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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 17 — Aug. 26, 2013
  • pp: 19709–19717
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Directional terahertz emission from corrugated InAs structures

Jong-Hyuk Yim, Hoonil Jeong, Muhammad Irfan, Eun-Hye Lee, Jin-Dong Song, and Young-Dahl Jho  »View Author Affiliations


Optics Express, Vol. 21, Issue 17, pp. 19709-19717 (2013)
http://dx.doi.org/10.1364/OE.21.019709


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Abstract

The terahertz (THz) radiation from transient dipoles, formed by distinct diffusion coefficients between oppositely charged carriers as often observed in low band gap semiconductors, propagates with an anisotropic amplitude distribution perpendicular to the dipole axis along the diffusive motion. By directionally adjusting the electronic diffusion, we conceptualize groove-patterned THz emitters based on (100) InAs thin films and demonstrate the unidirectional radiation. Line-of-sight emission along the surface-normal direction is greatly enhanced in a distributed asymmetric trapezoid with its period similar to the electronic diffusion length of InAs. This directional enhancement is in clear contrast to the constant emission amplitude along the lateral direction, regardless of pattern scale, which manifests the role of groove patterns as microscale reflectors in laterally corrugating the carrier density. In contrast to the rather limited nonlinearity in (100) plane, the azimuthal angle dependence of the THz field amplitude in corrugated samples shows a combined effect of diffusive transport and second-order nonlinearity, whose compositional contributions varies in different structures.

© 2013 OSA

1. Introduction

As an important practical source of pulsed electromagnetic radiation at terahertz (THz) frequencies, the photo-excitation of semiconductor surfaces by femtosecond (fs) laser pulses has been widely used over the past two decades. A vast array of compound semiconductors has been examined with regard to their material parameters, including InAs, InSb, GaAs, and InP [1

1. See, e.g., P. Gu and M. Tani, “Terahertz radiation from semiconductor surfaces,” in Terahertz Optoelectronics, K. Sakai, eds. (Springer, 2005), pp. 63–97. [CrossRef]

]. The THz radiation emitted from these materials has been attributed to either transient dipole current generation caused by the potential gradient in depletion regions or the large diffusion velocity difference between electrons and holes (referred to as the photo-Dember effect) while the nonlinearity contribution is sometimes ignored in single crystalline materials, as in the case of semiconductors grown along the [100] axis (in the case of zinc-blende semiconductors [2

2. K. Liu, J. Xu, T. Yuan, and X. -C. Zhang, “Terahertz radiation from InAs induced by carrier diffusion and drift,” Phys. Rev. B 73, 155330 (2006). [CrossRef]

]) or c-axis (in the case of wurzite semiconductors [3

3. K. I. Lin, J. T. Tsai, T. S. Wang, J. S. Hwang, M. C. Chen, and G. C. Chi, “Drift current dominated terahertz radiation from InN at low-density excitation,” Appl. Phys. Lett. 93, 262102 (2008). [CrossRef]

]) at low excitation fluence regime. In the case of GaAs, THz radiation has been found to originate from surge currents by the surface electric field [4

4. M. B. Johnston, D. M. Whittaker, A. Corchia, A. G. Davies, and E. H. Linfield, “Simulation of terahertz generation at semiconductor surfaces,” Phys. Rev. B 65, 165301 (2002). [CrossRef]

, 5

5. D. -F. Liu and D. Xu, “Comparative study of terahertz radiation from n-InAs and n-GaAs,” Appl. Opt. 46(5), 789–794 (2007). [CrossRef] [PubMed]

], whereas the radiation from InAs is mainly governed either by the photo-Dember effect in a thick scale (similar to that of the diffusion length) [2

2. K. Liu, J. Xu, T. Yuan, and X. -C. Zhang, “Terahertz radiation from InAs induced by carrier diffusion and drift,” Phys. Rev. B 73, 155330 (2006). [CrossRef]

, 6

6. P. Gu, M. Tani, S. Kono, K. Sakai, and X. -C. Zhang, “Study of terahertz radiation from InAs and InSb,” J. Appl. Phys. 91(9), 5533–5537 (2002). [CrossRef]

] or by carrier drift motion in the smaller thickness region (similar to the thickness of the surface-space charge layer (SCL)) [7

