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1. Sub-volt high-speed silicon MOSCAP microring modulator driven by high-mobility conductive oxide

   https://doi.org/10.1038/s41467-024-45130-4  

   Hsu, Wei-Che; Nujhat, Nabila; Kupp, Benjamin; Conley, Jr, John_F; Rong, Haisheng; Kumar, Ranjeet; Wang, Alan_X (January 2024, Nature Communications)

   Abstract Silicon microring modulator plays a critical role in energy-efficient optical interconnect and optical computing owing to its ultra-compact footprint and capability for on-chip wavelength-division multiplexing. However, existing silicon microring modulators usually require more than 2 V of driving voltage (V_pp), which is limited by both material properties and device structures. Here, we present a metal-oxide-semiconductor capacitor microring modulator through heterogeneous integration between silicon photonics and titanium-doped indium oxide, which is a high-mobility transparent conductive oxide (TCO) with a strong plasma dispersion effect. The device is co-fabricated by Intel’s photonics fab and our in-house TCO patterning processes, which exhibits a high modulation efficiency of 117 pm/V and consequently can be driven by a very low V_ppof 0.8 V. At a 11 GHz modulation bandwidth where the modulator is limited by the RC bandwidth, we obtained 25 Gb/s clear eye diagrams with energy efficiency of 53 fJ/bit. 

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2. Si(bzimpy) ₂ – a hexacoordinate silicon pincer complex for electron transport and electroluminescence

   https://doi.org/10.1039/C8CC07681B  

   Kocherga, Margaret; Castaneda, Jose; Walter, Michael G.; Zhang, Yong; Saleh, Nemah-Allah; Wang, Le; Jones, Daniel S.; Merkert, Jon; Donovan-Merkert, Bernadette; Li, Yanzeng; et al (December 2018, Chemical Communications)

   A neutral hexacoordinate silicon complex containing two 2,6-bis(benzimidazol-2′-yl)pyridine (bzimpy) ligands has been synthesized and explored as a potential electron transport layer and electroluminescent layer in organic electronic devices. The air and water stable complex is fluorescent in solution with a λ max = 510 nm and a QY = 57%. Thin films grown via thermal evaporation also fluoresce and possess an average electron mobility of 6.3 × 10 −5 cm 2 V −1 s −1 . An ITO/Si(bzimpy) 2 /Al device exhibits electroluminescence with λ max = 560 nm. 

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3. Miniature, highly sensitive MOSCAP ring modulators in co-optimized electronic-photonic CMOS

   https://doi.org/10.1364/PRJ.438047  

   Gevorgyan, Hayk; Khilo, Anatol; Wade, Mark T.; Stojanović, Vladimir M.; Popović, Miloš A. (January 2022, Photonics Research)

   Convergence of high-performance silicon photonics and electronics, monolithically integrated in state-of-the-art CMOS platforms, is the holy grail for enabling the ultimate efficiencies, performance, and scaling of electronic-photonic systems-on-chip. It requires the emergence of platforms that combine state-of-the-art RF transistors with optimized silicon photonics, and a generation of photonic device technology with ultralow energies, increased operating spectrum, and the elimination of power-hungry thermal tuning. In this paper, in a co-optimized monolithic electronics-photonics platform (GlobalFoundries 45CLO), we turn the metal-oxide-semiconductor (MOS) field-effect transistor’s basic structure into a novel, highly efficient MOS capacitor ring modulator. It has the smallest ring cavity (1.5 μm radius), largest corresponding spur-free free spectral range ( FSR = 8.5    THz ), and record 30 GHz/V shift efficiency in the O-band among silicon modulators demonstrated to date. With 1 V pp RF drive, we show an open optical eye while electro-optically tuning the modulator to track over 400 pm (69 GHz) change in the laser wavelength (using 2.5 V DC range). A 90 GHz maximum electro-optic resonance shift is demonstrated with under 40 nW of power, providing a strong nonthermal tuning mechanism in a CMOS photonics platform. The modulator has a separately optimized body layer but shares the gate device layer and the gate oxide with 45 nm transistors, while meeting all CMOS manufacturability design rules. This type of convergent evolution of electronics and photonics may be the future of platforms for high-performance systems-on-chip. 

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4. Low-loss composite photonic platform based on 2D semiconductor monolayers

   Ipshita Datta, Sang Hoon (January 2020, Nature photographer)

   Two dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs) are promising for optical modulation, detection, and light emission since their material properties can be tuned on-demand via electrostatic doping1–21. The optical properties of TMDs have been shown to change drastically with doping in the wavelength range near the excitonic resonances22–26. However, little is known about the effect of doping on the optical properties of TMDs away from these resonances, where the material is transparent and therefore could be leveraged in photonic circuits. Here, we probe the electro-optic response of monolayer TMDs at near infrared (NIR) wavelengths (i.e. deep in the transparency regime), by integrating them on silicon nitride (SiN) photonic structures to induce strong light -matter interaction with the monolayer. We dope the monolayer to carrier densities of (7.2 ± 0.8) × 1013 cm-2, by electrically gating the TMD using an ionic liquid [P14+] [FAP-]. We show strong electro-refractive response in monolayer tungsten disulphide (WS2) at NIR wavelengths by measuring a large change in the real part of refractive index ∆n = 0.53, with only a minimal change in the imaginary part ∆k = 0.004. We demonstrate photonic devices based on electrostatically gated SiN-WS2 phase modulator with high efficiency ( ) of 0.8 V · cm. We show that the induced phase change relative to the change in absorption (i.e. ∆n/∆k) is approximately 125, that is significantly higher than the ones achieved in 2D materials at different spectral ranges and in bulk materials, commonly employed for silicon photonic modulators such as Si and III-V on Si, while accompanied by negligible insertion loss. Efficient phase modulators are critical for enabling large-scale photonic systems for applications such as Light Detection and Ranging (LIDAR), phased arrays, optical switching, coherent optical communication and quantum and optical neural networks27–30. 

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5. Computational Analysis of a 200 GHz Phased Array Using Lens-Coupled Annular-Slot Antennas

   https://doi.org/10.3390/app12031407  

   Li, Peizhao; Shi, Yu; Deng, Yijing; Liu, Lei (February 2022, Applied Sciences)

   We report the design, simulation, and analysis of a THz phased array, using lens-coupled annular-slot antennas (ASAs) for potential beyond 5G or 6G wireless communications. For a prototype demonstration, the ASA employed was designed on a high resistivity Si substrate with a radius of 106 μm, and a gap width of 6 um for operation at 200 GHz. In order to achieve higher antenna gain and efficiency, an extended hemispherical silicon lens was also used. To investigate the effect of the silicon lens on the ASA phased array, a 1 × 3 array and 1 × 5 array (the element distance is 0.55λ) were implemented with a silicon lens using different extension lengths. The simulation shows that for a 1 × 3 array, a ±17° scanning angle with an about −10 dB sidelobe level and 11.82 dB gain improvement (compared to the array without lens) can be achieved using a lens radius of 5000 μm and an extension length of 1000 μm. A larger scanning angle of ±31° can also be realized by a 1 × 5 array (using a shorter extension length of 250 μm). The approach of designing a 200 GHz lens-coupled phased array reported here is informative and valuable for the future development of wireless communication technologies. 

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