In this work, vibrational spectroscopic methods (resonance Raman [RR] and infrared absorption [IR]) were used for the investigation of phytochromes. Phytochromes are bistable photoreceptor proteins that bind bilins (BV, PCB, PΦB) as chromophores. Various plant, cyanobacterial, and bacterial variants regulate biological processes through the light d...
We present the time-resolved spectral analysis of the settling process in a pulsed external-cavity quantum-cascade laser (EC-QC laser) emitting in the wavelength range around 7.4 mu m. Due to mode competition between the two cavities formed by the laser-chip on one hand and the external-cavity on the other hand, a time-dependent spectral emission o...
An overview of quantum cascade detector technology for the near- and mid-infrared wavelength range will be given. Thanks to photovoltaic instead of photoconductive operation, quantum cascade detectors offer great opportunities in terms of detection speed, room temperature operation, and detectivity. Besides some crucial issues dealing with fabricat...
Phonons are considered as a most important origin of scattering and dissipation for electronic coherence in nanostructures. The generation of coherent acoustic phonons with femtosecond laser pulses opens the possibility to control phonon dynamics in amplitude and phase. We demonstrate a new experimental technique based on two synchronized femtoseco...
We report on scalable photoconductive antennas for both emission and detection of terahertz (THz) radiation. The concept yields THz emitters with high efficiencies for the conversion of near-infrared into far-infrared radiation, and provides detectors that do not require tight focusing of both the THz beam and the near-infrared gating beam. GaAs su...
We report large current- and temperature-induced beam-steering effects, observed in the far-field distribution of InP-based quantum-cascade lasers emitting around 7.8-µm wavelength operated in pulsed mode Changing the temperature within a narrow range of about 10 °C around room-temperature leads to a change in the direction of the output beam, as g...
The doping profile in different n-doped GaAs homoepitaxial structures grown by molecular beam epitaxy is investigated in the time domain by employing a laser based picosecond ultrasound technique in a contactless and noninvasive way. Experiments based on asynchronous optical sampling employ two femtosecond lasers, which allow us to detect changes i...
Detection of terahertz radiation by two dimensional electron plasma in high electron mobility GaAs/GaAlAs transistors was investigated at cryogenic temperatures in quantizing magnetic fields. Shubnikov-de Haas oscillations of the detection signal were observed. A double (optical and electrical) modulation technique applied allowed us to study the i...
A large-area interdigitated terahertz emitter based on molecular-beam epitaxy grown GaInAsN with an additional AlGaAs heterostructure is investigated as a terahertz source for excitation wavelengths between 1.1 and 1.5 mu m. The optical and electrical properties of the emitter material exhibit absorption up to a wavelength of 1.5 mu m and have a re...
Scalable antenna structures based on photoconducting GaAs substrates are excellent devices for both generation and detection of pulsed terahertz radiation. Scalable emitters yield more intense radiation as compared to conventional emitters excited with a typical titanium-sapphire laser oscillator system. For the detectors materials with different c...
