Develop Ultralow Power Cryogenic-VCSEL for 4K Fiber Data Link
Abstract
For meeting the ever-increasing demands in global computational power and speed requirements due to cloud computing, artificial intelligence (AI) and machine learning (ML), the optical link requires to reduce (energy/bit) by 100 times (~ 0.2 pJ/bit). While it has become difficult for improvement in conventional silicon-based technology, the single-flux-quantum (SFQ) superconducting computing provides a new path to next-generation ultrafast and ultralowpower processors. Optical link based on cryogenic VCSELs has been proposed as a promising solution due to low loss and thermal load compared to electrical interconnect. Furthermore, Cryo- VCSELs take advantage of the greatly reduced e-h recombination lifetime in quantum-wells at cryogenic temperature so that ultra-fast modulation speed is possible. Under IARPA Supercable Project in 2021, we have successful developed Cryo-VCSEL operating lowest temperature at 2.6K with a threshold ITH = 0.18 mA for data modulated by superconducting processor to achieve 12.5 Gb/s NRZ error-free (1E -12) transmission at relative low operating current, I = 1.8 mA (I = 10 x ITH). For this work, the energy/bit was reported ~ 370 fJ/bit. This research program will be conducted by Professor Milton Feng of the University of Illinois at Urbana-Champaign on ARO BAA W911NF-17-S-002-12 for the topic ii. Electronics (2) Optoelectronics. In this proposal, we offer to develop ultralow power Cryo-VCSELs for 4K fiber data link and to investigate scaling oxide-VCSEL. Several improvements have been identified to allow us to improve energy/bit efficiency by 40 x towards ~ 10 fJ/bit. In Phase 1 (budget $373,418), we plan to optimize epi design to reduce ITH = 0.1 mA at 4 K for the DC operation towards I = 1 mA. Thus, we expected energy/bit can be reduced to < 200 fJ/bit for 12.5 Gb/s errorfree optical link. Furthermore, a photoreceiver with a low noise floor and better responsivity will be investigated to greatly enhance receiver SNR and improve coupling efficiency to ~50% for achieving 4K Cryo-VCSEL (energy/bit) to 100 fJ/bit. In Phase 2 (budget $376,405), our goal is to improve VCSEL ITH ~ 0.02mA for operating power toward I = 0.2 mA and further improve VCSEL/fiber coupling efficiency > 60%. This implies high speed data modulation can be reached from 12.5 Gb/s to 50 Gb/s at 0.2 mA for reducing energy/bit from 100 fJ/bit to 10 fJ/bit. In addition, we plan to establish 4K on-wafer probing Cryo-VCSEL measurement system for allowing us to measure S-parameters for bandwidth, f-3dB > 100 GHz.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 11, 2022
- Source ID
- W911NF2210229
Entities
People
- Milton Feng
Organizations
- Army Contracting Command
- United States Army
- University of Illinois Urbana–Champaign