7. H. Jeong, S. H. Shin, S. Y. Kim, J. D. Song, S. B. Choi, D. S. Lee, J. Lee, and Y. D. Jho, “Relation between phase and generation mechanisms of THz waves in InAs,” Curr. Appl. Phys. 12, 668–672 (2012). [CrossRef]

]. Although the photo-Dember effect in bulk (100) InAs [6

6. P. Gu, M. Tani, S. Kono, K. Sakai, and X. -C. Zhang, “Study of terahertz radiation from InAs and InSb,” J. Appl. Phys. 91(9), 5533–5537 (2002). [CrossRef]

] is further enhanced with increased electron mobility accompanied by higher excess energy of photo-carriers, the second-order nonlinear effect becomes crucial in other crystal faces such as (110) and (111) plane [8

8. M. Reid, I. V. Cravetchi, and R. Fedosejevs, “Terahertz radiation and second-harmonic generation from InAs: Bulk versus surface electric-field-induced contributions,” Phys. Rev. B 72, 035201 (2005). [CrossRef]

]. Sometimes, the polycrystalline nature of inhomogeneous semiconductors shows the nonlinear emission from grain boundaries [9

9. Y. Ko, S. Sengupta, S. Tomasulo, P. Dutta, and I. Wilke, “Emission of terahertz-frequency electromagnetic radiation from bulk Gax In1−x As crystals,” Phys. Rev. B 78, 035201 (2008). [CrossRef]

].

Further technological advances in the field of THz technology have been made in the form of efficient radiation sources with higher output powers and/or tunability [10

10. M. Tonouchi, “Cutting-edge terahertz technology,” Nat. Photonics 1, 97–105 (2007). [CrossRef]

], and with better spatial resolution that is sometimes beyond the diffraction limit [11

11. See, e.g., M. Wächter, M. Nagel, and H. Kurz, “Tapered photoconductive terahertz field probe tip with subwavelength spatial resolution,” Appl. Phys. Lett. 95, 041112 (2009). [CrossRef]

]. Recently, THz waves with increased amplitude and bandwidth have been reported in periodically metal-patterned In0.53Ga0.47As and GaAs by breaking lateral symmetry in their diffusion currents [12

12. G. Klatt, F. Hilser, W. Qiao, M. Beck, R. Gebs, A. Bartels, K. Huska, U. Lemmer, G. Bastian, M. B. Johnston, M. Fischer, J. Faist, and T. Dekorsy, “Terahertz emission from lateral photo-Dember currents,” Opt. Express 18(5), 4939–4947 (2010). [CrossRef] [PubMed]

, 13

13. G. Klatt, B. Surrer, D. Stephan, O. Schubert, M. Fischer, J. Faist, A. Leitenstorfer, R. Huber, and T. Dekorsy, “Photo-Dember terahertz emitter excited with an Er:fiber laser,” Appl. Phys. Lett. 98, 021114 (2011). [CrossRef]

]. At the same time, the transfer of THz waves over long distances was demonstrated using either a laser-plasma filament [14

14. C. D’Amico, A. Houard, M. Franco, B. Prade, and A. Mysyrowicz, “Conical forward THz emission from femtosecond-laser-beam filamentation in air,” Phys. Rev. Lett. 98, 235002 (2007). [CrossRef]

], or an optical fiber coupled with tilted InAs tips retaining superior spatial resolution [15

15. M. Yi, K. Lee, J. Lim, Y. Hong, Y. D. Jho, and J. Ahn, “Terahertz waves emitted from an optical fiber,” Opt. Express 18(13), 13693–13699 (2010). [CrossRef] [PubMed]

].

Despite the moderate efficiency of semiconductor-based THz transmitters, significant obstacles persist for realizing more accessible industrial applications, including bio-medical imaging [16

16. A. Fitzgerald, E. Berry, N. Zinovev, G. Walker, M. Smith, and J. Chamberlain, “An introduction to medical imaging with coherent terahertz frequency radiation,” Phys. Med. Biol. 47, R67–R84 (2002). [CrossRef] [PubMed]

], nondestructive evaluation [17

17. C. D. Stoik, M. J. Bohn, and J. L. Blackshire, “Nondestructive evaluation of aircraft composites using transmissive terahertz time domain spectroscopy,” Opt. Express 16(21), 17039–17051 (2008). [CrossRef] [PubMed]

