Abstract
The design of bowtie antennas for carbon nanotube (CNT) photodetectors has been investigated. CNT photodetectors have shown outstanding performance by using CNT as sensing element. However, detection wavelength is much larger than the diameter of the CNT, resulting in small fill factor. Bowtie antenna can confine light into a subwavelength volume based on plasmonic resonance, thus integrating a bowtie antenna to CNT photodetectors can highly improve photoresponse of the detectors. The electric field enhancement of bowtie antennas was calculated using the device geometry by considering fabrication difficulties and photodetector structure. It is shown that the electric field intensity enhancement increased exponentially with distance reduction between the CNT photodetector to the antenna. A redshift of the peak resonance wavelength is predicted due to the increase of tip angles of the bowtie antennas. Experimental results showed that photocurrent enhancement agreed well with theoretical calculations. Bowtie antennas may find wide applications in nanoscale photonic sensors.
Highlights
With the development of nanotechnologies, one-dimensional (1D) materials, including nanowires and nanotubes, emerged as important components in photonics and optoelectronics [1]
We have demonstrated that carbon nanotube (CNT) photodetectors exhibited outstanding performance to detect IR signals, and the sensitivity of photodetectors with asymmetric metal structure was much better than the ones with symmetric metal structures [22]
The design of bowtie antennas integrating to the CNT photodetectors was studied
Summary
With the development of nanotechnologies, one-dimensional (1D) materials, including nanowires and nanotubes, emerged as important components in photonics and optoelectronics [1]. The radial sizes of CNTs are much smaller than detection wavelengths, resulting in low fill factor and responsivity. Motivated by this challenge, optical antennas were designed to integrate with CNT photodetectors so as to bridge the gap between nanosize sensing elements and microsize wavelengths. Optical antennas can confine strong optical near fields in a volume far below a cubic wavelength of excitation light. This can greatly enhance photon absorption owing to the increase of coupling between CNT and vibrating electrical fields of photons. By integrating CNT photodetectors with optical antennas, the nanoscale photodetectors can be made with outstanding performance and photon absorption efficiency
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