Silicon photonics MEMS switch (Wu group)
Photonics and Optical Interconnects
A. Antenna-LED to Waveguide Optical Link
The Wu and Yablonovitch groups demonstrated an optical link by coupling the photoluminescence output of a high-efficiency III-V antenna-LED to an integrated optical waveguide.4 The optical antenna-LED, invented in the Center for E3S by Wu and Yablonovitch, is a fast and efficient nanoscale light source with spontaneous emission enhancements of more than 200 times under electrical excitation.1 This is competitive with stimulated emission in lasers, but at drastically reduced power consumption. Using electromagnetic design techniques, the team engineered and optimized coupling efficiencies of antenna-LEDs to single mode optical waveguides. Epitaxial materials with different active regions were grown in collaboration with MIT researchers, as specified by modeling results from the BETR team (Figure 1, top). Figure 1 (middle) shows the structure after substrate removal. The dark field outline of the device is given at the bottom of Figure 1, with the overlaid photoluminescence map of the device. The average waveguide-coupling efficiency was estimated to be 85.9%. This remarkable result was obtained by calculating the ratio between the light coming from the grating to the total light collected from the structure and was confirmed by simulation methods.
Figure 1. Top. Cross-sectional schematic of antenna-waveguide coupled structure. Middle. Optical micrograph of structure after substrate removal. Bottom. Dark field image of structure with 2D (heat map) and 1D counts overlaid.
B. IR-to-UV Generic Electroluminescence Device
The Javey group developed a unique light-emitting device that can excite electroluminescence from a wide variety of materials that emit in the long-wave infrared to ultraviolet wavelength range.5 By using a porous carbon nanotube (CNT) network as the source contact and applying an a.c. gate voltage, band bending was generated, which can overcome carrier-injection barriers in transient mode operation and eliminates the need for emitter-specific charge-injection layers (Figure 2). The design allows the emitter layers to be deposited directly on top of the source contact, which lifts limitations on the processability of the light-emitting material. The team showed that an array of devices can be used to generate multiplexed electroluminescence emission, where each emitting material is deposited on one pixel of the array. They also demonstrated that the device can be used as a platform for electroluminescence spectroscopy and sensing. This approach creates opportunities for the development of light-emitting devices at extreme wavelengths, as well as the use of electroluminescence spectroscopy as a metrology and sensing technique for materials previously inaccessible to this type of analysis.
Figure 2. a) Device structure with an assembled CNT network on SiO2/Si and patterned source contact. The device operates by applying a.c. voltage between the metal grid on the CNT network (S) and Si backgate (G). b) Uniform EL can be excited with different emitters, including colloidal quantum dots and metal-organic complexes. Devices are measured with a 15-V, 100-kHz square wave. Scale bar, 0.1 mm.
- S. A. Fortuna, A. Taghizadeh, E. Yablonovitch, and M. C. Wu, “Toward 100 GHz Direct Modulation Rate of Antenna Coupled NanoLED,” IEEE Photonics Conference, Jan 2016.
- K. Settaluri, C. Lalau-Keraly, E. Yablonovitch, and V. Stojanović, “First Principles Optimization of Opto-Electronic Communication Links,” IEEE Transactions on Circuits and Systems I: Regular Papers , vol.64, no.5, pp. 1270-1283, May 2017.
- D.-H. Lien, M. Amani, S.B. Desai, G.H. Ahn, K. Han, J.-H. He, J.W. Ager, M.C. Wu, and A. Javey, “Large-Area and Bright Pulsed Electroluminescence in Monolayer Semiconductors,” Nature Communications, vol. 9, pp. 1229, Mar 2018.
- N. M. Andrade, Y. Kim, S. Hooten, E. Yablonovitch, J. Kim, M. C. Wu, “Efficient Coupling of an Optical Antenna-LED to a Single-Mode Waveguide,” IEEE Photonics Conference, Oct 2020.
- Y. Zhao, V. Wang, D.-H. Lien, and A. Javey, “A Generic Electroluminescent Device for Emission from Infrared to Ultraviolet Wavelengths,” Nature Electronics, vol. 3, pp. 612-621, Oct 2020.