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Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 8 — Apr. 9, 2012
  • pp: 8700–8709

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Vanadium dioxide based plasmonic modulators

Luke A. Sweatlock and Kenneth Diest  »View Author Affiliations


Optics Express, Vol. 20, Issue 8, pp. 8700-8709 (2012)
http://dx.doi.org/10.1364/OE.20.008700


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Abstract

Actively tunable metal-insulator-metal waveguides that employ vanadium dioxide films as the active medium are analyzed numerically. Vanadium dioxide exhibits strong contrast between the optical properties of its insulating and metallic phases. In particular, the large optical absorption in the metallic phase makes it straightforward to implement broadband attenuation modulators and switches, but this strong loss can also complicate the design of other types of devices. We present a plasmonic waveguide that functions as an index modulator with Δn > 20% at λ0 = 1550nm (0.80 eV), by using a thin active layer to strike a balance between maximizing index contrast while mitigating attenuation. A second device is configured as a band-stop absorption modulator, taking advantage of symmetry to selectively suppress the TM1 and TM3 modes, with relatively minimal attenuation of the TM0 and TM2 modes.

© 2012 OSA

1. Introduction

Surface Plasmon Polaritons (SPPs) are a form of electromagnetic surface waves that have been studied extensively for their ability to achieve high field concentration of optical-frequency fields, and circumvent the diffraction limit of traditional photonic devices. The compact nature of plasmonic waveguides allows such devices to be integrated on chip with electronic components and bridge the gap in size between individual electronic devices and photonic components. The field of “active plasmonics”, or integration of plasmonic waveguides with actively tunable materials, has been studied extensively in recent years [1

S. I. Bozhevolnyi, ed. Plasmonic nanoguides and circuits (Pan Stanford Publishing, 2008). [CrossRef]

–4

J. A. Dionne, L. A. Sweatlock, M. T. Sheldon, A. P. Alivisatos, and H. A. Atwater, “Silicon-based plasmonics for on-chip photonics,” IEEE J. Sel. Top. Quantum Electron. 16, 295–306 (2010) [CrossRef]

], allowing one to manipulate optical signals at the nano-scale and therefore representing one promising avenue toward functional nanophotonic circuits.

One plasmonic device archetype is the the planar Metal-Insulator-Metal (MIM) waveguide [5

J. A. Dionne, L. A. Sweatlock, A. Polman, and H. A. Atwater, “Plasmon slot waveguides: towards chip-scale propagation with subwavelength-scale localization,” Phys. Rev. B 73, 035407 (2006). [CrossRef]

]. By changing the individual materials used within the device as well as engineering the relative layer thicknesses, the dispersion of the device can be tuned over a wide range of visible and infrared frequencies. By incorporating active materials as the dielectric layer within the waveguide, the metal layers act as both optical cladding and electrical contacts. Generally speaking, MIM waveguides are suitable to make very small electrooptical devices, as small changes in the waveguide index can significantly impact the SPP propagation length and wavevector. This structure has been utilized to produce tunable color filters using lithium niobate as the active medium [6

K. Diest, J. A. Dionne, M. Spain, and H. A. Atwater, “Tunable color filters based on metal-insulator-metal resonators,” Nano Lett. 9, 2579–2583 (2009). [CrossRef] [PubMed]

], electro-optic switches employing doped silicon [7

J. A. Dionne, K. Diest, L. A. Sweatlock, and H. A. Atwater, “PlasMOStor: a metal-oxide-Si field effect plasmonic modulator,” Nano Lett. 9, 897–902 (2009). [CrossRef] [PubMed]

], and Mach-Zehnder interferometers employing a non-linear polymer [8

M. Pu, N. Yao, C. Hu, X. Xin, Z. Zhao, C. Wang, and X. Luo, “Directional coupler and nonlinear Mach–Zehnder interferometer based on metal-insulator-metal plasmonic waveguide,” Opt. Express 18, 21030–21037 (2010). [CrossRef] [PubMed]

].

Another class of materials which has shown emerging promise in the field of active photonics is solid state phase change media. An example is vanadium dioxide (VO2), which undergoes a structural phase transition between an semiconducting monoclinic phase and a semi-metallic, tetragonal phase. This change can be induced thermally, electrically, or optically. The phase transition, when optically induced in a 50nm thin film, can occur on a time scale of less than 300fs. The reverse transition is governed primarily by relatively slow thermal cooling. Lysenko et al. report that the rate of recovery depends strongly on the thermal environment and optical pump intensity, observing relaxation times which vary from 3ns to 1ms under a range of conditions [9

S. Lysenko, A. Rua, F. Fernandez, and H. Liu, “Optical nonlinearity and structural dynamics of VO2 films,” J. Appl. Phys. 105, 043502 (2009). [CrossRef]

