Abstract: Typical L-type photonic crystal (PC) microcavities have a dynamic range of approximately 3-4 orders of magnitude in biosensing. We experimentally demonstrated that multiplexing of PC sensors with different geometry can achieve a wide dynamic range covering 6 orders of magnitude with potential for 8 or more orders with suitable optimization.   We fabricated PCWs on silicon-on-insulator (SOI) devices with a 250nm top silicon layer, a 3µm buried oxide layer

Chun-Ju Yang

Hai Yan

Ray T Chen

Swapnajit Chakravarty

Yi Zou

Zheng Wang

CiteSeerX

STh4H.5.pdf CLEO:2014 © 2014 OSA
Wide Dynamic Range Sensing in Photonic Crystal 
Microcavity Biosensors  
 
Chun-Ju Yang
1
, Yi Zou
1
, Swapnajit Chakravarty
1
*, Hai Yan
1
, Zheng Wang
1
, Ray T. Chen
1
,
2
* 
 
1Dept. Electrical and Computer Engineering, The University of Texas at Austin, 10100 Burnet Rd, PRC/MER 160, Austin, Tx78758, USA 
2Omega Optics, Inc., 10306 Sausalito Dr, Austin, TX78759, USA 
 
chunjuyang@utexas.edu, swapnajit.chakravarty@omegaoptics.com, ray.chen@omegaoptics.com, Fax: +1-512-471-8575  
 
Abstract: Typical L-type photonic crystal (PC) microcavities have a dynamic range of 
approximately 3-4 orders of magnitude in biosensing. We experimentally demonstrated that 
multiplexing of PC sensors with different geometry can achieve a wide dynamic range covering 6 
orders of magnitude with potential for 8 or more orders with suitable optimization. 
OCIS codes: (280.0280) Remote sensing and sensors (050.5298) Photonic crystals (130.0130) Integrated Optics 
 
In several applications in biosensing, particularly in drug discovery and therapeutic drug monitoring, it is essential to 
have sensors that can register concentrations of analytes over a wide dynamic range of at least five orders of 
magnitude. Recently, numerous optical devices have been investigated for label free detectors, such as ring 
resonators [1], surface plasmon resonance (SPR) [2], wire waveguides [3], and photonic crystal (PC) microcavities 
[4] . Among all the label free detectors and optical devices, photonic crystal (PC) has provided the unique 
characteristics with slow light effect which enhance the interaction between traveling light the analyte. The slow 
light effect in PC sensors has been investigated by our group in numerous applications such as near-IR absorption 
chemical and bio-sensing [6], gaseous contaminant detection [7], and two-dimensional PC biosensors for 
chip-integrated microarray applications in proteomics [8]. However, each PC microcavity sensor in a triangular 
lattice PC, that we have demonstrated, L3, L13 or L55 where Ln represents that the PC microcavity is formed by 
removing n air holes in a row along the Γ K direction, the PC cavity being located next to a W1 photonic crystal 
waveguide (PCW)), have a dynamic range of approximately 4 orders of magnitude, with the linear region of the 
S-shaped concentration versus wavelength shift curve being linear over just 3 orders of magnitude. Integrated optics 
however provides the unique ability to multiplex sensors on the same chip that can be measured simultaneously at 
the same time with the same sample due to the miniature dimensions of the sensors. In this paper, we experimentally 
demonstrate a novel design for achieving wide dynamic detection range whereby multimode interference (MMI) 
devices are multiplexed with photonic crystal microcavities of different geometries, each covering a different 
concentration range and thereby achieving a wide dynamic range of 7-8 orders of magnitude. 
We fabricated PCWs on silicon-on-insulator (SOI) devices with a 250nm top silicon layer, a 3µm buried oxide 
layer. Fig. 1 shows a scanning electron micrograph (SEM) of the individual PC sensors. Four distinct sensors with 
four different geometries, L3, L13H, L55 and L21 are fabricated where L13H denotes that defect holes that are 
smaller is size than the radius of the holes in the bulk PC lattice are interrogated. The four PC microcavities are 
layed on the 4 arms of a 1×4 MMI in designs previously demonstrated [4, 9]. The respective SEMs are shown in 
Figs. 1(a)-(d). With L3, L55 and L21, the adjacent coupling PCW is of the W1 which indicates that the width of 
PCW is √3a, where a is the lattice constant. For L13H, the width of the coupling PCW is 0.935√3a. The PC 
consists of a triangular lattice of air holes with lattice constant a=392.5 nm. The air holes have radius r=0.277a. The 
air hole diameter is d=0.53a, and silicon slab thickness is h=0.63a. The diameter of defect holes in L13H is 0.4d and 
thus indicated as L13H0.4 in Fig. 1 and Fig. 2. 
A typical transmission spectrum of the four different PCWs with PC microcavities of different geometry coupled 
to the PCW in water is shown in Fig 2(a)-(d). The sensor works on the principle that refractive index changes in the 
vicinity of the PC microcavities lead to a shift in the resonance wavelength, the sensitivity of the sensor determined 
by the magnitude of the resonance wavelength change for a given change in refractive index in chemical sensing, or 
a given change in biomolecule concentration in biosensing. Bio sensing experiments were conducted by selecting 
biotin as the probe immobilized to the patterned silicon substrate and avidin as target protein. In contrast to our 
previous demonstrations in lung cancer cell line lysate detection where each PC microcavity on the four arms of the 
MMI were of the same geometry and were immobilized with different probes to show both sensing and specificity 
of detection[9], in this paper, all the four PC microcavities on the 4 arms were immobilized with the same probe. 
The resonance shift as a function of concentration was measured for each individual PC microcavity, as shown in 
STh4H.5.pdf CLEO:2014 © 2014 OSA
Fig. 3. The dashed red line indicates the minimum detection limit for each PC microcavity, limited by the 
wavelength resolution of our optical spectral analyzer of +/- 0.02nm. The detection range is from 10-15 to 10-9 was 
achieved by combining the individual ranges from the different PC microcavities.  
 
