**9. References**

252 Photonic Crystals – Innovative Systems, Lasers and Waveguides

expensive tunable elements. Moreover, since the output power can be continuously monitored (several power values per second can be measured), a real-time sensing is performed, which allows an instantaneous observation of the interactions taking place in the

The initial spectral alignment between the source and the sensor will determine the sensitivity and the linearity of the device. Eq. 1 describes the relative power variation at the output (in dB) as a function of the initial spectral overlap between source and sensor (*BW*) and the shift of the guided band's edge due to a change in the refractive

<sup>10</sup> 10 log 1 *BW*

Fig. 17 shows the output power variation depending on the initial overlap between the source and the sensor. A high initial overlap leads to a linear response of the sensor, although a lower sensitivity is obtained. On the other hand, as the initial overlap is reduced, the sensitivity increases but a more non-linear behaviour is observed. However, a proper modeling and calibration of the sensor response will allow working in the non-linear

Fig. 17. Power variation versus wavelength shift for different initial alignments between the

Another advantage of this readout technique is the possibility of continuously acquire the output power of the device (rigorously talking, many output power samples are taken each second). This will not only allow us to instantaneously observe any interaction taking place within the sensing device, but it will also allow to perform a temporal averaging of the power values and reduce the noise, thus leading to a significant reduction of the detection

Integrated planar photonic structures are one of the main candidates for the development of label-free biosensing devices, and among them, photonic crystal based structures. In this

source and the sensor. BW indicates the initial overlapping bandwidth.

regime, with a significant increase in the sensor sensitivity.

 

(1)

sensing structure.

limit of the device.

**7. Conclusion** 

index (Δ*λ*).


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**13** 

*Italy* 

Remo Proietti Zaccaria et al.\*

**Photonic Crystals for Plasmonics: From** 

*Nanobiotech Facility, Italian Institute of Technology, Genova* 

**Fundamentals to Superhydrophobic Devices** 

In the last couple of decades we have been witnessing an enormous technological advancement in the field of micro-technology to the extent that nowadays we talk about nanotechnology. Faster computers, LCD based mobiles, nanoparticles for UV absorption in suntan lotions are just few of many examples where nanotechnology plays a fundamental role. The merit of this is mainly in the advance of the fabrication methods. Present techniques such as Focused Ion Beam (FIB) lithography guarantee a resolution of less than 10 nanometers which is about five times more precise than ten years before. Also Photonic Crystals (PhCs), among the others, take advantage from this extremely high resolution level allowing a downscale that permits the realization of structures which in principle can work at vey high energy. Historically PhCs were known as Bragg mirrors and only in 1987 (Yablonovitch, 1987; Sajeev, 1987) with the works of Yablonovitch and Sajeev the term Photonic Crystals was introduced. Nowadays, besides their natural application as filters in particular under full band gap conditions, PhCs see a number of applications: optical fibers (Birks et al., 1997; Zhao et al., 2010), vertical cavity surface emitting lasers (Yokouchi et al., 2003), high reflection coatings, temperature sensors (Song et al., 2006), high efficiency solar cells (Bermel et al., 2007), electric field detectors (Song & Proietti Zaccaria, 2007), non-linear analysis (Malvezzi et al., 2002; Malvezzi et al., 2003), just to name a few. Many are the techniques for the fabrication of PhCs, for example by means of focused-ion beam (Cabrini et al., 2005), two-photon fabrication (Deubel et al., 2004), laser-interference (Proietti Zaccaria et al., 2008a) or waver-fusion techniques (Takahashi et al., 2006). Here we shall focus on the role that PhCs can play for another exciting discipline known as *Plasmonics*. It refers to the capability of some devices of sustaining an *optical surface* mode, namely an electromagnetic wave travelling at the interface between two different materials such as a dielectric and a metal. Such a wave originates from the coupling of incident photons on the interface with

 Anisha Gopalakrishnan1, Gobind Das1, Francesco Gentile1**,**2, Ali Haddadpour3, Andrea Toma1, Francesco De Angelis1, Carlo Liberale1, Federico Mecarini1, Luca Razzari1, Andrea Giugni1, Roman

**1. Introduction** 

 \*

Krahne1 and Enzo Di Fabrizio1,2

*Graecia University, viale Europa, Catanzaro, Italy* 

*1Nanobiotech Facility, Italian Institute of Technology, Genova ,Italy 2BIONEM lab., Departement of Clinical and Experimental Medicine, Magna* 

*3Department of Electrical and Computer Engineering, University of Tabriz, Iran* 

Zlatanovic, S., Mirkarimi, L. W., Sigalas, M. M., Bynum, M. A., Chow, E., Robotti, K. M., Burr, G. W., Esener, S., & Grot, A. (2009). Photonic crystal microcavity sensor for ultracompact monitoring of reaction kinetics and protein concentration. *Sensors and Actuators, B: Chemical*, Vol. 141, No. 1, (August 2009), pp. 13-19, ISSN 0925- 4005
