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An optoelectronic InGaAs-based terahertz (THz) receiver for heterodyne detection up to 1 THz is demonstrated for the first time operating at 1.5 μm. This wavelength allows for a fully fiber-coupled heterodyne system, which simplifies applications spectroscopy and THz communications.
We investigate optimal Be-doping conditions of low-temperature-grown InGaAs/InAlAs photoconductive antennas with respect to their carrier lifetimes and carrier mobility. Employed as THz-TDS receiver bandwidths of 5.8 THz with a dynamic range of up to 80 dB is achieved.
A new receiver drastically increases the signal-to-noise ratio of 1.5µm cw THz photomixing systems. The obtained SNR of 105 dB at 100 GHz and 45 dB at 2 THz are the highest values reported in literature and superior to 800 nm setups. This is a milestone in the evolution of cw THz photomixing systems.
Photoconductive cw THz receivers with buried interdigital finger contacts feature a 20-fold higher conversion efficiency than their planar counterpart. Applied to a 1.5 µm cw THz photomixing system, a SNR up to 95 dB @ 100 GHz was achieved.
We measured pulsed THz emission from high-mobility MBE grown InGaAs/InAlAs multi-nanolayer structures. The detected average THz power was 32 μW at 32 mW optical excitation power. The bandwidth of the THz pulses exceeds 4 THz.
We demonstrate pulsed THz emission and detection in low temperature (LT) MBE grown Be-doped InGaAs/InAlAs multi-nanolayer structures for an excitation wavelength of 1030 nm. We obtained spectra with a bandwidth of up to 3 THz. Furthermore, we performed differential transmission experiments to investigate the material’s relaxation time constants.
An integrated photonic chip allows for full control of the THz signal in cw THz photomixing systems. This THz control unit does provide direct access to the THz amplitude and phase via standard electronics as well as continuous tuning of the beat frequency over a frequency range larger than 1 THz
We present first results of pulsed THz emission from low temperature (LT) MBE grown Be-doped InGaAs/InAlAs multi-nanolayer structures at an excitation wavelength of 1030 nm. The spectra obtained reach 3 THz. We further investigate the material's relaxation time constants by differential transmission experiments.
Electro-optical control of the THz phase enables instantaneous determination of THz phase and amplitude in cw THz photomixing systems. By a novel optical inline modulation technique of the THz phase, ultrafast THz measurements become possible without the drawback of phase instabilities.
Telecom components and electro-optic THz phase control allow the realization of an integrated THz control unit. It enables to control any parameter of the THz signal in CW THz photomixing systems with standard electronic equipment. This significantly reduces size and cost of future CW THz systems.
Photoconductive antennas (PCAs) based on InGaAs/InAlAs for operation at 1.5 μm are improved by employing special structuring techniques, i.e. mesa etching. The detected THz amplitude is increased by a factor of over 27. The spectra show a significantly increased bandwidth exceeding 4 THz.
THz at 1.5 μm is pushed for replacing Ti:sapphire by pulsed fiber lasers. But telecom technologies offer much more advantages. This paper describes key developments towards telecom based THz systems for real world applications.
A cw terahertz spectrometer operating without optical amplifiers and without mechanical delay line is presented. Fiber-coupled 1.5 μm DFB lasers in a “butterfly” housing drive a photodiode emitter, which provides 5 μW output at 0.5 THz. A coherent photoconductive receiver yields an SNR up to 75 dB.
Implementation of interdigital electrodes and etching isolating trenches has improved InGaAs/InAlAs photoconductive antennas. The signal-to-noise ratio of continuous wave systems at 1.5 μm has been increased up to 80 dB and its operation range up to 2.1 THz.
Mesa-structuring of InGaAs/InAlAs photoconductive layers has been employed for improving THz antennas. The developed devices are evaluated in a time domain spectrometer operating at 1.5 μm wavelengths. Order-of-magnitude improvements versus planar antennas are demonstrated.
Terahertz antennas for 1.5 μm operation are improved by mesa-etching of the InGaAs/InAlAs photoconductive layers. The performance in terms of dark current, signal amplitude and bandwidth has been improved significantly.
THz imaging holds a strong potential for applications such as industrial quality assurance. However, the slow scan speed still limits the broad market introduction. In this paper, we present three different approaches based on photoconductive antenna transmitters and receivers, which aim to increase the speed of THz time-domain imaging. Firstly, multi-channel measurements, with several transmitter...
CW THz systems are improved by combining high power photodiode based emitters with coherent photoconductive receivers. The fiber coupled system operates up to 1.5 THz.
The worldwide first all-fiber THz time-domain spectrometer for operation at 1.5 mum is presented. Applications up to 3 THz are demonstrated. Key devices are photoconductive antennas based on novel LT InGaAs/InAlAs multi-layer structures.
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