinear coefficient along the material. In this work we developed an all-epitaxial process to fabricate orientation-patterned AlxGa1-xAs and orientation-patterned GaP structures, used for both bulk-like and waveguide devices.; Our orientation-patterned GaAs template is fabricated in three steps. First, we use the polar-on-nonpolar growth of GaAs/Ge/GaAs heterostructure to control the lattice inversion. The orientation pattern is then defined by a combination of photolithography and a series of selective chemical etching steps. Template and waveguide growth is completed in the MBE regrowth. Critical regrowth issues are elimination of antiphase defects within each single domain while still maintaining the induced antiphase domains at the pattern boundaries. Appropriate growth conditions were developed to obtain low-corrugation template. The regrowth QPM periods demonstrated are short enough to phasematch any interaction in the transparency range of AlxGa1-xAs.; Various nonlinear optical interactions have been demonstrated using this technique, with low-loss AlxGa1-xAs QPM waveguides as a typical example. We fabricated waveguide devices and demonstrated second harmonic generation with a pump laser at 1.55 mum. A waveguide loss, ∼4.5 dB/cm at 1.55 mum, was measured, which is close to that of the unpatterned waveguides. Record-high conversion efficiency, 43%W-1, was demonstrated. These achievements provide solid basis for the fabrication of highly efficient nonlinear optical devices based on the GaAs/AlGaAs material system.; We also investigated the growth of single-phase GaP on Si, aiming at transferring growth technologies of GaAs on Ge to GaP on Si. We successfully obtained two distinct single-phase GaP on Si and fabricated first orientation-patterned GaP template. These progresses will lead to GaP-based nonlinear devices for high power operation.