OSA's Digital Library

Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 22 — Nov. 4, 2013
  • pp: 26677–26687
« Show journal navigation

Near-field effect in the infrared range through periodic Germanium subwavelength arrays

Wei Dong, Toru Hirohata, Kazutoshi Nakajima, and Xiaoping Wang  »View Author Affiliations


Optics Express, Vol. 21, Issue 22, pp. 26677-26687 (2013)
http://dx.doi.org/10.1364/OE.21.026677


View Full Text Article

Acrobat PDF (4300 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

Using finite-difference-time-domain simulation, we have studied the near-field effect of Germanium (Ge) subwavelength arrays designed in-plane with a normal incidence. Spectra of vertical electric field component normal to the surface show pronounced resonance peaks in an infrared range, which can be applied in a quantum well infrared photodetector. Unlike the near-field optics in metallic systems that are commonly related to surface plasmons, the intense vertical field along the surface of the Ge film can be interpreted as a combination of diffraction and waveguide theory. The existence of the enhanced field is confirmed by measuring the Fourier transform infrared spectra of fabricated samples. The positions of the resonant peaks obtained in experiment are in good agreement with our simulations.

© 2013 Optical Society of America

1. Introduction

In this paper, we achieve an alternative generation of near-field effect in the infrared range using a non-metallic structure—Germanium (Ge) subwavelength arrays—for overcoming SP loss. Through the three-dimensional finite-difference-time-domain (3D-FDTD) method, an intense, vertical electric field (indicated as Ez field in the following paragraphs) was observed on the surface of a free-standing film, which is comparable to that of an Au film with similar parameters. After adding an InP substrate below the free-standing structure, we investigated the potential applications of the enhanced Ez field for designing a real device such as a QWIP.

This paper is organized as follows. Section 2 begins with the simulation of free-standing Ge subwavelength arrays using the 3D-FDTD method. Section 3 presents the obtained EM field response and the field distributions in the cross-section. Section 4 presents the parameter investigation and the basic understanding of the phenomena. Section 5 compares our simulations and the fabricated samples when an InP substrate is added for a practical application. Section 6 states the conclusion.

2. Simulation method and structures

We use the FullWAVE simulation tool (Rsoft product) to perform the 3D-FDTD analysis. For simplicity and generalization, free-standing Ge subwavelength array consisting of periodic Ge stripes is studied at a polarized normal incidence. We study the optical properties of the structure in an infrared range from 1.6 to 8 μm. In this range, Ge has a high real part of refractive index (n>4, much larger than usual materials) and a zero imaginary part (no absorption), which is beneficial for light confinement. After obtaining the characteristics and the mechanism of the free-standing subwavelength arrays, an InP substrate with a much larger thickness than that of the Ge film was added below the structure for studying the application potential. Details of the simulated structures are shown in Fig. 1
Fig. 1 Schematic of the simulated periodic Ge stripes. The positions of the monitors are indicated in both the cross-sections and top views.
. Periodic stripes are arranged along the x-axis with an infinite length along the y-axis. Therefore, in the simulation model, we build one period of the structure in the x domain, much longer length in the y domain, and about 4 μm in the z domain (large enough compared with the thickness), then we use the periodic boundary condition in the x and y domain to achieve the periodic symmetry of the structure, and the perfectly matched layers (PML) condition in the z domain for the removal of stray light. The normal incidence is x-polarized so that the electric field is perpendicular to the stripe direction. The field response can be recorded by a monitor set at the edge of the opening just beneath the outgoing surface, as indicated in Fig. 1. In our simulation, we apply frequency-dependent dielectric constants obtained from literature [16

16. E. D. Palik, Handbook of Optical Constants of Solids: Index (Academic press, 1998).

].

3. EM field response and field distribution

We investigate the EM fields of periodic Ge stripes. As a comparison, we further investigate the EM fields of a free-standing periodic Au stripes with the lattice constant a = 2.9 μm, the width d = 1.5 μm, and the thickness t = 0.24 μm. The monitors record enhanced Ez field responses with much larger intensity than the normal incidence in both structures. The normalized intensities, obtained by dividing the monitor values of the Ez field by the normal incidence, are shown in Fig. 2
Fig. 2 A comparison of the normalized Ez fields of periodic Ge stripes and periodic Au stripes with the lattice constant a = 2.9 μm, the width d = 1.5 μm, and the thickness t = 0.24 μm.
.

