Photoconductive arrays on insulating substrates for high-field terahertz generation

Abstract

We report on the design, fabrication and characterisation of large-area photoconductive THz array structures, consisting of a thin LT-GaAs active region transferred to an insulating substrate using a wafer-scale bonding process. The electrically insulating, transparent substrate reduces the parasitic currents in the devices, allowing peak THz-fields as high as 120 kV cm−1 to be generated over a bandwidth >5 THz. These results are achieved using lower pulse energies than demanded by conventional photoconductive arrays and other popular methods of generating high-field THz radiation. Two device sizes are fully characterised and the emission properties are compared to generation by optical rectification in ZnTe. The device can be operated in an optically saturated regime in order to suppress laser noise.

Ultrafast Two-Dimensional Time-Domain Spectroscopy of Hydrogen-Like Impurity Centers in Germanium

“…Owing to imperfect thermal coupling to the cold finger, there is also a non-vanishing population of the 1s(T2) state, therefore, two additional transitions occur in absorption spectra to the 2p0 and 2p± states. A photoconductive array [9] and a BNA crystal [10] were used to producing peak fields of 60 kVcm -1 , labelled and respectively. An amplified laser system generating 40 fs pulses at a center wavelength of 800 nm at a repetition rate of 1 kHz was used to excite both emitters.…”

“…Further results, including THz excitation field dependence will be presented. is generated using a PCA [9] whilst is generated using a BNA crystal [10]. The peak field of both pulses on the sample was measured as 60 kVcm -1 .…”

“…4. Four signal states acquired from a measurement at a single τ delay (1.31 ps).is generated using a PCA[9] whilst is generated using a BNA crystal[10]. The peak field of both pulses on the sample was measured as 60 kVcm -1 .…”

Femtosecond Broadband Frequency Switch of Terahertz Three-Dimensional Meta-Atoms

“…Our next step is to combine this ultrafast frequency switch with the ISB transition dipoles of parabolic quantum wells to operate in the strong coupling regime at room temperature . We will avoid perturbing the active semiconductor cavity with the NIR pump pulse by illuminating the Lt-GaAs layer from the back, using a transparent substrate as recently demonstrated . This system would constitute a valuable tool to investigate the dynamics of polariton build-up, along with the possibility to generate nonclassical states of light via the mechanism of dynamic Casimir radiation at room temperature. , The devices presented in this work also hold good promise as ultrafast THz amplitude modulators with a picosecond modulation speed.…”

“…20 We will avoid perturbing the active semiconductor cavity with the NIR pump pulse by illuminating the Lt-GaAs layer from the back, using a transparent substrate as recently demonstrated. 40 This system would constitute a valuable tool to investigate the dynamics of polariton build-up, along with the possibility to generate nonclassical states of light via the mechanism of dynamic Casimir radiation at room temperature. 41,42 The devices presented in this work also hold good promise as ultrafast THz amplitude modulators with a picosecond modulation speed.…”