Large area photoconductive terahertz emitter for 1.55 μm excitation based on an InGaAs heterostructure

Abstract

We present scalable large area terahertz (THz) emitters based on a nanoscale multilayer InGaAs/InAlAs heterostructure and a microstructured electrode pattern. The emitters are designed for pump lasers working at the telecommunication wavelength of 1.55 μm. Electric THz fields of more than 2.5 V cm⁻¹ are reached with moderate pump powers of 80 mW, the corresponding spectrum extends up to 3 THz. The saturation characteristics have been investigated for different pump laser spot sizes. For small pump powers of less than 50 mW the emitted THz field is nearly independent of the spot size, for higher pump powers and small spot sizes a clear saturation of the generated THz pulse can be observed. Hence the use of scalable emitters is especially promising for high power fibre laser systems. The spectral content of the generated radiation is nearly independent of the parameters spot size, pump power, and bias voltage, which allows for stable operation in spectroscopic applications.

Nanoplasmonics enhanced terahertz sources

“…Previously, nanoplasmonic structures have been investigated to enhance the performance of THz detectors [17][18][19]. The main advantage of the nanoplasmonic structure for detection is to create a fast sweep out time, and thereby allow for the usage of a low-cost high-mobility long carrier lifetime substrate like semi-insulating GaAs [18,[20][21][22], as opposed to other less common substrates with short carrier lifetimes (such as low-temperature GaAs or GaBiAs) [23][24][25][26][27][28][29][30][31]. For pulsed THz sources, however, the carrier lifetime is not a limiting factor [32], yet nanoplasmonic structures can still provide an advantage, as we will investigate in this work.…”

A Broadband THz-TDS System Based on DSTMS Emitter and LTG InGaAs/InAlAs Photoconductive Antenna Detector

“…The band coverage of LTG InGaAs/InAlAs based PC antennas can reach up to 5 THz but the center frequency is mainly less than 0.8 THz242526. In contrast, the center frequency and the bandwidth of DSTMS emitters and detectors are much better.…”

Dynamic Tuning of Mean Carrier Momentum Relaxation Time in InGaAs–InAlAs THz Photoconductive Switches

“…Although in small bandgap materials, like InGaAs, heating by elevated bias voltages or optical fluxes can result in further heating by activation of intrinsic carriers [25,26], this effect is not relevant in the devices reported here as indicated by the absence of runaway effects at certain power and by the fact that the reduction in amplitude is more severe for the receiver than for the emitter. If a further significant carrier activation, due to its bias the emitter should be affected more than the receiver is.…”