], and wireless communications [18

18. J. Federici and L. Moeller, “Review of terahertz and subterahertz wireless communications,” J. Appl. Phys. 107, 111101 (2010). [CrossRef]

], particularly with regard to low emission power, beam path interference, and difficulty in directional control. For example, in conventional THz time-domain spectroscopy (THz-TDS) systems with fs laser illumination, InAs sources are tilted with an angle of 45° to the incident beam; the generated THz waves inevitably diverge in free space. We also note that the directionally controlled diffusion currents in InAs, with a maximized photo-Dember field, could offer efficient THz emitters, resulting in THz rays primarily aligned along the line-of-sight path favorable for imaging and data transmission through free space. In this work, we have implemented micro-scale groove patterns in InAs-based structures, with the aim of producing enhanced directional emission of THz waves, as measured in various detection geometries.

2. Experimental setup

We performed THz-TDS measurements under excitation with a pulsed Ti:sapphire laser at 300 K (pulse duration ∼ 150 fs, centered at 800 nm). The incident angle θ of the IR beam (defined from the InAs surfaces in this work for a convenience’s sake) was either 45° in the conventional reflective geometry or 90° in the transmissive geometry. The generated THz waves were collected using a pair of gold-coated 4-in. parabolic mirrors and guided via a silicon (Si) lens coupled with a photo-conductive antenna (PCA). In both cases, the acceptance angles of the THz waves are about 14° (cf. insets of Fig. 2) from the propagation axis. When θ =90°, for comparison purposes, the pair of PCA and Si lens was placed ∼ 1 mm away from the sample, along the surface in the lateral detection geometry without the parabolic mirrors [cf. inset of Fig. 3(a)]. The acceptance angle of the THz waves in lateral detection geometry was 31° from the surface in Fig. 3. The pump beam orthogonally polarized relative to the groove axis supplies an excitation fluence of about 0.9 μJ/cm2 on an 800 μm beam diameter.

Fig. 1 Illustrations of THz generation processes (a) without and (b) with groove patterns. Excitation laser beams (shaded red cone) are incident at surface normal angle (θ≡ 90°), and diffusion direction of the photo-generated electrons (red dots) and holes (blue dots) determine THz radiation patterns (green divergent cones) accordingly. (c) SEM images of the fabricated patterns with W of 0.5 μm (left), 1.2 μm (middle) and 2.5 μm (right).
Fig. 2 THz time-domain signals from (a) 1 μm-thick bare InAs layer without patterns at different incident angles (θ =45° or θ =90°), and (b) InAs layers with different pattern widths W in a transmission geometry (non-solid lines), in comparison to InAs layer without patterns (solid line). Insets in (a,b) show reflective (θ =45°) and transmissive (θ =90°) detection schemes. (c) Fourier transform spectra obtained from Fig. 2(b).
Fig. 3 THz time-domain signals in lateral detection geometry, emitted from (a) groove patterned InAs layers (non-solid lines) in comparison to InAs layer without groove patterns (solid line). The offsets adjusted for clarity of signals. (b) Fourier transformed spectra, obtained from (a). (c) THz emission amplitude enhancement ratios of the patterned layer to the bare layer in the normal and lateral detection geometries.

3. Results and discussions

The lateral photo-carrier density modulation for surface-normal incidence could remove a major hindrance that affected the transmission emission suppression. When the asymmetric trapezoidal patterns were periodically configured for activating lateral diffusion current modulation, the THz wave amplitude increased with evident pattern scale (W) dependence, as demonstrated in Fig. 2 (b). The signals from these patterned structures (non-solid lines) were maximized by rotating samples around the (100) axis and compared to those from a bare sample without patterns (solid line); this comparison revealed a role of laterally modulated dipole ensemble density in the enhanced emission amplitude along the line-of-sight direction. The strongest amplitude was observed in a sample with W of 1.2 μm, which was similar to the reported value of the maximum diffusion length of 1.3 μm [21

21. C. T. Que, T. Edamura, M. Nakajima, M. Tani, and M. Hangyo, “Terahertz radiation from InAs films on silicon substrates excited by femtosecond laser pulses,” Jpn. J. Appl. Phys. 48, 010211 (2009). [CrossRef]

