A simple terahertz (THz) Fourier transform spectrometer is theoretically and experimentally demonstrated with a low-reflectivity Fabry-Perot interferometer. Composed with only two parallel low reflectivity surfaces, this simple spectrometer has the ability to measure the spectrum over more than one octave with a controllable resolution. The emission spectra of a wavelength-tunable photonic transmitter excited by an optical coherent control system are determined by the spectrometer. With a simple algorithm for the spectral reconstruction and a compact structure with easy alignment, the demonstrated spectrometer will meet the needs of many important applications where a compact and convenient spectrometer is required in the frequency range from sub-THz wave up to even visible light.

In this study we investigated the frequency tunability of an edge-coupled membrane photonic transmitter. Its frequency tunability was found to be determined, not only by the radiation loss of the device and antenna pattern, but also by the frequency response of the photodetector. With a properly designed device pattern with a slot dipole antenna, which is known to have a strong resonant peak, both high-power conversion efficiency and a broadband response can be achieved. A wide frequency tuning range from Ͻ100 GHz up to 1.1 THz is demonstrated from a single terahertz photonic transmitter. Combined with coherent-controlled quasicontinuous-wave optical excitation, this optoelectronic-based device also exhibits a record-high light-THz power-conversion efficiency of 0.33%.

The accurate detection of minute amounts of chemical and biological substances has been a major goal in bioanalytical technology throughout the twentieth century [1]. Fluorescence dye labeling detection remains the effective analysis method [2,3], but it modifies the surroundings of molecules and lowering the precision of detection [4][5][6][7]. An alternative label free detecting tool with little disturbance of target molecules is highly desired. Theoretical calculations and experiments have demonstrated that many biomolecules have intrinsic resonance due to vibration or rotation level transitions [8,9], allowing terahertz (THz)-probing technique as a potential tool for the label-free and noninvasive detection of biomolecules. In this paper, we first ever combined the THz optoelectronic technique with biochip technology to realize THz biosensing. By transferring the edge-coupled photonic transmitter into a thin glass substrate and by integrating with a polyethylene based biochip channel, near field THz detection of the biomolecules is demonstrated. By directly acquiring the absorption micro-spectrum in the THz range, different boiomecules can then be identified according to their THz fingerprints. For preliminary studies, the capability to identity different illicit drug powders is successfully demonstrated. This novel biochip sensing system has the advantages including label-free detection, high selectivity, high sensitivity, ease for sample preparation, and ease to parallel integrate with other biochip functionality modules. Our demonstrated detection capability allows specifying various illicit drug powders with weight of nano-gram, which also enables rapid identification with minute amounts of other important molecules including DNA, biochemical agents in terrorism warfare, explosives, viruses, and toxics.