Search results

1

Efficient Terahertz Pulse Generation in Laser-Induced Gas Plasmas

100%

Löffler T., Kress M., Thomson M., Roskos H.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

99-108

EN

In this contribution, we review the development of sources for far-infrared (terahertz) radiation based on laser-generated gas plasmas. We describe several generation mechanisms based on ponderomotive forces, external field screening, and optical second-harmonic biasing. These methods are compared with the standard techniques with respect to the achievable terahertz pulse energy.

2

Ultrafast Optical and Magneto-Optical Dynamics in Colossal-Magnetoresistance Manganites

100%

Dorosinets V., Richter P., Jakob G., Roskos H.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

211-214

EN

Transient pump-probe reflectance measurements on La_{0.67}Ca_{0.33}MnO_3/MgO and La_{0.67} Ca_{0.33}MnO_3/SrTiO_3 thin films reveal a hitherto unknown magnetization-dependent energy gap that determines the relaxation process of the optically excited charge carriers on the picosecond time scale. In the case of La_{0.67}Ca_{0.33}MnO_3/SrTiO_3, the subsequent reflectance dynamics at low temperatures is determined to be substrate-induced strain that drives the sample into a metastable state characterized by an increased number of paramagnetic domains.

3

Dynamics of the Electric Field in a GaAs/AlGaAs Superlattice after Femtosecond Optical Excitation: Application of Time-Resolved Spectroscopic Techniques

76%

Lisauskas A., Blöser C., Sachs R., Roskos H., Juozapavičius A., Valušis G., Köhler K.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

250-255

EN

We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the evolution of the internal field in a GaAs/AlGaAs superlattice after pulsed optical excitation at low temperature. The electric field dynamics is investigated by tracing the spectral position of the Wannier-Stark transitions as a function of delay time. We determine the electron sweep-out time, extract detailed information about the picosecond-time-scale drift of the charge carriers by comparing the measured data with the results of semi-classical self-consistent model calculations, and evaluate the two experimental techniques with respect to their ability to provide information about the carrier and field dynamics.

4

Strong Electric Field Driven Carrier Transport Non-Linearities in n-Type GaAs/AlGaAs Superlattices

64%

Subačius L., Venckevičius R., Kašalynas I., Seliuta D., Valušis G., Schmidt J., Lisauskas A., Roskos H., Alekseev K., Köhler K.

Acta Physica Polonica A

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2011

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vol. 119

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issue 2

167-169

EN

Nanosecond pulsed technique was used to study and discriminate strong electric field induced effects in carrier transport in silicon doped GaAs/Al_{0.3}Ga_{0.7}As superlattices at room temperature. The experiment shows that the superlattice can serve as gain media to employ parametric phenomena for microwave amplification.

5

Few-Cycle Laser Pulses: The Carrier-Envelope Phase, Its Role in the THz Emission from Laser-Generated Plasmas and a New Way to Measure It

52%

Kress M., Löffler T., Thomson M., Roskos H., Dörner R., Gimpel H., Zrost K., Ergler T., Moshammer R., Morgner U., Ullrich J.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

769-776

EN

Terahertz emission from laser-generated air plasmas has recently been identified as an interesting source for THz radiation. High intensities and a large bandwidth of the THz pulses can be achieved. We briefly review several mechanisms which were employed to generate the quasi-static dipole moment needed for the optical rectification process. This leads us to a discussion of a specific application of THz emission from an air plasma, namely the investigation of the carrier-envelope phase of few-cycle optical pulses. Such pulses of a duration of less than 10 fs induce a spatial charge asymmetry in the plasma directly via non-linear tunneling ionization. The asymmetry, and with it the emission of the THz radiation from the plasma, depend on the carrier-envelope phase, with the consequence that one can determine the phase by measurement of the amplitude and polarity of the THz pulse.

6

Broad Band THz Sensing by 2DEG Bow-Tie-Type Diodes

52%

Valušis G., Seliuta D., Tamošiūnas V., Širmulis E., Balakauskas S., Gradauskas J., Sužiedėlis A., Ašmontas S., Anbinderis T., Narkūnas A., Papsujeva I., Lisauskas A., Roskos H., Köhler K.

Acta Physica Polonica A

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2005

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vol. 107

|

issue 1

184-187

EN

We suggest a novel approach to detect broad band, 0.078-2.52 THz, electromagnetic radiation at room temperature using an asymmetrically-shaped bow-tie diode based on a modulation-doped GaAs/AlGaAs structure. We show that the voltage sensitivity in the range from 0.078 THz up to 0.8 THz has a plateau and its value is within 0.3-0.5 V/W. We consider the bow-tie diode design to increase the sensitivity of the device.

Refine search results

Efficient Terahertz Pulse Generation in Laser-Induced Gas Plasmas

Ultrafast Optical and Magneto-Optical Dynamics in Colossal-Magnetoresistance Manganites

Dynamics of the Electric Field in a GaAs/AlGaAs Superlattice after Femtosecond Optical Excitation: Application of Time-Resolved Spectroscopic Techniques

Strong Electric Field Driven Carrier Transport Non-Linearities in n-Type GaAs/AlGaAs Superlattices

Few-Cycle Laser Pulses: The Carrier-Envelope Phase, Its Role in the THz Emission from Laser-Generated Plasmas and a New Way to Measure It

Broad Band THz Sensing by 2DEG Bow-Tie-Type Diodes