]. The phase transition is accompanied by a large change in the resistivity [10

J. Lappalainen, S. Heinilehto, S. Saukko, W. Lantto, and H. Jantunen, “Microstructure dependent switching properties of VO2 thin films,” Sens. Actuators, A 142, 250–255 (2008). [CrossRef]

] and electromagnetic permittivity [11

G. Xu, C. M. Huang, P. Jin, M. Tazawa, and D. M. Chen, “Nano-Ag on vanadium dioxide. I. Localized spectrum tailoring,” J. Appl. Phys. 104, 053101 (2008). [CrossRef]

]. VO2 has been integrated into active photonic devices including ring resonator based modulators [12

R. M. Briggs, I. M. Pryce, and H. A. Atwater, “Compact silicon photonic waveguide modulator based on the vanadium dioxide metal-insulator phase transition,” Opt. Express 18, 11192–11201 (2010). [CrossRef] [PubMed]

,13

J. Nag, J. D. Ryckman, M. T. Hertkorn, B. K. Choi, R. F. Haglund, and S. M. Weiss, “Ultrafast compact silicon-based ring resonator modulators using metal-insulator switching of vanadium dioxide,” Proc. SPIE 7597, 759710 (2010). [CrossRef]

], photonic crystals [14

V. G. Golubev, V. Y. Davydov, N. F. Kartenko, D. A. Kurdyukov, A. V. Medvedev, A. B. Pevtsov, A. V. Scherbakov, and E. B. Shadrin, “Phase transition-governed opal-VO2 photonic crystal,” Appl. Phys. Lett. 79, 2127–2129 (2001). [CrossRef]

], and strongly tunable plasmonic visible-light scatterers [15

D. Y. Lei, K. Appavoo, Y. Sonnefraud, R. F. Haglund Jr., and S. A. Maier, “Single-particle plasmon resonance spectroscopy of phase transition in vanadium dioxide,” Opt. Lett. 35, 3988–3990 (2010). [CrossRef] [PubMed]

]. Active metamaterial-based components incorporating VO2 include broadband terahertz filters [16

M. Seo, J. Kyoung, H. Park, S. Koo, H.-S. Kim, H. Bernien, B. J. Kim, J. H. Choe, Y. H. Ahn, H.-T. Kim, N. Park, Q.-H. Park, K. Ahn, and D.-S. Kim“Active terahertz nanoantennas based on VO2 phase transition,” Nano Lett. 10, 2064–2068 (2010). [CrossRef] [PubMed]

] and reconfigurable gradient index devices [17

M. D. Goldflam, T. Driscoll, B. Chapler, O. Khatib, N. M. Jokerst, S. Palit, D. R. Smith, B.-J. Kim, G. Seo, H.-T. Kim, M. Di Ventra, and D. N. Basov“Reconfigurable gradient index using VO2 memory metamaterials,” Appl. Phys. Lett. 99 044103 (2011). [CrossRef]

].

Neither of the two phases of VO2 would conventionally be considered an ideal constituent material for SPP waveguides. The monoclinic form VO2(M) is transparent but noticeably dispersive, while the tetragonal form VO2(T) is a lossy semi-metal which damps rather than supports surface waves. However, the optical properties of the two phases exhibit extremely high contrast; ellipsometric measurement [18

M. J. Dicken, K. Aydin, I. M. Pryce, L. A. Sweatlock, E. M. Boyd, S. Walavalkar, J. Ma, and H. A. Atwater, “Frequency tunable near-infrared metamaterials based on VO2 phase transition,” Opt. Express 17, 18330–18339 (2009). [CrossRef] [PubMed]

] indicates that at ω = 1550nm (0.80eV) the permittivity can be switched from ε(M) = (9.7 + 2.9i) to ε(T) = (−14.1 + 30.5i). Therefore, VO2 is a particularly promising material for manipulating light with a minimal volume of active material. An MIM waveguide in which the core is entirely composed of VO2 can make an effective broadband shutter or switch, since the VO2(T) phase renders even a short (length ≈ λ) section of waveguide essentially opaque. In this work, we explore the suitability of 4- and 5-layer MIM geometries that achieve other types of device actuation by using a thin VO2 active layer to strike a balance between maximizing index contrast while mitigating attenuation. We present a plasmonic waveguide that produces index modulation with Δn > 20% at λ0 = 1550nm (0.80 eV), and a band-stop absorption modulator that takes advantage of symmetry to selectively suppress only the TM1 and TM3 modes. The result illustrates the possibility for a broad variety of plasmonic devices incorporating solid state phase change active media.