The Ez field generated at the interface of Ge and air is comparable to that of an Au subwavelength array with similar parameters. We can divide the curves into two parts, as indicated by the vertical dashed lines in Fig. 2. In part 1, both of the structures have a major peak (3350 cm−1 for Ge and 3400 cm−1 for Au) in the frequency range of 3000 – 4000 cm−1 whose intensity can be up to ten times the normal incidence. The lowered resonant peak at 3400 cm−1 in the periodic Au stripes is caused by the SP loss in the infrared range. In part 2, a group of small peaks occur at a higher frequency range beyond 4000 cm−1 in the case of Ge stripes (e.g. ~5150 cm−1 and ~6200 cm−1 peak), which can never be observed in Au structure. Furthermore, the ~5150 cm−1 peak in the Ge stripes can be as obvious as the Part 1 peak and its performance will be further improved if the parameters are adjusted properly. The characteristics of this Part 2 peak will be studied and exploited later in this paper.

To look further into the differences of these two kinds of peaks, the cross-section field distributions of one period of the array are recorded, providing the intuitive visions of the spatial patterns. The Ez field distribution of the Part 1 peak in periodic Ge stripes is presented in Fig. 3(a)
Fig. 3 Cross-section distribution of EM field magnitude at the Part 1 peak in one period of the subwavelength arrays: (a) Ez and (b) Hy of periodic Ge stripes, and (c) Ez and (d) Hy of periodic Au stripes. The dashed rectangle indicates the area of Ge or Au. The source is set below the bottom side of each structure.
. The field pattern shows an evanescent feature with most of the intensity concentrated at the corners. The corner-preferred Ez field and the similar evanescent pattern can also be observed at the resonant peak in periodic Au stripes, which are caused by SPs [17

17. S.-H. Chang, S. Gray, and G. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]

], as Fig. 3(c) indicates. The major difference between the Ge stripes and the Au stripes is the Hy field distribution. As indicated in Fig. 3(b) and Fig. 3(d), the Hy field mainly concentrates inside the Ge stripe because of the zero absorption. In Au stripes, the Hy field can only stay on the surface.

For the Part 2 peak, the field distributions along the cross-section of periodic Ge stripes at the resonant frequency of 5150 cm−1 are presented in Fig. 4(a)
Fig. 4 Cross-section distribution of EM field magnitude at the Part 2 peaks in one period of periodic Ge stripes: (a) Ez and (b) Hy at the 5150 cm−1 peak, and (c) Hy at the 6200 cm−1 peak. The dashed rectangle indicates the area of Ge. The source is set below the bottom side of each structure.
and Fig. 4(b). In Fig. 4(a), the Ez at 5150 cm−1 shows similar evanescent features as the Part 1 peak, but the intensity maxima distribute along the surface of the stripe instead of concentrating only at the corners. This property is more suitable for a QWIP device because it helps to increase the effective area of the Ez field, an essential factor of detectivity [6

6. B. Levine, “Quantum‐well infrared photodetectors,” J. Appl. Phys. 74(8), R1–R81 (1993). [CrossRef]

]. The surface-preferred distribution is reminiscent of the similar EM properties of a waveguide mode propagating inside an optical microfiber/nanofiber. A more obvious example can be seen in Fig. 4(b). There is a strong Hy field (indicated by 19.0657 on the color scale) forming a waveguide-mode-like pattern. This pattern has three rounds concentrating only inside the Ge stripe indicating a propagation length of 3π (in simulation, one round represents a phase shift of π). At the other Part 2 peak (6200 cm−1 in Fig. 2), a five-round Hy pattern is observed, as shown in Fig. 4(c). This type of Hy pattern is totally different from that of the Part 1 peak that has “tails” left outside the Ge stripe (Fig. 3(b)). In addition, there is a π /2 phase shift between the Hy and Ez fields due to the half-round dislocation observed in the patterns of Fig. 4(a) and Fig. 4(b).

4. Parameter investigation and mechanism interpretation

4.1. Parameter investigation

The position and the intensity of the peaks vary as the change of structure parameters. Three main parameters are investigated in periodic Ge stripes: the lattice constant a, the stripe width d, and the thickness t. During the investigation, a standard structure with a = 2.9 μm, d = 1.5 μm, and t = 0.24 μm was chosen and then one of the parameters was changed while the other two remained the same.

The performance of the peaks is strongly affected by the thickness t. If the thickness is small, there is little Ez field recorded. When the thickness is as large as 0.15 μm, the peaks start to be observable, as shown in Fig. 5(a)
Fig. 5 Ez field response of periodic Ge stripes with the change of different parameters: (a) the thickness t, (b) the width d, and (c) the lattice constant a. The red line indicates the standard structure with a = 2.9 μm, d = 1.5 μm, and t = 0.24 μm. The Part 1 peak of each curve is indicated by an asterisk.
. The Part 1 peak, indicated by the asterisk, stays nearly at the same position; however, the Part 2 peaks quickly grow and shift to lower frequencies as the thickness increases. When the thickness reaches 0.4 μm, one Part 2 peak moves to a frequency even lower than the Part 1 peak frequency, and the peak intensity becomes much stronger (see the 2800 cm−1 peak of the green line in Fig. 5(a)). Throughout the investigation of the thickness, the Part 2 peak performs better with larger thickness. This is another difference from the Au film, in which the generated Ez field by SPs is stronger with thicknesses less than 0.2 μm [18

