by Keyword: Distributed feedback lasers
de Goede, Michiel, Chang, Lantian, Mu, Jinfeng, Dijkstra, Meindert, Obregón, Raquel, Martínez, Elena, Padilla, Laura, Mitjans, Francesc, Garcia-Blanco, Sonia M., (2019). Al2O3:Yb3+ integrated microdisk laser label-free biosensor Optics Letters 44, (24), 5937-5940 
Whispering gallery mode resonator lasers hold the promise of an ultralow intrinsic limit of detection. However, the widespread use of these devices for biosensing applications has been hindered by the complexity and lack of robustness of the proposed configurations. In this work, we demonstrate biosensing with an integrated microdisk laser. Al2O3doped with Yb3+ was utilized because of its low optical losses as well as its emission in the range 1020–1050 nm, outside the absorption band of water. Single-mode laser emission was obtained at a wavelength of 1024 nm with a linewidth of 250 kHz while the microdisk cavity was submerged in water. A limit of detection of 300 pM (3.6 ng/ml) of the protein rhS100A4 in urine was experimentally demonstrated, showing the potential of the proposed devices for biosensing.
JTD Keywords: Distributed feedback lasers, Fiber lasers, Laser modes, Microdisk lasers, Single mode lasers, Tunable lasers
de Goede, M., Dijkstra, M., Obregón, R., Ramón-Azcón, J., Martínez, Elena, Padilla, L., Mitjans, F., Garcia-Blanco, S. M., (2019). Al2O3 microring resonators for the detection of a cancer biomarker in undiluted urine Optics Express 27, (13), 18508-18521
Concentrations down to 3 nM of the rhS100A4 protein, associated with human tumor development, have been detected in undiluted urine using an integrated sensor based on microring resonators in the emerging Al2O3 photonic platform. The fabricated microrings were designed for operation in the C-band (λ = 1565 nm) and exhibited a high-quality factor in air of 3.2 × 105. The bulk refractive index sensitivity of the devices was ~100 nm/RIU (for TM polarization) with a limit of detection of ~10−6 RIU. A surface functionalization protocol was developed to allow for the selective binding of the monoclonal antibodies designed to capture the target biomarker to the surface of the Al2O3 microrings. The detection of rhS100A4 proteins at clinically relevant concentrations in urine is a big milestone towards the use of biosensors for the screening and early diagnosis of different cancers. Biosensors based on this microring technology can lead to portable, multiplexed and easy-to-use point of care devices.
JTD Keywords: Distributed feedback lasers, Effective refractive index, Laser coupling, Polarization maintaining fibers, Refractive index, Scanning electron microscopy