2. Device calculations

The two planar plasmonic geometries studied are shown in Figs. 1 and 2 and were analyzed using numerical solutions of Maxwell’s Equations under steady state conditions. We consider transverse magnetic waves propagating in the direction x̂. The waveguide is 2-dimensional, consisting of N material layers enumerated l ∈ {1,2,...,N} stacked normal to the direction ẑ, and of infinite extent in ŷ. The top (l = N) and bottom (l = 1) layers are considered to be semi-infinite in the ẑ direction, corresponding to metallic cladding layers which are thick compared to the skin depth of surface waves. Intermediate or “core” layers have finite thickness t2,tl,...,tN–1. The total thicknesses of the devices studied here are 550nm and 420nm, respectively. This is thick enough so that at visible and near infrared frequencies the waveguides are multimode, supporting both a gap plasmon or TM0 mode, and one or more additional propagating TM modes with mixed photonic/plasmonic character.

Fig. 1 Normalized Ex fields of the optical modes supported from 0.5 – 3 eV within the 4-layer waveguide shown. Field calculations were performed using the optical properties of monoclinic VO2(M) (device off state).
Fig. 2 Normalized Ex fields of the optical modes supported from 0.5 – 3 eV within the 5-layer MIM waveguide shown. Field calculations were performed using the optical properties of monoclinic VO2(M) (device off state).

Each layer is composed of a material described by a potentially complex frequency dependent permittivity, εl(ω). The silver layers are modeled by interpolation to the Lorentz-Drude parameterization by Rakić et al. [19

A. D. Rakić, A. B. Djurišić, J. M. Elazar, and M. L. Majewski, “Optical properties of metallic films for vertical-cavity optoelectronic devices.” Appl. Opt. 37, 5271–5283 (1998). [CrossRef]

] of data from the Handbook of Optical Constants of Solids [20

D. W. Lynch and W. R. Hunter, “Comments on the optical constants of metals,” in Handbook of optical constants of solids , E. D. Palik, ed. (Academic, 1985) pp. 275–367.

]. The active layer is treated by direct ellipsometric measurement of VO2 films as grown on sapphire by pulsed laser deposition, reported previously [18

M. J. Dicken, K. Aydin, I. M. Pryce, L. A. Sweatlock, E. M. Boyd, S. Walavalkar, J. Ma, and H. A. Atwater, “Frequency tunable near-infrared metamaterials based on VO2 phase transition,” Opt. Express 17, 18330–18339 (2009). [CrossRef] [PubMed]

]; data corresponding to the monoclinic and tetragonal phases were taken at room temperature and 85 °C respectively. The passive component layers of the core are treated as a constant dielectric with index n = 1.6.

The propagation characteristics of these waveguides can be expressed as a dispersion relation, that is, an expression or graph relating complex-valued wavevector kx to real energies h̄ω. The energy is a parameter corresponding to monochromatic excitation of the guided mode, alternatively expressed as a free-space wavelength λ0 = (2πc)/ω. The wavevector describes the propagation of guided modes; the real part is inversely related to the mode effective wavelength,
λ=(2π)/𝔕{ kx}
(1)

The imaginary part of the wavevector is a measure of attenuation and can alternatively be expressed as a propagation length,
L=1/(2⋅𝔌{ kx})
(2)

We find the dispersion relation by analyzing a system of equations connecting kx and ω. Two sub-expressions involving kx are used for conciseness:
βl= kx2− εl ( ω/c)2 ηl=i kx/ βl
(3)

Then we take the following ansatz form for TM solutions of the wave equation, Eyl = Bxl = Bzl = 0, that are harmonic in the propagation direction and exponential in the transverse direction, cf. Economou [21

E. N Economou, “Surface plasmons in thin films,” Phys. Rev. , 182, 539–554 (1969). [CrossRef]

], and Raether [22

H. Raether, Surface plasmons on smooth and rough surfaces and on gratings (Springer-Verlag, 1988), pp. 4–7.

].
E xl= e i( kxx−ωt)[ alexp( βlz)+ blexp(− βlz)] E zl= ηl e i( kxx−ωt)[− alexp( βlz)+ blexp(− βlz)] B yl=− ω c kx εl E zl
(4)

This introduces a set of 2N unknowns: the two field coefficients al, bl for each material layer. Two constraints come from enforcing appropriate asymptotic behavior,
b1=0 aN=0
(5)

Electromagnetic boundary conditions give the remaining 2N – 2 constraints, namely, continuity of the tangential E field Ex,l = Ex,l+1 and normal D field εlEz,l = εl+1Ez,l+1 evaluated at every interface between layers. Let dl represent the ẑ coordinate of each of the (N – 1) interfaces. With the first interface at the origin by definition, d1 = 0, the position of the other boundaries is simply the sum of the underlying layer thicknesses, dl= ∑2l( tl) for l ∈ {2,...,(N – 1)}. Then the boundary value relations can be written in the form:
alexp( βl dl)+ blexp(− βl dl)= a l+1exp( β l+1 dl)+ b l+1exp(− β l+1 dl) εl ηl[− alexp( βl dl)+ blexp(− βl dl)]= ε l+1 η l+1[− a l+1exp( β l+1 dl)+ b l+1exp(− β l+1 dl)]
(6)