18. S. C. Lee, S. Krishna, and S. R. Brueck, “Quantum dot infrared photodetector enhanced by surface plasma wave excitation,” Opt. Express 17(25), 23160–23168 (2009). [CrossRef] [PubMed]

20

20. K.-L. Lee, S.-H. Wu, and P.-K. Wei, “Intensity sensitivity of gold nanostructures and its application for high-throughput biosensing,” Opt. Express 17(25), 23104–23113 (2009). [CrossRef] [PubMed]

]. It should be noted that only the Part 2 peak shows the waveguide-mode-like Hy pattern, so we can easily tell whether a peak belongs to the Part 1 or the Part 2 peak by checking its Hy pattern.

When the width d changes, the Part 1 peak still does not move, as can be seen in Fig. 5(b). On the other hand, this peak increases with the increase of width, at first, and then it decreases as the continuous increase of the width d. Finally, the peak diminishes to a small amount until the stripe is wide enough to make a narrow air slit (d = 2.5 μm, a-d = 0.4 μm). On the contrary, the Part 2 peaks rise and shift to lower frequencies monotonically with new peaks coming into the frequency range one by one, indicating that more modes are appearing. The position of the Part 1 peak only shifts to a lower frequency when the lattice constant a increases, as indicated in Fig. 5(c). As the Part 1 peak moves to the lower frequency, it seems that the Part 2 peaks (see the red line and blue line in Fig. 5(c)) also feel this change and follow with smaller shifts.

4.2. The origins of the two kinds of peaks

In the case of periodic Au stripes, the position of the Part 1 peak is caused by SP excitations [4

4. C. Genet and T. W. Ebbesen, “Light in tiny holes,” Nature 445(7123), 39–46 (2007). [CrossRef] [PubMed]

]. According to the momentum-matching conditions, the position of the Part 1 peak in Au stripes can be given in a first approximation by:
λsp=aεmεdεm+εd
(1)
where εm and εd are respectively the dielectric constants of the metal and the dielectric material in contact with the metal. In the case of periodic Ge stripes, the theory of SPs is no longer applicable. Around the Part 1 peak, there are always the well-known Wood-Rayleigh anomalies which are usually observed in the zero-order transmission spectra of a grating-like structure [11

11. M. Treacy, “Dynamical diffraction explanation of the anomalous transmission of light through metallic gratings,” Phys. Rev. B 66(19), 195105 (2002). [CrossRef]

, 21

21. H. Ghaemi, T. Thio, D. Grupp, T. W. Ebbesen, and H. Lezec, “Surface plasmons enhance optical transmission through subwavelength holes,” Phys. Rev. B 58(11), 6779–6782 (1998). [CrossRef]

, 22

22. C. Genet, M. P. van Exter, and J. Woerdman, “Fano-type interpretation of red shifts and red tails in hole array transmission spectra,” Opt. Commun. 225(4-6), 331–336 (2003). [CrossRef]

]. The position of the Part 1 peaks in Ge stripes can be estimated according to the grating equations:
λ=ansub
(2)
where nsub is the refractive index of the substrate. Although the two structures consisting of Au and Ge are working in different mechanisms, it seems that both of them can be classified as Fano-type resonance [23

23. U. Fano, “Effects of configuration interaction on intensities and phase shifts,” Phys. Rev. 124(6), 1866–1878 (1961). [CrossRef]

], which attributes the phenomena to conversions between continuous radiation states and a discrete localized in-plane state [22

22. C. Genet, M. P. van Exter, and J. Woerdman, “Fano-type interpretation of red shifts and red tails in hole array transmission spectra,” Opt. Commun. 225(4-6), 331–336 (2003). [CrossRef]

]. As a result, they show similar evanescent features of the Ez pattern.

On the other hand, the origin of the Part 2 peaks in periodic Ge stripes was studied in detail. As indicated in Fig. 4(a) and Fig. 4(b), the field patterns of the Part 2 peak show the features of a waveguide mode. In order to verify whether it is a waveguide mode, a simple Ge waveguide model was introduced in the FDTD simulation. Figure 6(a)
Fig. 6 (a) Schematic of a simple Ge waveguide model with d = 1.5 μm and t = 0.24 μm. Cross-section distributions of Hy magnitude at the 5150 cm−1 peak of the simplified Ge waveguide model with (b) bottom end irradiated, and (c) both ends irradiated. Cross-section distributions of Hy magnitude at the 5750 cm−1 peak with (d) the bottom end irradiated, and (e) both ends irradiated. The dashed rectangle indicates the area of Ge.
shows the schematic of this model. One Ge stripe is extracted and turned by 90 degrees as a short planar waveguide with two normal sources, one irradiated each end of the stripe. The length of the waveguide coincides with the stripe width d and thickness t. We also investigate the case of only one source irradiating at the bottom end. The Hy field response is recorded using a monitor at the lateral interface. Even with only one end of the stripe irradiated, many guided modes are generated inside the Ge stripe.

