In the present work, a hyperspectral imaging system (imaging spectrometer) using a commercial webcam has been designed and developed. This system was able to capture two-dimensional spectra (in emission, transmission and reflection modes) directly from the scene in the desired wavelengths. Imaging of the object is done directly by linear sweep (pushbroom method). To do so, the spectrometer is equipped with a suitable collecting lens and a linear travel stage. A 1920 x 1080 pixel CMOS webcam was used as a detector. The spectrometer has been calibrated by the reference spectral lines of standard lamps. The spectral resolution of this system was about 2nm and its spatial resolution was about 1 mm for a 10 cm long object. The hardware solution is based on data acquisition working on the USB platform and controlled by a LabVIEW program. In this system, the initial output was a three-dimensional matrix in which two dimensions of the matrix were related to the spatial information of the object and the third dimension was the spectrum of any point of the object. Finally, the images in different wavelengths were created by reforming the data of the matrix. The free spectral range (FSR) of the system was 400 to 1100 nm. The system was successfully tested for some applications, such as plasma diagnosis as well as applications in food and agriculture sciences.

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In this paper, tunability of four near-infrared semiconductor lasers which typically lase at 783nm, 808 nm, 892 nm and 980 nm is studied. Both Littrow (wavelength dependent beam direction setup) and Littman (wavelength independent beam direction setup) configurations have been used for single mode tuning. In addition, the tunability of 783 nm laser in dual mode tuning is studied in both Littrow and Litman configurations. The wavelength and the power of the output beam of the laser have been measured. In all four cases, Littrow configuration shows a little better tuning range. In both Littrow and Littman configurations, the wavelengths near the main wavelength of the laser had more power. The highest achieved power of these lasers in the Littrow setup was more than that of the Littman setup. Moreover, the tuning speed and effect of tuning on the bandwidth of the laser were investigated.@en

In this paper, current pulse that propagates in Terahertz antenna was simulated as a propagated surface wave. The surface wave modes which propagate in electrode were studied. It was found that the current pulse propagates as a bulk electromagnetic wave in the antenna gap and that the current pulse propagates as a surface wave in the electrodes. Phase velocity and loss of each mode were investigated. The relation between thickness of the antenna electrode and optical properties of the substrate, such as absorption and refraction index, with surface wave characteristics was studied. After solving surface wave equation for the three-layer structure, dielectric-metal-dielectric, it was found that two surface wave modes, slow mode and fast mode are allowed to propagate in the electrode layer and that surface wave cannot propagate in the antenna gap region.@en

In this paper, tunability of three near-infrared semiconductor lasers which typically lase at 808 nm, 892 nm and 980 nm is studied. Both Littrow (wavelength dependent beam direction setup) and Littman (wavelength independent beam direction setup) configurations have been used. The wavelength and the power of the output beam of the laser have been measured. In all three cases, Littrow configuration shows a little better tuning range. In both Littrow and Littman configurations the wavelengths near the main wavelength of the laser had more power. The highest achieved power of these lasers in the Littrow setup was more than that of the Littman setup.@en

We present a simple setup for laser-induced breakdown spectroscopy using the spatially resolved technique (SRLIBS). We show that, without any need for time-gated ICCD and pulse generator, the signal-to-background ratio is enhanced. We develop a homemade spectrograph with a movable slit located at its entrance to detect different parts of the plasma emission. For optimizing the position of the slit, we use the shadowgraphy technique to study the plasma expansion. In this low cost setup, with nanosecond laser pulses, we perform SRLIBS experiments on the plasma induced in air and iron. Our results show that the signal-to-background ratio for iron and air is enhanced up to 15 and 8 times, respectively.@en

A micro-discharge air plasma jet was developed operated at low frequency (50 Hz) ac high voltage (kV). The micro-discharge plasma jet was generated by feeding air through a dielectric installed between two disk-shaped electrodes with a hole of 1 mm diameter in the center. Both of the electrodes were made of copper. The micro-discharge in the dielectric is evolved as a plasma jet from the outer electrode through its hole. The ac power supply was a neon light transformer. Optical emission spectroscopy was employed to study the plasma discharge characteristics. Specair software was used to analyze the collected spectrum. The reduced electric field and electron density of plasma as well as rotational and vibrational temperatures, referring to ion or gas and electron temperature respectively were measured by processing emission spectrum.

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Over the past several years, the demand for high quality agricultural products has been remarkably increased. Thus, it is important to use non-destructive methods for product quality monitoring. LED-induced fluorescence spectroscopy has proved its potential for nondestructive detection of some defects in agricultural products, such as tissue browning and bruising. Due to such defects, changes in the polyphenol and chlorophyll contents occur which can be considered as the visible marks of decreasing fruit quality. In the present work, a fluorescence spectrometer (spectrofluorometer) controlled by LabVIEW software was designed and developed. In this spectrometer, a consumer-grade webcam was used as an imaging sensor. The spectrometer was able to measure the fluorescence spectra directly from the fruit and vegetable surface in the desired regions. To do so, the spectrometer was equipped with a suitable fiber-optic probe. The hardware solution was based on data acquisition working on the USB platform and controlled by the application running on the PC. In this system, light emitting diodes with different wavelengths were used as the excitation sources for inducing fluorescence spectra of some famous fruits and vegetables.

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