], but still larger than the vertical diffusion length measured in our sample [7

7. H. Jeong, S. H. Shin, S. Y. Kim, J. D. Song, S. B. Choi, D. S. Lee, J. Lee, and Y. D. Jho, “Relation between phase and generation mechanisms of THz waves in InAs,” Curr. Appl. Phys. 12, 668–672 (2012). [CrossRef]

]. It could possibly be more associated with the optimized lateral diffusion than other values of W. The reduced performance of the structure with W of 2.5 μm could be more influenced from the symmetric nature of the groove structure, rather than from the actual value of the groove period. On the other hand, the out-coupling efficiency in the corrugated samples was not improved to that in the bare epilayer, as inferred from the persistently observed Fabry-Perot oscillations in samples either with or without patterns. The ratios of the peak amplitudes to the Fabry-Perot peaks were estimated and turned out almost the same among the samples shown in Fig. 2(b). These results are somewhat intuitive, because the wavelength of the THz waves is much larger than the groove scale and we would not expect enhanced scattering at the interfaces of the patterned samples along the surface-normal direction. In Fig. 2(c), the Fourier-transformed spectra were taken from Fig. 2(b). In the corrugated samples, the lower frequency side (≤ 0.25 THz) was found to be more greatly enhanced when compared with the bare sample, which is not clearly understood at this moment. However, there is a possible examinable point to show the difference: The surface normal emission in patterned samples could also be affected by the diffusion along the [110] direction [cf. Fig. 1(b)] with a higher electron effective mass [22

22. I. Säidi, S. B. Radhia, and K. Boujdaria, “Band parameters of GaAs, InAs, InP, and InSb in the 40-band k·p model,” J. Appl. Phys. 107, 043701 (2010). [CrossRef]

], thus leading to reduced carrier mobility in the Einstein diffusion equation of μ = eτm/m*, where m* is the effective mass and τm is the scattering time. The polar radiation patterns from the high density ensemble of dipoles diffusing along the [110] direction could encompass the emissions along the surface-normal direction [4

4. M. B. Johnston, D. M. Whittaker, A. Corchia, A. G. Davies, and E. H. Linfield, “Simulation of terahertz generation at semiconductor surfaces,” Phys. Rev. B 65, 165301 (2002). [CrossRef]

]. The scattering in the IR range at the air-InAs interface in patterned samples could restrict further emission amplitude enhancements, leading to further complexities in guiding the THz waves along the line-of-sight direction.

Lateral emission measurements, under the same IR pumping conditions as those described for Fig. 2(b), were taken on the corrugated samples and on the bare epilayer without patterns. The corresponding results are shown in Fig. 3(a) for the time-domain transients and in Fig. 3(b) for the Fourier-transformed spectra. The geometrical schematic for the lateral detection setup is depicted in the inset of Fig. 3(a), where the focal spot position of the IR pump beam was displaced by approximately 2 mm and the Si lens coupled with the PCA was 1 mm away from the sample edge, respectively. The typical time-domain traces in the lateral detection geometry did not show any distinct features among the samples. The similar line-shapes among different structures in Fig. 3(a), expanded over the longer timescale, imply that the lateral emission is rather influenced by the propagation effect through the GaAs substrates; this propagation is also manifested in the narrower spectrum shown in Fig. 3(b) and observed in waveguide structures with attenuation and dispersion [23

23. See, e.g., M. Nagel, A. Marchewka, and H. Kurz, “Low-index discontinuity terahertz waveguides,” Opt. Express 14(21), 9944–9954 (2006). [CrossRef] [PubMed]

]. Also, a similar emission amplitude in the lateral detection geometry among samples implies that the diffusion along the growth direction is still efficient, irrespective of the pattern fabrication. The amplitude enhancement ratio in Fig. 3(c) was derived from the THz signal intensities, either in the transmissive geometry or in the lateral detection geometry, and normalized relative to those taken from the bare sample. In the transmissive detection, the amplitude enhancement ratio from the sample with W of 1.2 μm was seven times that of the bare sample, whereas the ratio from a sample with periodic apertures (W=2.5 μm) was not significantly different from the bare sample. In contrast, in the lateral detection, almost no amplitude enhancement was observed, indicating that the patterns affected the diffusion in a limited manner along the lateral direction. The scale and the structural dependence of these amplitude enhancements could lead to opportunities for both amplitude and directional controllability. The optimally adjusted doping concentrations [2

2. K. Liu, J. Xu, T. Yuan, and X. -C. Zhang, “Terahertz radiation from InAs induced by carrier diffusion and drift,” Phys. Rev. B 73, 155330 (2006). [CrossRef]

, 24

24. R. Adomaviius, A. Urbanowicz, G. Molis, A. Krotkus, and E. Satkovskis, “Terahertz emission from p-InAs due to the instantaneous polarization,” Appl. Phys. Lett. 85(13), 2463–2465 (2004). [CrossRef]

] and improved groove shapes for the effective role of the micro-scale mirrors could further enhance these emissions along the line-of-sight.

