Vertically tapered waveguide spot size converters fabricated via a linewidth controlled grey tone lithography for InP-based photonic integrated circuits.

We report a novel and simple fabrication process to realize vertically tapered spot size converters (SSC) on InP photonic integrated circuits. The vertical tapering was achieved via a linewidth controlled local optical dose variation, leading to a grey tone photoresist profile. The fabricated SSCs are compact, polarization insensitive and demonstrate a very high mode conversion efficiency of 95%.

Two-photon photodetector in a multiquantum well GaAs laser structure at 1.55 microm.

We report two-photon photocurrent in a GaAs/AlGaAs multiple quantum well laser at 1.55 microm. Using 1ps pulses, a purely quadratic photocurrent is observed.

Quantum dots for terahertz generation.

Nanostructures made of semiconductors, such as quantum wells and quantum dots (QD), are well known, and some have been incorporated in practical devices. Here we focus on novel structures made of QDs and related devices for terahertz (THz) generation. Their potential advantages, such as low threshold current density, high characteristic temperature, increased differential gain, etc, make QDs promising candidates for light emitting applications in the THz region.

Two-photon absorption-induced self-phase modulation in GaAs-AlGaAs waveguides for surface-emitted second-harmonic generation.

Performance-limiting asymmetric distortion is observed in the spectra of fundamental pulses transmitted through GaAs-Al(0.9)Ga(0.1)As multilayer waveguides designed for surface-emitted second-harmonic generation.

Coupled electron-phonon modes in optically pumped resonant intersubband lasers.

Intersubband lasing at 12-16 microm based on a CO2 laser pumped stimulated resonant Raman process in GaAs/AlGaAs three-level double-quantum-well structures is reported. The presence, or lack of, lasing action provides evidence for resonantly coupled modes of collective electronic intersubband transitions and longitudinal optical phonons. An anticrossing behavior of these modes is clearly seen when the difference between the pump and lasing energies (i.