In recent years, standard CMOS microprocessors have approached their maximum power dissipation per unit area, effectively placing a limit on computational power. This highlights the urgent need to explore alternative technologies. One promising avenue is the use of superconductors, which demonstrate zero resistivity below a critical temperature. However, circuits based on superconductors necessitate the use of cryostats to maintain low temperatures, presenting challenges in data transfer with the room temperature environment. While coaxial cables are often employed for this purpose, they suffer from limited data transfer rates and contribute significantly to heat load. On the contrary, photonics integrated circuits (PICs) coupled with optical fibers present a viable solution. They enable scalable, cost-effective, and power-efficient optical interconnections capable of supporting high data transfer rates while minimizing heat transfer. In this presentation, We will discuss the latest advancements in cryogenic PICs, focusing on their application in interfacing with cryogenic computing systems such as single-flux-quantum logic circuits and superconducting qubits.
Multi-wavelength laser sources on silicon photonics can enable large spectral coverage for DWDM optical I/O links and leverage the scalability of a CMOS compatible process simultaneously. In this work, we report a laser array of four four-wavelength distributed feedback lasers that produce in total sixteen wavelength channels simultaneously with a wavelength spacing of 200 GHz and output power of 17 dBm per laser. We show integrated III-V/Si hybrid lasers on the same die with wafer-level bonded epitaxial III-V layer that spans a spectral coverage of 17 nm through the 16 wavelength channels. We also measured the relative intensity noise (RIN) of all sixteen wavelength channels to be under -135 dB/Hz and the Lorentzian linewidth to be less than 300 kHz.
Multi-wavelength laser sources have gained significant interest for future high-bandwidth density DWDM optical links, enabling improved energy efficiency and bandwidth scaling. In this work, we present an integrated III-V/Si hybrid four-wavelength DFB laser with 200 GHz wavelength spacing and <10 dBm output power per wavelength. The wavelength spacing and total output power variations are <±25 GHz and <1 dB, respectively, for an ambient temperature change of 30°C. We also measured the relative intensity noise (RIN) and Lorentzian linewidth of the laser to be <-135 dB/Hz and <300 kHz, respectively.
On-chip optical isolators constitute an essential building block for photonic integrated circuits. Monolithic magnetooptical isolators on silicon, while featuring unique benefits such as scalable integration and processing, fully passive operation, large dynamic range, and simple device architecture, had been limited by their far inferior performances compared to their bulk counterparts. Here we discuss our recent work combining garnet material development and isolator device design innovation, which leads to a monolithic optical isolator with an unprecedented low insertion loss of 3 dB and an isolation ratio up to 40 dB. To further overcome the bandwidth and polarization limitations, we demonstrated broadband optical isolators capable of operating for both TM and TE modes. These results open up exciting opportunities for scalable integration of nonreciprocal optical devices with chip-scale photonic circuits.
We demonstrate a Sagnac based fiber optic current sensor using only 10cm of terbium doped fiber with a high Verdet constant of 15.5 rad/Tm at a wavelength of 1300nm. Measurements of the fiber inside a solenoid show over 40dB of open loop dynamic range as well as a minimum detectable current of 0.1mA. In order to decrease size while increasing sensitivity even further, we consider integrated magneto-optic waveguides as the sensing element. Using silicon waveguides alongside magneto-optic material such as cerium doped yttrium iron garnet (Ce:YiG), we model the Verdet constant to be as high as 10,000 rad/Tm. This improvement by three orders of magnitude shows potential for magnetooptic waveguides to be used in ultra-high sensitivity optical magnetometers and current sensors. Finally, we propose a fully integrated optical current sensor using heterogeneous integration for silicon photonics.
Experimental demonstration of net electro-luminescent cooling in a diode, or equivalently electroluminescence with wall-plug efficiency greater than unity, had eluded direct observation for more than five decades. We review experiments demonstrating light emission from a light-emitting diode in which the electron population is pumped by a combination of electrical work and heat.
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