The second-order nonlinear effects from the bulk (100) InAs is not allowed at surface-normal incidence [25

25. M. Reid and R. Fedosejevs, “Terahertz emission from InAs surfaces at high excitation fluences,” Appl. Phys. Lett. 86, 011906 (2005). [CrossRef]

], which was also confirmed from suppressed THz signal as a function of crystallographic rotation in our sample (not shown here). Nevertheless, a contribution from nonlinear effects, possibly due to additional electric field components from lateral electron density modulation other than the vertical surface depletion field in SCL and different crystal symmetries among exposed crystal planes in patterned structures, could be examined in comparison to the contribution from photo-Dember effects. We also note that the χ2 process conventionally leads to a well-defined periodicity in axial measurements such as four-fold symmetry in (100) and six-fold symmetry in (111) InAs [8

8. M. Reid, I. V. Cravetchi, and R. Fedosejevs, “Terahertz radiation and second-harmonic generation from InAs: Bulk versus surface electric-field-induced contributions,” Phys. Rev. B 72, 035201 (2005). [CrossRef]

] as long as we can ignore the surface electric field induced nonlinear response in SCL. In this regard, we traced the peak amplitude in transient THz signals as a function of azimuthal angle ϕ in reflective and transmissive geometries, as shown in Fig. 4.

Fig. 4 (a) The azimuthal angle dependence of THz wave amplitude in reflection geometry, measured from groove-patterned layers (open dot) in comparison to non-patterned layer (solid dot). The azimuthal angle dependence of THz wave amplitude in transmission geometry (open dot), measured in patterned layers with W equal to (b) 1.2 μm, (c) 0.5 μm and (d) 2.5 μm. In (b–d), experimental data is compared to fitting curves (solid lines) whose relevant 1.2 μm parameters are displayed in insets.

The corrugated samples were rotated around the [100] crystal axis and the azimuthal angle ϕ was set to zero when the p-polarized incident IR beam was perpendicular to the groove orientation. The PCA was also adjusted to be sensitive to p-polarized THz emission; thus, lateral photo-Dember currents along the perpendicular direction to the groove axis would result in cosϕ dependence as the groove patterns were rotated by ϕ. Nevertheless, in reflective detection geometry, THz amplitudes in patterned samples showed almost the same behavior as the bare InAs layer in Fig. 4(a) in a way that the signals vary as cos2ϕ. The four-fold symmetry of the oscillation (∼ 12% of signal) in Fig. 4(a) without cosϕ dependency indicates that the THz waves along the reflective direction is not influenced by groove patterns as manifested in lateral detection geometry [cf. Fig. 3(a)]. The similar non-oscillatory offset amplitude (∼ 88% of signal) among samples with or without patterns further implies that the vertical photo-Dember currents contribute to the THz wave generation in a similar way in corrugated samples [2

2. K. Liu, J. Xu, T. Yuan, and X. -C. Zhang, “Terahertz radiation from InAs induced by carrier diffusion and drift,” Phys. Rev. B 73, 155330 (2006). [CrossRef]

, 6

6. P. Gu, M. Tani, S. Kono, K. Sakai, and X. -C. Zhang, “Study of terahertz radiation from InAs and InSb,” J. Appl. Phys. 91(9), 5533–5537 (2002). [CrossRef]

].

4. Conclusion

Acknowledgments

The authors would like to thank J. Ahn at KAIST for helpful discussions. This work was supported by the Bio-Imaging Research Center at GIST and by the Basic Science Research Program through the National Research Foundation of Korea ( NRF-2012-042232). The work at KIST was supported by the KIST Institutional Program including Dream Project, MEST 2012K001280 and the Korea-Sweden Research Cooperation Program.

References and links

1.

