Latent Heat Flux Profiles from Collocated Airborne Water Vapor and Wind Lidars during IHOP_2002

Latent heat flux profiles in the convective boundary layer (CBL) are obtained for the first time with the combination of the DLR water vapor differential absorption lidar (DIAL) and the NOAA high resolution Doppler wind lidar (HRDL). Both instruments were integrated nadir viewing on board the DLR “Falcon” research aircraft during the International H2O Project (IHOP_2002) over the U.S. Southern Great Plains. Flux profiles from 300 – 2500 m AGL are computed from high spatial resolution (150 m horizontal and vertical) two-dimensional water vapor and vertical velocity lidar cross sections using the eddy covariance technique. All cospectra show significant contributions to the flux between 1 and 10 km wavelength, with peaks between 2 and 6 km, originating from large eddies. The main flux uncertainty is due to low sampling (55 % rmse at mid-CBL), while instrument noise (15 %) and systematic errors (7 %) play a minor role. The combination of a water vapor and a wind lidar on an aircraft appears as an attractive new tool that allows measuring latent heat flux profiles from a single over-flight of the investigated area

Electro-optically tunable microring resonators in lithium niobate

Optical microresonators have recently attracted a growing attention in the photonics community. Their applications range from quantum electro-dynamics to sensors and filtering devices for optical telecommunication systems, where they are likely to become an essential building block. The integration of nonlinear and electro-optical properties in the resonators represents a very stimulating challenge, as it would incorporate new and more advanced functionality. Lithium niobate is an excellent candidate material, being an established choice for electro-optic and nonlinear optical applications. Here we report on the first realization of optical microring resonators in submicrometric thin films of lithium niobate. The high index contrast films are produced by an improved crystal ion slicing and bonding technique using benzocyclobutene. The rings have radius R=100 um and their transmission spectrum has been tuned using the electro-optic effect. These results open new perspectives for the use of lithium niobate in chip-scale integrated optical devices and nonlinear optical microcavities.Comment: 15 pages, 8 figure

UV integrated optics devices based on beta-barium borate

We report on our recent progress in development of ultraviolet (UV) integrated optics devices based on beta-barium borate (BBO). Planar optical waveguides with a thickness of a few micrometers have been formed by the implantation of He+ ions with energies of around 2 MeV. Two alternative methods based on the femtosecond-laser assisted micromachining and lithographic structuring for the fabrication of ridge-type channel optical waveguides in implanted BBO crystals have been developed, and the transmission properties of the obtained waveguides have been studied. We demonstrate a big potential of the fabricated channel waveguides for the second harmonic generation of continuous-wave deep-UV laser light with a power of the order of 1 mW, exploiting the nonlinear optical properties of BBO crystal. In addition, a low-voltage electro-optic waveguide modulator for the deep-UV light (half-wave voltage times electrode length Vπ × l = 43 V cm at 257 nm) was realized for the first time

Gravity waves over the eastern Alps: A synopsis of the 25 October 1999 event (IOP 10) combining in-situ and remote sensing measurements with a high-resolution simulation

In situ and lidar data acquired during six repetitive flight legs across Grossglockner (3797 m, highest summit of the eastern Alps) reveal a coherent structure of the mountain-wave field generated by a south-westerly cross-Alpine flow on 25 October 1999 during Intensive Observing Period (IOP) 10 of the Mesoscale Alpine Programme (MAP). The downward-looking laser system sampling at 100 Hz provides distinct wave-induced signatures in the layered clouds below the cruising altitude of about 11 km. Data obtained from three sondes dropped from the aircraft hint at mid-tropospheric wave breaking in the lee of the main Alpine crest. The measurements are juxtaposed with results from a nested, non-hydrostatic simulation (2 km horizontal resolution for the finest grid). Wave-cloud signatures in satellite images (from Meteosat and the National Oceanic and Atmospheric Administration satellites) are used for comparisons with the simulation in a region away from the aircraft track. Sensitivity experiments reveal the regular wave response to be induced by the background profile and re-enforced by the suitably spaced terrai

Optical waveguides in Sn2P2S6 by low fluence MeV He+ ion implantation

Planar waveguides in nonlinear optical crystals of Sn2P 2S6 have been produced by He+ ion implantation. The effective indices of the waveguide have been determined and refractive index profiles have been evaluated for the indices along all three principal axes of the optical indicatrix. The depth of the induced optical barrier is Δn1 = -0.07, Δn2 = -0.07 and Δn 3 = -0.09 at λ= 0.633μm for a fluence Φ = 0.5 × 1015ions/cm2. Propagation losses for hybrid-n1 modes are α ≃ 10dB/cm

High resolution airborne water vapour DIAL during IHOP_2002

During the Int. H2O Project (IHOP_2002) DLR's 100 Hz airborne water vapour DIAL enabled two-dimensional scans of small-scale humidity srtuctures in the boundary layer with unprecedented spatial resolution. At an airraft speed of 130 m/s the horizontal/vertical resolution in the humidity field is 200/100m which fulfills the stringent requirements for the determination of the turbulent moisture transport in the PBL