Prospectus, September 2, 2015

Foreign language enrollment decreases, Professors take center stage in faculty exhibit, Alternative buying options keep textbook costs low, Campus resources help students struggling with academics, Married professors show students how to keep an open mind, Study finds peak months for college students’ 1st drug use(AP), Director Wes Craven dies at 76(AP), Sanders says he would be prepared to use military force(AP), Cobras looking to strike this season, Men’s basketball reloading for high expectations, Parkland clubs highlighted at Student Activities Fair,https://spark.parkland.edu/prospectus_2015/1014/thumbnail.jp

High Speed Coherent CW Terahertz Spectrometer

In-fibre wavelength selective modulation of the optical phase enables the electro-optic control of the terahertz phase in continuous-wave photomixing terahertz systems without any free-space optics. Using a fully fibre-coupled terahertz setup, a coherent scan of a frequency range of 1.5 THz with 100 MHz resolution in less than 24 s is demonstrated. This sample rate of 1.6 ms/sample is more than 20 times faster than any previous broadband scans reported

Effizienz-verbessertes fasergekoppeltes Terahertzsystem

Die Erfindung betrifft ein Terahertzsystem zum Erzeugen und kohaerenten Detektieren von Terahertzstrahlung, umfassend eine Laserlichtquelle (1) und zwei jeweils ueber eine Lichtleitfaser (5) optisch mit der Laserlichtquelle (1) gekoppelte und durch Licht dieser Laserlichtquelle (1) aktivierbare THz-Antennen, von denen eine erste als Sendeantenne (2) und eine zweite als Empfaengerantenne (3) dient, wobei die THz-Antennen jeweils einen mit Antennenleitern (9) kontaktierten Halbleiterchip aufweisen, der mindestens eine photoempfindliche aktive Schicht (12) mit einer Bandkantenwellenlaenge, die groesser ist als eine Wellenlaenge der Laserlichtquelle (1)ngrenzende Schicht (13) mit einer Bandkantenwellenlaenge, die kleiner ist als die Wellenlaenge der Laserlichtquelle (1), umfasst, wobei die Bandkantenwellenlaenge der aktiven Schicht (12) mindestens einer der THz-Antennen mindestens 150 nm groesser ist als die Wellenlaenge der Laserlichtquelle (1)

Photoconductive Cw THz receiver with 20-fold increased THz conversion efficiency

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 mum cw THz photomixing system, a SNR up to 95 dB @ 100 GHz was achieved

Handheld terahertz systems based on telecom technologies

The potential of Terahertz technology for various applications in security or material inspection has now been demonstrated widely. However, THz systems have to shrink in size and price to become acceptable for real-world applications. Our way to approach this target is to exploit technologies developed and matured originally for 1.55 m fiber-optic telecom applications. Key devices are photoconductive antennas for 1.55 m operation. They were developed using a novel InGaAs/InAlAs multi-layer structure. The antennas are packaged into fiber coupled modules. These handheld THz heads are driven by a 1.55 m pulsed fiber laser. A tunable delay with both an oscillating mirror and a precise linear drive allow for real-time measurements as well as for high resolution spectroscopy. The system performance up to 4 THz is demonstrated

Towards integrated continuous wave THz systems

We present a photonic integrated circuit, which enables the full control of the THz signal in continuous wave photomixing THz systems via standard electronics. The device comprises two DFB-lasers and an optical phase modulator on a single chip. Due to a unique bidirectional operation technique, the chip provides the optical beat signal for both THz emitter and THz receiver and allows for manipulation of the THz phase via the optical phase modulator. To evaluate the performance of our solution, we realize a coherent cw THz system based on our photonic integrated circuit and compare it to discrete lasers and standard components. As the results show, both setups feature an identical signal-to-noise ratio, reaching 50 dB at a frequency of 1 THz for an integration time of 500 ms. This is the best reported performance of CW photomixing systems running at 1.5 µm optical wavelength

Improved InGaAs/InAlAs photoconductive THz receivers: 5.8 THz bandwidth and 80 dB dynamic range

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

Next generation continuous wave photomixing THz systems

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

Mesa structured photoconductive antennas for 1.5 µm: All-fibre THz-TDS spectroscopy beyond 4 THz

Photoconductive antennas (PCAs) based on InGaAs/InAlAs for operation at 1.5 m 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