Mass-producible and efficient optical antennas with CMOS-fabricated nanometer-scale gap

Abstract

Optical antennas have been widely used for sensitive photodetection, efficient light emission, high resolution imaging, and biochemical sensing because of their ability to capture and focus light energy beyond the diffraction limit. However, widespread application of optical antennas has been limited due to lack of appropriate methods for uniform and large area fabrication of antennas as well as difficulty in achieving an efficient design with small mode volume (gap spacing < 10nm). Here, we present a novel optical antenna design, arch-dipole antenna, with optimal radiation efficiency and small mode volume, 5 nm gap spacing, fabricated by CMOS-compatible deep-UV spacer lithography. We demonstrate strong surface-enhanced Raman spectroscopy (SERS) signal with an enhancement factor exceeding 10⁸ from the arch-dipole antenna array, which is two orders of magnitude stronger than that from the standard dipole antenna array fabricated by e-beam lithography. Since the antenna gap spacing, the critical dimension of the antenna, can be defined by deep-UV lithography, efficient optical antenna arrays with nanometer-scale gap can be mass-produced using current CMOS technology.

Enabling Ideal Selective Solar Absorption with 2D Metallic Dielectric Photonic Crystals

“…In Figure S1(d), a XeF 2 gas phased etch is used to etch the Poly Si only, thus leaving free-standing Al 2 O 3 cylindrical shells on the wafer surface. [23,24,34] Next, in Figure S1 Images of the device during and after fabrication are shown in Figure S2. In Figure S2(a) the photoresist is patterned with a square checkerboard photomask with a period 0.6 µm.…”

“…[2,22] Photos and SEM images of the 3 device are shown in Figure 1(c)-(f) where the multilayered structure was fabricated using the sidewall lithography technique across a 6" wafer (see supporting information). [23][24][25] cut-off frequency, the design of the cavities is also based on Q-matching formalism where maximum absorption occurs when the radiative Q rad and the absorption Q abs are equal. [22,26] The measured absorption spectrum shown in MDPhC layer agrees well with experiment, but diverges for , where transmission through the metal layer can no longer be assumed to be .…”

“…[2,22] Photos and SEM images of the device are shown in Figure 1(c)-(f) where the multilayered structure was fabricated using the sidewall lithography technique across a 6" wafer (see supporting information). [23][24][25] An 80 nm thick layer of ruthenium is used as the metal, which was deposited via atomic layer deposition (ALD) for conformal deposition purposes. The dielectric filling of HfO 2 is also deposited via ALD, and excess HfO 2 is removed via chemical mechanical polishing (CMP).…”

Comparison of Free-Space and Waveguide-Based SERS Platforms

“…Such Raman signals are, however, inherently weak. In the last decades, several methods have been developed to enhance Raman signals, such as coherent anti-Stokes scattering that relies on non-linear Raman scattering [1] or Surface-Enhanced Raman Spectroscopy (SERS) [2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Two types of SERS enhancement mechanisms have been proposed to explain the SERS effect—the electromagnetic (EM) mechanism and the chemical enhancement (CE) mechanism [16,17,18,19].…”

Waveguide excitation and collection of surface-enhanced Raman scattering from a single plasmonic antenna

“…However, most molecules have a very small Raman cross-section, resulting in extremely weak signals. Methods for enhancing these weak Raman signals have seen a tremendous progress over the last decades, typically based either on nonlinear Raman scattering processes, such as coherent anti-Stokes and stimulated Raman scattering [1,2], or on a strong local field enhancement, such as surface-enhanced Raman scattering [3][4][5][6][7][8][9][10][11][12][13][14][15] using either metals or dielectrics [16]. More recently, alternative geometries to the conventional microscope-based setup have been developed for collecting an increased amount of Raman scattering, such as hollow-core photonic crystal fibers [17] and nanophotonic waveguides on photonic integrated circuits (PICs) [18][19][20][21].…”