AN OPTICALLY CONTROLLED OPTOELECTRONIC SWITCH: FROM THEORY TO 50 GIGAHERTZ BURST-LOGIC DEMONSTRATION

ii For high-speed communication, it is essential to multiplex, demultiplex, and switch individual data bits at very rapid rates. Similarly, in wavelength division multiplexed (WDM) systems the ability to change wavelengths dramatically increases the potential connectivity of such transmission systems. This dissertation presents work on a unique optically controlled optical gate that is capable of both high speed optical gating and wavelength conversion. The optically controlled optical gates (OCOG) described herein alter the reflection of a surface-normal pulse of light in response to the presence or absence of a control light pulse. Low required switching energy is possible for two reasons: (1) separation of photogenerated electrons and holes creates large changes in the electric field and (2) the absorption of the multiple quantum wells in a p-i-n diode is strongly field-dependent due to the quantum confined Stark effect. The recovery mechanism used in these devices is based on diffusive conduction, a novel optoelectronic behavior tha

Observation of wavelength-converting optical switching at 2.5 GHz in a surface-normal illuminated waveguide

Abstract: We demonstrate proof-of-principle switching of a continuous wave (CW) signal that propagates in a p-i-n multiple quantum well waveguide illuminated from above with a modulated control beam. We observe modulation of the CW signal at 2.5 GHz using ~ 1mW control beam powers. Desirable features in optically-controlled optical switches include fast operating speeds, high contrast ratios, low switching power, and NxN scalability. Normally, waveguide modulators provide large contrast ratios but provide only 1xN scalability. By having surface-normal control of planar (waveguided) signals, NxN arrays could be achieved. Several groups have simply electrically interconnected surface-normal photodetectors with waveguide switches to achieve such a configuration [1-3]. In this paper we demonstrate an optically controlled waveguide switch that combines the detection and modulation function into a single device [4-5] that, in principle, can provide all of the above features. In addition to optically invoked modulation, we can enable (or disable) the device with an appropriate applied electrical bias. We demonstrate wavelength conversion capability of this device by employing different wavelengths for the control and signal beams (822 nm and 868 nm, respectively). The device is a multiple quantum well p-i-n diode with a waveguide structure, as seen in Fig. 1. The control beam is coupled into the diode through surface normal illumination while the CW signal is coupled in through the waveguiding direction of the device. Upon detection of the control beam, the absorption properties of the multiple quantum wells in the device are changed, which in turn modulates the CW signal. Consequently, data from the control beam can be encoded onto the CW signal. Thus, switching is achieved by performing detection of the control beam and modulation of the input signal with the same device. Because the detection and modulation occur in the same space, power consumption is decreased and electrical interconnection issues are eliminated. CW Signal (868 nm