The details are studied through the field distribution along the cross-section. Only the Hy field patterns are shown in Fig. 6 because of their strong dependence on the Ge material thus providing a clear view of the guided mode. The three-round pattern is observed at the frequency of 5150 cm−1 (Fig. 6(b) and Fig. 6(c)), coinciding with the result of the periodic Ge stripes. The maximum of Hy at 5150 cm−1 (indicated on the color scale) is enlarged in the case of both ends irradiated. There is also a four-round pattern at a frequency of 5750 cm−1 (Fig. 6(d)), and a five-round pattern at 6200 cm−1 (not shown here). A similar enhancement of Hy for both ends irradiated is also observed at 6200 cm−1 as in the case of 5150 cm−1, indicating constructive interference. However, the magnitude of Hy at the frequency of 5750 cm−1 decreases (the appearance of the pattern also changes) for both ends irradiated, indicating destructive interference (Fig. 6(e)). Note that the field response of the periodic Ge stripes in Fig. 2 only shows two Part 2 peaks, 5150 cm−1 and 6200 cm−1, which have a three-round pattern and a five-round pattern, respectively. There is no peak for an even-round pattern, which is destructive interference. Therefore, the comparison of Hy patterns at different peaks indicates that the guided modes generated from both ends of a Ge stripe will experience constructive or destructive interference, but only the constructive interference contributes to the Part 2 peak.

4.3. Explanation based on diffraction and waveguide theory

A more intuitive way to find out the coupling mechanism can be done by simply simulating a single slit in a wide Ge film with a normal incidence and PML boundary conditions. The result is shown in Fig. 7(a)
Fig. 7 (a) Cross-section distributions of Hy magnitude of a single slit in a wide Ge film with slit width of 1.4 μm and thickness of 0.24 μm. The dashed rectangle indicates the area of Ge. (b) Geometry of the generation of the Part 2 peak.
. There is propagation of guided mode observed in the lateral direction inside the Ge film. According to all the above proofs, we can explain the generation of the Part 2 peak in this way, as shown in Fig. 7(b): when the incident light comes across the surface of a subwavelength array, it will experience strong diffraction, since λ > a-d (the air opening), and will create diffracted modes in different directions [10

10. H. J. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]

], as the red arrows in Fig. 7(b) indicate. Since Ge has a relatively high refractive index (~4.1), the large difference in refractive index between Ge and the nearby layer (here is air) makes it a good waveguide for confining light. Every Ge stripe behaves as a short planar waveguide in the x-direction providing efficient channels for most of the diffracted modes coupled into the in-plane evanescent modes. As a result, the normal incident wavevector is turned by 90 degrees and becomes the in-plane wavevector (the blue arrows in Fig. 7(b)), thus the diffracted light is guided inside the Ge stripe. At certain frequencies such as 5150 cm−1, the guided modes from the two ends of the stripe can have constructive interference and then form standing waves. Therefore, an enhanced Ez field is generated.

The position of the resonant peaks can be verified according to waveguide theory [24

24. A. W. Snyder and J. Love, Optical waveguide theory (Springer, 1983).

] whose main function can be expressed as:
2Kzt+δIP+δIIP=2mπ
(3)
where Kz is the vertical wavevector, δIP and δIIP are the phase shifts of the TM mode caused by reflection at the top and bottom interfaces, respectively. They can be calculated from:
{tanδIP2=(n1n3)2sin2θi(n3n1)2cosθitanδIIP2=(n1n2)2sin2θi(n2n1)2cosθi
(4)
where n1, n2 and n3 are the refractive index of Ge, substrate and air, respectively. θi is the incident angle. Equation (3) is a transcendental equation that can be solved by graphic method in MATLAB. For example, in the current model, we obtain Kzt2.82 for the position of 5150 cm−1 (equal to 0.515 μm −1 in the calculation). Then the wavevector of the guided mode in Ge can be estimated by:
Kx=K02n12Kz2(2π0.515n1)2Kz26.11
(5)
which coincides with the three-round pattern of the Hy field since Kxd9.23π. The underlying physics describing the sensitivity of the field response of the Part 2 peaks to parameters, such as t and d in Section 4.1, can also be determined through this calculation.

