Mickael Mounaix

A multimode electromechanical parametric resonator array.

Electromechanical resonators have emerged as a versatile platform in which detectors with unprecedented sensitivities and quantum mechanics in a macroscopic context can be developed. These schemes invariably utilise a single resonator but increasingly the concept of an array of electromechanical resonators is promising a wealth of new possibilities. In spite of this, experimental realisations of such arrays have remained scarce due to the formidable challenges involved in their fabrication. In a variation to this approach, we identify 75 harmonic vibration modes in a single electromechanical resonator of which 7 can also be parametrically excited. The parametrically resonating modes exhibit vibrations with only 2 oscillation phases which are used to build a binary information array. We exploit this array to execute a mechanical byte memory, a shift-register and a controlled-NOT gate thus vividly illustrating the availability and functionality of an electromechanical resonator array by simply utilising higher order vibration modes.

Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix.

We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging.

Transmission-matrix-based point-spread-function engineering through a complex medium

When coherent light propagates through a disordered system, such as white paint or biological tissue, its spatial properties are mixed and the resulting transmitted field forms a speckle pattern. Although the size of a speckle grain is diffraction-limited, this complex interference figure is detrimental for all conventional imaging systems. Over the last decade, wavefront shaping techniques have opened a new way to perform imaging through disordered systems using spatial light modulators (SLM), which offer millions of degrees of freedom to control light propagation. Notably, several techniques have demonstrated the capacity of using a thick scattering medium as a “perfect scattering lens” to arbitrary focus light after the medium in a given position, with a spot size limited by the size of the speckle grain, i.e. diffraction [1]. Among these techniques, the optical transmission matrix (TM) of the scattering medium can be easily measured [2], and contains the linear relation between the input fields and the output fields.

Deterministic light focusing in space and time through multiple scattering media with a time-resolved transmission matrix approach

We report a method to characterize the propagation of an ultrashort pulse of light through a multiple scattering medium by measuring its time-resolved transmission matrix. This method is based on the use of a spatial light modulator together with a coherent time-gated detection of the transmitted speckle field. Using this matrix, we demonstrate the focusing of the scattered pulse at any arbitrary position in space and time after the medium. Our approach opens different perspectives for both fundamental studies and applications in imaging and coherent control in disordered media.

Temporal recompression through a scattering medium via a broadband transmission matrix

The transmission matrix is a unique tool to control light through a scattering medium. A monochromatic transmission matrix does not allow temporal control of broadband light. Conversely, measuring multiple transmission matrices with spectral resolution allows fine temporal control when a pulse is temporally broadened upon multiple scattering, but requires very long measurement time. Here, we show that a single linear operator, measured for a broadband pulse with a co-propagating reference, naturally allows for spatial focusing, and interestingly generates a two-fold temporal recompression at the focus, compared with the natural temporal broadening. This is particularly relevant for non-linear imaging techniques in biological tissues.

Temporal recompression of an ultrashort pulse of light with a broadband transmission matrix (Conference Presentation)

Spatial and temporal properties of an ultrashort pulse of light are naturally scrambled upon propagation in thick scattering media. Significant progresses have been realized over the last decade to manipulate light propagation in scattering media, mostly using monochromatic light. However, applications that require a broadband ultrashort pulse of light remain limited, as the pulse gets temporally broadened because of scattering effects. A monochromatic optical transmission matrix does not allow temporal control of broadband light. Although measuring multiple transmission matrices with spectral resolution allows fine temporal control, it requires lengthy measurements, as well as stability of the medium. In this work, we show that a single linear operator that we named Broadband Transmission Matrix, can be straightforwardly measured for a broadband pulse with a co-propagating reference. We exploit this operator for focusing purposes, and we analyze its phase conjugation properties. While the operator naturally allows for spatial focusing, unexpectedly, the focus duration is on average shorter than the natural temporal broadening due to the medium. More precisely, we observe a two-fold temporal recompression at the focus that we fully explain theoretically. We also explore the spectral content at the focus, and demonstrate a narrowing of the spectrum. These results are particularly relevant for non-linear imaging techniques in biological tissues, at depth where an ultrashort excitation pulse is broadened.

Deterministic light focusing in space and time through multiple scattering media with a Time-Resolved Transmission Matrix approach (Conference Presentation)

When an ultrashort pulse of light propagates in a scattering medium, its spatial and temporal properties get mixed and distorted because of the scattering process. Spatially, the output pattern is the result of the multiple interference between the scattered photons. Temporally, light gets stretched within the medium due to its characteristic confinement time, thus the output pulse is broadened in the time domain. Nonetheless, as the scattering process is linear and deterministic, the spatio-temporal profile of light at the output can be controlled by shaping the input light using a single spatial light modulator (SLM). We report the first experimental measurement of the Time-Resolved Transmission Matrix of a multiple scattering medium using a coherent time-gated detection system. This operator contains the relationship between the input field, controllable with a SLM, and the output field accessible with a CCD camera for a given arrival time of photons at the output of medium. The delay line of the time-gated detection system sets the arrival time at will within the time of flight distribution of photons of the output pulse. We exploit this time-resolved matrix to achieve spatio-temporal focusing of the output pulse at any arbitrary space and time position. The pulse is recompressed in time to its original Fourier-limited temporal width and spatially to the diffraction-limited size defined by the speckle grain size. We also generate more sophisticated spatio-temporal profiles such as pump-probe like pulse, thus opening interesting perspectives in coherent control, light-matter interaction and imaging in disordered media.

Sub-diffraction limit focusing through a complex medium by virtual Fourier filtering

We have recently reported on a method to design at will the spatial profile of transmitted coherent light after propagation through a strongly scattering sample, exploiting wavefront shaping in combination with a transmission matrix approach. In this paper, we explore experimentally and theoretically the ability of this approach to generate foci whose full width at half maximum are smaller than the diffraction-limited speckle grain size, using (Bessels) beam variations implemented with virtual annular filters.

Coherent spatiotemporal control of light through a multiply scattering medium

We report broadband characterization of the propagation of light through a multiply scattering medium by means of its Multi-Spectral Transmission Matrix. Using a single spatial light modulator, our approach enables the full control of both spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in coherent control and imaging.