Physics / mechanism
Electro-absorption modulators exploit the Franz-Keldysh effect (bulk semiconductors) or quantum-confined Stark effect (QCSE, quantum wells/dots) to shift a material’s absorption edge under applied electric field, switching light on/off without carrier injection. Key materials: InGaAsP/InP and Ge-on-Si. Applied reverse bias (typically 1–4 V) red-shifts the bandgap, increasing absorption at the operating wavelength. QCSE devices achieve extinction ratios of 6–10 dB, insertion loss ~3–5 dB, 3-dB bandwidth >50 GHz, and drive voltages below 2 V — critical for energy-per-bit targets sub-1 pJ/bit at 100G+ per lane. Monolithic integration with DFB lasers yields EML (electro-absorption modulated laser) modules dominant in datacenter optics.
Competitive landscape
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.