An optimization of terahertz local oscillators based on LT-GaAs technology.

We report on photonic technologies developed at the MPI fur Radioastronomy and the Research Center Julich to generate Terahertz Local Oscillator reference signals for use on e.g. ALMA/APEX and SOFIA. The principle is to mix two (NIR) laser colours in a biased LTG-GaAs layer, thus creating a high-frequency beat (difference) frequency signal. This output signal is coupled to free space through an antenna. In this work a systematic study of the photomixer design, in order to optimize the RF power, is presented. Part of the experiments were done with photomixers integrated to with a broadband spiral antenna designed for frequencies up to 1 THz. The LT GaAs photomixers are prepared on materials with various growth temperatures as well as using resonant cavity material structures and various finger contact geometries. An improvement in the output power up to around 3 μW of submillimeter radiation (0.5 THz) is demonstrated.

[1]  Didier Lippens,et al.  Terahertz frequency difference from vertically integrated low-temperature-grown GaAs photodetector , 2002 .

[2]  T. Löffler,et al.  Free-carrier dynamics in low-temperature-grown GaAs at high excitation densities investigated by time-domain terahertz spectroscopy , 2002 .

[3]  P. Mounaix,et al.  Frequency Difference Generation in the Terahertz Region Using LTG-GaAs Photodetector , 2000 .

[4]  P. Kiesel,et al.  Observation of THz Oscillations and Efficient THz Emission from Contacted Low Temperature Grown GaAs Structures , 2000 .

[5]  Simon Verghese,et al.  Increase in response time of low-temperature-grown GaAs photoconductive switches at high voltage bias , 1999 .

[6]  Shuji Matsuura,et al.  A traveling-wave THz photomixer based on angle-tuned phase matching , 1999 .

[7]  K. A. McIntosh,et al.  Spectroscopic applications and frequency locking of THz photomixing with distributed-Bragg-reflector diode lasers in low-temperature-grown GaAs , 1997 .

[8]  Simon Verghese,et al.  Cryogenic picosecond sampling using fiber-coupled photoconductive switches , 1997 .

[9]  Michael R. Melloch,et al.  The role of point defects and arsenic precipitates in carrier trapping and recombination in low‐temperature grown GaAs , 1996 .

[10]  O. B. McMahon,et al.  Terahertz photomixing with diode lasers in low‐temperature‐grown GaAs , 1995 .

[11]  J. P. Mattia,et al.  Milliwatt output levels and superquadratic bias dependence in a low‐temperature‐grown GaAs photomixer , 1994 .

[12]  C. L. Dennis,et al.  Measurements of optical‐heterodyne conversion in low‐temperature‐grown GaAs , 1993 .

[13]  E. Brown,et al.  Coherent millimeter‐wave generation by heterodyne conversion in low‐temperature‐grown GaAs photoconductors , 1993 .

[14]  M. Frankel,et al.  Integration of low-temperature GaAs on Si substrates , 1993 .

[15]  G. J. Simonis,et al.  Optical generation, distribution, and control of microwaves using laser heterodyne , 1990 .

[16]  J. S. Blakemore.  Semiconducting and other major properties of gallium arsenide , 1982 .

[17]  H. Lüth,et al.  Preparation and optimization of low-temperature grown GaAs photomixers , 2004 .

[18]  Ozeki,et al.  High-Resolution Terahertz Spectroscopy by a Compact Radiation Source Based on Photomixing with Diode Lasers in a Photoconductive Antenna , 1998, Journal of molecular spectroscopy.