Full length article Excitation of multi-order guided mode resonance for multiple color fluorescence enhancement Sakoolkan Boonruang a,⇑ , Nantarat Srisuai b , Ratthaphol Charlermroj c , Manlika Makornwattana c , Armote Somboonkaew a , Mati Horprathum b , Nitsara Karoonuthaisiri c a Photonics Technology Laboratory, Thailand National Electronics and Computer Technology Center (NECTEC), Pathumthani 10120, Thailand b Optical Thin-Film Technology Laboratory, Thailand National Electronics and Computer Technology Center (NECTEC), Pathumthani 10120, Thailand c Microarray Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), Pathumthani 10120, Thailand article info Article history: Received 17 January 2018 Received in revised form 6 March 2018 Accepted 25 April 2018 Available online 9 May 2018 Keywords: Guided mode resonance Two-dimensional grating Slowly leaky waveguide Surface enhanced fluorescence Microarray Fluorescence abstract Higher-order Guided Mode Resonance (GMR) in a symmetric two-dimensional embedded grating- waveguide structure is theoretically demonstrated in this paper through a phase matching mechanism of leaky modes along second-order diffraction planes. In addition to the fundamental-order, multiple res- onances are introduced at normal incidence and they are polarization independent. A strong localization of the resonance modes exists in both orders. The device is proposed for multiple color surface enhanced fluorescence that is compatible to a conventional fluorescence reader. The enhancement scheme is by increasing light absorption via the excitation of a strong evanescent wave as an extension of a resonance mode. GMR device is designed to have resonances overlapping fluorophores’ absorption spectra. The con- cept is verified using numerical calculations, Rigorous Coupled Wave Analysis and Homogeneous Waveguide Approach. The device is fabricated and experimentally performed for fluorescence enhance- ment using a microarray of Cyanine 3-labeled goat antibody and Cyanine 5-labeled goat antibody. The fluorescence signal is characterized using a low-cost CMOS array. This implementation can be very useful in a multiplex detection, where the cost of the reader can be minimized. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction Guided Mode Resonance (GMR) in a dielectric grating- waveguide structure [1–4] has been constantly studied and demonstrated in diverse applications. The resonance is due to phase matching of the diffraction waves and the guided modes in the structure. At resonance, light is coupled to a waveguide mode via diffracted waves and it is slowly leaked out with a constructive phase back to the incident side. That introduces total reflection with high spectral and angular selectivity. GMR devices were pro- posed for narrow band spectral reflection filters [5,6]. They were later applied for other filtering applications such as laser cavity’s mirrors [7], polarizers [8], and color filters [9]. Following the resonance’s phase matching mechanisms, resonance shifts proportional to an incident angle, as well as the structure’s param- eters (film’s optical properties and dimensions) and surrounding refractive index. GMR based devices have been utilized as a refrac- tive index sensor [10–13]. By integrating a sensing layer on the surface, GMR has been as well demonstrated for several label- free biosensors such as detection of virus [11], bacteria [12], and cellular interaction [13]. Resonance shifts proportionally to a molecular adsorption on the sensing film. At resonance, field localization occurs in the film layer, which allows GMR to be used as an efficient absorber in thin-film solar cell [14]. The field localization also introduces a strong evanes- cence wave as an extension of the resonance mode. Hence, GMR has been reported for surface enhanced emission in fluorescence –based biosensor [15] as well as in light emitting device [16,17] and for enhancing nonlinear harmonic generation in azo-polymer [18]. The enhancement approach is by increasing light excitation to fluorophores via a strong evanescent wave. This is the case when resonance matches the absorption peak of the fluorophores. More photon extraction is obtained when matching another resonance at the emission spectrum. Hence, multiple resonances are neces- sary specially to enhance multiple spectral emission. https://doi.org/10.1016/j.optlastec.2018.04.029 0030-3992/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: Sakoolkan.Boonruang@nectec.or.th (S. Boonruang), nantarat_ kmutt@hotmail.com (N. Srisuai), Ratthaphol.Cha@biotec.or.th (R. Charlermroj), Manlika.Mak@biotec.or.th (M. Makornwattana), Armote.Somboonkaew@nectec.or. th (A. Somboonkaew), Mati.Horprathum@nectec.or.th (M. Horprathum), Nitsara. Kar@biotec.or.th (N. Karoonuthaisiri). Optics and Laser Technology 106 (2018) 410–416 Contents lists available at ScienceDirect Optics and Laser Technology journal homepage: www.elsevier.com/locate/optlastec