Morten Thorhauge

Comprehensive FDTD modelling of photonic crystal waveguide components

Planar photonic crystal waveguide structures have been modelled using the finite-difference-time-domain method and perfectly matched layers have been employed as boundary conditions. Comprehensive numerical calculations have been performed and compared to experimentally obtained transmission spectra for various photonic crystal waveguides. It is found that within the experimental fabrication tolerances the calculations correctly predict the measured transmission levels and other major transmission features.

Ultralow-loss 3-dB photonic crystal waveguide splitter

A photonic crystal waveguide splitter that exhibits ultralow-loss 3-dB splitting for TE-polarized light is fabricated in silicon-on-insulator material by use of deep UV lithography. The high performance is achieved by use of a Y junction, which is designed to ensure single-mode operation, and low-loss 60 degrees bends. Zero-loss 3-dB output is experimentally obtained in the range 1560-1585 nm. Results from three-dimensional finite-difference time-domain modeling with no adjustable parameters are found to be in excellent agreement with the experimental results.

Efficient photonic crystal directional couplers

We demonstrate highly efficient and spectrally flat broadband coupling in photonic crystal directional couplers. The result is obtained by use of a novel design with smaller holes between coparallel photonic crystal waveguides for efficient channel-to-channel coupling. The system studied is based on a planar hexagonal photonic crystal lattice of holes made in silicon-on-insulator material. Results from three-dimensional finite-difference time domain modeling are shown to closely match results measured on fabricated samples.

Efficient propagation of TM polarized light in photonic crystal components exhibiting band gaps for TE polarized light

We have investigated the properties of TM polarized light in planar photonic crystal waveguide structures, which exhibit photonic band gaps for TE polarized light. Straight and bent photonic crystal waveguides and couplers have been fabricated in silicon-on-insulator material and modelled using a 3D finite-difference-time-domain method. The simulated spectra are in excellent agreement with the experimental results, which show a propagation loss as low as 2.5+/-4 dB/mm around 1525 nm and bend losses at 2.9+/-0.2 dB for TM polarized light. We demonstrate a high coupling for TM polarized light in a simple photonic crystal coupler with a size of ~ 20 m x 20 m. These promising features may open for the realization of ultra-compact photonic crystal components, which are easily integrated in optical communication networks.

Tunable intra-cavity SHG of CW Ti:Sapphire lasers around 785 nm and 810 nm in BiBO-crystals

Phasematch curves as well as sensitivity to angular and wavelength misalignment for generation of second-harmonic of 785 nm and 810 nm in Bi(3)BO(6) crystal was calculated. Measurements were done for intra-cavity CW SHG in a Ti:Sapphire laser. The BiBO crystal was found to be excellent for this application. Temperature dependance was uncritical for both crystals, while power stability was good. Maximum blue output was 53 mW at 392 nm and 100 mW at 405 nm; corresponding to pump-to-blue optical conversion efficiencies of 0.96% and 1.82% respectively.

Properties of directional couplers using photonic crystal waveguides

Coupled photonic crystal waveguides have been designed and modelled with a 3D finite-difference-time-domain method, and fabricated in silicon-on-insulator material. Good agreement between modelled and measured results has been found.

Synchronized actively Q-switched Nd:YAG laser generating 3 W average power at 589 nm

Yellow-orange light in the range 580–600 nm is one of the remaining laser lines not reachable by direct emission from solid-state, crystal based laser materials, or by Second Harmonic Generation (SHG). Q-switched sources in this wavelength range are of importance in areas such as medicine, isotope separation, and fluorescence analysis. In this paper we present a new scheme for generating 589 nm light with good efficiency and high power.

100 mW of blue light at 405 nm from intracavity doubling of CW Ti:sapphire laser utilising BiBO-crystal

100 mW of coherent blue light with a wavelength of 405 nm was generated utilising a BiB3O6 (BiBO) nonlinear crystal to frequency double a Ti:Sapphire laser. Phase match curves as well as sensitivity to angular misalignment was calculated. The BiBO crystal was found to be excellent for this application. Temperature dependance was uncritical for this crystal, while power stability was good. The pump-to-blue optical conversion efficiency was approximately 2%. Unfortunately catastrophic coating damage was observed.

Very high coupling of TM polarised light in photonic crystal directional couplers

The experimental and simulated spectra for TE and TM polarised light for the transmission through photonic crystal directional couplers are presented. The 3D FDTD simulations successfully explain all the major features of the experimental spectra as well as the actual transmission level. Especially noteworthy is the transmission level, experimentally found to be above -3 dB in the wavelength range 1520-1690 nm, for TM polarised light in the coupled channel. It is noted that even though band calculations show that the propagation of the TM polarisation takes place below the TM valence band, very high and spectrally smooth coupling is observed for the TM polarisation in this wavelength range.

Propagation of TE and TM polarised light through smoothed sixty degree bends in planar photonic crystal waveguides

In this paper, bends in planar PCWs are investigated by introducing two smoothed 60/spl deg/ bends each having one hole. The PCWs are defined by leaving out single rows of holes. In and out coupling of light to the PCWs is obtained utilising tapered ridge waveguides. Transmission spectra are recorded for both the TE and TM polarisation with an optical spectrum analyser by using two LED sources centred at 1330 nm and 1550 nm. The 3D FDTD simulations successfully explain the observed bend losses both for the TE and TM polarisations.