5. Experimental verification of the application potential

In applications of semiconductor devices, a substrate is always necessary. For example, a QWIP has InGaAs/AlGaAs multi-quantum-well structure on a substrate of InP. However, when such a semiconductor layer is added beneath the Ge subwavelength arrays, the difference of the refractive index between Ge and the nearby layer (InP) becomes much smaller and the confinement of the Ge structure declines. As a result, the intensity of the Ez field at the Part 2 peak decreases drastically and many peaks disappear. Again, this situation can be explained by waveguide theory. The mode number in a waveguide can be estimated as:

Modenumber2tλ0n12nsub2
(6)

A substrate with a high refractive index (nsub ~3.2) will cause many modes to leak from the Ge layer and thus the waveguide becomes easily cutoff. One way to alleviate this deterioration is to increase the thickness t as both Eq. (6) and the results in Section 4.1 indicate. For example, when the thickness was increased from 0.24 μm to 0.8 μm, a large Ez field was observed. Further increase of the thickness will certainly enlarge the Ez field, but such a large thickness will make the fabrication of narrow slits (a-d = 0.4 μm) difficult to achieve with the current techniques. As a result, we limit the thickness to less than 1 μm.

We fabricate arrays of 1D periodic Ge stripes on raw InP. First, a smooth Ge film was deposited by evaporation on a plain InP plate. Periodic stripes were then fabricated through the film by sputtering using a focused-ion-beam (FIB) system (40 keV Ga ions, resolution 5 nm). The quality of the fabricated structures was tested using a scanning electron microscope (SEM). A SEM image of the sample is shown in Fig. 8(a). The uniformity and the surface conditions are excellent, except for some inevitable slight slopes in the milled slits. It should be noted that the length of the stripe was designed to be 500 μm to approach the idealized condition of infinity in the y-axis, but it is difficult to keep the uniformity of the narrow slits on such a large scale. The sample was fabricated by composing 7 repeats of 70-μm-long stripes with a small gap of 2 μm between each repeat. Over 150 repeats were fabricated to ensure the periodicity in the simulation, so that the whole area for one sample is 500 × 500 μm. We fabricate three same structures at different positions of the Ge film to avoid the fluctuation or random error caused by surface defects and other reasons. Measurement results show similar performance of these samples indicating good fabrication uniformity.

The zero-order transmission spectra of the fabricated samples were recorded using a NICOLET 8700 FTIR spectrometer. It should be noted that the light path of the configuration has a focused angle of 5° which differs from the normal incidence condition in our simulation. However, the obtained spectra still show the main characteristics. Figure 8(b) shows the FTIR zero-order transmitted intensities of the fabricated periodic Ge stripes, the smooth Ge (no stripes) and the source. Two distinct absorption peaks (1970 and 2850 cm−1) are observed in the periodic Ge stripes, which are labeled by asterisks to indicate that they share similar positions as the simulation results (2000 and 2800 cm−1) in Fig. 8(c). The deviation can be caused by processing errors, surface roughness and the 5° angle in the measurement.

The instinct absorption peaks (~1600 cm−1 and ~3700 cm−1: water absorption; ~2350 cm−1: CO2 absorption) are also observed. The absorption of the designed peaks caused by the subwavelength array can be nearly half of the CO2 level indicating a strong localization of the EM field. A more obvious indication can be found in the transmission spectra in Fig. 8(d), which is obtained by dividing the source intensity. Though some fake peaks (~2300 cm−1 and ~3750 cm−1) are caused by the instinct absorption, two peaks with over 20% absorption are observed. The positions of these peaks also coincide with the simulation (the simulated transmission spectrum is copied to overlay with the real spectrum for an easy comparison).

6. Conclusion

Resonant peaks showing excellent near-field effects in the Ez and Hy field can be obtained through periodic Ge subwavelength arrays in the FDTD simulations. These peaks are located at different frequency positions from the Part 1 peak calculated by the grating equation. The peak intensities are comparable to that of the Au case, but there are no SPs participating in Ge material in the infrared range. Field distributions show that the evanescent Ez field mainly concentrates along the surface of the Ge structure, which is different from the Ez field for Au that focuses only at the corners of the opening. Analyzing the waveguide-mode-like Hy pattern, the phenomena can be interpreted by coupled diffraction and waveguide theory. The property of the structure is considered to be an alternative for making a QWIP.

