Integrated Photonic Biosensors: Enabling Next-Generation Lab-on-a-Chip Platforms

Integrated photonic biosensors are quickly changing the game in lab-on-a-chip technologies. These tiny yet powerful devices enable rapid detection of biological and chemical substances without labels or complex processing and deliver high sensitivity in a compact form. In this review, we walk through the core principles behind how these sensors work, how they are designed, and how they are combined with microfluidic systems to create smart, efficient diagnostic platforms. We examine several sensing approaches including resonant photonic structures and interferometric techniques, each bringing its own strengths in terms of accuracy, responsiveness, and scalability. Particular attention is given to complementary metal-oxide semiconductor-compatible materials like silicon and silicon nitride, which play a crucial role in enabling the efficient, high-volume, and cost-effective production of these devices. We highlight recent advances like optofluidic photonic crystal cavities and integrated detector arrays, and their promising applications in healthcare, environmental monitoring, and food safety. While challenges remain, such as processing complex biological samples and ensuring consistent large-scale production, emerging materials, flexible electronics, and AI-driven data analysis are paving the way forward. Ultimately, integrated photonic biosensors are poised to lead to a new era of portable, affordable, and high-performance diagnostic tools for real-world use.