Day :
- Lasers and Nonlinear Optics | Photonics| Industrial Applications of Laser and Photonics Optoelectronics | Applied Industrial Optics
Location: 1
Chair
Changhui Rao,
Institute of Optics and Electronics, Chinese Academy of Sciences, China
Session Introduction
Changhui Rao
Institute of Optics and Electronics, Chinese Academy of Sciences, China
Title: Progress on 1.8m Solar Telescope CLST
Biography:
Abstract:
For better understanding and forecasting of the solar activity, high resolution solar observations are required. From 2011, we started to develop the Chinese Large Solar Telescope (CLST), which is a classic Gregorian configuration telescope with a 1.8-meter honeycomb sandwich fused silica lightweight primary mirror with ULE material and active cooling. Th e CLST is being integrated in our Institute. A solar adaptive optics system, which consists of a 451-element deformable mirror, a low-order wavefront sensor with 9×9 array, and a real-time controller, had been built for first light high resolution solar observations in G-band, Hα band, and TiO band. In this presentation the main system configuration and the corresponding post focal instruments are described. Furthermore, the latest progress and first light on-sky solar observational results of the CLST are also reported.
Andrey Ionin
P N Lebedev Physical Institute-RAS, Russia
Title: Si-based laser-made nanocoatings for destroying bacterial biofi lms
Biography:
Abstract:
Antibacterial coatings were fabricated by laser ablation of silicon in liquid media. Laser radiation (λ=1030 nm,τ=10 ps, E=10 μJ) was focused onto the Si wafer under the 5-mm layer of liquid carbon disulfi de (CS2) and raster-scanned across the surface. The resulting laser-induced morphology consisted of nanosheets (NS) with high height-to-width ratio, and its antibacterial properties were tested on S. aureus strain. Th e S. aureus strain was grown in a nutrient medium and incubated for 24 h at 37°C on the surface of Si NS, smooth Si wafer and silica glass as a control. Their staining with “Live/Dead Biofi lm Viability Kit” allowed assuming, that no any biofilm was formed onthe Si NS, unlike smooth Si and silica glass. The bacterial death was possibly caused by the mechanical damage of the cell membrane on the sharp edges of Si NS, or its possible chemical activity. Another type of antibacterial coating was fabricated by placing Si nanoparticles (NPs) on a smooth Si wafer. NPs were prepared by laser ablation (λ=1064 nm,τ=120 ns, E=0.1 mJ) of silicon plate under the 3-mm layer of either isopropanol or deionized water. Th e resulting Si NP colloidal solutions were air-dried, and their antibacterial activity and hydrophobic properties were tested using S. aureus and P. aeruginosa.
Yangyi Liu
Institute of Optics and Electronics,China
Title: Fast visible imaging spectrometer for 1.8-m solar telescope CLST
Biography:
Abstract:
The Fast Visible Imaging Spectrometer (FVIS), which consists of three rotating pre-fi lters, an air gap based Fabry-Perot interferometer (FPI) and an imager, is being developed as one of the post instruments of the 1.8-m Chinese Large Solar Telescope (CLST). The FPI is placed behind the adaptive optics system to acquire the high resolution solar images. By changing the plate separation of FPI, the position and gap of a series of equidistant transmission peaks are tunable. Multiple by the unchanged transmission profile of the pre-filters, the transmission peak at working wavelength is selected. The centre wavelength of three pre-filters are at 5890, 6562.8 and 8542 angstrom corresponding to the Na I, Hα and Ca II line of the solar spectrum respectively. By changing the pre-filters with a rotator, the FVIS is able to image at three wavelengths with resolving power about 74700@5890A, 68400@6562.8A and 54000@8542A. Th e FVIS can image at tens of different wavelength positions in a few seconds because the quick response of the Piezoelectric actuators for cavity length regulation. In this presentation, the scientific requirement, design, parameters and experiment plan of the FVIS will be presented.
