Articles by Karl Welna in JoVE
Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities Christopher Paul Reardon1, Isabella H. Rey1, Karl Welna1, Liam O'Faolain1, Thomas F. Krauss1 1School of Physics & Astronomy, University of St Andrews Use of photonic crystal slow light waveguides and cavities has been widely adopted by the photonics community in many differing applications. Therefore fabrication and characterization of these devices are of great interest. This paper outlines our fabrication technique and two optical characterization methods, namely: interferometric (waveguides) and resonant scattering (cavities).
Other articles by Karl Welna on PubMed
Integrated Polymer Microprisms for Free Space Optical Beam Deflecting Optics Express. Mar, 2009 | Pubmed ID: 19259180 We demonstrate beam deflection and multiple channel communication in free space optical communications using microprisms integrated directly onto an array of vertical cavity surface emitting lasers (VCSELs). The design and fabrication of such a transmitter is presented, and shown to achieve beam deflection of up to 10 degrees in a planar configuration. A location discovery application, for use within a distributed network, is put forward and analysed.
Low-power Continuous-wave Generation of Visible Harmonics in Silicon Photonic Crystal Nanocavities Optics Express. Dec, 2010 | Pubmed ID: 21165010 We present the first demonstration of frequency conversion by simultaneous second- and third-harmonic generation in a silicon photonic crystal nanocavity using continuous-wave optical excitation. We observe a bright dual wavelength emission in the blue/green (450-525 nm) and red (675-790 nm) visible windows with pump powers as low as few microwatts in the telecom bands, with conversion efficiencies of âˆ¼ 10 (-5) /W and âˆ¼ 10/ W(2) for the second- and third-harmonic, respectively. Scaling behaviors as a function of pump power and cavity quality-factor are demonstrated for both second- and third order processes. Successful comparison of measured and calculated emission patterns indicates that third-harmonic is a bulk effect while second-harmonic is a surface-related effect at the sidewall holes boundaries. Our results are promising for obtaining practical low-power, continuous-wave and widely tunable multiple harmonic generation on a silicon chip.