Direct intensity modulation and wireless data transmission characteristics of terahertz-oscillating resonant tunnelling diodes (RTDs) is reported. A direct intensity modulation of the RTD oscillators was demonstrated, and the frequency response was measured. It was found that the 3 dB cutoff modulation frequency was limited by the parasitic elements of the external circuit, and increased up to 4.5 GHz by reducing such parasitic elements. Wireless data transmission by direct amplitude shift keying was demonstrated using an RTD oscillating at 542 GHz with cutoff frequency of 1.1 GHz. The BERs for bit rates of 2 and 3 Gbit/s were found to be 2 × 10 28 and 3 × 10 25 , respectively.Introduction: High-capacity short-distance wireless communication is an important application of the terahertz (THz) range [1, 2]. Thus, compact and coherent solid-state THz sources that can be modulated directly are highly desirable. A good candidate for THz sources is the resonant tunnelling diode (RTD), which can oscillate in the THz range at room temperature [3][4][5][6]. We have reported RTDs with fundamental oscillation of 1.04 THz [4] and high output power ( 400 mW) oscillation at around 550 GHz [5]. The modulation of the output of THz sources is important for communication. In this Letter, we demonstrate a direct modulation of the output power of an RTD oscillator and measure its frequency response. In addition, we also demonstrate wireless data transmission by a direct amplitude shift keying (ASK) of the RTD.

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The optical input–output characteristics of a 1.55 μm vertical-cavity surface-emitting laser (VCSEL) with external light injection to its fundamental mode were investigated. Appropriate wavelength detuning of external light enables abrupt modal switching in an injection-locked VCSEL. We found that the obtained nonlinear transfer function is strongly dependent on the distance between a VCSEL and an input lensed fiber. As the distance was changed, different optical input–output characteristics were observed, demonstrating that such a VCSEL can be employed in various optical signal-processing schemes, for example as an optical regenerator or an optical inverter.