Photonic Digital-to-Analog Converters (PDACs): Architectures, Performances, and Technology Roadmaps

The growing demand for ultra-fast and energyefficient data conversion in modern communication, computing, and sensing systems has motivated increased interest in photonic digital-to-analog converters (PDACs). Unlike their electronic counterparts, PDACs exploit the broad bandwidth and low crosstalk of optical carriers to achieve terahertz-scale performance and exceptionally low electro-optic drive energy per conversion step (often <1 pJ per DAC bit). To ensure transparency and methodological rigor, this paper conducts a systematic and quantitative review of PDAC technologies using a PRISMAinspired literature-selection protocol. Reported architectures are classified into three main categories: parallel, serial, and segmented/hybrid, highlighting their underlying principles, modulation formats, and integration strategies. Key demonstrations from 1976 to 2025 are compared in terms of effective number of bits (ENOB), linearity, energy efficiency, and scalability across silicon, lithium niobate (LN), and hybrid photonic platforms. Emerging trends, including coherent-field summation, LN-oninsulator (LNOI) modulators, and plasmonic enhancement, are discussed in the context of broadband communication and photonic signal-generation systems. The analysis identifies PDACs as a transformative bridge between digital electronics and photonic analog synthesis, offering a pathway toward compact, low-latency, and programmable optical transmitters for nextgeneration integrated photonic platforms.