According to literature [25

25. J. Andersson and L. Lundqvist, “Grating-coupled quantum-well infrared detectors: Theory and performance,” J. Appl. Phys. 71(7), 3600–3610 (1992). [CrossRef]

, 26

26. L. Lundqvist, J. Andersson, Z. Paska, J. Borglind, and D. Haga, “Efficiency of grating coupled AlGaAs/GaAs quantum well infrared detectors,” Appl. Phys. Lett. 63(24), 3361–3363 (1993). [CrossRef]

], gratings have already been used to improve the detectivity of QWIPs since 1990s. For example, a lamellar grating [25

25. J. Andersson and L. Lundqvist, “Grating-coupled quantum-well infrared detectors: Theory and performance,” J. Appl. Phys. 71(7), 3600–3610 (1992). [CrossRef]

] can make the change of the wavevector through only diffraction, while the method of crossed grating and a waveguide [26

26. L. Lundqvist, J. Andersson, Z. Paska, J. Borglind, and D. Haga, “Efficiency of grating coupled AlGaAs/GaAs quantum well infrared detectors,” Appl. Phys. Lett. 63(24), 3361–3363 (1993). [CrossRef]

] makes an advancement by combining diffraction and waveguide. The distinction of our work is that we not only exploit diffraction and waveguide, but also use a high refractive index material (nGe>nsub>nair) to improve the light confinement. In addition, the simultaneously generated constructive interference will also help to enhance the near field, thus amplify the vertical field drastically. Through parameter investigations, it is found that increasing the thickness t and the width d will help generate a stronger Ez field for the device. If possible, it is better to use a free-standing configuration to improve the performance [15

15. S. Kalchmair, R. Gansch, S. I. Ahn, A. M. Andrews, H. Detz, T. Zederbauer, E. Mujagić, P. Reininger, G. Lasser, W. Schrenk, and G. Strasser, “Detectivity enhancement in quantum well infrared photodetectors utilizing a photonic crystal slab resonator,” Opt. Express 20(5), 5622–5628 (2012). [CrossRef] [PubMed]

], as we also indicate in our study.

Although the mechanism of the near-field effect in Ge subwavelength arrays can be easily understood by our interpretation, the in-plane periodic subwavelength structure is reminiscent of a photonic crystal. Further study should be arranged by introducing photonic bandstructure to interpret this phenomenon. It will help to better exploit the near-field effect in novel applications such as infrared sensing, near-field microscopy and other semiconductor devices.

Acknowledgments

We thank Shohei Hayashi for FIB fabrication of our samples, and Yoshitaka Kurosaka and Kazuyoshi Hirose for discussions. We are also grateful for some advice given by T. W. Ebbesen regarding FTIR measurements.

References and links

1.

T. W. Ebbesen, H. Lezec, H. Ghaemi, T. Thio, and P. Wolff, “Extraordinary optical transmission through sub-wavelength hole arrays,” Nature 391(6668), 667–669 (1998). [CrossRef]

2.

W. L. Barnes, A. Dereux, and T. W. Ebbesen, “Surface plasmon subwavelength optics,” Nature 424(6950), 824–830 (2003). [CrossRef] [PubMed]

3.

W. Wu, A. Bonakdar, and H. Mohseni, “Plasmonic enhanced quantum well infrared photodetector with high detectivity,” Appl. Phys. Lett. 96(16), 161107 (2010). [CrossRef]

4.

C. Genet and T. W. Ebbesen, “Light in tiny holes,” Nature 445(7123), 39–46 (2007). [CrossRef] [PubMed]

5.

K. Okamoto, I. Niki, A. Shvartser, Y. Narukawa, T. Mukai, and A. Scherer, “Surface-plasmon-enhanced light emitters based on InGaN quantum wells,” Nat. Mater. 3(9), 601–605 (2004). [CrossRef] [PubMed]

6.

B. Levine, “Quantum‐well infrared photodetectors,” J. Appl. Phys. 74(8), R1–R81 (1993). [CrossRef]

7.

S. A. Maier, Plasmonics: fundamentals and applications (Springer, 2007).

8.

T. Thio, H. Ghaemi, H. Lezec, P. Wolff, and T. Ebbesen, “Surface-plasmon-enhanced transmission through hole arrays in Cr films,” J. Opt. Soc. Am B. 16(10), 1743–1748 (1999). [CrossRef]

9.

P. A. Hobson, S. Wedge, J. A. Wasey, I. Sage, and W. L. Barnes, “Surface Plasmon Mediated Emission from Organic Light‐Emitting Diodes,” Adv. Mater. 14(19), 1393–1396 (2002). [CrossRef]

10.

H. J. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express 12(16), 3629–3651 (2004). [CrossRef] [PubMed]

11.

M. Treacy, “Dynamical diffraction explanation of the anomalous transmission of light through metallic gratings,” Phys. Rev. B 66(19), 195105 (2002). [CrossRef]

12.

Z. Ruan and M. Qiu, “Enhanced transmission through periodic arrays of subwavelength holes: the role of localized waveguide resonances,” Phys. Rev. Lett. 96(23), 233901 (2006). [CrossRef] [PubMed]

13.

