Application of superlattice multipliers for high-resolution terahertz spectroscopy

Abstract

Frequency multipliers based on superlattice (SL) devices as nonlinear elements have been developed as radiation sources for a terahertz (THz) laboratory spectrometer. Input frequencies of 100 and 250 GHz from backward wave oscillators have been multiplied up to the 11th harmonic, producing usable frequencies up to 2.7 THz. Even at these high frequencies the output power is sufficient for laboratory spectroscopy. Comparisons to conventional high-resolution microwave spectroscopy methods reveal several superior features of this new device such as very high line frequency accuracies, broadband tunability, high output power levels at odd harmonics of the input frequency up to high orders, and a robust applicability.

Phase-locking of a 2.7-THz quantum cascade laser to a mode-locked erbium-doped fibre laser

“…The emission spectrum measured by a Fourier-transform spectrometer shows a singlemode line at 2.735 THz. To realize a THz reference from a MRS we apply two stages of frequency multiplication; first with a multiplier chain consisting of a Schottky-doubler andtripler (×2×3), a power amplifier, and a varactor-doubler (×2), and then with a harmonic generator based on a superlattice (SL) nonlinear device [15], [16], operated at room temperature, whose higher order harmonics are at THz frequencies. The core of such a device is a MBE-grown superlattice structure with 18 periods.…”

Lyapunov stability of charge transport in miniband semiconductor superlattices

“…28 Therefore, until now Lyapunov stability of the charge transport in minband SLs has been limited by the estimation of the largest Lyapunov exponent from time series. 28 With this, recent experimental works [29][30][31][32] report on high-frequency mixing and highly nonlinear charge transport, which are apparently accompanied by complex spatially temporal dynamics of charge in miniband heavily doped SLs. Understanding of these dynamical regimes and instabilities associated with them in the appropriate models is important for further development and new design of the SL devices.…”

“…Thus, the models considered in this paper take into account application of various fields used in a range of experimental [29][30][31][32][33] and theoretical works. 6,34,35 We analytically and numerically show that when the electron transport in the SL is static, the method demonstrates good agreement with the nL criterion, conventionally used for the prediction of electric domain instability.…”

Dimethyl ether: laboratory spectra up to 2.1 THz

“…The line survey from 550−610 GHz and transition frequencies above 900 GHz were carried out with BWOs in combination with superlattice frequency multipliers as the radiation source. For more technical details see Endres et al (2007). Both setups used InSb hot electron bolometers for detection and an absorption cell of 3 m length.…”