A microring resonator sensor device for sensitive detection of the explosive 1,3,5-trinitrotoluene (TNT) is presented. It is based on the combination of a silicon microring resonator and tailored receptor molecules.

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Conventional fiber optic evanescent-field gas sensors are based on a high number of total reflections while the gas is passing the active bare core fiber and of course a suitable laser light source. The use of miniaturized laser sources for sensitive detection of CO(2) in gaseous and water-dissolved phase for environmental monitoring are studied for signal enhancing purposes. Additionally, the fiber optic sensor, consisting of a coiled bare multimode fiber core, was sensitized by an active polymer coating for the detection of explosive TNT. The implementation of ZnO waveguiding nanowires is discussed for surface and sensitivity enhancing coating of waveguiding elements, considering computational and experimental results.

In this Letter, a novel all-polymer arrayed waveguide grating (AWG) device with an operating wavelength around 850 nm is reported. The all-polymer AWG consists of polymer ridge waveguides fabricated on a thin poly(methyl methacrylate) foil via microscope projection photolithography. The developed device is suitable to be integrated into optical circuits, e.g., a planar polymer foil and, along with other optical integrated devices, to be used for different sensing applications. The functionality of the device is demonstrated by using a fiber Bragg grating sensor and performing strain measurements.

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Nowadays, much attention is given to the detection of explosives in order to prevent terrorist activities and assure security at airports, aviation, public transportation, convention halls, concerts, and so on. The location of undetonated and buried landmines is also a matter of great importance that could help to minimize fatalities and injuries among civilians caused by mines detonating. Another problem related to the use of explosives is the fact that nitrogen-based explosives, such as trinitrotoluene (TNT), are toxic and able to rapidly penetrate the skin, leading to significant health problems [1,2]. For this reason, the sensing of hazardous substances may be of great interest at many facilities, where explosive materials were/are still manufactured and deposited, in order to avoid contamination of the soil or groundwater with the toxic compounds that can result from improper waste disposal, and to ensure the safety of both workers and nearby residents.As can be seen, the detection of explosives is a significant task in the field of security and environmental analysis. Over the last several years major efforts have been focused on developing innovative sensing devices, capable of detecting hazardous species. In contrast to commonly used methods, such as ion mobility spectrometry (IMS), gas chromatography, or mass spectrometry, that require sampling for performing analysis and are relatively cost-intensive, optical methods are ideally suited for a fast online and in situ detection of hazardous substances due to their contact-free and nondestructive operation.However, at the present time, there is no sensing system available which can identify all explosive compounds, promising high sensitivity, selectivity, and low false-alarm rate, simultaneously. Depending on the nature of the applications, sensing devices based on different laser spectroscopic methods have been developed, each of them offering high efficiency for a specific type of explosive material. A reliable detection of explosive traces in the vapor phase or in the form of particles, essential for security applications, can only be achieved by combining the sensing methods and their respective features. In the following, an overview of several laser-

A microring resonator is used as a photonic sensor device for the detection of the explosive trinitrotoluene (TNT). Selectivity is achieved by coating the sensor chip with specially designed receptor molecules. The measurand is the shift in resonance frequency of the microring resonator induced by the change in effective index of refraction of the waveguide materials due to adsorption/intercalation of the analyte. The response is linear with concentration and reversible, i.e. the TNT molecules desorb from the sensor surface when it is flushed with carrier gas. This enables online measurements since the sensor can be used again after flushing and no sampling is needed. Insensitivity to other substances is demonstrated. Some chemically similar molecules induce a shift also, but the sensitivity is much lower. The sensing limit for TNT is determined to be 0.5ppb. Simultaneous operation of two ring resonators is demonstrated, proving the capability of a multi species monitor ing when the rings are coated with different receptor molecules