大孔径光电导天线及其太赫兹辐射特性研究
摘要
太赫兹(THz,1 THz=1012 Hz)频段是指频率从0.1 THz到10 THz,介于微波与红外光之间的电磁辐射区域,其光谱和成像技术可以提供传统的微波和X射线技术所不能提供的信息,在物理、化学、生物医学、通信、雷达、安全检查等各方面均有广阔的应用前景。近十几年来,太赫兹脉冲的产生技术发展迅速,大孔径光电导天线作为重要的太赫兹脉冲产生源,具有较高的辐射功率和相对较大的谱宽。作者拟通过天线设计、实验分析、规律总结,力争提高大孔径光电导天线的太赫兹波辐射性能。
本论文详细介绍了光电导天线的制作过程并制作了几种不同电极几何结构、不同半导体材料的光电导天线。搭建了一套高效的基于温控大孔径光电导天线的太赫兹时域光谱系统,得到了优化的系统设定和实验参数。使用这套光谱系统对比分析了七种不同电极几何结构的光电导天线太赫兹辐射性能,发现工字型是辐射性能较好的电极几何结构。用工字型电极几何结构制作了三种不同半导体材料的光电导天线,结果表明,表面多层生长砷化镓材料的太赫兹波辐射性能较好。
在前面实验的基础上,使用表面多层生长砷化镓材料的工字型天线在经过优化的光谱系统中进行了太赫兹发射光谱实验,发现光电导天线发射的太赫兹波强度与加在天线两极的偏置电压成正比,并且所获得的频域谱峰值频率随偏置电压的增大而增高;产生的太赫兹波信号强度还与照射在光电导天线上的泵浦光光强呈饱和递增关系。这个结论很好地验证了理论推测。
综上所述,本文对大孔径光电导天线的制作方法以及不同条件对大孔径光电导天线太赫兹波辐射性能的影响做了较为全面、系统的分析和探索,不仅通过实验得到了优化的参数和有价值的规律,同时也总结出了相关的研究思路和方法,可作为今后进一步研究和探索的基础和参考。
The terahertz (THz, 1 THz=1012 Hz) wave, categorized between the microwave and the infrared light in the electromagnetic spectrum, with the frequency lying in 0.1 THz and 10 THz. THz imaging and sensing technologies can provide the information that difficult to be obtained by the conventional methods such as microwave and X-ray techniques. It is believed that THz technique has a good future in many different fields, such as physics, chemistry, biomedicine, communication, radar, security inspection, and so on. In the last decade, the generation techniques of THz wave made rapid progress. Photoconductive antenna (PCA) of the large aperture can provide reasonably good peak power and spectral width of THz generation. In this thesis, we carried out a series of experiments to improve the radiation performance of PCA. The fabrication process of PCA was given in detail, several kinds of PCAs with different electrode geometric structure and semiconductor material were introduced. We presented a high efficient, temperature controlled THz time-domain spectroscopy (TDS) system. Using this system, the experimental comparison of seven PCAs with different electrode geometric structures was drawn. The PCA with I-shaped geometric structure has the best performance during the comparison. Using I-shaped geometric structure, we measured three PCAs with different photoconductive materials. In the experiment, we find that the THz radiation performance of the PCA with multi-layer grown GaAs material is comparatively better than others.
Base on the experimental results above, the experiment research of THz radiation properties was conducted by the high efficient THz TDS using the PCA with I-shaped geometric structure and multi-layer grown GaAs material. The results show that, the peak of THz electric field and the peak frequency of spectrum increase linearly as a function of bias field, and tend to saturation as a function of pump power. These experimental results are explained by the corresponding theory.
In summary, the comprehensive analyses about fabrication process and THz radiation performance of PCA were done. In this thesis, not only did we obtain the optimized parameters and valuable laws, but also summarized correlative research thoughts and methods. This work is a good reference for investigating and fabricating the high efficient THz radiation source by the large aperture PCA.