 
 
 
 
(a) 
 
 
 
 
 
(b) 
 
 
 
 
 
(c) 
 
 
 
 
 
(d) 
 
Fig 1. SEM image of PC microcavities coupled to PCW in (a) L3 (b)L13H0.4 defect hole cavity (c) L55and (d) L21 PC microcavities 
 
 
    
Fig 2. Transmission spectrum of (a) L3 (b) L13H0.4 defect hole cavity (c) L55and (d) L21 PC microcavities 
 
Fig. 3. Bio sensing spectral shifts in L13, L21, L55 and L13 defect holed cavity. 
 
In summary, we demonstrated 6 orders of magnitude dynamic range concentration detection by using PC 
microcavities of different geometry. Additional methods to increase the dynamic range include increasing the 
diameter of the defect holes in L13H PC microcavity, increasing the diameter of holes in the bulk lattice as well as 
reducing the size of the PC microcavity to below L3. Spectral characterization of such PC microcavities has been 
completed and biosensing data, integrated on a 1×4 MMI will be presented in the future with an anticipated 8 orders 
of magnitude dynamic range. 
References  
[1] M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, IEEE J. Sel. Top. 
Quantum Electron.16, 654 (2010).  
[2] H. Sipova, S. Zhang, A. M. Dudley, D. Galas, K. Wang, and J. Homola, Anal. Chem. 82, 10110 (2010).  
[3] A. Densmore, M. Vachon, D. X. Xu, S. Janz, R. Ma, Y. H. Li, G. Lopinski, A. Delage, J. Lapointe, C. C. Luebbert, Q. Y. Liu, P. Cheben, and 
J. H. Schmid, Opt. Lett. 34, 3598 (2009).  
[4] Y. Zou, S. Chakravarty, W.-C. Lai, C.-Y. Lin and R. T. Chen, Lab Chip, 2012, 12, 2309–2312.  
[6] W. Lai, S. Chakravarty, Y. Zou, and R. T. Chen, Opt. Lett. 37, 1208–1210 (2012). 
[7]  W.-C. Lai, S. Chakravarty, X. Wang, C. Lin, and R. T. Chen, Optics Letters 36, 984–6 (2011) 
[8]  S. Chakravarty, Y. Zou, W.-C. Lai, and R.T. Chen, Biosensors & Bioelectronics 38, 170 (2012) 
[9] S. Chakravarty, W-C. Lai, Y. Zou, H.A. Drabkin, G.R. Simon, S.H. Chin, R. M. Gemmill, R.T. Chen, Biosens. Bioelectron. 43, 50 (2013). 


Wide Dynamic Range Sensing in Photonic Crystal Microcavity Biosensors

http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=0C3E892ED7F9FC7845FB317E3066DCC3?doi=10.1.1.1045.2159&rep=rep1&type=pdf

Wide Dynamic Range Sensing in Photonic Crystal Microcavity Biosensors

Abstract

Similar works

Full text

Available Versions

CiteSeerX