Embedded Files
Ultrafast optical processing of light achieve operations at speeds several orders higher than in electronics due to the huge ~ THz bandwidth of optical systems and signals.
Particularly, the employ of resonant optical structures have successfully implement diverse functionality, such as Integral Transform (Fourier, Hilbert), temporal operations (differentiation, integration), pulse shaping, pulse repetition rate multiplication or pulses burst generation, with most of the recent interest centred in microwave photonics.
During my previous research, I have studied and proposed a number of solutions for a variety of ultra-fast processing functionalities.
I have been particularly interested in high-order optical cavities structures, based on ring resonators and Bragg gratings.
Feasible fiber Bragg gratings in transmission mode by phase-modulated uniform-coupling grating
Feasible fiber Bragg gratings in transmission mode by phase-modulated uniform-coupling grating
Bragg gratings can perform ultra-fast processing by the scattered multiple reflections in their photonic structure.
Transmission mode offers very interesting properties, such as optimum energy efficiency, no requirement for an optical circulator to extract the reflection mode output, and robustness against fabrication errors.
A number of groups have been investigating the transmissible use of Bragg gratings during many years. However, many of the numerically demonstrated designed transmissible Bragg gratings are unpractical due to the challenging coupling coefficient obtained for its fabrication, typically composed of high peaks and irregular ripples. (See Figure below)
We have demonstrated a technique that enables the implementation of phase-modulated Bragg grating by only modulating the grating period, while keeping the coupling coefficient mostly uniform (much more challenging to accurately control), which leads to a huge relaxation in the fabrication process.
This technique is based on the high degree of freedom in the design of transmission mode of Bragg gratings, where there are infinite solutions to provide a spectral response, to relax the challenge of fabrication by numerical optimisation.
Check for data-sets for designed gratings and more info in Resources.
(c) Phase-modulated Bragg grating design. The grating period is much easier to accurately control in practical fabrication than the coupling coefficient!
(d) Manufacturer reaction to a phase-modulated design of a transmissive Bragg grating.
Wide-band ultra-fast processors based on dual chirped Bragg gratings
Wide-band ultra-fast processors based on dual chirped Bragg gratings
We have proposed ultra-fast processors based on two oppositely chirped fibre Bragg gratings. One grating can be used to expand and spectral shape the desired ultra-fast spectral response of the generated chirp pulse, while the second grating compensates the dispersion introduced by the first grating.
This approach is particularly interesting for very wide bandwidth, where a non-chirped approach could require incredibly and unfeasible high coupling coefficient concentrated in a small length, while our chirped approach let the coupling coefficient be distributed along a longer grating.
Furthermore, this approach has the possibility of adjusting the bandwidth and tuning the central wavelength.
"Ultrafast all-optical Nth-order differentiator based on chirped fiber Bragg gratings," Miguel A. Preciado, Víctor García-Muñoz, and Miguel A. Muriel, Opt. Express 15, 7196-7201 (2007)
Pulse-repetition rate multiplication with an all-pass single optical cavity (APOC) 2x, 3x, 4x
Pulse-repetition rate multiplication with an all-pass single optical cavities structures 3x, 4x, 8x and 12x
All-pass optical cavities structures for pulse repetition rate multiplication with maximum energy efficiency
All-pass optical cavities structures for pulse repetition rate multiplication with maximum energy efficiency
We have proposed and demonstrated the application of all-pass optical cavities structures to increase the repetition rate of a pulsed laser outside a laser cavity , with a maximum theoretical 100 % of energy efficiency. All-pass ring resonators structures (or equivalent Gires-Tournois interferometers) can be used in the implementation.
All-pass optical structures for repetition rate multiplicationMiguel A Preciado, Miguel A MurielOptics express 16(15), 11162-1168 (2008)
Optical temporal differentiation and integration.
Photonic processors can perform basic operations at ultra-fast speeds. We have investigated and proposed seveal approaches to perform a temporal differentiation and a temporal integration of an optical signal based on fiber Bragg gratings.
"Design of an ultrafast all-optical differentiator based on a fiber Bragg grating in transmission." Preciado, Miguel A., and Miguel A. Muriel, Optics letters 33.21 (2008): 2458-2460.
"Experimental demonstration of an optical differentiator based on a fiber Bragg grating in transmission" MA Preciado, X Shu, P Harper, K Sugden - Optics letters, 2013
"Ultrafast all-optical Nth-order differentiator and simultaneous repetition-rate multiplier of periodic pulse train." Preciado, Miguel A., and Miguel A. Muriel., Optics express 15, no. 19 (2007): 12102-12107.
"Ultrafast all-optical integrator based on a fiber Bragg grating: proposal and design," Miguel A. Preciado and Miguel A. Muriel, Opt. Lett. 33, 1348-1350 (2008)
Pulses bursts generation by phase only filtering using all-pass optical cavities structures, with ~100 % energy efficiency.
We have proposes a simple lossless method for the generation of flat-topped intensity pulses bursts from a single utrashort pulse. From the application of numerical optimisation to high order optical structures, we have found optimum solutions corresponding to different numbers of cavities and burst pulses, showing that the proposed all-pass structures of optical cavities, properly designed, can generate close to flat-topped pulse busts.
"Proposed flat-topped pulses bursts generation using all-pass multi-cavity structures," Miguel A. Preciado and Miguel A. Muriel, Opt. Express 17, 13875-13880 (2009)
Google Sites
Report abuse