本论文详细介绍了光电导天线的制作过程并制作了几种不同电极几何结构、不同半导体材料的光电导天线。搭建了一套高效的基于温控大孔径光电导天线的太赫兹时域光谱系统,得到了优化的系统设定和实验参数。使用这套光谱系统对比分析了七种不同电极几何结构的光电导天线太赫兹辐射性能,发现工字型是辐射性能较好的电极几何结构。用工字型电极几何结构制作了三种不同半导体材料的光电导天线,结果表明,表面多层生长砷化镓材料的太赫兹波辐射性能较好。
在前面实验的基础上,使用表面多层生长砷化镓材料的工字型天线在经过优化的光谱系统中进行了太赫兹发射光谱实验,发现光电导天线发射的太赫兹波强度与加在天线两极的偏置电压成正比,并且所获得的频域谱峰值频率随偏置电压的增大而增高;产生的太赫兹波信号强度还与照射在光电导天线上的泵浦光光强呈饱和递增关系。这个结论很好地验证了理论推测。
综上所述,本文对大孔径光电导天线的制作方法以及不同条件对大孔径光电导天线太赫兹波辐射性能的影响做了较为全面、系统的分析和探索,不仅通过实验得到了优化的参数和有价值的规律,同时也总结出了相关的研究思路和方法,可作为今后进一步研究和探索的基础和参考。
The terahertz (THz, 1 THz=1012 Hz) wave, categorized between the microwave and the infrared light in the electromagnetic spectrum, with the frequency lying in 0.1 THz and 10 THz. THz imaging and sensing technologies can provide the information that difficult to be obtained by the conventional methods such as microwave and X-ray techniques. It is believed that THz technique has a good future in many different fields, such as physics, chemistry, biomedicine, communication, radar, security inspection, and so on. In the last decade, the generation techniques of THz wave made rapid progress. Photoconductive antenna (PCA) of the large aperture can provide reasonably good peak power and spectral width of THz generation. In this thesis, we carried out a series of experiments to improve the radiation performance of PCA. The fabrication process of PCA was given in detail, several kinds of PCAs with different electrode geometric structure and semiconductor material were introduced. We presented a high efficient, temperature controlled THz time-domain spectroscopy (TDS) system. Using this system, the experimental comparison of seven PCAs with different electrode geometric structures was drawn. The PCA with I-shaped geometric structure has the best performance during the comparison. Using I-shaped geometric structure, we measured three PCAs with different photoconductive materials. In the experiment, we find that the THz radiation performance of the PCA with multi-layer grown GaAs material is comparatively better than others.
Base on the experimental results above, the experiment research of THz radiation properties was conducted by the high efficient THz TDS using the PCA with I-shaped geometric structure and multi-layer grown GaAs material. The results show that, the peak of THz electric field and the peak frequency of spectrum increase linearly as a function of bias field, and tend to saturation as a function of pump power. These experimental results are explained by the corresponding theory.
In summary, the comprehensive analyses about fabrication process and THz radiation performance of PCA were done. In this thesis, not only did we obtain the optimized parameters and valuable laws, but also summarized correlative research thoughts and methods. This work is a good reference for investigating and fabricating the high efficient THz radiation source by the large aperture PCA.
引文
[1] S.W.Smye and J M Chamberlain et al., The interaction between Terahertz radiation and biological tissue [J], Phys. Med. Biol., 2001, 46: R101
[2] A.G.Markelz and A.Roitberg et al., Pulsed terahertz spectroscopy of DNA, bovine serum albumin and collagen between 0.1 and 2.0 THz [J], Chem. Phys. Lett., 2000, 320: 42
[3] M. Brucherseifer, M. Nagel, and P. Haring Bolivar et al., Label-free probing of the binding state of DNA by time-domain terahertz sensing [J], Appl. Phys. Lett., 2000, 77: 4049~4051
[4] D. M. Mittleman, Rune H. Jacobsen and Martin C. Nuss, T-ray imaging [J], IEEE J. Selected Topics in Quantum Electronics, 1996, 2: 679
[5] T. Loffler, T. Bauer and K. J. Siebert et al., Terahertz dark-field imaging of biomedical tissue [J], Opti. Expr., 2001, 9: 616
[6] D. M. Mittleman, M. Gupta and R. Neelamani et al., Recent advances in terahertz imaging [J], Appl. Phys. B, 1999, 68: 1085
[7] A. Rice, Y. Jin and X. C. Zhang et al. Terahertz optical rectification from <110> zinc-blende crystals [J], Appl. Phys. Lett., 1994, 64: 1324~1326
[8] P Y Han and X. C. Zhang, Free-space coherent broadband terahertz time-domain spectroscopy [J], Meas. Sci. Technol., 2001, 12: 1747~1756
[9] D. H. Auston and P. R. Smith, Generation and detection of millimeter waves by picosecond photoconductivity [J], Appl. Phys. Lett., 1983, 43: 631