Consider that the undetermined coefficients are collected in a column vector, a = [a1, b1, a2, b2,..., aN, bN]T. Then the system of constraint equations can be written as a linear system,
𝕃a=0
(7)

Equation (6) contributes blocks 𝔸l : 𝔸l [al, bl, al+1, bl+1]T = 0,
𝔸l= ( exp( βl dl) exp(− βl dl) −exp( β l+1 dl) −exp(− β l+1 dl) − εl βlexp( βl dl) εl βlexp(− βl dl) ε l+1 β l+1exp( β l+1 dl) − ε l+1 β l+1exp(− β l+1 dl))
(8)

And therefore matrix 𝕃 has the form:
𝕃= ( 0 1 0 0 0 0 0 ⋯ 0 ⌈ 𝔸1 ⌉ 0 0 0 ⋯ 0 ⌊ ⌋ 0 0 0 ⋯ 0 0 0 ⌈ 𝔸2 ⌉ 0 ⋯ 0 0 0 ⌊ ⌋ 0 ⋯ 0 ⋮ ⋱ ⋮ 0 ⋯ 0 0 0 ⌈ 𝔸 N−1 ⌉ 0 ⋯ 0 0 0 ⌊ ⌋ 0 ⋯ 0 0 0 0 0 1 0)
(9)

The first and last rows come from Eq. (5). Waveguide modes allowed by the system of boundary conditions correspond to the cases in which matrix 𝕃 is singular, and therefore solutions to Eq. (7) are non-unique. Generally speaking, such solutions of det(𝕃) = 0 exist in the domain where both wavevector and frequency are complex valued. Here, we impose the additional constraint that frequency, ω, is strictly real, an appropriate convention for analysis of steady state illumination by monochromatic light. Given ω real, we must search for approximate solutions, |det(𝕃)| ≤ δ ≈ 0. Following the solution technique developed by Dionne [5

J. A. Dionne, L. A. Sweatlock, A. Polman, and H. A. Atwater, “Plasmon slot waveguides: towards chip-scale propagation with subwavelength-scale localization,” Phys. Rev. B 73, 035407 (2006). [CrossRef]

] we discretize the plane (𝔕{kx},ω) and use numerical minimization to solve for the value of the imaginary part 𝔌{kx} that minimizes |det(𝕃)| at each point. At this step, every point in the plane now has an associated value of |det(𝕃)|. The next step is to apply a criteria to select the subset of points at which the determinant is sufficiently small. In this work, rather than attempt to define a global solution tolerance δ appropriate for a wide range of waveguide conditions and frequencies, we instead use a peak-finding algorithm to identify a locus of points at which |det(𝕃)| is minimized locally in the plane. We consider “solutions” to be points which are members of this set and that additionally meet the condition 𝔕{kx} > 𝔌{kx}.

In dispersion diagrams, Figs. 3 and 4 we display these solutions in two different projections. The top panel of each figure is a conventional view; the horizontal axis is the real part of wavevector 𝔕{kx} and the vertical axis is energy h̄ω. As points of reference, dotted horizontal lines indicate several benchmark energies of 1.825eV, 1.266eV, and 0.8eV corresponding to excitation wavelengths 680nm, 980nm, and 1550nm repectively. A diagonal marks the lightline corresponding to index n = 1.6, which qualitatively divides the space into photonic modes in the region to the upper-left and plasmonic modes on the lower-right. The color scale is defined by a logarithmic figure of merit,
f= log 10 𝔕{ kx} 𝔌{ kx}
(10)

Fig. 3 Dispersion calculations for the MIM waveguide in Fig. 1 for VO2 in the device off (a) and on (b) states. The bottom panels in (a) and (b) show the corresponding figures of merit f = log10(𝔕{kx}/𝔌{kx}), as a function of wavevector. The colormap in each panel is scales so that “white” points corresponds to a f < 0 and “black” points to f > 2.
Fig. 4 Dispersion calculations for the MIM waveguide in Fig. 2 for VO2 in the device off (a) and on (b) states. The bottom panels in (a) and (b) show the corresponding figures of merit f = log10(𝔕{kx}/𝔌{kx}), as a function of wavevector. The colormap in each panel is scales so that “white” points correspond to a f < 0 and “black” points to f > 2.

Points colored in black have a f > 2, meaning that the energy attenuation length is hundreds of times longer than the modal wavelength. Since nanophotonic functional elements may be on the order of ten wavelengths in size, these are applicable for a variety of devices or even small scale integrated networks. Points colored in light grey have an f value around 1, not ideal for guided wave systems, but suitable for MIM metamaterials only a few wavelengths thick. The color scale fades to white at f ≤ 0, at which point the energy attenuation length is comparable to the modal wavelength. The bottom panel of our graphical dispersion relations are an alternate projection of the data along the axes (𝔕{kx}, f). This view doubles as a color scale, since the grey-scale color intensity is linear with the vertical axis. It is also useful for graphically estimating the cut-off wavevector (horizontal axis intercept) for each branch, and for comparing side by side the f of the off (left column) and on (right column) device states.

