Jacopo Mocci

Real-time adaptive optics testbed to investigate point-ahead angle in pre-compensation of Earth-to-GEO optical communication

We explore adaptive optics (AO) pre-compensation for optical communication between Earth and geostationary (GEO) satellites in a laboratory experiment. Thus, we built a rapid control prototyping breadboard with an adjustable point-ahead angle where downlink and uplink can operate both at 1064 nm and 1550 nm wavelength. With our real-time system, beam wander resulting from artificial turbulence was reduced such that the beam hits the satellite at least 66% of the time as compared to merely 3% without correction. A seven-fold increase of the average Strehl ratio to (28 ± 15)% at 18 μrad point-ahead angle leads to a considerable reduction of the calculated fading probability. These results make AO pre-compensation a viable technique to enhance Earth-to-GEO optical communication.

Fast stabilization of a high-energy ultrafast OPA with adaptive lenses

The use of fast closed-loop adaptive optics has improved the performance of optical systems since its first application. Here we demonstrate the amplitude and carrier-envelope phase stabilization of a high energy IR optical parametric amplifier devoted to Attosecond Science exploiting two high speed adaptive optical systems for the correction of static and dynamic instabilities. The exploitation of multi actuator adaptive lenses allowed for a minimal impact on the optical setup.

Adaptive optics with combined optical coherence tomography and scanning laser ophthalmoscopy for in vivo mouse retina imaging

Optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) are two state-of-the-art imaging technologies commonly used to study retina. Adaptive Optics (AO) methodologies enable high-fidelity correction of ocular aberrations, resulting in improved resolution and sensitivity for both SLO and OCT systems. Here we present work integrating OCT into a previously described mouse retinal AO-SLO system, allowing simultaneous reflectance and fluorescence imaging. The new system allows simultaneous data acquisition of AO-SLO and AO-OCT, facilitating registration and comparison of data from both modalities. The system has data acquisition speed of 200 kHz A-scans/pixel, and high volumetric resolution.

High-energy OPA stability control with adaptive lenses

Adaptive Optics (AO) is a key technology for ground-based astronomical telescopes, allowing to overcome the limits imposed by atmospheric turbulence and obtain high resolution images. This technique however, has not been developed for small size telescopes, because of its high cost and complexity. We realized an AO system based on a Multi-actuator Adaptive Lens and a Shack-Hartmann wavefront sensor (WFS), allowing for a great compactness and simplification of the optical design. The system was integrated on a 11” telescope and controlled by a consumer-grade laptop allowing to perform Closed-Loop AO correction up to 400 Hz.

Adaptive optics on small astronomical telescope with multi-actuator adaptive lens

Adaptive Optics (AO) is a key technology for ground-based astronomical telescopes, allowing to overcome the limits imposed by atmospheric turbulence and obtain high resolution images. This technique however, has not been developed for small size telescopes, because of its high cost and complexity. We realized an AO system based on a Multi-actuator Adaptive Lens and a Shack-Hartmann wavefront sensor (WFS), allowing for a great compactness and simplification of the optical design. The system was integrated on a 11” telescope and controlled by a consumer-grade laptop allowing to perform Closed-Loop AO correction up to 400 Hz.

Effect of a contact lens on mouse retinal in vivo imaging: Effective focal length changes and monochromatic aberrations

