We present Terahertz (THz) imaging with a 1D multichannel time-domain spectroscopy (TDS) system which operates with a photoconductive array of 15 detection channels excited by a 1030 nm femtosecond fiber laser. The emitter and detector are photoconductive antennas based on InGaAs/InAlAs multi-layer heterostructures (MLHS). We characterized the THz optics and the resolution of the system. The performance is demonstrated by the multichannel imaging of two samples. A simultaneous measurement of 15 THz pulses with a pixel pitch of 1 mm increases the measurement speed of the TDS system by factor 15.
We present a flexible technology to generate broadband antireflection (AR) structures for the terahertz (THz) frequency range on planar and curved surfaces of silicon optics. Ultrashort laser pulses are used to ablate the surface to form a pattern of conical pillars with a period of 30 μm. These subwavelength structures act as an effective medium with gradual transition of the refractive index from air to silicon, which reduces the Fresnel reflection losses. The characterization with the THz time-domain spectroscopy system shows an AR effect for a frequency range of 0.1-1.5 THz with a maximum enhancement of the spectral amplitude by ca. 32% at 0.4 THz for planar surfaces. In addition, we demonstrate laser-generated AR structures on convex silicon lenses of both photoconductive emitter and detector devices. Here, the THz pulse amplitude can be increased by about 28%, and single frequencies even show an improvement of the spectral amplitude up to 58%.
We investigate properties of MBE grown photoconductive terahertz (THz) antennas based on the InGaAs/InAlAs/InP material system aimed for an excitation wavelength of approx. 1060 nm. Therefore, we analyze several different approaches concerning growth parameters, layer and material compositions as well as doping. The carrier dynamics are probed via transient white-light pump-probe spectroscopy as well as THz Time Domain Spectroscopy (TDS) measurements. We find that the electron capture probability is reduced for higher electron energies. By adjusting the material band gap this can be resolved and lifetimes of 1.3 ps are obtained. These short lifetimes enable the detection of THz TDS spectra with a bandwidth exceeding 4 THz
We present Terahertz imaging with a 1D multichannel time-domain spectroscopy system (TDS) which operates with a photoconductive array of 15 detection channels excited by a 1030 nm femtosecond fiber laser. The emitter and detector are photoconductive antennas based on InGaAs/InAlAs multi-layer heterostructures (MLHS). The simultaneous measurement of 15 THz pulses with a pixel pitch of 1 mm increases the measurement speed by factor 15
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