We assign mode labels (TM0, TM1, etc.) to connected sets or “branches” of solutions by observing the periodicity of electric fields along the ẑ axis. At any given solution point on the dispersion curve β(kx,ω) is determined by Eq. (3), and the fields are found by solving system Eq. (7) for the vector of coefficients a, given β and one additional arbitrary assumption to fix the fields’ absolute magnitude, e.g. a1 = 1. The fields can be generated by iteration, solving the pair of equations Eq. (6) for al+1 and bl+1 in terms of al and bl.

3. Device performance

3.1. Index modulation

The first structure studied is shown in Fig. 1. Here, optically thick silver films form the top and bottom layers of the device, with 50 nm of VO2 and 500 nm of a dielectric layer with n = 1.6 and k ≃ 0 (such as silicon dioxide or sapphire) as the waveguide core. The normalized Ex fields of the optical modes supported within this structure from 0.5 – 3 eV are plotted as a function of position within the waveguide, to the right of the structure in Fig. 1. Here, the TM0 through TM4 mode profiles correspond to those in the dispersion diagram shown in Fig. 3. These calculations correspond to VO2(M) in the monoclinic phase, and each mode profile was plotted at an energy (see legend) which is neither close to mode cutoff, nor to the lightline. We consider the electric field profiles shown here to be typical, as generally the field distributions were observed to be qualitatively similar among all points common to a given branch. Interesting exceptions include near-crossing points and the transition of TM1 from photonic (maximum intensity in core) to plasmonic (maximum intensity at surface) character as it crosses the lightline.

The dispersion diagram corresponding to the structure in Fig. 1 is shown in the top panels of Fig. 3. Figure 3(a) illustrates the allowable modes that characterize the plasmonic modulator when the active layer is in the semiconducting monoclinic phase VO2(M), while Fig. 3(b) characterizes the modulator when the active layer is in the semi-metallic tetragonal phase VO2(T). To illustrate the switching behavior of this device, three specific operating points are analyzed: 1.825eV, 1.266eV, and 0.8eV. The mode index and figure of merit f corresponding to points A through F in Fig. 3 are listed in Table 1.

Table 1  MIM Modal Properties from Figure 3.
PointOperating PointMode TypeMode Indexf[log10]Δn
A0.80 eV (1550 nm)TM11.2319
B0.80 eV (1550 nm)TM10.967.222%
C1.27 eV (980 nm)SPP2.214.2
D1.27 eV (980 nm)SPP1.681924%
E1.83 eV (600 nm)TM31.039.7mode driven into cutoff
F1.83 eV (600 nm)TM30.411.2

Of particular interest in this diagram is the pair of points A and B, representing the transmission of infrared light with photon energy of 0.80eV, propagating in the form of a fundamental TM1 photonic mode. Figure 3 and Table 1 both show a 22% difference in the mode index between points A and B. Strong index modulation is also observed at points C and D, representing the transmission of infrared light at 1.27eV, propagating in the form of a surface plasmon polariton (SPP) mode. Finally, a distinct mode of operation is indicated by the pair of points E and F, representing the transmission of visible light at 1.83eV, propagating in the form of a higher order TM3 photonic mode. When the device is activated, this mode is attenuated to the point of critically damping the propagation of energy in the device, and pushing it into “cutoff”. Under these operating conditions, the device can be used as an attenuation modulator with an on/off ratio of 9 dB.

3.2. Mode-selective attenuation modulator

The second structure studied is shown in Fig. 2. As in Section 3.1, optically thick silver films form the top and bottom layers of the device; however, the waveguide core is now comprised of 200 nm of n = 1.6 and k ≃ 0 dielectric above and below a 20 nm layer of VO2 in the waveguide center. Again, the normalized Ex fields of the optical modes supported within this structure from 0.5 – 3 eV are plotted as a function of position within the waveguide, to the right of the structure in Fig. 2. For this device, only four optical modes are supported, and the plots correspond to VO2 in the monoclinic phase. In this device configuration, a key operating principle is that only the “odd-numbered” modes have an electric field maximum in the active layer, and therefore are selectively sensitive to actuation.

The corresponding dispersion diagram for the structure in Fig. 2 is shown in Fig. 4. As in the previous section, Fig. 4(a) illustrates the allowable modes that characterize the 5-layer plasmonic modulator when the active layer is in the VO2(M) phase, while Fig. 4(b) characterizes the modulator when the active layer is in the VO2(T) phase. To illustrate the switching behavior of this device, pairs of points were analyzed at 0.80 and 0.94eV. The performance characteristics at those operating points are tabulated in Table 2.