[10] D. H. Auston and K. P. Cheung, Coherent time-domain far-infrared spectroscopy [J], J. Opt. Soc. Am. B, 1984, 45: 284
[11] C. Fattinger and D. Grischkowsky, Terahertz Beams [J], Appl. Phys. Lett., 1989, 54: 490
[12] M. V. Exter, C. Fattinger and D. Grischkowsky, Terahertz time-domain spectroscopy of water vapor [J], Opt. Lett., 1989, 14: 1128
[13] D. Grischkowsky, M.B. Ketchen and C. C. Chi et al., Capacitance Free Generation and Detection of Sub-Picosecond Electrical Pulses on Coplanar Transmission Lines [J], IEEE J. Quantum Electronics, 1988, 24: 221
[14] P. U. Jepsen and S. R. Keiding, Radiation patterns from lens-coupled terahertz antennas [J], Opt. Lett., 1995, 20: 807
[15] Q. Wu and X. C. Zhang, Electro-optic sampling of freely propagating THz field [J], Optics & QuantumElectronics, 1996, 28: 945
[16] A. Nahata, D. H. Auston, and T. F. Heinz et al. Coherent detection of freely propagating terahertz radiation by electro-optic sampling [J], Appl. Phys. Lett., 1996, 68: 150
[17] Q. Wu and X. C. Zhang, Electro-optic sampling of freely propagating THz field [J], Optics & Quantum Electronics, 1996, 28: 945
[18] Y.Cai and I. Brener et al., Coherent terahertz radiation detection: Direct comparison between free-space electro-optic sampling and antenna detection [J], Appl. Phys. Lett., 1998, 73: 444
[19] Zhang T Y, Cao J C. Temporal characterization of THz pulses generated by large aperture photoconductive antennas [J]. Chinese Journal of Rare Metals, 2004, 28 (3): 588~589
[20] Darrow J T, Zhang X C, Auston D H, et al.. Saturation properties of large-aperture photoconducting antennas [J]. IEEE J. Quantum Electron., 1992, 28 (6): 1607~1616
[21] Hattori T, Tukamoto K, Nakatsuka H. Time-resolved study of intense terahertz pulses generated by a large-aperture photoconductive antenna [J]. Jpn. J. Appl. Phys., 1992, 40 (8): 4907~1912
[22] Darrow J T, Zhang X C, Auston D H. Power scaling of large-aperture photoconducting antennas [J]. Appl. Phys. Lett., 1991, 58 (25): 25-27
[23] Jia W L, Ji W L, Shi W. Two-dimensional Monte Carlo simulation of screening of the bias field in terahertz generation from semi-insulated GaAs photoconductors [J]. Acta Phys. Sin., 2007, 56 (4): 2042~2046
[24] Shi Wei, Zhang X B, Jia W L, et al.. Investigation on terahertz generation with GaAs photoconductor triggered by femto-second laser pulse [J]. Chinese Journal of Semiconductors, 2004, 25 (12): 1735~1738
[25] P. K. Benicewicz, J. P. Roberts, and A. J. Taylor, Scaling of terahertz radiation fromlarge-aperture biased photoconductors [J], J. Opt. Soc. Am. B, 1994, 11: 2533
[26] Shi Wei, Zhang X B, Jia W L, et al.. Investigation on terahertz generation with GaAs photoconductor triggered by femto-second laser pulse [J]. Chinese Journal of Semiconductors, 2004, 25 (12): 1735~1738
[27] Rodriguez R, Caceres S R, Taylor A J. Modeling of terahertz radiation from biased photoconductors: transient velocity effects [J]. Optics Letters, 1994, 19 (23): 1994~1996
[28] Zhang T Y, Cao J C. Temporal characterization of THz pulses generated by large aperture photoconductive antennas [J]. Chinese Journal of Rare Metals, 2004, 28 (3): 588~589
[29] Hattori T, Tukamoto K, Nakatsuka H. Time-resolved study of intense terahertz pulses generated by a large-aperture photoconductive antenna [J]. Jpn. J. Appl. Phys., 1992, 40 (8): 4907~1912
[30] Chang Q, Yang D X, Wang L, et al.. Study on terahertz generation from large-aperture photoconductive antenna [J]. Laser Technology, 2006, 30 (6): 574~577
[31] Sun J H, Zhao G Z, Zhang L L, et al.. Effect of applied electric and magnetic field on THz radiation [J]. Chinese J. Lasers, 2005, 32 (2): 192~195
[2] A.G.Markelz and A.Roitberg et al., Pulsed terahertz spectroscopy of DNA, bovine serum albumin and collagen between 0.1 and 2.0 THz [J], Chem. Phys. Lett., 2000, 320: 42
[3] M. Brucherseifer, M. Nagel, and P. Haring Bolivar et al., Label-free probing of the binding state of DNA by time-domain terahertz sensing [J], Appl. Phys. Lett., 2000, 77: 4049~4051
[4] D. M. Mittleman, Rune H. Jacobsen and Martin C. Nuss, T-ray imaging [J], IEEE J. Selected Topics in Quantum Electronics, 1996, 2: 679
[5] T. Loffler, T. Bauer and K. J. Siebert et al., Terahertz dark-field imaging of biomedical tissue [J], Opti. Expr., 2001, 9: 616