Junyong Kang
Xiamen University, China
Title: Abnormal radiative interband transitions and tailorable orbital-state coupling in High- Al-Content AlGaN quantum wells
Biography:
Abstract:
It is widely held that the confinement of carriers at lowest quantum level is more pronounced than that of higher quantum levels, which has been long established on the conventional continuous potential wells and favourable for efficient light emission. We observed the abnormal behavior of the carrier confinement from the c-plane of high-Alcontent AlGaN quantum well (QW) due to the dispersive crystal field split-off hole composed of pz orbitals. [ACS Photonics 4, 2197–2202 (2017)]. The orientational pz orbitals are sensitive to the confi ning directions which affect the orbital inter-coupling. The barrier potential for the confi nement is then determined by the joint effect of orbital inter-coupling and the band off set. We have performed theoretical calculations by constructing Al0.75Ga0.25N/ AlN quantum well models with variable lattice orientations to further investigate the orbital inter-coupling among atoms between the well and barrier regions. It is found that, the barrier potential as well as the transition rate of the band edge is enhanced by the orbital engineering with the well plane inclined from 0º to 90º with a step of 30º, referring to the (0001) plane. Experimentally, the concept of the orbital engineering is demonstrated through the construction of inclining well planes on the semi- and non-polar planes implemented in the micro-rods. The higher emission intensity from the QW on the non-polar plane is confirmed by localized cathodoluminescence (CL). The orbital engineering presented in this work aims to spur on the further improvement of high-Al-content AlGaN optoelectronic devices and the design of other innovative devices.
Yong Bo
Technical Institute of Physics and Chemistry-CAS, China
Title: High power high-repetition-rate microsecond pulse sodium beacon laser
Biography:
Abstract:
Sodium laser guide star is generated by resonant scattering of a 589nm laser with sodium atoms in the upper atmosphere of the altitude of 80-105 km. As a beacon with the sodium laser guide star, an adaptive optics system can correct the wavefront aberration due to atmospheric turbulence and improve greatly the large ground telescope resolving power. In the letter, a high power high-repetition-rate microsecond pulse sodium beacon laser prototype was developed. Th e sodium beacon laser is based on sum-frequency mixing between the 1064 nm and 1319 nm beams in a LBO crystal. Both the 1064 nm and 1319 nm lasers are produced from diode-side-pumped Nd:YAG master oscillator power amplifi er (MOPA) laser systems. At the repetition rate of 500 Hz and pulse width of about 120 μs, the average output power of 65 W is achieved with the wavelength of 589.159nm. Th e beam quality factor of M2 is 1.4 and the linewidth is about 0.3 GHz. By using the sodium beacon laser prototype, a bright sodium laser guide star with a photon return of 1820 photons.cm-2.s-1 was generated and observed with the projected power of 32W by the telescope in Xinglong site. What is more, a high resolution image of a star with the sodium laser guide star generated was obtained by the 1.8m telescope with the adaptive optics in Lijiang site.
Caroline Kulcsár
Laboratoire Charles Fabry - Institut d’Optique Graduate School-CNRS, France
Title: What high performance control can do for you? The example of adaptive optics
Biography:
Abstract:
Adaptive optics (AO) systems aim at compensating in real time optical aberrations induced by atmospheric turbulence, so as to retrieve quasi diff raction-limited imaging on ground-based telescopes. A deformable mirror is inserted in the optical path, and actuators, located under its reflecting surface, are controlled thanks to measurements of the wavefront aft er correction. Th e fi rst on-sky demonstration of AO was realized in 1989 at the Observatoire de Haute Provence (France) on a 1.52 m telescope, by a French-ESO consortium (European Southern Observatory). Twelve years aft er, in 2001, an AO system was installed on ESO’s Very Large Telescope (VLT) in Chile. First light results were impressive, with this system operating at a loop frequency of 600 Hz and controlling in real time 185 actuators from 270 measurements. Nevertheless, unexpected guests invited themselves with the atmospheric turbulence: vibrations (propagated from the telescope structure due to wind, vans, coolers, etc.) induced sometimes a severe performance loss. Recent and future AO systems thus feature high performance controllers designed to mitigate the many spurious signals affecting imaging quality. They are about to replace, at least partially,the so-called “integrator”, a standard controller prized for its simplicity. Why do integrators work (or not)? What can be expected from high performance controllers? When should they be considered as a relevant alternative for optical systems feedback loops? And at last, are they really implementable in real-time, in the era of giant telescopes featuring AO systems with thousands of degrees of freedom? Qualitative answers will be proposed, along with many illustrative examples.