"Non-stoichiometry and point native defects in non-oxide non-linear optical large single crystals: advantages and problems"

Advances and limitations in the field of growing large, a high optical quality single crystals of AgGaS2 (AGS), AgGaGeS4 (AGGS), ZnGeP2 (ZGP), LiInS2 (LIS), LiGaS2 (LGS), LiInSe2 (LISe), LiGaSe2 (LGSe)...

ANALYSIS OF METHODS FOR SYNTHESIS OF A BORON-DOPED LITHIUM NIOBATE CHARGE USED FOR GROWING SINGLE CRYSTALS

Проведен анализ известных методов синтеза шихты ниобата лития, легированной бором, которая используется при выращивании монокристаллов высокого оптического качества методом Чохральского. Установлено, что способ гомогенного легирования (шихта получается из прекурсора NbO :B и LiCO) по сравнению с твердофазным (шихта получается из смеси LiCO: NbO : HBO ) позволяет выращивать кристаллы LiNbO: B с более однородным распределением в них примеси бора, а также в объеме расплава, при этом упрощаются технологические режимы, устанавливаемые при росте кристаллов. В работе впервые рассмотрен жидкофазный метод синтеза шихты, исключающий стадию прокалки гомогенизированной смеси пентаоксида ниобия и карбоната лития. Результаты имеют важное значение при выборе технологии выращивания легированных бором монокристаллов ниобата лития для конкретных областей техники. Known methods of a boron doped lithium niobate charge synthesis were analyzed. Such a charge is applied for the growth by Czochralski of single crystals with high optical quality. Homogeneous doping (the charge is obtained from precursor NbO:B and LiCO) was compared with solid phase doping (the charge is obtained from the mixture LiCO: NbO: HBO). Homogeneous doping was determined to help produce LiNbO: B crystals with a more uniform distribution of a boron dopant, boron distributes more uniform in the melt volume; technological regimes established during crystal growth become easier. For the first time the paper considers liquid-phase charge synthesis method; the method excludes the stage of annealing of homogenized mixture of niobium pentoxide and lithium carbonate. Results are crucial for the choice of technology at growing of boron doped lithium niobate crystals for exact areas of technics.

III-V nanostructures with different dimensionality on silicon

The possibility of AlGaAs nanowires with GaAs quantum dots and InP nanowires with InAsP quantum dots growth by molecular-beam epitaxy on silicon substrates has been demonstrated. Results of GaAs quantum dots optical properties studies have shown that these objects are sources of single photons. In case of InP nanowires with InAsP quantum dots, the results we obtained indicate that nearly 100% of coherent nanowires can be formed with high optical quality of this system on a silicon surface. The presence of a band with maximum emission intensity near 1.3 μm makes it possible to consider the given system promising for further integration of optical elements on silicon platform with fiber-optic systems. Our work, therefore, opens new prospects for integration of direct bandgap semiconductors and singlephoton sources on silicon platform for various applications in the fields of silicon photonics and quantum information technology.

Photonic contact thermometry using silicon ring resonators and tuneable laser-based spectroscopy

Photonic sensors offer the possibility of purely optical measurement in contact thermometry. In this work, silicon-based ring resonators were used for this purpose. These can be manufactured with a high degree of reproducibility and uniformity due to the established semiconductor manufacturing process. For the precise characterisation of these photonic sensors, a measurement setup was developed which allows laser-based spectroscopy around 1550 nm and stable temperature control from 5 °C to 95 °C. This was characterised in detail and the resulting uncertainty influences of both the measuring set-up and the data processing were quantified. The determined temperature stability at 20 °C is better than 0.51 mK for the typical acquisition time of 10 s for a 100 nm spectrum. For a measurement of >24 h at 30 °C a standard deviation of 2.6 mK could be achieved. A hydrogen cyanide reference gas cell was used for traceable in-situ correction of the wavelength. The determined correction function has a typical uncertainty of 0.6 pm. The resonance peaks of the ring resonators showed a high optical quality of 157 000 in the average with a filter depth of up to 20 dB in the wavelength range from 1525 nm to 1565 nm. When comparing different methods for the determination of the central wavelength of the resonance peaks, an uncertainty of 0.3 pm could be identified. A temperature-dependent shift of the resonance peaks of approx. 72 pm/K was determined. This temperature sensitivity leads together with the analysed uncertainty contributions to a repeatability of better than 10 mK in the analysed temperature range from 10 °C to 90 °C.