F. Gu, L. Zhang, X. Yin, and L. Tong, “Polymer single-nanowire optical sensors,” Nano Lett. 8(9), 2757–2761 (2008). [CrossRef] [PubMed]

14.

C. Peng, Y. Liang, K. Sakai, S. Iwahashi, and S. Noda, “Three-dimensional coupled-wave theory analysis of a centered-rectangular lattice photonic crystal laser with a transverse-electric-like mode,” Phys. Rev. B 86(3), 035108 (2012). [CrossRef]

15.

S. Kalchmair, R. Gansch, S. I. Ahn, A. M. Andrews, H. Detz, T. Zederbauer, E. Mujagić, P. Reininger, G. Lasser, W. Schrenk, and G. Strasser, “Detectivity enhancement in quantum well infrared photodetectors utilizing a photonic crystal slab resonator,” Opt. Express 20(5), 5622–5628 (2012). [CrossRef] [PubMed]

16.

E. D. Palik, Handbook of Optical Constants of Solids: Index (Academic press, 1998).

17.

S.-H. Chang, S. Gray, and G. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express 13(8), 3150–3165 (2005). [CrossRef] [PubMed]

18.

S. C. Lee, S. Krishna, and S. R. Brueck, “Quantum dot infrared photodetector enhanced by surface plasma wave excitation,” Opt. Express 17(25), 23160–23168 (2009). [CrossRef] [PubMed]

19.

V. Canpean and S. Astilean, “Multifunctional plasmonic sensors on low-cost subwavelength metallic nanoholes arrays,” Lab Chip 9(24), 3574–3579 (2009). [CrossRef] [PubMed]

20.

K.-L. Lee, S.-H. Wu, and P.-K. Wei, “Intensity sensitivity of gold nanostructures and its application for high-throughput biosensing,” Opt. Express 17(25), 23104–23113 (2009). [CrossRef] [PubMed]

21.

H. Ghaemi, T. Thio, D. Grupp, T. W. Ebbesen, and H. Lezec, “Surface plasmons enhance optical transmission through subwavelength holes,” Phys. Rev. B 58(11), 6779–6782 (1998). [CrossRef]

22.

C. Genet, M. P. van Exter, and J. Woerdman, “Fano-type interpretation of red shifts and red tails in hole array transmission spectra,” Opt. Commun. 225(4-6), 331–336 (2003). [CrossRef]

23.

U. Fano, “Effects of configuration interaction on intensities and phase shifts,” Phys. Rev. 124(6), 1866–1878 (1961). [CrossRef]

24.

A. W. Snyder and J. Love, Optical waveguide theory (Springer, 1983).

25.

J. Andersson and L. Lundqvist, “Grating-coupled quantum-well infrared detectors: Theory and performance,” J. Appl. Phys. 71(7), 3600–3610 (1992). [CrossRef]

26.

L. Lundqvist, J. Andersson, Z. Paska, J. Borglind, and D. Haga, “Efficiency of grating coupled AlGaAs/GaAs quantum well infrared detectors,” Appl. Phys. Lett. 63(24), 3361–3363 (1993). [CrossRef]

OCIS Codes
(050.2770) Diffraction and gratings : Gratings
(130.3060) Integrated optics : Infrared
(230.7400) Optical devices : Waveguides, slab
(310.6628) Thin films : Subwavelength structures, nanostructures

ToC Category:
Diffraction and Gratings

History
Original Manuscript: August 9, 2013
Revised Manuscript: October 5, 2013
Manuscript Accepted: October 15, 2013
Published: October 29, 2013

Citation
Wei Dong, Toru Hirohata, Kazutoshi Nakajima, and Xiaoping Wang, "Near-field effect in the infrared range through periodic Germanium subwavelength arrays," Opt. Express 21, 26677-26687 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-22-26677


