Continues wave terahertz imaging has been used widely in the field of security inspection and nondestructive
examination because of its simplicity and stability. In this presentation, we proposed an image method with continues
wave terahertz interferometry to obtain the sample's phase information. In the experiment, a reference terahertz beam
was added into the exiting continues wave terahertz imaging system to be a Michelson interferometer. With three maps
obtained at three fixed phase-shift positions, a phase image is obtained by using a phase shift algorithm. Afterwards, this
phase image is unwrapped to get its accurate phase profile. By this method, a bulk of foam with two height steps
structure is imaged. The result shows that the inner structures of samples can be identified clearly and the relative optical
depth profiles of samples can be obtained.
A method for measuring the refractive index of metal bulks in the terahertz region with terahertz time domain vertical
reflection spectroscopy is proposed. In the experiment, the terahertz wave forms generated by laser induced air plasma
and reflected by a silicon wafer and metal bulks are measured respectively. The Kramers-Kronig transformation is used
to reduce the phase shift error that influences the accuracy on the experimental results. The refractive index of a silicon
wafer, which was measured with terahertz time domain transmission spectroscopy, is used as a reference in the terahertz
time domain reflection spectroscopy. Therefore the complex refractive index of metal has been obtained by the Fresnel
law in the presence of the known silicon refractive index. By this method, the refractive indices of aluminum and copper
plates in the terahertz region are measured, furthermore, these experimentally obtained results are discussed with the
simple Drude model.
Single frequency, single mode laser output from a monolithic resonator was amplified by a double-clad D-shape fiber of 4.4 meters long. When the signal laser is 200mw, up to 6.65 W single frequency laser output was obtained, slope efficiency is 30.6%. The amplifier is Yb3+ doped glass fiber pumped by a laser diode array at 976nm with signal at 1064nm. Single frequency amplification has been proved by a Fabri-Parrot interferometer. It is shown from the
experiments that the signal input has not been saturated. By increasing the input signal, amplification can be increased further under the same pumping power. Experimental results meet well with theoretical calculation.
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