See, e.g., P. Gu and M. Tani, “Terahertz radiation from semiconductor surfaces,” in Terahertz Optoelectronics, K. Sakai, eds. (Springer, 2005), pp. 63–97. [CrossRef]

2.

K. Liu, J. Xu, T. Yuan, and X. -C. Zhang, “Terahertz radiation from InAs induced by carrier diffusion and drift,” Phys. Rev. B 73, 155330 (2006). [CrossRef]

3.

K. I. Lin, J. T. Tsai, T. S. Wang, J. S. Hwang, M. C. Chen, and G. C. Chi, “Drift current dominated terahertz radiation from InN at low-density excitation,” Appl. Phys. Lett. 93, 262102 (2008). [CrossRef]

4.

M. B. Johnston, D. M. Whittaker, A. Corchia, A. G. Davies, and E. H. Linfield, “Simulation of terahertz generation at semiconductor surfaces,” Phys. Rev. B 65, 165301 (2002). [CrossRef]

5.

D. -F. Liu and D. Xu, “Comparative study of terahertz radiation from n-InAs and n-GaAs,” Appl. Opt. 46(5), 789–794 (2007). [CrossRef] [PubMed]

6.

P. Gu, M. Tani, S. Kono, K. Sakai, and X. -C. Zhang, “Study of terahertz radiation from InAs and InSb,” J. Appl. Phys. 91(9), 5533–5537 (2002). [CrossRef]

7.

H. Jeong, S. H. Shin, S. Y. Kim, J. D. Song, S. B. Choi, D. S. Lee, J. Lee, and Y. D. Jho, “Relation between phase and generation mechanisms of THz waves in InAs,” Curr. Appl. Phys. 12, 668–672 (2012). [CrossRef]

8.

M. Reid, I. V. Cravetchi, and R. Fedosejevs, “Terahertz radiation and second-harmonic generation from InAs: Bulk versus surface electric-field-induced contributions,” Phys. Rev. B 72, 035201 (2005). [CrossRef]

9.

Y. Ko, S. Sengupta, S. Tomasulo, P. Dutta, and I. Wilke, “Emission of terahertz-frequency electromagnetic radiation from bulk Gax In1−x As crystals,” Phys. Rev. B 78, 035201 (2008). [CrossRef]

10.

M. Tonouchi, “Cutting-edge terahertz technology,” Nat. Photonics 1, 97–105 (2007). [CrossRef]

11.

See, e.g., M. Wächter, M. Nagel, and H. Kurz, “Tapered photoconductive terahertz field probe tip with subwavelength spatial resolution,” Appl. Phys. Lett. 95, 041112 (2009). [CrossRef]

12.

G. Klatt, F. Hilser, W. Qiao, M. Beck, R. Gebs, A. Bartels, K. Huska, U. Lemmer, G. Bastian, M. B. Johnston, M. Fischer, J. Faist, and T. Dekorsy, “Terahertz emission from lateral photo-Dember currents,” Opt. Express 18(5), 4939–4947 (2010). [CrossRef] [PubMed]

13.

G. Klatt, B. Surrer, D. Stephan, O. Schubert, M. Fischer, J. Faist, A. Leitenstorfer, R. Huber, and T. Dekorsy, “Photo-Dember terahertz emitter excited with an Er:fiber laser,” Appl. Phys. Lett. 98, 021114 (2011). [CrossRef]

14.

C. D’Amico, A. Houard, M. Franco, B. Prade, and A. Mysyrowicz, “Conical forward THz emission from femtosecond-laser-beam filamentation in air,” Phys. Rev. Lett. 98, 235002 (2007). [CrossRef]

15.

M. Yi, K. Lee, J. Lim, Y. Hong, Y. D. Jho, and J. Ahn, “Terahertz waves emitted from an optical fiber,” Opt. Express 18(13), 13693–13699 (2010). [CrossRef] [PubMed]

16.

A. Fitzgerald, E. Berry, N. Zinovev, G. Walker, M. Smith, and J. Chamberlain, “An introduction to medical imaging with coherent terahertz frequency radiation,” Phys. Med. Biol. 47, R67–R84 (2002). [CrossRef] [PubMed]

17.

C. D. Stoik, M. J. Bohn, and J. L. Blackshire, “Nondestructive evaluation of aircraft composites using transmissive terahertz time domain spectroscopy,” Opt. Express 16(21), 17039–17051 (2008). [CrossRef] [PubMed]

18.

