We infiltrate a perdeuterated liquid crystal with a reduced infrared absorption in a photonic crystal fiber. The H atoms of this liquid crystal were substituted with D atoms in order to move the vibration bands which cause absorption loss to longer wavelengths and therefore reduce the absorption in the spectral range of 1–2 μm. We achieve in the middle of the near-infrared transmission bandgap the lowest loss (about 1 dB) ever reported for this kind of devices.

We design and fabricate a compact tunable and rotatable polarization controller using liquid crystal photonic band gap fibers. The electrically and thermally induced phase shift in the Poincaré sphere and corresponding birefringence change are measured. The direction of the electric field is managed by connecting four electrodes in different electrode configurations, and the thermal tunability is controlled by on-chip heaters. According to the results, a quarter-wave plate and a half-wave plate working in the wavelength range of 1520–1600 nm are experimentally demonstrated.

Higher eco-design requirements from the EU Directives and higher lighting standard requirements for working places open a new and challenging chapter of development for the illumination systems of the future. Electricity consumption due to illumination in offices in Europe will continue to rise due to the increasing number of offices and due to the new illumination standards. The total annual primary energy consumption of the European office lighting stock in 2005 was 281 PJ, of which 271.73 PJ was due to electricity use. It is estimated that office lighting generates 519 kton of non- hazardous (or landfill) waste and 7.2 kton hazardous (or incinerated) waste; 12.5 Mt CO2-eq. greenhouse gas emissions; 73 kt SO2-eq. acidifying gasses. It emits heavy metals in an amount of 5.7 ton Ni-eq. to air and 2.7 ton Hg to water. This paper discusses the question: What kind of considerations should the photonic industry take into account when designing future low-carbon illumination systems to efficiently reduce the CO2 emissions, when evaluating the possibilities for the future?

We investigate the tunability of splay-aligned liquid crystals for the use in solid core photonic crystal fibers. Finite element simulations are used to obtain the alignment of the liquid crystals subject to an external electric field. By means of the liquid crystal director field the optical permittivity is calculated and used in finite element mode simulations. The suitability of liquid crystal photonic bandgap fiber devices for filters, waveplates or sensors is highly dependent on the tunability of the transmission spectrum. In this contribution we investigate how the bandgap tenability is determined by the parameters of the liquid crystals. This enables us to identify suitable liquid crystals for tunable photonic bandgap fiber devices.

An ytterbium-doped photonic bandgap fiber amplifier operating at the long wavelength edge of the ytterbium gain band is investigated for high power amplification. The spectral filtering effect of the photonic bandgap efficiently suppresses amplified spontaneous emission at the conventional ytterbium gain wavelengths and thus enables high power amplification at 1178 nm. A record output power of 167 W, a slope efficiency of 61% and 15 dB saturated gain at 1178 nm have been demonstrated using the ytterbium-doped photonic bandgap fiber.

Higher eco-design requirements from the EU Directives and higher lighting standard requirements for working places open a new and challenging chapter of development for the illumination systems of the future. Electricity consumption due to illumination in offices in Europe will continue to rise due to the increasing number of offices and due to the new illumination standards. The total annual primary energy consumption of the European office lighting stock in 2005 was 281 PJ, of which 271.73 PJ was due to electricity use. It is estimated that office lighting generates 519 kton of nonhazardous (or landfill) waste and 7.2 kton hazardous (or incinerated) waste; 12.5 Mt CO2-eq. greenhouse gas emissions; 73 kt SO2-eq. acidifying gasses. It emits heavy metals in an amount of 5.7 ton Ni-eq. to air and 2.7 ton Hg to water. This paper discusses the question: What kind of considerations should the photonic industry take into account when designing future low-carbon illumination systems to efficiently reduce the CO2 emissions, when evaluating the possibilities for the future?

An electrically tunable bandpass filter is designed and fabricated by integrating two solid-core photonic crystal fibers filled with different liquid crystals in a double silicon v-groove assembly. By separately controlling the driving voltage of each liquid-crystal-filled section, both the short-wavelength edge and the long-wavelength edge of the bandpass filter are tuned individually or simultaneously with the response time in the millisecond range.

xi Resumé (Danish abstract) xiii PhD publication list xv

We design and fabricate an on-chip tunable long-period grating device by integrating a liquid crystal photonic bandgap fiber on silicon structures. The transmission axis of the device can be electrically rotated in steps of 45 degrees as well as switched on and off with the response time in the millisecond range. The strength of the loss peak is controlled electrically, and the spectral position of the loss peak is thermally tunable. This compact design results in a stable grating and permits this device to be more easily applied in practical systems. (C) 2009 Optical Society of America

We infiltrate liquid crystals doped with BaTiO 3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant.New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope.The tunability of the device is achieved by varying the amplitude and the frequency of the applied external electric field.The threshold voltage for doped and undoped liquid crystals in a silica capillary and in a glass cell are also measured as a function of the frequency of the external electric field and the achieved results are compared.

SU-8 structures are built up to increase the fiber coupling efficiency of liquid crystal photonic bandgap fiber components. The resolution reduction of UV exposure is minimized to 4%, and insertion loss is reduced to 2.7 dB.

A simulation scheme for the transmission spectrum of a photonic crystal fiber infiltrated with a nematic liquid crystal and subject to an external bias is presented. The alignment of the biased liquid crystal is simulated using the finite element method to solve the relevant system of coupled partial differential equations. From the liquid crystal alignment the full tensorial dielectric permittivity in the capillaries is derived. The transmission spectrum for the photonic crystal fiber is obtained by solving the generalized eigenvalue problem deriving from Maxwell's equations using a vector element based finite element method. We demonstrate results for a splay aligned liquid crystal infiltrated into the capillaries of a four-ring photonic crystal fiber and compare them to corresponding experiments.

A dual-function all-in-fiber device based on negative dielectric liquid crystal photonic bandgap fibers is presented. This device can work both as an electrically tunable waveplate in the range 1520nm-1580nm, and as a polarimeter at 1310nm. (C)2008 Optical Society of America

Electrically tunable liquid crystal photonic bandgap fiber device based optically-fed microwave true-time delay is demonstrated. A maximum ~60° phase shift and an averaged ~7.2ps true time delay are obtained over the modulation frequency range 1GHz-19GHz.

Thick photoresist coating for electrode patterning in an anisotropically etched V-groove is investigated for electrically controlled liquid crystal photonic bandgap fibre devices. The photoresist step coverage at the convex corners is compared with and without soft baking after photoresist spin coating. Two-step UV exposure is applied to achieve a complete exposure for the thick photoresist layer at the bottom of the V-groove, and minimise the reduction in resolution and image distortion. The resolution reduction of the different open window width for electrode pattern transfer is also experimentally found.

We demonstrate the photonic bandgap effect and the thermal tunability of bandgaps in microstructured polymer optical fibers infiltrated with liquid crystal.Two liquid crystals with opposite sign of the temperature gradient of the ordinary refractive index (E7 and MDA-00-1444) are used to demonstrate that both signs of the thermal tunability of the bandgaps are possible.The useful bandgaps are ultimately bounded to the visible range by the transparency window of the polymer.