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We demonstrate the use of an area selective zinc in-diffusion process as a simple and efficient technique for the fabrication of integrated photonic devices. By controlling the profile of the diffusion front and the zinc depth the insertion losses of the devices can be minimized. Using this technique an integrated 1x2 Mach-Zehnder analog modulator was fabricated. Our experimental results demonstrate that the modulator exhibits excellent linearity for both TE and TM polarizations over a wavelength range of 40nm. The measured on-chip losses in the order of 3dB are obtained, which is significantly lower compared to the use of isolation trenches.

An integrated 1x4InP-based optical switch is reported. The device is quite simple and full device operation is achieved by injecting electrical currents to two electrodes. Since the operation of the switch relies on current spreading, using the carrier-induced refractive index change in InGaAsP multiple quantum wells, an area-selective zinc in-diffusion process is used to regulate the current spreading and optimize device performance. As a result, the fabricated 1x4 switch exhibits a -14dB crosstalk between channels over a wavelength range of 30nm, while maintaining low electrical power consumption and allowing the switch to be operated uncooled and under d.c. current conditions.

The intermixing characteristics of three widely used combinations of InP-based quantum wells (QW) are investigated using the impurity-free vacancy disordering (IFVD) technique. We demonstrate that the bandgap energy shift is highly dependent on the concentration gradient of the as-grown wells and barriers, as well as the thickness of the well, with thinner wells more susceptible to interdiffusion at the interface between the barrier and well. According to our results, the InGaAsP/InGaAsP and InGaAs/InP are well suited for applications requiring a wide range of bandgap values within the same wafer. In the case of the InGaAs/InGaAsP system, its use is limited due to the significant broadening of the photoluminescence spectrum that was observed. The effect of the top InGaAs layer over the InP cladding is also investigated, which leads to a simple way to obtain three different bandgaps in a single intermixing step.

We present progress to date in the production of quantum dots etched from multiple quantum well structures for use in all-optical and electro-optical switches. Details of fabrication and comparisons to self-assembled quantum dot materials are described, and the direction of our continuing research is outlined.