Monolithically integrated solid-state terahertz transceivers

Recent advances in microfabricated terahertz quantum cascade lasers have achieved coherent power and frequency performance previously possible only with much larger gas- or vacuum-tube sources. A significant advantage offered by terahertz quantum cascade lasers lies in the potential to integrate them with other components on the same chip. Such terahertz photonic integrated circuits would help close the terahertz technology gap between microwave electronics and infrared photonics. Here, we describe the first successful monolithic integration of a terahertz quantum cascade laser and diode mixer to form a simple but generically useful terahertz photonic integrated circuit-a microelectronic terahertz transceiver. We show that this terahertz photonic integrated circuit performs all the basic functions (for example, transmission of a coherent carrier, heterodyne reception of an external signal, frequency locking and tuning) of discrete-component terahertz photonic systems, but at a small fraction of the size and in a robust platform scalable to semiconductor fabrication production.