Table 2  MIM Modal Properties from Figure 4.
PointOperating PointMode TypeMode Indexf[log10]Δn
A0.80 eV (1550 nm)TM10.744.3TM1 mode suppressed
B0.80 eV (1550 nm)N/A—¡0.01
C0.94 eV (1310 nm)TM11.1314TM1 mode suppressed
D0.94 eV (1310 nm)N/A—¡0.01

The lower panel of Fig. 4(a) and (b) again corresponds to the figure of merit f for each optical mode in the respective dispersion diagram directly above, with the grayscale color limits limits (0 < f < 2). Unlike the previous device, the actuation of this structure causes a major perturbation to the optical mode spectrum allowed within the device. As a result, the lowest order photonic mode (TM1) is essentially no longer supported in the waveguide when the vanadium dioxide is switched to its tetragonal phase. This is illustrated at the pair of points A and B. Point A represents the guiding of infrared light at 0.80eV. Point B indicates total absence of a TM1 mode at this photon energy, as seen in Fig 4(b). Points C and D illustrate the same effect at 0.94eV. Therefore, assuming the use of mode-selective insertion this device can be used as a band-stop attenuation modulator with an on/off ratio over 20 dB.

4. Conclusions

Two dynamically tunable MIM waveguides have been presented that employ vanadium dioxide thin films as the active element. The 4-layer asymmetric device geometry notably can function as an index modulator, in which the balance of index modulation performance against parasitic attenuation can be engineered through variations on this design, specifically, by varying the thickness of the active layer. Here, the device we discuss in detail was configured with relatively high Δn on the order of 20% for the SPP and TM1 mode. The device also provides strong control over the cutoff frequency of guided modes.

The second device geometry studied was a symmetric 5-layer stack with active vanadium dioxide layer at the core. By switching the vanadium dioxide layer to its metallic phase, the TM1 photonic mode is strongly suppressed. This results in an on/off ratio of > 20 dB when the appropriate operating wavelengths are chosen. A notable feature of this configuration is the mode-selective nature of the device, which can be used to achieve band-stop filtering action.

Acknowledgments

A portion of the technology which is discussed in this manuscript is the subject of one or more pending patent applications. We gratefully acknowledge Dr. Ryan Briggs, Prof. Nader Engheta, Dr. James Ma, Dr. Merrielle Spain, and Dr. Daniel Marthaler for a number of stimulating discussions, and especially thank Prof. Jennifer Dionne and Dr. Sarah Sweatlock for invaluable advice on implementation of numerical methods.

References and links

1.

S. I. Bozhevolnyi, ed. Plasmonic nanoguides and circuits (Pan Stanford Publishing, 2008). [CrossRef]

2.

M. L. Brongersma and P. G. Kik, eds. Surface plasmon nanophotonics (Springer, 2007). [CrossRef]

3.

K. F. MacDonald and N. I. Zheludev, “Active plasmonics: current status,” Laser Photonics Rev. 4, 562–567 (2010). [CrossRef]

4.

J. A. Dionne, L. A. Sweatlock, M. T. Sheldon, A. P. Alivisatos, and H. A. Atwater, “Silicon-based plasmonics for on-chip photonics,” IEEE J. Sel. Top. Quantum Electron. 16, 295–306 (2010) [CrossRef]

5.

J. A. Dionne, L. A. Sweatlock, A. Polman, and H. A. Atwater, “Plasmon slot waveguides: towards chip-scale propagation with subwavelength-scale localization,” Phys. Rev. B 73, 035407 (2006). [CrossRef]

6.

K. Diest, J. A. Dionne, M. Spain, and H. A. Atwater, “Tunable color filters based on metal-insulator-metal resonators,” Nano Lett. 9, 2579–2583 (2009). [CrossRef] [PubMed]

7.

J. A. Dionne, K. Diest, L. A. Sweatlock, and H. A. Atwater, “PlasMOStor: a metal-oxide-Si field effect plasmonic modulator,” Nano Lett. 9, 897–902 (2009). [CrossRef] [PubMed]

8.

M. Pu, N. Yao, C. Hu, X. Xin, Z. Zhao, C. Wang, and X. Luo, “Directional coupler and nonlinear Mach–Zehnder interferometer based on metal-insulator-metal plasmonic waveguide,” Opt. Express 18, 21030–21037 (2010). [CrossRef] [PubMed]

9.

S. Lysenko, A. Rua, F. Fernandez, and H. Liu, “Optical nonlinearity and structural dynamics of VO2 films,” J. Appl. Phys. 105, 043502 (2009). [CrossRef]

10.

J. Lappalainen, S. Heinilehto, S. Saukko, W. Lantto, and H. Jantunen, “Microstructure dependent switching properties of VO2 thin films,” Sens. Actuators, A 142, 250–255 (2008). [CrossRef]

11.

