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Frontiers of Optoelectronics

Front. Optoelectron.    2015, Vol. 8 Issue (1) : 98-103     DOI: 10.1007/s12200-015-0488-9
Time behavior of field screening effects in small-size GaAs photoconductive terahertz antenna
Tianyi WANG,Zhengang YANG(),Si ZOU,Kejia WANG,Shenglie WANG,Jinsong LIU
Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
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The field screening effects in small-size GaAs photoconductive (PC) antenna are investigated via the well-known pump and probe terahertz (THz) generation technique. The peak amplitude of the THz pulses excited by the probe laser pulse as a function of the pump-probe time delay was measured. An equivalent-circuit model was used to simulate the experimental data. Based on the good agreement between the results of simulation and experiment, the time behavior of the radiation and space-charge fields was simulated. The results show that the space-charge screening dominantly determines the device response in the whole time, while the radiation filed screening plays a key role in initial time which strongly affects the peak THz field. The parameter analysis was performed, which may be valuable on the optimum design for the antenna as a THz emitter.

Keywords GaAs photoconductive (PC) antenna      field screening effects      terahertz (THz) emitter     
Corresponding Authors: Zhengang YANG   
Issue Date: 13 February 2015
 Cite this article:   
Tianyi WANG,Zhengang YANG,Si ZOU, et al. Time behavior of field screening effects in small-size GaAs photoconductive terahertz antenna[J]. Front. Optoelectron., 2015, 8(1): 98-103.
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Tianyi WANG
Zhengang YANG
Kejia WANG
Shenglie WANG
Jinsong LIU
Fig.1  (a) Experimental setup; (b) measured peak amplitude of the THz pulses excited by the probe laser pulse as a function of the pump-probe time delay under different pump powers. The power of the probe beam is set to 2 mW. The applied bias voltage is 55 V (field across the gap: 11 kV/cm). The displayed data normalized to 100% for t = 0 . fs: femtosecond; BS: beam splitter; HWP: half-wave plate; PBS: polarization beam splitter
Fig.2  (a) Schematically representing the equivalent circuit of GaAs antenna, four circuit elements in series with each other, V b is the bias voltage of antenna, Z a is the antenna impedance accounted for the THz radiation screening, Z p ( t ) models the time-varying impedance of the photo gap, and V sc is the polarization induced by the separation of charge carries; (b) calculated and measured peak THz field as a function of the pump-probe time delay for fixed pump power at 10 mW
Fig.3  Measured (solid curves) and calculated peak THz field around t = 0 under different pump powers
Fig.4  Calculated time dependencies of (a) radiation field and (b) space-charge field under different pump laser powers. The inset in (a) shows the calculated temporal evolution of the local electric field in the antenna, plotted together with the radiation and space-charge fields for a fixed pump power at 20 mW
Fig.5  Calculated normalized peak THz field changes with (a) the strip-line spacing d , and (b) the trapping time τ c under different laser excitation powers
1 Auston D H, Cheung K P, Smith P R. Picosecond photoconducting Hertzian dipoles. Applied Physics Letters, 1984, 45(3): 284–286
doi: 10.1063/1.95174
2 Katzenellenbogen N, Grischkowsky D. Efficient generation of 380 fs pulses of THz radiation by ultrafast laser pulse excitation of a biased metal-semiconductor interface. Applied Physics Letters, 1991, 58(3): 222–224
doi: 10.1063/1.104695
3 Tonouchi M, Kawasaki N, Yoshimura T, Wald H, Seidel P. Pump and probe terahertz generation study of ultrafast carrier dynamics in low-temperature grown-GaAs. Japanese Journal of Applied Physics, 2002, 41(Part 2, No. 6B): L706–L709
doi: 10.1143/JJAP.41.L706
4 Siebert K J, Lisauskas A, L?ffler T, Roskos H. Field screening in low-temperature-grown GaAs photoconductive antennas. Japanese Journal of Applied Physics, 2004, 43(3): 1038–1043
doi: 10.1143/JJAP.43.1038
5 Yano R, Gotoh H, Hirayama Y, Miyashita S. Systematic pump-probe terahertz wave emission spectroscopy of a photoconductive antenna fabricated on low-temperature grown GaAs. Journal of Applied Physics, 2004, 96(7): 3635–3638
doi: 10.1063/1.1786667
6 Loata G C, Thomson M D, L?ffler T, Poskos H C. Radiation field screening in photoconductive antennae studied via pulsed terahertz emission spectroscopy. Applied Physics Letters, 2007, 91(23): 232506-1–232506-3
7 Pedersen J E, Lyssenko V G, Hvam J M, Jepsen P U, Keiding S R, So?rensen C B, ?Lindelof P E. Ultrafast local field dynamics in photoconductive THz antennas. Applied Physics Letters, 1993, 62(11): 1265–1267
doi: 10.1063/1.108702
8 Jacobsen R H, Birkelund K, Holst T, Jepsen P U, Keiding S R. Interpretation of photocurrent correlation measurements used for ultrafast photoconductive switch characterization. Journal of Applied Physics, 1996, 79(5): 2649–2657
doi: 10.1063/1.361135
9 Jepsen P U, Jacobsen R H, Keiding S R. Generation and detection of terahertz pulses from biased semiconductor antennas. Journal of the Optical Society of America B, Optical Physics, 1996, 13(11): 2424–2436
doi: 10.1364/JOSAB.13.002424
10 Loata G C. Investigation of low-temperature-grown GaAs photoconductive antennae for continuous-wave and pulsed terahertz generation. Dissertation for the Doctoral Degree. Frankfurt:?Universit?tsbibliothek Frankfurt am Main, 2007
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