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Ultraviolet and visible integrated photonics enable applications in quantum information, sensing, and spectroscopy, among others. Few materials support low-loss photonics into the UV, and the relatively low refractive index of known depositable materials limits the achievable functionality. Here, we present a high-index integrated photonics platform based on HfO2and Al2O3composites deposited via atomic layer deposition (ALD) with low loss in the visible and near UV. We show that Al2O3incorporation dramatically decreases bulk loss compared to pure HfO2, consistent with inhibited crystallization due to the admixture of Al2O3. Composites exhibit refractive indexnfollowing the average of that of HfO2and Al2O3, weighted by the HfO2fractional compositionx. Atλ = 375 nm, composites withx = 0.67 exhibitn = 2.01, preserving most of HfO2’s significantly higher index, and 3.8(7) dB/cm material loss. We further present fully etched and cladded waveguides, grating couplers, and ring resonators, realizing a single-mode waveguide loss of 0.25(2) dB/cm inferred from resonators of 2.6 million intrinsic quality factor atλ = 729 nm, 2.6(2) dB/cm atλ = 405 nm, and 7.7(6) dB/cm atλ = 375 nm. We measure the composite’s thermo-optic coefficient (TOC) to be 2.44(3) × 10−5RIU/°C nearλ = 397 nm. This work establishes (HfO2)x(Al2O3)1−xcomposites as a platform amenable to integration for low-loss, high-index photonics spanning the UV to NIR.
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High Performance Multiwall Carbon Nanotube–Insulator–Metal Tunnel Diode Arrays for Optical Rectification
Abstract This work reports important fundamental advancements in multiwall carbon nanotube (MWCNT) rectenna devices by creating and optimizing new diode structures to allow optical rectification with air‐stable devices. The incorporation of double‐insulator layer tunnel diodes, fabricated for the first time on MWCNT arrays, enables the use of air‐stable top metals (Al and Ag) with excellent asymmetry for rectification applications. Asymmetry is increased by as much as 10 times, demonstrating the effectiveness of incorporating multiple dielectric layers to control electron tunneling in MWCNT diode structures. MWCNT tip opening also reduces device resistance up to 75% due to an increase in diode contact area to MWCNT inner walls. This effect is consistent for different oxide materials and thicknesses. A number of insulator layers, including Al2O3, HfO2, TiO2, ZnO, and ZrO2, in both single‐ and then double‐insulator configurations are tested. Resistance increases exponentially with insulator thickness and decreases with electron affinity. These results are used to characterize double‐insulator diode performance. Finally, for the most asymmetric device structure, Al2O3‐HfO2(4/4 nm), optical rectification at a frequency of 470 THz (638 nm) is demonstrated. These results open the door for designing efficient MWCNT rectenna devices with more material flexibility, including air‐stable, transparent, and conductive top electrode materials.
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- Award ID(s):
- 1748413
- PAR ID:
- 10050254
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Electronic Materials
- Volume:
- 4
- Issue:
- 3
- ISSN:
- 2199-160X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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