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.

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.

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In this paper, the surface wave theory is used to study the spectral response of a terahertz antenna detector when the surrounding dielectric material is changed. As simulation shows, surrounding dielectrics affect the velocity of the current pulse propagation on electrodes. The propagation spectrum of the bow-tie and the dipole antenna on the LT-GaAs substrate is simulated through the FDTD method using the CST software. The current pulse generated in the antenna gap is also calculated with the Drude model. It is found that the type and the thickness of surrounding dielectrics affect the spectral responses of detector antennas as far as the peaks of the corresponding spectra shift down to one terahertz.

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