Experimental results of homodyne terahertz interferometric 2-D imaging of RDX are presented. Continuous waves at
0.25-0.6 THz are used to obtain images of a C-4 sample at several THz frequencies. The performance of an N element
detector array is imitated by only one detector placed at N positions. The distance between the C-4 sample and the
detector array is ~30 cm. By taking interferometric images at several THz frequencies RDX can be recognized by the
spectral peak at 0.82 THz. Simulations of interferometric images of two point sources of spherical waves are presented.
The terahertz interferometric imaging method can be used in defense and security applications to detect concealed
weapons, explosives as well as chemical and biological agents.
Experimental results of two-dimensional homodyne terahertz interferometric imaging are presented. The
performance of an N element detector array is imitated by only one detector placed at N positions.
Continuous waves at 0.25-0.3 THz are used to detect concealed objects: a metal object and an RDX
sample. The terahertz interferometric imaging method can be used in defense and security applications to
detect concealed weapons, explosives as well as chemical and biological agents.
Experimental results of homodyne terahertz interferometric 1-D and 2-D imaging are presented. Continuous waves at 0.25-0.3 THz are used to detect a metal object behind a barrier. The performance of an N element detector array is imitated by only one detector placed at N positions. The reconstructed images are in a good agreement with theoretical predictions. The terahertz interferometric imaging method can be used in defense and security applications to detect concealed weapons, explosives as well as chemical and biological agents.
We report on the application of poled electro-optic (EO) polymer films in a gap-free, broadband terahertz (THz) system. Using polymer films consisting of 40% Lemke/60% APC (LAPC) as an emitter-sensor pair and a Ti:sapphire regenerative laser pulse amplifier operated at 800-nm-wavelength, we generated and detected transient THz waves, via the optical rectification and EO effect, respectively. We obtained ~12-THz bandwidth from this system with no absorption gaps. The absence of resonant absorption gaps normally seen in THz systems based on crystalline EO materials is attributed to the amorphous form of the polymer films, making our EO polymer emitter-sensor pair advantageous over EO crystals in a gap-free, broadband THz time-domain-spectroscopy (THz-TDS) system. A model has been developed to simulate the spectrum from THz systems and the simulation results were compared with the experimental results. We also report our experiments and simulations for the pulsed THz waves generated by a EO polymer film consisting of 40% DCDHF-6-V/60% APC (DAPC) and detected either by an 80-μm ZnCdTe or a 2-mm ZnTe sensor, with 1300-nm-wavelength pulses from an optical parametric amplifier (OPA). In addition, with the help of our model, we propose employing a wavelength tuning technique to achieve good phase-matching for polymer emitter/sensor pairs, which should lead to very broad bandwidth.
Electro-optic (EO) polymers are promising materials to be used as THz emitters and sensors due to their high nonlinear coefficients and good phase-matching conditions. We demonstrate efficient THz generation from an 80 μm thick EO polymer emitter which is equivalent to that of a 1000 μm thick ZnTe standard. Also, this kind of EO polymer allows a generation up to 20 THz with ultra-short laser pulses. We have observed resonance-enhanced THz generation in another kind of EO polymer composite near its absorption maximum. Due to a sharp resonance of the EO coefficient near the absorption maximum of the material, the amplitude of THz field generated from a 3.1 μm thick film of this composite is 15% larger than that from a 1000 μm thick ZnTe standard. The estimated EO coefficient of this composite at 800 nm is over 1200 pm/V.
Photopolymer material (PPM) is the organic I i ght-sensi tive medium. Due to light irradiation the polymerization of the initial monomer occurs causing the refractive index change. Therefore these materials al low the phase hologram recording with the high diffraction efficiency (DE). PPM used in holography can be separated by the three types : - Ii quid PPM based on the I i quid monomers which polymer1zatlon takes place between two plate glasses, - solid PPM with polymer matrix photocross- linking, - amorfous PPM containing matrix polymer fi Im and monomer, initiator and sensibilizator. Liquid arid sol i d PPM are elaborated for holography E 1-4], but they are used for a long time in the field of microelect ronics, reprography arid other photoprocesses. Amorfous PPM was created especially for holographic purposes. It attracts users by the real- t i ne record I ng, fac I I I ty of nter I al deve 1opnnt without any wet process. PPM described in E 5, 6) and PPM of' Du Pont De Nemours  are the nteria1s of this kind. In the present paper the chemical approach in the elaboration of anrfous PPM for the hologram recording by the HeNe- laser I s descr I bed. The pecul I ar i t i es of the recording process i n the new PPM are also dIscussed.
The principle of optical recording on photopolymer materials (PPM) is based on radical polymerization due to light irradiation. It causes the refractive index change, therefore, a PPM allows the volume phase hologram recording in real time. They are simple in treatment and don't need any additional devices for the recording. The elaboration and investigation achievements of our new patent pure photopolymer GFPM-633A are given in this report. The new material is also intended for volume phase hologram recording by coherent light at wavelength 620 - 680 nm.
Hologram amplification was found for the first time in the crystals of lithium niobate LiNbO3. This phenomenon has been observed in several kinds of recording media. The detailed phenomenological description of that effect is given. The photopolymer materials (PPM) are organic light-sensitive media. The light-induced radical polymerization in these materials causes refractive index increases. Increased diffraction efficiency of holograms in PPM due to one-beam postexposure was observed for the first time in the first half of the 1970s. The hologram amplification in the liquid photopolymer FPK-488 composition has been recently investigated in details. The postpolymerization amplification (PPA) in thermal reactions has been noted. The results of experiments for the coherent dynamic self-amplification (DSA) in that material are presented. The amplification mechanism has also been analyzed in these articles. The Du Pont de Nemours photopolymer materials allow thermal amplification of reflection holograms. Samples are heated to the temperature of 80 degree(s) - 125 degree(s)C after the recording and during 180 min. treatment the refractive index increases from 0.007 to 0.015 - 0.022.