G. Xu, C. M. Huang, P. Jin, M. Tazawa, and D. M. Chen, “Nano-Ag on vanadium dioxide. I. Localized spectrum tailoring,” J. Appl. Phys. 104, 053101 (2008). [CrossRef]

12.

R. M. Briggs, I. M. Pryce, and H. A. Atwater, “Compact silicon photonic waveguide modulator based on the vanadium dioxide metal-insulator phase transition,” Opt. Express 18, 11192–11201 (2010). [CrossRef] [PubMed]

13.

J. Nag, J. D. Ryckman, M. T. Hertkorn, B. K. Choi, R. F. Haglund, and S. M. Weiss, “Ultrafast compact silicon-based ring resonator modulators using metal-insulator switching of vanadium dioxide,” Proc. SPIE 7597, 759710 (2010). [CrossRef]

14.

V. G. Golubev, V. Y. Davydov, N. F. Kartenko, D. A. Kurdyukov, A. V. Medvedev, A. B. Pevtsov, A. V. Scherbakov, and E. B. Shadrin, “Phase transition-governed opal-VO2 photonic crystal,” Appl. Phys. Lett. 79, 2127–2129 (2001). [CrossRef]

15.

D. Y. Lei, K. Appavoo, Y. Sonnefraud, R. F. Haglund Jr., and S. A. Maier, “Single-particle plasmon resonance spectroscopy of phase transition in vanadium dioxide,” Opt. Lett. 35, 3988–3990 (2010). [CrossRef] [PubMed]

16.

M. Seo, J. Kyoung, H. Park, S. Koo, H.-S. Kim, H. Bernien, B. J. Kim, J. H. Choe, Y. H. Ahn, H.-T. Kim, N. Park, Q.-H. Park, K. Ahn, and D.-S. Kim“Active terahertz nanoantennas based on VO2 phase transition,” Nano Lett. 10, 2064–2068 (2010). [CrossRef] [PubMed]

17.

M. D. Goldflam, T. Driscoll, B. Chapler, O. Khatib, N. M. Jokerst, S. Palit, D. R. Smith, B.-J. Kim, G. Seo, H.-T. Kim, M. Di Ventra, and D. N. Basov“Reconfigurable gradient index using VO2 memory metamaterials,” Appl. Phys. Lett. 99 044103 (2011). [CrossRef]

18.

M. J. Dicken, K. Aydin, I. M. Pryce, L. A. Sweatlock, E. M. Boyd, S. Walavalkar, J. Ma, and H. A. Atwater, “Frequency tunable near-infrared metamaterials based on VO2 phase transition,” Opt. Express 17, 18330–18339 (2009). [CrossRef] [PubMed]

19.

A. D. Rakić, A. B. Djurišić, J. M. Elazar, and M. L. Majewski, “Optical properties of metallic films for vertical-cavity optoelectronic devices.” Appl. Opt. 37, 5271–5283 (1998). [CrossRef]

20.

D. W. Lynch and W. R. Hunter, “Comments on the optical constants of metals,” in Handbook of optical constants of solids , E. D. Palik, ed. (Academic, 1985) pp. 275–367.

21.

E. N Economou, “Surface plasmons in thin films,” Phys. Rev. , 182, 539–554 (1969). [CrossRef]

22.

H. Raether, Surface plasmons on smooth and rough surfaces and on gratings (Springer-Verlag, 1988), pp. 4–7.

OCIS Codes
(230.4110) Optical devices : Modulators
(240.6680) Optics at surfaces : Surface plasmons
(240.3990) Optics at surfaces : Micro-optical devices

ToC Category:
Optics at Surfaces

History
Original Manuscript: January 5, 2012
Revised Manuscript: March 5, 2012
Manuscript Accepted: March 6, 2012
Published: March 30, 2012

Citation
Luke A. Sweatlock and Kenneth Diest, "Vanadium dioxide based plasmonic modulators," Opt. Express 20, 8700-8709 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-8-8700


