Compact free-electron lasers as enablers of beyond-6G and quantum communication systems

Free-electron lasers (FELs) are disruptive light sources that offer ultrashort pulses, wide spectral tunability, and superior coherence, making them promising candidates for next-generation photonic technologies. However, conventional FEL facilities are large-scale and complex, limiting their integration into communication systems. This study investigates the potential of compact FELs as scalable and versatile light sources for beyond-6G and quantum communication infrastructures. A theoretical framework was established to model resonance conditions, gain dynamics, coherence properties, pulse-duration-limited bit rates, and signal-to-noise ratio (SNR). These models were implemented in MATLAB simulations using parameters representative of state-of-the-art compact FEL prototypes. The results demonstrate that compact FELs provide: broad tunability from the terahertz to the X-ray regime through variation of beam energy and undulator period; high small-signal gain, strongly dependent on beam current, enabling efficient amplification; petabit-per-second bit rates, achievable with attosecond-scale pulses; and superior SNR performance, sustaining values above 80 dB even at low power levels, ensuring secure and reliable transmission. Collectively, these findings confirm that compact FELs combine ultrashort pulse generation, high coherence, and multi-band operation, making them cornerstone technologies for future ultra-fast and quantum-secure communication networks. While challenges remain in efficiency, beam stability, and integration, ongoing advances in laser-plasma accelerators, dielectric undulators, and hybrid photonic systems provide promising pathways toward practical implementation.