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In this work we have studied the terahertz spectra of modern artificially aged and ancient paper samples using terahertz time-domain spectroscopy. Hydrothermal artificial aging was performed in closed and open reactors. Ancient paper samples were produced during the 15th century in European countries. The main aim of the work is the quantitative assessment of spectral feature observed by terahertz...
A THz wire grid polarizer on cyclo-olefin Zeonor polymer film that exhibits high extinction ratio and low losses is theoretically and experimentally investigated. The polarizer has an extinction ratio between 30 and 45 dB and insertion losses below 1 dB in the 0.3–2.5 THz range. The high-performance characteristics of the polarizer are preserved even when it is bent at a radius of 12.5 mm. Although...
We present an analytical model carefully describing the time-frequency behavior of all the stages composing our whole Terahertz Time Domain Spectroscopy laser based system, from the THz pulses generation via Optical Rectification, to their detection through Electro-Optic Sampling technique, by way of diffraction, collecting and focusing effects. In order to prove the effectiveness of our work, we...
An all-optical, sub-wavelength terahertz characterization technique based on an ultra-thin-knife-edge is demonstrated employing ultraviolet-pulse to project the blade image on a ZnTe crystal, where the free carriers excited on a blade-shaped area act as field-shield.
We demonstrate novel microcavity lasers in an integrated, CMOS compatible platform. This platform has promise for telecommunications and on-chip WDM optical interconnects.
A potential solution for the demand for highly stable pulsed lasers at hundreds of GHz repetition rates is represented by passively mode locked fiber lasers. These lasers are composed of a band-limited amplifier, a dispersive element and a nonlinear element. When a high finesse resonant filter is added intracavity, they emit pulses with a repetition rate equal to the filter free spectral range (FSR)...
We experimentally demonstrate an isolator based on a magnetic non-reciprocal retarder operating with broadband terahertz pulses. Our device depends on permanently magnetized Strontium Iron Oxide, where Faraday rotations up to (194º/T) were obtained.
We demonstrate a range of novel functions based on a high index doped silica glass CMOS compatible platform. This platform has promise for telecommunications and on-chip WDM optical interconnects for computing.
We summarize our recent results on the generation and of ultrafast optical signals in CMOS-compatible monolithic devices by exploiting the third order nonlinearity of glass based waveguides. We show that we can generate stable train of pulses at 200GHz rep rate with a novel passive mode-locking scheme based on an integrated ring resonator.
We report a novel design for an integrated optical parametric oscillator (OPO) in a CMOS-compatible microring. It exploits self-sustained lasing of the pump tuned to a microcavity resonance, preventing the OPO from dimming with thermal fluctuations.
We demonstrate a mode locked laser based on a integrated high-Q microring resonator that exhibits stable operation of two slightly shifted spectral optical comb replicas, generating a highly monochromatic radiofrequency modulation.
We show that by employing positively chirped optical probe pulses above a critical power it is possible to enhance the detection bandwidth and signal obtained by Air Biased Coherent Detection scheme for broadband terahertz fields.
We report on the signal enhancement in the Air Biased Coherent Detection scheme of broadband terahertz fields in the transition from below to above the critical power for self-focusing of positively chirped optical probe pulses.
We demonstrate a stable, low noise, 200GHz passively mode locked soliton laser based on a novel design that extends the Dissipative-FWM concept. It is based on a highly nonlinear, CMOS compatible integrated micro-ring resonator.
Nematicons, i.e., optical spatial solitons in nematic liquid crystals (NLC), have been attracting a great deal of attention due to their unique properties such as, for example, excitability at powers of a few hundred µW and the possibility to be electrically and/or optically (by other light beams) bent.[1] In this work we investigate, both experimentally and theoretically, the nematicon behavior for...
All-optical signal processing has been demonstrated extensively in Si including demultiplexing at 160Gb/s via four-wave mixing (FWM) [1] and optical regeneration [2], as well as in chalcogenide glass (ChG) waveguides[3]. The efficiency of all-optical devices can be improved by increasing the nonlinear parameter, γ = ω n2 / c Aeff (Aeff is the waveguide effective area, n2 is the Kerr nonlinearity)...
We present a device for full waveform characterization, exploiting FWM in a CMOS compatible photonic chip, working with pulse energies as low as 10pJ and with sub-picosecond (<;700fs) accuracy over a 100ps temporal window duration.
We present a dissipative four wave mixing tunable laser based on a integrated CMOS-compatible high-Q nonlinear ring resonator, emitting subpicosecond pulses at 200GHz-repetition rate. Quasi-sinusoidal 800GHz emission regime is also demonstrated.
We demonstrate a stable passively mode locked soliton laser that extends the Dissipative-FWM concept, in a highly nonlinear, CMOS compatible integrated micro-ring resonator. Operation at 200GHz, free of supermode instability, is demonstrated.
We demonstrated that Quasi-TEM modes in non-subwavelength dual wire THz waveguides (twin lead) can exhibit significant end-fire coupling (>10%) and broad band low dispersion below 1ps2/m
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