Marinus C. Flipse

The determination of first hyperpolarizabilities β using hyper-Rayleigh scattering : a caveat

Abstract A comparison of first hyperpolarizabilities β determined by hyper-Rayleigh scattering (HRS; β HRS ) and electric field-induced second-harmonic generation (EFISH; β EFISH ) for a series of donor-acceptor substitutetd π-conjugated organic compounds shows a marked discrepancy between β HRS and β EFISH values for NLO-chromophores which fluoresce in the frequency-doubled wavelength region (532 nm). For MONS and DANS it is unequivocally established that two-photon absorption (TPA) at the fundamental wavelength (1064 nm) occurs followed by Stokes and anti-Stokes fluorescence around the second-harmonic wavelength. Hence, hyper-Rayleigh scattering at 1064 nm is not suited to determining the β of these fluorescent NLO-chromophores.

Modal dispersion phase matching over 7 mm length in overdamped polymeric channel waveguides

Phase‐matched second harmonic generation over 7 mm is demonstrated using the modal dispersion of a composite 4‐dimethylamino‐4′‐nitrostilbene/polyetherimde channel waveguide. For a 1‐mm‐long sample a record figure of merit for polymers of η=P2ω/(PωL2)=14%/W cm2 was measured at 1550 nm. This is comparable to the value reported for LiNbO3 at that wavelength. The efficiency in longer samples is limited by fundamental and harmonic waveguide losses.

Key trade‐offs for second harmonic generation in poled polymers

We discuss the critical trade‐off between the spectral dispersion in the second order nonlinearity d(2) and the linear absorption coefficient for second harmonic generation (SHG) by the mixing of copropagating or counterpropagating fundamental beams in poled polymers. The 4‐dimethylamino–4′‐nitrostilbene side‐chain polymer is used as a specific example. The predictive power of the classical two‐level model for SHG is also assessed.

POLYMER WAVEGUIDES WITH OPTIMIZED OVERLAP INTEGRAL FOR MODAL DISPERSION PHASE-MATCHING

Modal dispersion phase-matched second harmonic generation is demonstrated in new poled polymer waveguide geometries with a nonlinear optical core consisting of two side-chain polymers with different glass transition temperatures. After poling above and between the respective glass transitions, the sign of the nonlinear optical coefficient is reversed in the two polymers, thereby improving the overlap integral. Conversion efficiencies up to 7%/W cm2 were achieved in the first experiments.

High hyperpolarizabilities of donor-p-acceptor-functionalized calix[4]arene derivatives by pre-organization of chromophores

A systematic investigation of the conceptofpre-organization of nonlinear optical (NLO) active chromophoric groups in calix[4]arene derivatives and the influence on the absolute second-order nonlinear optical coefficients is reported. Several calix[4]arenes were synthesized by modification of the electron-withdrawing groups at the upper rim of the aromatic and extension of the conjugated system of the pre-organized chromophoric groups. Electrical field induced second harmonic generation (EFISH) experiments showed high (0) values up to 1165·10-48 esu. Compared with the corresponding reference compounds, enhancements of the (0) values varying up to 2.5 times per chromophore were observed which proves the benefit of pre-organization of NLO-active units in a multi-chromophoric system. Another important advantage is that the increase in NLO activity observed for these systems is not accompanied with a shift of the absorption band to longer wavelengths exceeding 20 nm. This makes these calix[4]arene derivatives promising building blocks for the development of stable, NLO-active materials that are suitable for frequency doubling.

Reliability assurance of polymer-based solid state optical switches

BeamBox polymer based fiber-optic space switches have been submitted to a reliability qualification program. The results of this program show that these switches meet the requirements for telecommunication applications. Highly stable switches have been obtained by proper design, testing, and optimization of materials, parts, and production processes.

Reliability and Environmental Stability of Polymer based Solid State Optical Switches

The development of reliable and environmentally stable photonic space switches based on the BeamBoxaTM Solid State Optical Switch technology is described. The realization of a robust temperature stable (-40°C to 75°C) fiber pigtail attachment joint is presented.

Preparation of chi (2) -inverted waveguides with poled polymers for efficient second-harmonic generation

Modal dispersion phase-matched second harmonic generation is demonstrated in polymer-based waveguides with a nonlinear optical core consisting of two side-chain polymers with different glass-transition temperatures. For an optimized overlap integral, a step like nonlinearity profile (chi(2)-inverted structure) is required across the core thickness. The chi(2)-inverted structure is achieved by two consecutive thermally assisted poling steps above and between the respective glass-transition temperatures, with an opposite poling field in the second poling step. The achieved chi(2)-inverted structure is monitored by in- situ electro-optic measurements and proved by electro-optic and second harmonic generation thermal analysis. Conversion efficiencies up to 7%/Wcm2 were achieved in first waveguide second-harmonic generation experiments.

Reliability Assurance for Thermo-Optic Solid State Optical Switches

The reliability assurance program for the BeamBox TM thermo-optic solid state optical switches is presented. The different phases of the program are discussed, and some of the results are described.

Modal dispersion phase-matching in polymer waveguides with inverted poling structure

Efficient second-harmonie generation (SHG), widely used for the fabrication of compact blue light sources, can also be employed for the demonstration of all-optical switching, spatial solitary waves, etc, through cascading of second-order nonlinear effects1