Terahertz (THz) radiation, an electromagnetic wave that lies between the infrared and microwave regions, has broad applications in medical imaging, security screening, materials analysis, wireless communication, and astronomy due to its unique characteristics such as non-ionizing nature, high security, high penetration depth in the visible spectrum, and high data transmission bandwidth [[1], [2], [3], [4]]. Developing compact, cost-effective, high power and room temperature continuous tunable THz light sources has become a focused area of research in the past decade [5,6]. In recent years, several semiconductor laser based approaches for generating THz waves have been reported, such as optical phase-locked loops [7], mode-locked semiconductor lasers [8,9], sideband injection locking [10], and optical heterodyne of signals from dual wavelength semiconductor lasers [[11], [12], [13]]. Among them, optical heterodyne stands out as a flexible and convenient approach by combining the output from two single-wavelength lasers with a slight difference in wavelength and coupled into a broadband photo-mixer to produce a THz radiation signal at a frequency corresponding to the wavelength difference between the two single-mode lasers. Tunable room temperature THz emission can be achieved by adjusting the wavelength difference of the two lasers either thermally or electrically [14].

Previous research works have reported optical heterodyne methods for generating THz waves based on integrated photonic chip with multiple semiconductor lasers and photonic components [15,16], but results some far reported suffered from very low output optical power, and laser linewidth were typically in the MHz range, which limits THz signal generation efficiency.

In this study, we propose a high-power multiple wavelengths distributed feedback (DFB) diode laser array chip for generating tunable continuous-wave (CW) THz signals. Each laser in the array operates with a single-mode output power exceeding 90 mW, with a maximum power of 120 mW and laser narrow linewidth as low as 32.6 kHz. By selecting correct combination of laser pairs from the array and adjusting the current bias conditions, based on the optical heterodyne generation technique we were able to generate a room temperature continuous and tunable THz signal spanning the frequency range of 0.075 THz to 2.63 THz. Compared with previous work, our DFB laser array chip has the widest continuous tuning range for terahertz emission while simultaneously achieving high power output and narrow linewidth.