Arash Mokhtari

Fully-tunable microwave photonic filter with complex coefficients using tunable delay lines based on frequency-time conversions

A fully electrically tunable microwave photonic filter is realized by the implementation of delay lines based on frequency-time conversion. The frequency response and free spectral range (FSR) of the filter can be engineered by a simple electrical tuning of the delay lines. The method has the capability of being integrated on a silicon photonic platform. In the experiment, a 2-tap tunable microwave photonic filter with a 3-dB bandwidth of 2.55 GHz, a FSR of 4.016 GHz, a FSR maximum tuning range from -354 MHz to 354 MHz and a full FSR translation range is achieved.

Rigorous 3D Vectorial Gaussian Beam Modeling of Demultiplexing Performance of Virtually-Imaged-Phased-Arrays

We extend our previously-derived generalized closed-form representation for spectral dispersing performance of the Virtually- Imaged-Phased-Array (VIPA) based on a 3D vectorial Gaussian beam formulation to demultiplexing application. To analyze VIPA in the demultiplexer scheme, a spherical lens is added after the VIPA, so that the device plane is superimposed on the focal plane of the lens. The calculated output proflle at previous step is reformulated > in a matrix form in this step. Finally, the derived closed-form is simulated, and the numerical outcomes are compared with the previous results. The 3D output radiation of VIPA demultiplexer pattern is also depicted and found to be very intuitive and promising for some applications especially WDM demultiplexer and optical Code Division Multiple Access (CDMA).

Tunable microwave-photonic filter using frequency-to-time mapping-based delay lines

A new implementation of microwave-photonic filters (MPFs) based on tunable optical delay lines is proposed and demonstrated. The variable delay is based on mapping of the spectral components of an incoming waveform onto the time domain, the application of linearly-varying temporal phase offsets, and an inverse mapping back to the frequency domain. The linear phase correction is equivalent to a frequency offset, and realized though suppressed-carrier single-sideband modulation by a radio-frequency sine wave. The variable delay element, controlled by the selected frequency, is used in one arm of a two-tap MPF. In a proof-of-concept experiment, the free spectral range (FSR) of the MPF was varied by over a factor of four: between 1.2 GHz and 5.3 GHz.

Rigorous vectorial Gaussian beam modeling of spectral dispersing performance of virtually imaged phased arrays

We have developed a generalized closed-form representation of the virtually imaged phased array (VIPA) output profile based on a 3D vectorial Gaussian beam formulation. Tracing the input vectorial elliptic Gaussian beam (GB), the output profile of the VIPA is represented as an array of virtual images. Furthermore, employing GB propagation and summing up all the virtual image profiles, the VIPA output profile has been calculated on a vertical plane at an arbitrary distance from the device. Finally, the derived closed-form representation is applied to the different sources (i.e., circular and elliptic GBs) and the results are compared with previous work.

Effect of a phasor group delay ripple on the performance of phase-modulator based microwavephotonic filter

We have developed an analytic approach to investigate the effect of a sinusoid group delay ripple on the performance of phase-modulated microwave photonic filter. Frequency of fabricated sinusoid ripple determines the poles frequency of the resulted transfer function. Comparison of our proposed analytical approach with simulated OptiSystem results shows a good agreement.

The group delay ripple effects on the performance of phase-modulator based microwave-photonic filter

We have developed an analytic approach to investigate the effect of group delay ripple on the performance of phase-modulated microwave photonic filter. Two cases with and without ripple are analyzed to clarify the ripples effects on the performance of microwave-photonic filter. Comparison of our proposed analytical approach with simulated OptiSystem© results shows a good agreement.