New optoelectronic integrated device for optically controlled microwave oscillators

A new optoelectronic integrated device for the design of optically tuned microwave oscillators is presented. The device consists of an n-GaAs optically controlled field effect transistor (OPFET) and a p-AlGaAs/p-GaAs/n⁺-AlGaAs surface emitting double heterostructure light emitting diode (DH-LED) which are developed vertically on a p⁺-GaAs substrate and separated by a semi-insulating (SI) GaAs layer. This new device is referred to as a light source integrated OPFET (LSI-OPFET). The proposed device structure is such that optical radiation generated by the LED is fed back into the OPFET as back illumination. The level of back illumination to the OPFET may be controlled by simply changing the bias current of the LED. The back illumination is used as the control signal to the OPFET to change certain parameters of the device such as the transconductance, gate-source and gate-drain capacitances etc. This makes the LSI-OPFET device suitable for the design of optically controlled microwave amplifiers and oscillator circuits. The proposed device is demonstrated in optically tuned common-source and common-drain microwave oscillators in which the frequency of oscillation may be controlled by the level of back illumination from the LED into the OPFET.