ABSTRACT For in vivo mouse retinal imaging, especially with Adaptive Optics instruments, application of a contact lens is desirable, as it allows maintenance of cornea hydration and helps to prevent cataract formation during lengthy imaging sessions. However, since the refractive elements of the eye (cornea and lens) serve as the objective for most in vivo retinal imaging systems, the use of a contact lens, even with 0 Dpt. refractive power, can alter the systems optical properties. In this investigation we examined the effective focal length change and the aberrations that arise from use of a contact lens. First, focal length changes were simulated with a Zemax mouse eye model. Then ocular aberrations with and without a 0 Dpt. contact lens were measured with a Shack‐Hartmann wavefront sensor (SHWS) in a customized AO‐SLO system. Total RMS wavefront errors were measured for two groups of mice (14‐month, and 2.5‐month‐old), decomposed into 66 Zernike aberration terms, and compared. These data revealed that vertical coma and spherical aberrations were increased with use of a contact lens in our system. Based on the ocular wavefront data we evaluated the effect of the contact lens on the imaging system performance as a function of the pupil size. Both RMS error and Strehl ratios were quantified for the two groups of mice, with and without contact lenses, and for different input beam sizes. These results provide information for determining optimum pupil size for retinal imaging without adaptive optics, and raise critical issues for design of mouse optical imaging systems that incorporate contact lenses. HIGHLIGHTSContact lens induced changes to mouse ocular aberrations are studied in detail using simulation and experiments.Application of the contact lens increases the effective focal length of the mouse eye and affects system resolution.Contact lens introduce two major aberrations: spherical and vertical coma (if not aligned properly).High spatial and temporal wavefront sensing allows accurate mapping of mouse eye aberrations, enabling photoreceptor imaging.

High-speed adaptive deformable lens for boosting an high-energy optical parametric amplifier

Intense ultrafast laser sources in the mid-IR have attracted in the recent years lot of attention in strong-field physics. A possible implementation for such sources relies in: a) the generation of a short IR seed by intra-pulse difference frequency generation (DFG) of a broadband continuum generated in an hollow-core fiber (HCF); b) optical parametric amplification (OPA) of the seed to the mJ level [1]. This approach yields a major advantage, namely the passive stabilization of the carrier-envelope phase (CEP) owing to the DFG process, enabling applications like the generation of isolated attosecond pulses in the soft X-rays. Nevertheless the CEP stability performances are limited with respect to those achievable with active stabilization techniques. Moreover, OPA setups require a very good beam quality as well as a robust stability of the pumping source and this can hinder the scalability towards higher pulse energies.

Wavefront control with a multi-actuator adaptive Lens in imaging applications

The use of adaptive lenses instead of deformable mirrors can simplify the implementation of an adaptive optics system. The recently introduced Multi-actuator Adaptive Lens (MAL) can be used in closed loop with a wavefront sensor to correct for time-variant wavefront aberrations. The MAL can guarantee a level of correction and a response time similar to the ones obtained with deformable mirrors. The adaptive lens is based on the use of piezoelectric actuators and, without any obstruction or electrodes in the clear aperture, can guarantee a fast response time, less than ~10ms. Our tests show that the MAL can be used both in combination with a wavefront sensor in a “classical” adaptive optics closed loop, or in a wavefront sensorless configuration. The latter has allowed us to design more compact and simple imaging systems for different microscopy platforms. We will show that the Multi-actuator Adaptive Lens has been successfully used for in-vivo OCT ophthalmic imaging in both mice and humans, as well as confocal and two photon microscopy. We tested and compared different optimization strategies such as coordinate search and the DONE algorithm. The results suggest that the MAL optimization can correct for eye aberrations with a pupil of 5mm or sample induced aberrations in microscopy.

Fault model qualification by assertion mining

The process of measuring the quality of a fault model is a key ingredient for implementing effective verification/testing phases based on fault injection. Most of the existing approaches for the qualification of a fault model base their evaluation on the comparison of the achieved fault coverage against other code coverage metrics, or against the fault coverage achieved by different fault models, sometimes at the varying of the abstraction level. However, these approaches do not explicitly provide a measure of the accuracy of the fault injection with respect to the actual functional behaviours implemented in the design under verification/testing (DUV/T). Thus, the achievement of 100% fault coverage does not necessarily imply that all the designs behaviours have been accurately perturbed by the selected fault model. To provide a more accurate evaluation of fault models, this paper proposes a methodology based on assertion mining, i.e., automatic extraction of temporal assertions from the simulation of the DUV/T. Mined assertions are then used to highlight behaviours of the DUV/T that are not accurately perturbed by the selected fault model.