Czochralski growth of mixed cubic sesquioxide crystals in the ternary system Lu2O3–Sc2O3–Y2O3

Cubic rare-earth sesquioxide crystals are strongly demanded host materials for high power lasers, but due to their high melting points investigations on their thermodynamics and the growth of large-size crystals of high optical quality remain a challenge. Detailed thermal investigations of the ternary system Lu2O3–Sc2O3–Y2O3 revealing a large range of compositions with melting temperatures below 2200°C and a minimum of 2053°C for the composition (Sc0.45Y0.55)2O3 are presented. These reduced temperatures enable for the first time the growth of high optical quality mixed sesquioxide crystals with disordered structure by the conventional Czochralski method from iridium crucibles. An (Er0.07Sc0.50Y0.43)2O3 crystal is successfully grown and characterized with respect to its crystallographic properties as well as its composition, thermal conductivity and optical absorption in the 1 µm range.

Elastic ice microfibers

Ice is known to be a rigid and brittle crystal that fractures when deformed. We demonstrate that ice grown as single-crystal ice microfibers (IMFs) with diameters ranging from 10 micrometers to less than 800 nanometers is highly elastic. Under cryotemperature, we could reversibly bend the IMFs up to a maximum strain of 10.9%, which approaches the theoretical elastic limit. We also observed a pressure-induced phase transition of ice from Ih to II on the compressive side of sharply bent IMFs. The high optical quality allows for low-loss optical waveguiding and whispering-gallery-mode resonance in our IMFs. The discovery of these flexible ice fibers opens opportunities for exploring ice physics and ice-related technology on micro- and nanometer scales.

Highly Sensitive Sensor Structure Based on Sol-Gel Waveguide Films and Grating Couplers

The technologies of optical planar evanescent wave chemical and biochemical sensors require chemically resistant, high refractive index waveguide films having very good optical transmission properties. In this paper we present such two-compound SiOx:TiOy waveguide films fabricated by using the sol-gel method and the dip-coating technique. These films not only have high optical quality and low propagation losses but also an extremely high refractive index of >1.90 (λ = 632.8 nm). Further we demonstrate efficient and simple sensing structures, designed and fabricated based on these films. For this purpose, grating couplers with a period of Λ = 417 nm were fabricated on the interface between a waveguide film and cover using the single-step nanoimprint method. These sensing structures were tested as planar refractometers. The results of the theoretical analysis on the basis of which the structures were designed as well as results of their experimental characterization are presented in this work. Consequently, the relationship between parameters and the sensitivity of investigated sensing structures is discussed. As a result, the profitable properties of the designed grating coupler sensors are verified and excellent consistency between the results of the theoretical analysis and experimental results is achieved.

A Nanoscale Photonic Crystal Cavity Optomechanical System for Ultrasensitive Motion Sensing

Optomechanical nanocavities open a new hybrid platform such that the interaction between an optical cavity and mechanical oscillator can be achieved on a nanophotonic scale. Owing to attractive advantages such as ultrasmall mass, high optical quality, small mode volume and flexible mechanics, a pair of coupled photonic crystal nanobeam (PCN) cavities are utilized in this paper to establish an optomechanical nanosystem, thus enabling strong optomechanical coupling effects. In coupled PCN cavities, one nanobeam with a mass meff~3 pg works as an in-plane movable mechanical oscillator at a fundamental frequency of . The other nanobeam couples light to excite optical fundamental supermodes at and 1554.464 nm with a larger than 4 × 104. Because of the optomechanical backaction arising from an optical force, abundant optomechanical phenomena in the unresolved sideband are observed in the movable nanobeam. Moreover, benefiting from the in-plane movement of the flexible nanobeam, we achieved a maximum displacement of the movable nanobeam as 1468 . These characteristics indicate that this optomechanical nanocavity is capable of ultrasensitive motion measurements.