J. Federici and L. Moeller, “Review of terahertz and subterahertz wireless communications,” J. Appl. Phys. 107, 111101 (2010). [CrossRef]

19.

J. H. Yim, K. Min, H. Jeong, E. H. Lee, J. D. Song, and Y. D. Jho, “Nexus between directionality of terahertz waves and structural parameters in groove patterned InAs,” J. Appl. Phys. 113, 136505 (2013). [CrossRef]

20.

Y. -S. Lee, Principle of Terahertz Science and Technology (Springer, 2009), pp. 21–24.

21.

C. T. Que, T. Edamura, M. Nakajima, M. Tani, and M. Hangyo, “Terahertz radiation from InAs films on silicon substrates excited by femtosecond laser pulses,” Jpn. J. Appl. Phys. 48, 010211 (2009). [CrossRef]

22.

I. Säidi, S. B. Radhia, and K. Boujdaria, “Band parameters of GaAs, InAs, InP, and InSb in the 40-band k·p model,” J. Appl. Phys. 107, 043701 (2010). [CrossRef]

23.

See, e.g., M. Nagel, A. Marchewka, and H. Kurz, “Low-index discontinuity terahertz waveguides,” Opt. Express 14(21), 9944–9954 (2006). [CrossRef] [PubMed]

24.

R. Adomaviius, A. Urbanowicz, G. Molis, A. Krotkus, and E. Satkovskis, “Terahertz emission from p-InAs due to the instantaneous polarization,” Appl. Phys. Lett. 85(13), 2463–2465 (2004). [CrossRef]

25.

M. Reid and R. Fedosejevs, “Terahertz emission from InAs surfaces at high excitation fluences,” Appl. Phys. Lett. 86, 011906 (2005). [CrossRef]

26.

D. H. McMahon, W. A. Dyes, R. F. Cooper, W. C. Robinson, and A. Mahapatra, “Echelon grating multiplexers for hierarchically multiplexed fiber-optic communication networks,” Appl. Opt. 26(11), 2188–2196 (1987). [CrossRef] [PubMed]

27.

H. Ko, K. Takei, R. Kapadia, S. Chuang, H. Fang, P. W. Leu, K. Ganapathi, E. Plis, H. S. Kim, S. -Y. Chen, M. Madsen, A. C. Ford, Y. -L. Chueh, S. Krishna, S. Salahuddin, and A. Javey, “Ultrathin compound semiconductor on insulator layers for high-performance nanoscale transistors,” Nature 468, 286–289 (2010). [CrossRef] [PubMed]

OCIS Codes
(160.6000) Materials : Semiconductor materials
(220.4000) Optical design and fabrication : Microstructure fabrication
(300.6495) Spectroscopy : Spectroscopy, teraherz

ToC Category:
Optical Devices

History
Original Manuscript: July 1, 2013
Revised Manuscript: August 2, 2013
Manuscript Accepted: August 2, 2013
Published: August 14, 2013

Citation
Jong-Hyuk Yim, Hoonil Jeong, Muhammad Irfan, Eun-Hye Lee, Jin-Dong Song, and Young-Dahl Jho, "Directional terahertz emission from corrugated InAs structures," Opt. Express 21, 19709-19717 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-17-19709


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References

  1. See, e.g., P. Gu and M. Tani, “Terahertz radiation from semiconductor surfaces,” in Terahertz Optoelectronics, K. Sakai, eds. (Springer, 2005), pp. 63–97. [CrossRef]
  2. K. Liu, J. Xu, T. Yuan, and X. -C. Zhang, “Terahertz radiation from InAs induced by carrier diffusion and drift,” Phys. Rev. B73, 155330 (2006). [CrossRef]
  3. K. I. Lin, J. T. Tsai, T. S. Wang, J. S. Hwang, M. C. Chen, and G. C. Chi, “Drift current dominated terahertz radiation from InN at low-density excitation,” Appl. Phys. Lett.93, 262102 (2008). [CrossRef]
  4. M. B. Johnston, D. M. Whittaker, A. Corchia, A. G. Davies, and E. H. Linfield, “Simulation of terahertz generation at semiconductor surfaces,” Phys. Rev. B65, 165301 (2002). [CrossRef]
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