Observation of Spontaneous Brillouin Cooling

While radiation-pressure cooling is well known, the Brillouin scattering of light from sound is considered an acousto-optical amplification-only process. It was suggested that cooling could be possible in multi-resonance Brillouin systems when phonons experience lower damping than light. However, this regime was not accessible in traditional Brillouin systems since backscattering enforces high acoustical frequencies associated with high mechanical damping. Recently, forward Brillouin scattering in microcavities has allowed access to low-frequency acoustical modes where mechanical dissipation is lower than optical dissipation, in accordance with the requirements for cooling. Here we experimentally demonstrate cooling via such a forward Brillouin process in a microresonator. We show two regimes of operation for the Brillouin process: acoustical amplification as is traditional, but also for the first time, a Brillouin cooling regime. Cooling is mediated by an optical pump, and scattered light, that beat and electrostrictively attenuate the Brownian motion of the mechanical mode.Comment: Supplementary material include

Bridging ultrahigh-Q devices and photonic circuits

Optical microresonators are essential to a broad range of technologies and scientific disciplines. However, many of their applications rely on discrete devices to attain challenging combinations of ultra-low-loss performance (ultrahigh Q) and resonator design requirements. This prevents access to scalable fabrication methods for photonic integration and lithographic feature control. Indeed, finding a microfabrication bridge that connects ultrahigh-Q device functions with photonic circuits is a priority of the microcavity field. Here, an integrated resonator having a record Q factor over 200 million is presented. Its ultra-low-loss and flexible cavity design brings performance to integrated systems that has been the exclusive domain of discrete silica and crystalline microcavity devices. Two distinctly different devices are demonstrated: soliton sources with electronic repetition rates and high-coherence/low-threshold Brillouin lasers. This multi-device capability and performance from a single integrated cavity platform represents a critical advance for future photonic circuits and systems

Stimulated optomechanical excitation of surface acoustic waves in a microdevice

Stimulated Brillouin interaction between sound and light, known to be the strongest optical nonlinearity common to all amorphous and crystalline dielectrics, has been widely studied in fibers and bulk materials but rarely in optical microresonators. The possibility of experimentally extending this principle to excite mechanical resonances in photonic microsystems, for sensing and frequency reference applications, has remained largely unexplored. The challenge lies in the fact that microresonators inherently have large free spectral range, while the phase matching considerations for the Brillouin process require optical modes of nearby frequencies but with different wavevectors. We rely on high-order transverse optical modes to relax this limitation. Here we report on the experimental excitation of mechanical resonances ranging from 49 to 1400 MHz by using forward Brillouin scattering. These natural mechanical resonances are excited in ~100 um silica microspheres, and are of a surface-acoustic whispering-gallery type

Analysis of genetic control of â-carotene and L-ascorbic acid accumulation from a wild cherry orange-brownish tomato accession

[EN] An additive-dominance, additive 9 additive (ADAA) and genotype 9 environment interaction mix model was used to study the genetic control of beta-carotene and L-ascorbic acid in six basic generations (P-1, P-2, F-1, F-2, BC1P1 and BC1P2) of tomato derived from the cross CDP8779 accession (Solanum lycopersicum L.) x CDP4777 accession (S. lycopersicum var. cerasiforme). The study was performed in two environments: (1) open field; (2) protected environment, consisting of hydroponic cultivation in a glasshouse. The results indicate that beta-carotene accumulation was mainly additive (32.2% of the genetic component), with a small dominant component (4.2%) and an important additive x environment interaction contribution (63.6%). In target environments with moderate to high temperatures and no limiting radiation, this the expression additive x environment interaction could substantially enhance the beta-carotene content. This trait showed also a high narrow-sense heritability (h(2) = 0.62). Ascorbic acid accumulation was also mainly additive (61.7% of the genetic component), with a minor additive epistatic component (21.5%). This epistatic effect caused a negative heterosis that reduced the positive main additive effect. Nevertheless, in the described target environments, the additive 9 environment interaction contribution (16.8%) may enhance the ascorbic acid content and compensate for the negative heterosis effect. The total narrow-sense heritability of this trait can be considered useful (h(2) = 0.52). In conclusion, the CDP4777 accession is a very interesting donor parent for the joint improvement of beta-carotene (without diminishing lycopene content) and ascorbic acid content in commercial nutraceutical tomato breeding programmes; the F-1 hybrids derived from this accession showed nearly 450% of the commonly reported average beta-carotene content and close to 130% of the ascorbic acid content of the female parent.This research was financed by the Spanish Ministry of Science and Innovation (MICINN) (project AGL2005-08083-C03-01). The authors thank Dr. Luis Mejia and the Universidad de San Carlos of Guatemala for providing the CPD4777 accession, among others. The authors thank Professor Jun Zhu, director of the Bioinformatics Institute, Zhejiang University, China, for his comments and for kindly providing the software used in the data analyses.Adalid Martinez, AM.; Rosello Ripolles, S.; Valcárcel Germes, M.; Nuez Viñals, F. (2011). Analysis of genetic control of â-carotene and L-ascorbic acid accumulation from a wild cherry orange-brownish tomato accession. Euphytica. 184(2):251-263. doi:10.1007/s10681-011-0584-xS251263184