Abstract
An electro-optic dendrimer (EO dendrimer) material has been designed for high power terahertz generation. An ordinary poly (amidoamine organosilicon) (PAMAMOS) dendrimer was modified via doping and poling to generate a high electro-optic coefficient nanomaterial. Measured EO coefficient varied from ~130 pm/V at 633 nm to ~90 pm/V at 1553 nm. An emitter designed from this EO dendrimer generates milliwatts of continuous wave (CW) terahertz radiation (T-ray) when pumped by a CW laser of suitable wavelength. The mechanism termed as the dendrimer dipole excitation (DDE) works via excitation of the dipole population generated by the doping process. The doping protocol also generates a distribution of dipole moments, as opposed to fixed dipoles in the lattice of a crystalline material; thus, when excited by a suitable pump laser, these dipoles radiate a broadband frequency that range from 0.1 THz to ~ 30 THz. A terahertz time-domain spectrometer (TeraSpectra) was designed with this DDE terahertz source. As a test of the spectrometer functionality, a standard polyethylene calibration was conducted. It was found that TeraSpectra reproduces several known absorbance peaks of polyethylene. It also produces additional absorbance peaks not observed before. It is surmised that the ultra-high sensitivity of T-ray enables observation and discovery of additional absorbance peaks that are not visible via other spectroscopy such as visible, UV, FTIR or Raman.
Highlights
The so-called difference frequency generation (DFG) process [1] eliminates the use of a femto-second pulsed laser method for pulsed terahertz generation such as photo-conduction [2] and optical rectification [3]
If this dipole distribution is excited by a suitable pump laser, a broadband emission is expected which falls in the terahertz range
We describe an electro-optic dendrimer exhibiting higher electro-optic coefficient and higher second order susceptibility leading to a high power, wide broadband terahertz generation
Summary
The so-called difference frequency generation (DFG) process [1] eliminates the use of a femto-second pulsed laser method for pulsed terahertz generation such as photo-conduction [2] and optical rectification [3]. If this dipole distribution is excited by a suitable pump laser, a broadband emission is expected which falls in the terahertz range. It is known that dendrimers form a self-assembled multilayer on substrates whose thickness can be controlled by manipulating the dendrimer generation, surface and solution chemistry [6] Because of their highly organized structure, dendrimers form high quality films that are suitable for lithographic fabrication of waveguide based photonic devices. High χ (2) value plays an important role for both the up conversion and the bandwidth, as will be described later
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