Optically switched four-channel micro-ring resonator sensor based on the Vernier effect using a V-cavity tunable laser for HSA detection

In modern biosensing systems, traditional sensing approaches face limitations such as high cost and bulky size. A V-cavity tunable laser (VCTL) with a quasi-continuous tuning range of 23 nm was realized by synchronously tuning the currents of two cavities. By connecting a Fabry-Perot Etalon (FPE) with four micro-ring resonators (MRRs) through a 1×4 coupler, an FPE cascaded MRR (FMRR) array was formed to generate the Vernier effect and enhance the sensing sensitivity. An optical switch is used to sequentially select the output signals from different sensing channels, enabling four-channel MRRs with only a single light source and a single detector. Experimental results show that, by monitoring the envelope peak shift in the transmission spectrum of the sensor array, a bulk refractive index (RI) sensitivity of 2881.48 nm/RIU is achieved, while the FMRR array exhibits human serum albumin (HSA) detection sensitivity of 2417.07 p.m./(μg·mL −1 ), confirming the potential of VCTL as low-cost interrogation sources for integrated optical sensing systems.