Silicon Photonic Transmitter Achieves Cryogenic Operation at 25 Gbps for HEP Readout
Preprint demonstrates a cryogenic silicon photonic transmitter reaching 25 Gbps with low BER at 4 K, offering a potential power-efficient path for future HEP data links. Evidence rests on bench tests without radiation exposure. Stronger validation requires beam tests and reliability data before adoption in collider upgrades.
The device monolithically integrates a Mach-Zehnder modulator, grating coupler, and on-chip laser on a 220 nm SOI platform, packaged with a custom cryogenic PCB and tested in a dilution refrigerator. Electrical-to-optical conversion efficiency remained above 0.3 W/A down to 4 K, with no carrier freeze-out observed in the doped waveguides. Radiation tolerance was simulated rather than beam-tested.
Current LHC and DUNE front-end links consume hundreds of milliwatts per channel and suffer from thermal load at the cold stage. The photonic approach cuts electrical power by roughly an order of magnitude while providing optical fan-out that decouples the detector volume from the counting room. This directly addresses the projected 5-10 Tb/s aggregate bandwidth required for HL-LHC pixel upgrades.
The work extends earlier silicon-photonics programs at CERN and FNAL but is the first to publish full cryogenic BER curves on a single chip. Missing elements include proton irradiation data and long-term laser reliability at 4 K; both are prerequisites for any experiment adoption. Next milestones are a multi-channel demonstrator and integration with 65 nm CMOS driver ASICs already qualified for HL-LHC.
CERN EP-ESE group: Radiation-hardened version passes 10^15 n_eq/cm² fluence with <1 dB penalty by Q4 2026.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2608.19258)
- [2]Supporting Source(https://iopscience.iop.org/article/10.1088/1748-0221/18/02/C02023)