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References

  1. S. I. Bozhevolnyi, ed. Plasmonic nanoguides and circuits (Pan Stanford Publishing, 2008). [CrossRef]
  2. M. L. Brongersma and P. G. Kik, eds. Surface plasmon nanophotonics (Springer, 2007). [CrossRef]
  3. K. F. MacDonald and N. I. Zheludev, “Active plasmonics: current status,” Laser Photonics Rev.4, 562–567 (2010). [CrossRef]
  4. J. A. Dionne, L. A. Sweatlock, M. T. Sheldon, A. P. Alivisatos, and H. A. Atwater, “Silicon-based plasmonics for on-chip photonics,” IEEE J. Sel. Top. Quantum Electron.16, 295–306 (2010) [CrossRef]
  5. J. A. Dionne, L. A. Sweatlock, A. Polman, and H. A. Atwater, “Plasmon slot waveguides: towards chip-scale propagation with subwavelength-scale localization,” Phys. Rev. B73, 035407 (2006). [CrossRef]
  6. K. Diest, J. A. Dionne, M. Spain, and H. A. Atwater, “Tunable color filters based on metal-insulator-metal resonators,” Nano Lett.9, 2579–2583 (2009). [CrossRef] [PubMed]
  7. J. A. Dionne, K. Diest, L. A. Sweatlock, and H. A. Atwater, “PlasMOStor: a metal-oxide-Si field effect plasmonic modulator,” Nano Lett.9, 897–902 (2009). [CrossRef] [PubMed]
  8. M. Pu, N. Yao, C. Hu, X. Xin, Z. Zhao, C. Wang, and X. Luo, “Directional coupler and nonlinear Mach–Zehnder interferometer based on metal-insulator-metal plasmonic waveguide,” Opt. Express18, 21030–21037 (2010). [CrossRef] [PubMed]
  9. S. Lysenko, A. Rua, F. Fernandez, and H. Liu, “Optical nonlinearity and structural dynamics of VO2 films,” J. Appl. Phys.105, 043502 (2009). [CrossRef]
  10. J. Lappalainen, S. Heinilehto, S. Saukko, W. Lantto, and H. Jantunen, “Microstructure dependent switching properties of VO2 thin films,” Sens. Actuators, A142, 250–255 (2008). [CrossRef]
  11. G. Xu, C. M. Huang, P. Jin, M. Tazawa, and D. M. Chen, “Nano-Ag on vanadium dioxide. I. Localized spectrum tailoring,” J. Appl. Phys.104, 053101 (2008). [CrossRef]
  12. R. M. Briggs, I. M. Pryce, and H. A. Atwater, “Compact silicon photonic waveguide modulator based on the vanadium dioxide metal-insulator phase transition,” Opt. Express18, 11192–11201 (2010). [CrossRef] [PubMed]
  13. J. Nag, J. D. Ryckman, M. T. Hertkorn, B. K. Choi, R. F. Haglund, and S. M. Weiss, “Ultrafast compact silicon-based ring resonator modulators using metal-insulator switching of vanadium dioxide,” Proc. SPIE7597, 759710 (2010). [CrossRef]
  14. V. G. Golubev, V. Y. Davydov, N. F. Kartenko, D. A. Kurdyukov, A. V. Medvedev, A. B. Pevtsov, A. V. Scherbakov, and E. B. Shadrin, “Phase transition-governed opal-VO2 photonic crystal,” Appl. Phys. Lett.79, 2127–2129 (2001). [CrossRef]
  15. D. Y. Lei, K. Appavoo, Y. Sonnefraud, R. F. Haglund, and S. A. Maier, “Single-particle plasmon resonance spectroscopy of phase transition in vanadium dioxide,” Opt. Lett.35, 3988–3990 (2010). [CrossRef] [PubMed]
  16. M. Seo, J. Kyoung, H. Park, S. Koo, H.-S. Kim, H. Bernien, B. J. Kim, J. H. Choe, Y. H. Ahn, H.-T. Kim, N. Park, Q.-H. Park, K. Ahn, and D.-S. Kim“Active terahertz nanoantennas based on VO2 phase transition,” Nano Lett.10, 2064–2068 (2010). [CrossRef] [PubMed]
  17. M. D. Goldflam, T. Driscoll, B. Chapler, O. Khatib, N. M. Jokerst, S. Palit, D. R. Smith, B.-J. Kim, G. Seo, H.-T. Kim, M. Di Ventra, and D. N. Basov“Reconfigurable gradient index using VO2 memory metamaterials,” Appl. Phys. Lett.99044103 (2011). [CrossRef]
  18. M. J. Dicken, K. Aydin, I. M. Pryce, L. A. Sweatlock, E. M. Boyd, S. Walavalkar, J. Ma, and H. A. Atwater, “Frequency tunable near-infrared metamaterials based on VO2 phase transition,” Opt. Express17, 18330–18339 (2009). [CrossRef] [PubMed]
  19. A. D. Rakić, A. B. Djurišić, J. M. Elazar, and M. L. Majewski, “Optical properties of metallic films for vertical-cavity optoelectronic devices.” Appl. Opt.37, 5271–5283 (1998). [CrossRef]
  20. D. W. Lynch and W. R. Hunter, “Comments on the optical constants of metals,” in Handbook of optical constants of solids, E. D. Palik, ed. (Academic, 1985) pp. 275–367.
  21. E. N Economou, “Surface plasmons in thin films,” Phys. Rev., 182, 539–554 (1969). [CrossRef]
  22. H. Raether, Surface plasmons on smooth and rough surfaces and on gratings (Springer-Verlag, 1988), pp. 4–7.

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