Victor Torres-Company

Dispersion requirements in coherent frequency-to-time mapping

The frequency-to-time mapping technique (also known as the temporal far-field phenomenon) usually requires a significant amount of dispersion to stretch an ultrashort optical pulse so that the intensity profile becomes a scaled replica of its optical spectrum. In this work, we study the near-to-far-field transition and find that the far-field condition can be relaxed in some cases relevant for radio-frequency (RF) waveform generation. This observation has allowed us to achieve intensity signals with an ultrabroad RF bandwidth content.

Multitap microwave photonic filters with programmable phase response via optical frequency comb shaping

We present a programmable multitap microwave photonic filter with an arbitrary phase response operating over a broad bandwidth. Complex coefficient taps are achieved by optical line-by-line pulse shaping on a 10 GHz flat optical frequency comb using a novel interferometric scheme. Through high-speed real-time measurements, we demonstrate programmable chirp control of a waveform via phase filtering. This achievement enables us to compress broadband microwave signals to their corresponding bandwidth-limited pulse duration.

Arbitrary Waveform Generator Based on All-Incoherent Pulse Shaping

An all-incoherent technique for the generation of arbitrary electromagnetic intensity profiles is presented. It is based on spectral filtering of a broadband continuous-wave light source so that the filtered spectral density function (SDF) becomes the user-defined waveform. After large temporal modulation and subsequent distortion in a first-order dispersive medium, the incoherent mapping of the filtered SDF to the time domain occurs. Finally, optical-to-electrical conversion in a fast photodiode allows the optical intensity to be mapped into the electrical domain

Multichannel Radio-Frequency Arbitrary Waveform Generation Based on Multiwavelength Comb Switching and 2-D Line-by-Line Pulse Shaping

We demonstrate a multichannel time-multiplexed radio-frequency arbitrary waveform generator. The system combines a switching scheme of multiwavelength optical frequency combs with a novel 2-D line-by-line pulse shaper featuring broad bandwidth operation over large temporal windows. Switching times within a clock period of 200 ps among the four channels is successfully achieved. With finer pulse shaper resolution, the number of channels can be scaled up without increasing the number of switching components.

Ultrafast electrooptic dual-comb interferometry

Dual-comb interferometry is a particularly compelling technique that relies on the phase coherence of two laser frequency combs for measuring broadband complex spectra. This method is rapidly advancing the field of optical spectroscopy and empowering new applications, from nonlinear microscopy to laser ranging. Up to now, most dual-comb interferometers were based on modelocked lasers, whose repetition rates have restricted the measurement speed to ~kHz. Here we demonstrate a dual-comb interferometer that is based on electrooptic frequency combs and measures consecutive complex spectra at an ultra-high refresh rate of 25 MHz. These results pave the way for novel scientific and metrology applications of frequency comb generators beyond the realm of molecular spectroscopy, where the measurement of ultrabroadband waveforms is of paramount relevance.

Space-Time Analogies in Optics

Abstract The so-called space-time analogy constitutes a source of inspiration to understand, engineer, and implement new systems for ultrafast optical signal processing based on concepts borrowed from the well-established field of Fourier Optics. In this review, we start by describing in a comprehensive manner the most basic notions of this analogy and discuss some recent developments with state-of-the-art technology, including the silicon-chip-based time lens and ultra-dispersive Raman devices, among others. Apart from the applications in optical communications, special emphasis is paid on the collateral benefits that the “ultra” appellative brings in fields as diverse as optical frequency comb generation, arbitrary waveform generation, optical coherence tomography, sensors, imaging, or quantum information processing.

Simultaneous broadband microwave downconversion and programmable complex filtering by optical frequency comb shaping

High-repetition-rate optical frequency combs can act as broadband photonic mixers and downconvert a microwave signal to an intermediate frequency (IF) band so that it becomes accessible with high-speed electronics. In this Letter, we show that with line-by-line pulse shaping and dispersive propagation, the photonic mixer can simultaneously perform programmable multitap complex-coefficient-filtering within the IF band. This solution opens new possibilities for microwave signal processing by combining the flexibility of optoelectronic frequency comb technology with high-speed analog-to-digital converters.

Octave-spanning supercontinuum generation in a silicon-rich nitride waveguide

We generate supercontinuum (817-2250 nm at -30dB) in a dispersion-engineered silicon-rich nitride waveguide by pumping fs pulses with 82 pJ from an erbium-fiber oscillator. Spectral broadening mechanisms include soliton fission and dispersive wave generation.

Noise Comparison of RF Photonic Filters Based on Coherent and Incoherent Multiwavelength Sources

A filtered microwave photonic (MWP) link implemented with an optical frequency comb as a multitap optical source offers a significant improvement in noise characteristics when compared to a spectrally sliced broadband incoherent source with the same number of taps and identical tap delay. Our results show that frequency combs also enable a better use of the optical bandwidth for filtering with minimum noise-induced fluctuations. These results highlight the potential of optical frequency comb technology to operate over large distances in MWP filter links.

Inverse dispersion engineering in silicon waveguides

We present a numerical tool that searches an optimal cross section geometry of silicon-on-insulator waveguides given a target dispersion profile. The approach is a gradient-based multidimensional method whose efficiency resides on the simultaneous calculation of the propagation constant derivatives with respect to all geometrical parameters of the structure by using the waveguide mode distribution. The algorithm is compatible with regular mode solvers. As an illustrative example, using a silicon slot hybrid waveguide with 4 independent degrees of freedom, our approach finds ultra-flattened (either normal or anomalous) dispersion over 350 nm bandwidth in less than 10 iterations.