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. T. W. Ebbesen, H. Lezec, H. Ghaemi, T. Thio, and P. Wolff, “Extraordinary optical transmission through sub-wavelength hole arrays,” Nature391(6668), 667–669 (1998). [CrossRef]
  2. W. L. Barnes, A. Dereux, and T. W. Ebbesen, “Surface plasmon subwavelength optics,” Nature424(6950), 824–830 (2003). [CrossRef] [PubMed]
  3. W. Wu, A. Bonakdar, and H. Mohseni, “Plasmonic enhanced quantum well infrared photodetector with high detectivity,” Appl. Phys. Lett.96(16), 161107 (2010). [CrossRef]
  4. C. Genet and T. W. Ebbesen, “Light in tiny holes,” Nature445(7123), 39–46 (2007). [CrossRef] [PubMed]
  5. K. Okamoto, I. Niki, A. Shvartser, Y. Narukawa, T. Mukai, and A. Scherer, “Surface-plasmon-enhanced light emitters based on InGaN quantum wells,” Nat. Mater.3(9), 601–605 (2004). [CrossRef] [PubMed]
  6. B. Levine, “Quantum‐well infrared photodetectors,” J. Appl. Phys.74(8), R1–R81 (1993). [CrossRef]
  7. S. A. Maier, Plasmonics: fundamentals and applications (Springer, 2007).
  8. T. Thio, H. Ghaemi, H. Lezec, P. Wolff, and T. Ebbesen, “Surface-plasmon-enhanced transmission through hole arrays in Cr films,” J. Opt. Soc. Am B.16(10), 1743–1748 (1999). [CrossRef]
  9. P. A. Hobson, S. Wedge, J. A. Wasey, I. Sage, and W. L. Barnes, “Surface Plasmon Mediated Emission from Organic Light‐Emitting Diodes,” Adv. Mater.14(19), 1393–1396 (2002). [CrossRef]
  10. H. J. Lezec and T. Thio, “Diffracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays,” Opt. Express12(16), 3629–3651 (2004). [CrossRef] [PubMed]
  11. M. Treacy, “Dynamical diffraction explanation of the anomalous transmission of light through metallic gratings,” Phys. Rev. B66(19), 195105 (2002). [CrossRef]
  12. Z. Ruan and M. Qiu, “Enhanced transmission through periodic arrays of subwavelength holes: the role of localized waveguide resonances,” Phys. Rev. Lett.96(23), 233901 (2006). [CrossRef] [PubMed]
  13. F. Gu, L. Zhang, X. Yin, and L. Tong, “Polymer single-nanowire optical sensors,” Nano Lett.8(9), 2757–2761 (2008). [CrossRef] [PubMed]
  14. C. Peng, Y. Liang, K. Sakai, S. Iwahashi, and S. Noda, “Three-dimensional coupled-wave theory analysis of a centered-rectangular lattice photonic crystal laser with a transverse-electric-like mode,” Phys. Rev. B86(3), 035108 (2012). [CrossRef]
  15. S. Kalchmair, R. Gansch, S. I. Ahn, A. M. Andrews, H. Detz, T. Zederbauer, E. Mujagić, P. Reininger, G. Lasser, W. Schrenk, and G. Strasser, “Detectivity enhancement in quantum well infrared photodetectors utilizing a photonic crystal slab resonator,” Opt. Express20(5), 5622–5628 (2012). [CrossRef] [PubMed]
  16. E. D. Palik, Handbook of Optical Constants of Solids: Index (Academic press, 1998).
  17. S.-H. Chang, S. Gray, and G. Schatz, “Surface plasmon generation and light transmission by isolated nanoholes and arrays of nanoholes in thin metal films,” Opt. Express13(8), 3150–3165 (2005). [CrossRef] [PubMed]
  18. S. C. Lee, S. Krishna, and S. R. Brueck, “Quantum dot infrared photodetector enhanced by surface plasma wave excitation,” Opt. Express17(25), 23160–23168 (2009). [CrossRef] [PubMed]
  19. V. Canpean and S. Astilean, “Multifunctional plasmonic sensors on low-cost subwavelength metallic nanoholes arrays,” Lab Chip9(24), 3574–3579 (2009). [CrossRef] [PubMed]
  20. K.-L. Lee, S.-H. Wu, and P.-K. Wei, “Intensity sensitivity of gold nanostructures and its application for high-throughput biosensing,” Opt. Express17(25), 23104–23113 (2009). [CrossRef] [PubMed]
  21. H. Ghaemi, T. Thio, D. Grupp, T. W. Ebbesen, and H. Lezec, “Surface plasmons enhance optical transmission through subwavelength holes,” Phys. Rev. B58(11), 6779–6782 (1998). [CrossRef]
  22. C. Genet, M. P. van Exter, and J. Woerdman, “Fano-type interpretation of red shifts and red tails in hole array transmission spectra,” Opt. Commun.225(4-6), 331–336 (2003). [CrossRef]
  23. U. Fano, “Effects of configuration interaction on intensities and phase shifts,” Phys. Rev.124(6), 1866–1878 (1961). [CrossRef]
  24. A. W. Snyder and J. Love, Optical waveguide theory (Springer, 1983).
  25. J. Andersson and L. Lundqvist, “Grating-coupled quantum-well infrared detectors: Theory and performance,” J. Appl. Phys.71(7), 3600–3610 (1992). [CrossRef]
  26. L. Lundqvist, J. Andersson, Z. Paska, J. Borglind, and D. Haga, “Efficiency of grating coupled AlGaAs/GaAs quantum well infrared detectors,” Appl. Phys. Lett.63(24), 3361–3363 (1993). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited