Analysis of short-term polarization stability using Allan variance.

The application of Allan variance to characterize the stability of optical signals affected by stochastic polarization fluctuations and the identification of the underlying power law noise processes is explored. Allan variance can ease the comparison regarding polarization stability of optical systems affected by polarization noise and define a near-optimum integration interval to reveal trends. Examples of the application of Allan variance to optical systems with stable polarization conditions show that white noise and random walk terms can be observed.

Particle Size Inversion from Spectrally Resolved Full-Field Forward Scattering.

Ensemble particle sizing has traditionally relied on inversion of extinction measurements for the characterization of the particle size distribution (PSD) in particulate media. However, particulate media induce complex phase changes that contain valuable information about their structure. Here, we propose the use of coherent detection to derive particle size distributions in inhomogeneous samples from light scattering.

Single trace terahertz spectroscopic ellipsometry.

A new technique for terahertz time-domain ellipsometry is presented. Information of reflection coefficients of the sample in two orthogonal polarizations is encoded on the same terahertz trace by using a birefringent medium. This allows for single measurement refractive index extraction without the need for a moving analyzer.

Determination of refractive index and thickness of a multilayer structure with a single terahertz time domain spectroscopy measurement.

A processing technique for the determination of the average refractive index and thickness of a two-layer system is presented. It is based on a single measurement with a standard terahertz time-domain spectrometer and the multilayer system thickness. The technique relies on the interference caused by the main pulse with the echoes produced in each material.

Birefringence measurement in the terahertz range based on double Fourier analysis.

A method for obtaining the average refractive indexes of a birefringent material in the terahertz region in a single measurement with a standard terahertz time-domain spectrometer is presented. The method is based on processing the frequency-domain interference between terahertz pulses and echoes through the Fourier transform of the terahertz spectrum. The technique also allows the determination of the optical axis orientation of the material by making two measurements with different angles of the sample optical axis.

Terahertz radiation shaping based on optical spectrum modulation in the time domain.

A terahertz shaping system based on optical fiber components as opposed to traditional free-space solutions is proposed. It is based on the time-domain modulation of the optical source spectrum. Standard single-mode fiber distributes and disperses the pulse before filtering its spectral components by means of the cross-gain and cross-phase modulation effects taking place in an interferometric semiconductor optical amplifier structure.

Variable carrier reduction in radio-over-fiber systems for increased modulation efficiency using a Si3N4 tunable extinction ratio ring resonator.

Variable optical carrier reduction via the use of a Si(3)N(4) ring resonator notch filter with tunable extinction ratio is demonstrated in a 10 GHz radio-over-fiber system for improving the modulation efficiency. The extinction of the filter notch is tuned with micro-heaters, by setting the Mach-Zehnder coupler of the ring. Experimental results showing a modulation depth improvement of up to 20 dB are provided.

All-optical WDM multi-tap microwave filter with flat bandpass.

An incoherent photonic microwave filter implementing multiple positive and negative coefficients based on two sets of optical carriers and dispersive media is proposed and demonstrated. Positive and negative coefficients are obtained thanks to the pi phase inversion in a single electro-optic Mach-Zehnder modulator as well as the modulator Vpi dependence with wavelength. To show the feasibility of this technique to implement practical filter transfer functions, the Parks-McClellan algorithm has been used to design a 5-tap flat bandpass filter.