arXiv subjects

Pedro D. Garcia

Publications and source records attributed to Pedro D. Garcia.

4 recordsLinked to original sources

arXiv2022

Optomechanical generation of coherent GHz vibrations in a phononic waveguide

Nanophononics has the potential for information transfer, in an analogous manner to its photonic and electronic counterparts. The adoption of phononic systems has been limited, due to difficulties associated with the generation, manipulation, and detection of phonons, especially at GHz frequencies. Existing techniques often require piezoelectric materials with an external radiofrequency excitation that are not readily integrated into existing CMOS infrastructures, while non-piezoelectric demonstrations have been inefficient. In this work, we explore the optomechanical generation of coherent phonons in a suspended 2D silicon phononic crystal cavity with a guided mode around 6.8 GHz. By incorporating an air-slot into this cavity, we turn the phononic waveguide into an optomechanical platform that exploits localized photonic modes resulting from inherent fabrication imperfections for the transduction of mechanics. Such a platform exhibits very fine control of phonons using light, and is capable of coherent self-sustained phonon generation via mechanical lasing around 6.8 GHz. The ability to generate high frequency coherent mechanical vibrations within such a simple 2D CMOS-compatible system could be a first step towards the development of sources in phononic circuitry and the coherent manipulation of other solid-state properties.

physics.optics↗

arXiv2019

A self-assembled two-dimensional thermo-functional material for radiative cooling

The regulation of temperature at the macro and microscale is a major energy-consuming process of humankind. Modern cooling systems account for 15% of the global energy consumption and are responsible for 10% of greenhouse gas emissions. Due to global warming, a ten-fold growth in the demand of cooling technologies is expected in the next 30 years, thus linking global warming and cooling needs through a worrying negative feedback loop. Here, we propose an inexpensive solution to this global challenge based on a single-layer of silica microspheres self-assembled on a soda-lime glass substrate. This two-dimensional (2D) crystal acts as a visibly translucent thermal blackbody for above-ambient daytime radiative cooling and can be used to passively improve the thermal performance of devices that undergo critical heating during operation. The temperature of a crystalline silicon wafer was found to be 14K lower during daytime when covered with our thermal emitter, reaching an average temperature difference of 19K when the structure was backed with a silver layer. In comparison, the soda-lime glass used as a reference in our measurements lowered the temperature of the silicon wafer by just 5 K. The cooling power density of this rather simple radiative cooler under direct sunlight was found to be up to 350 W/m2 when applied to hot surfaces with relative temperatures of 50 K above the ambient. This is crucial to radiatively cool down electronic devices, such as solar cells, where an increase in temperature has drastic effects on performance. Our 2D thermo-functional material includes a single layer of spheres emitting long-wave radiation through the infrared atmospheric window and over a broad wavelength ange, thus providing effective radiative cooling using the outer space as a heat sink at 3 K.

physics.app-ph↗

arXiv2013

Statistical measurements of quantum emitters coupled to Anderson-localized modes in disordered photonic-crystal waveguides

Optical nanostructures have proven to be meritorious for tailoring the emission properties of quantum emitters. However, unavoidable fabrication imperfections may represent a nuisance. Quite remarkably, disorder offers new opportunities since light can be efficiently confined by random multiple scattering leading to Anderson localization. Here we investigate the effect of such disorder-induced cavities on the emission dynamics of single quantum dots embedded in disordered photonic-crystal waveguides. We present time-resolved measurements of both the total emission from Anderson-localized cavities and from single emitters that are coupled to the cavities. We observe both strongly inhibited and enhanced decay rates relative to the rate of spontaneous emission in a homogeneous medium. From a statistical analysis, we report an average Purcell factor of 2 in without any control on the quantum dot - cavity detuning. By spectrally tuning individual quantum dots into resonance with Anderson-localized modes, a maximum Purcell factor of 23.8 is recorded, which lies at the onset of the strong coupling regime. The presented data quantify the potential of naturally occurring Anderson-localized cavities for controlling and enhancing the light-matter interaction strength, which is of relevance not only for cavity quantum-electrodynamics experiments but potentially also for efficient energy harvesting and controllable random lasing.

physics.optics↗

arXiv2012

An Anderson-localized random nanolaser

Precision is a virtue throughout science in general and in optics in particular where carefully fabricated nanometer-scale devices hold great promise for both classical and quantum photonics [1-6]. In such nanostructures, unavoidable imperfections often impose severe performance limits but, in certain cases, disorder may enable new functionalities [7]. Here we demonstrate on-chip random nanolasers where the cavity feedback is provided by the intrinsic disorder in a semiconductor photonic-crystal waveguide, leading to Anderson localization of light [8]. This enables highly efficient and broadband tunable lasers with very small mode volumes. We observe an intriguing interplay between gain, dispersion-controlled slow light, and disorder, which determines the cross-over from ballistic transport to Anderson localization. Such a behavior is a unique feature of non-conservative random media that enables the demonstration of all-optical control of random lasing. Our statistical analysis shows a way towards ultimate thresholdless random nanolasers.

physics.optics↗