Andre Sarker Andy

Estimation of dark and active dielectric constants in the sub-THz frequency domain of an optically tunable organic semiconductor blend of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester

The dielectric properties of a 95% poly(3-hexylthiophene):5% phenyl-C61-butyric acid methyl ester blend are measured in the dark and under white light illumination by quasi-optical transmissometry and terahertz time-domain spectroscopy. The real part of the dielectric constant varies monotonically between 2.75 and 3.50, in agreement with the literature, and displays a reversible photoinduced drop of 0.05–0.55 at sub-THz. The imaginary part fluctuates between 0.1 and 1.5 in the dark and displays a reversible increase upon illumination of 0.10–0.52 at sub-THz. The corresponding charge carrier concentration under illumination (using transient and steady-state photoconduction) is 1014 to 1015 cm−3.

Measurements of non-linear sub-THz quasi-optical devices

The paper presents recent developments in designing quasi-optical multipliers in the sub-THz frequency domain. An extensive measurement campaign is described in detail in which issues are addressed concerning the non-trivial nature of the problems met. In particular, attention is paid to impedance measurements of the core element, the integrated antenna-multiplier (dubbed the ‘multenna’), together with the associated experimental apparatus for detection of its higher-order harmonics. Finally, use of a light-sensitive semiconducting organic polymer is demonstrated as a tuneable dielectric that will enable elements of a multenna array to be phase-locked for generation of coherent emission.