[6] D. M. Mittleman, M. Gupta and R. Neelamani et al., Recent advances in terahertz imaging [J], Appl. Phys. B, 1999, 68: 1085
[7] A. Rice, Y. Jin and X. C. Zhang et al. Terahertz optical rectification from <110> zinc-blende crystals [J], Appl. Phys. Lett., 1994, 64: 1324~1326
[8] P Y Han and X. C. Zhang, Free-space coherent broadband terahertz time-domain spectroscopy [J], Meas. Sci. Technol., 2001, 12: 1747~1756
[9] D. H. Auston and P. R. Smith, Generation and detection of millimeter waves by picosecond photoconductivity [J], Appl. Phys. Lett., 1983, 43: 631
[10] D. H. Auston and K. P. Cheung, Coherent time-domain far-infrared spectroscopy [J], J. Opt. Soc. Am. B, 1984, 45: 284
[11] C. Fattinger and D. Grischkowsky, Terahertz Beams [J], Appl. Phys. Lett., 1989, 54: 490
[12] M. V. Exter, C. Fattinger and D. Grischkowsky, Terahertz time-domain spectroscopy of water vapor [J], Opt. Lett., 1989, 14: 1128
[13] D. Grischkowsky, M.B. Ketchen and C. C. Chi et al., Capacitance Free Generation and Detection of Sub-Picosecond Electrical Pulses on Coplanar Transmission Lines [J], IEEE J. Quantum Electronics, 1988, 24: 221
[14] P. U. Jepsen and S. R. Keiding, Radiation patterns from lens-coupled terahertz antennas [J], Opt. Lett., 1995, 20: 807
[15] Q. Wu and X. C. Zhang, Electro-optic sampling of freely propagating THz field [J], Optics & QuantumElectronics, 1996, 28: 945
[16] A. Nahata, D. H. Auston, and T. F. Heinz et al. Coherent detection of freely propagating terahertz radiation by electro-optic sampling [J], Appl. Phys. Lett., 1996, 68: 150
[17] Q. Wu and X. C. Zhang, Electro-optic sampling of freely propagating THz field [J], Optics & Quantum Electronics, 1996, 28: 945
[18] Y.Cai and I. Brener et al., Coherent terahertz radiation detection: Direct comparison between free-space electro-optic sampling and antenna detection [J], Appl. Phys. Lett., 1998, 73: 444
[19] Zhang T Y, Cao J C. Temporal characterization of THz pulses generated by large aperture photoconductive antennas [J]. Chinese Journal of Rare Metals, 2004, 28 (3): 588~589
[20] Darrow J T, Zhang X C, Auston D H, et al.. Saturation properties of large-aperture photoconducting antennas [J]. IEEE J. Quantum Electron., 1992, 28 (6): 1607~1616
[21] Hattori T, Tukamoto K, Nakatsuka H. Time-resolved study of intense terahertz pulses generated by a large-aperture photoconductive antenna [J]. Jpn. J. Appl. Phys., 1992, 40 (8): 4907~1912
[22] Darrow J T, Zhang X C, Auston D H. Power scaling of large-aperture photoconducting antennas [J]. Appl. Phys. Lett., 1991, 58 (25): 25-27
[23] Jia W L, Ji W L, Shi W. Two-dimensional Monte Carlo simulation of screening of the bias field in terahertz generation from semi-insulated GaAs photoconductors [J]. Acta Phys. Sin., 2007, 56 (4): 2042~2046
[24] Shi Wei, Zhang X B, Jia W L, et al.. Investigation on terahertz generation with GaAs photoconductor triggered by femto-second laser pulse [J]. Chinese Journal of Semiconductors, 2004, 25 (12): 1735~1738
[25] P. K. Benicewicz, J. P. Roberts, and A. J. Taylor, Scaling of terahertz radiation fromlarge-aperture biased photoconductors [J], J. Opt. Soc. Am. B, 1994, 11: 2533
[26] Shi Wei, Zhang X B, Jia W L, et al.. Investigation on terahertz generation with GaAs photoconductor triggered by femto-second laser pulse [J]. Chinese Journal of Semiconductors, 2004, 25 (12): 1735~1738
[27] Rodriguez R, Caceres S R, Taylor A J. Modeling of terahertz radiation from biased photoconductors: transient velocity effects [J]. Optics Letters, 1994, 19 (23): 1994~1996
[28] Zhang T Y, Cao J C. Temporal characterization of THz pulses generated by large aperture photoconductive antennas [J]. Chinese Journal of Rare Metals, 2004, 28 (3): 588~589
[29] Hattori T, Tukamoto K, Nakatsuka H. Time-resolved study of intense terahertz pulses generated by a large-aperture photoconductive antenna [J]. Jpn. J. Appl. Phys., 1992, 40 (8): 4907~1912
[30] Chang Q, Yang D X, Wang L, et al.. Study on terahertz generation from large-aperture photoconductive antenna [J]. Laser Technology, 2006, 30 (6): 574~577
[31] Sun J H, Zhao G Z, Zhang L L, et al.. Effect of applied electric and magnetic field on THz radiation [J]. Chinese J. Lasers, 2005, 32 (2): 192~195