Paulina S. Kuo

Single-phase growth studies of GaP on Si by solid-source molecular beam epitaxy

GaP/Si heterostructures were grown under different growth conditions by molecular beam epitaxy in order to obtain single-phase GaP on Si. The growth results were examined by reflective high-energy electron diffraction, anisotropic etching, atomic force microscopy, and x-ray diffraction. The results showed that high quality, single-phase GaP was grown on Si at a high growth temperature, about 500u200a°C, with a low P/Ga flux ratio of 2.5×, while at a lower temperature, a second phase with a 90° in-plane rotation was grown.

Conditions for two-photon interference with coherent pulses

We study the conditions for two-photon classical interference with coherent pulses. We find that the temporal overlap between optical pulses is not required for interference However, coherence within the same inputs is found to be essential for the interference.

Multi-photon absorption and nonlinear refraction of GaAs in the mid-infrared

We report the wavelength dependences of the two- and three-photon absorption coefficients and nonlinear refractive indices of undoped GaAs in the spectral range 1.3-3.5 mum. We have used 100-fs-long optical pulses and the Z-scan method.

Polarization-Diverse Parametric Processes in Zincblende Crystals

Quasi-phasematched, non-birefringent nonlinear materials, like orientation-patterned GaAs, allow efficient mixing of diverse polarization states. We investigate parametric processes in these materials, including the six coupled-wave equations that describe them and implications for all-optical signal processing.

Temperature dependent noise in quantum frequency conversion (Conference Presentation)

Hybrid quantum networks will be based on nodes that operate at different wavelengths, requiring quantum channel standardization via quantum frequency conversion (QFC). QFC is typically based on highly efficient sum- or difference-frequency generation in second-order nonlinear materials, such as periodically poled lithium niobate waveguides. The presence of the strong pump beam in such a nonlinear medium leads to unwanted nonlinear processes that produce noise. One of these noise processes is spontaneous Raman scattering (SRS). Typically, the pump is chosen to be the longest wavelength in the second-order nonlinear mixing process so that noise photons at the signal wavelength are produced by the less efficient anti-Stokes Raman scattering process rather than the Stokes scattering process. Since SRS is a temperature-dependent process, lowering the temperature reduces the Raman-scattered photons. We discuss the theory of temperature-dependent Raman scattering and present experimental results of the temperature dependence of dark count rates in a guided-wave QFC device.

New THz Source Based on Resonantly Enhanced Frequency Conversion in Periodically-Inverted GaAs

We report mW-average-power widely tunable (0.5-3.5 THz) monochromatic THz source based on frequency mixing in periodically-inverted GaAs, between the two closely spaced signal and idler waves, inside the resonant cavity of a synchronously-pumped picosecond OPO.

Pumping a GaAs Optical Parametric Oscillator with Circularly Polarized and Depolarized Light

We demonstrate an optical parametric oscillator based on GaAs pumped with both a circularly polarized and a pseudo-depolarized pump. High symmetry in the nonlinear susceptibility tensor of GaAs enables pumping with “exotic” polarizations.

Advances in Structured Nonlinear Semiconductor Crystals

Microstructured semiconductors, like orientation-patterned GaAs, achieve quasi-phasematching through controlled, periodic inversions of the crystallographic orientation. These nonlinear optical materials are becoming more mature and are being used to generate mid-infrared and THz radiation.