Gerstner and Tschudi,' in their paper on two-wavelength interferometry, claim they first demonstr... more Gerstner and Tschudi,' in their paper on two-wavelength interferometry, claim they first demonstrated stabilization of two semiconductor lasers by locking them to a common Fabry-Perot resonator. They are probably unaware of the work of deGroot and Kishner2 in which we used this technique to achieve relative stabilization of two semiconductor laser diodes, operating at wavelengths of 785 and 835 nm, to <0.014 ppm. Our application, like that of Gerstner and Tschudi, was two-wavelength interferometry.
This work presents theoretical and experimental studies of the processes of light field transform... more This work presents theoretical and experimental studies of the processes of light field transformations upon frequency-nondegenerate fourwave mixing (NFWM) in a nonlinear Fabry-Perot interferometer (FPI). The principal aims are the development of a theory for intracavity four-wave mixing in complex molecular media in conditions of scattering from dynamic gratings and resonator feedback; determination of a mechanism of light field transformations in dynamic holograms, and also by nonlinear interferometers; working out and introduction of novel nonlinear-optical methods to control the characteristics of light beams. High diffraction efficiency (up to 13.5%) with simultaneous infrared-to-visible frequency conversion of coherent images has been experimentally obtained by intracavity NFWM.
An experimental and numerical investigation of the dynamical, time-dependent effects accompanying... more An experimental and numerical investigation of the dynamical, time-dependent effects accompanying the formation and interaction of two-dimensional spatial screening solitons in a photorefractive strontium barium niobate crystal is performed. These effects include initial diffraction, collapse to the soliton shape, the oscillation of beam diameters, beam bending, and the rotation, twisting, and turning of soliton pairs. The dynamics of complex spiraling of two incoherent solitons is considered in more detail. ͓S1063-651X͑99͒05611-1͔
Gerstner and Tschudi,' in their paper on two-wavelength interferometry, claim they first demonstr... more Gerstner and Tschudi,' in their paper on two-wavelength interferometry, claim they first demonstrated stabilization of two semiconductor lasers by locking them to a common Fabry-Perot resonator. They are probably unaware of the work of deGroot and Kishner2 in which we used this technique to achieve relative stabilization of two semiconductor laser diodes, operating at wavelengths of 785 and 835 nm, to <0.014 ppm. Our application, like that of Gerstner and Tschudi, was two-wavelength interferometry.
The use of liquid-crystal light valves (LCLV s) as nonlinear elements in diffractive optical syst... more The use of liquid-crystal light valves (LCLV s) as nonlinear elements in diffractive optical systems with feedback leads to the formation of a variety of optical patterns. The spectrum of possible spatial instabilities is shown to be even richer when the LCLV's capability for polarization modulation is utilized and internal threshold and saturation eKects are considered. We derive a model for the feedback system based on a realistic description of the LCLV's internal function and coupling to a polarizer. Thresholds of pattern formation are compared to the common Kerr-type approximation and show transitions involving rolls, squares, hexagons, and tiled patterns. Numerical and experimental results con6rm our theoretical predictions and unveil how patterns and their typical length scales can be easily controlled by changes of the parameters.
We present the generalization of Kogelnik's theory of coupled waves for the case of the grating c... more We present the generalization of Kogelnik's theory of coupled waves for the case of the grating comprising several cells along the direction of light propagation. The cells have the same period and amplitude, but different phases. By choosing a set of phases of the cells, a grating with a desired wavelength transfer function can be synthesized. We demonstrate gratings suitable for WDM applications.
Bragg reflective gratings are efficiently used as a high quality narrow band optical filters. We ... more Bragg reflective gratings are efficiently used as a high quality narrow band optical filters. We report results of an analytical solution, based on a generalized Kogelnik's theory, that allows high-accuracy synthesis of the transfer function of a spectral optical filter for the case of an arbitrary number of phase-shifted cells of equal lengths. Using photorefractive BaTiO3:Co, we demonstrate the control of the position of the transfer function maximum by piecewise-linear phase-shift keying and the reconfiguration of the transfer function with one maximum into the transfer function having multiple maxima.
We present an analytic design method for the reproducible fabrication of double-chirped mirrors t... more We present an analytic design method for the reproducible fabrication of double-chirped mirrors to achieve simultaneously a high ref lectivity and dispersion compensation over an extended bandwidth compared with those of standard quarter-wave Bragg mirrors. The mirrors are fabricated by ion beam sputtering. Use of these mirrors in a Ti:sapphire laser leads to 6.5-fs pulses directly out of the laser. The method can also be applied to the design of chirped-fiber gratings and general optical filters.
We report on double-chirped mirrors with custom-tailored dispersion characteristics over a bandwi... more We report on double-chirped mirrors with custom-tailored dispersion characteristics over a bandwidth of 170 THz in the visible. The mirrors are used in a prismless compressor for a noncollinear optical parametric amplifier in the visible. The compressed pulses, characterized for the what is believed to be first time by use of the spectral phase interferometry for direct electric field reconstruction technique, display a nearly f lat phase from 510 to 710 nm and have a duration of 5.7 fs.
We investigate experimentally the interaction of two-dimensional solitary beams in photorefractiv... more We investigate experimentally the interaction of two-dimensional solitary beams in photorefractive strontium barium niobate crystal. We show that simultaneous collision of many solitons can result in complete annihilation of some of them. This effect depends on the relative phases of the solitons and may be useful for application in the formation of multiport waveguide junctions.
Spatial solitons permit optical waveguiding. This holds true for the soliton write beam (i.e. the... more Spatial solitons permit optical waveguiding. This holds true for the soliton write beam (i.e. the driving laser beam), as well as for additional probe beams, which may carry optically encoded information. This feature of spatial solitons is of significant interest for applications in optical telecommunication. We present systematic experimental investigations on single and multiple spatial solitons in the infrared spectral regime (i.e. around optical telecommunication wavelengths), applied as controllable all-optical devices. In particular, we present the implementations of a Y-coupler as an optical signal divider, a switchable Y-coupler as an optical add multiplexer, and a novel design for a 1 Â 3 optical beam switch, i.e. applied as a router for infrared signal beams. We report large waveguiding efficiencies up to 40% and transmission rates of 90 Tbit/s in our setups. The presented experimental data are confirmed by numerical simulations.
Journal of Optics B: Quantum and Semiclassical Optics, 1999
We present an experimental realization of an almost non-invasive stabilization and manipulation m... more We present an experimental realization of an almost non-invasive stabilization and manipulation method of coexisting and unstable states of pattern forming systems. In a photorefractive single feedback system, a control path is used to realize amplitude and phase-sensitive Fourier-plane filtering, utilizing only a few per cent of the system's intensity. By that means, we were able to stabilize desired but not predominantly excited patterns in parameter space regions where several patterns are present as coexisting or underlying solutions. Changing the phase of the control signal allows one to switch between different pattern states.
IEEE Journal of Selected Topics in Quantum Electronics, 1998
We demonstrate self-starting 6.5-fs pulses from a Kerr-lens-mode-locked Ti:sapphire laser with an... more We demonstrate self-starting 6.5-fs pulses from a Kerr-lens-mode-locked Ti:sapphire laser with an average output power of 200 mW at a pulse repetition rate of 86 MHz. We have achieved a mode-locking buildup time of only 60 s, using a broad-band semiconductor saturable absorber mirror to initiate the pulse formation. The dispersion has been compensated with a prism pair in combination with improved double-chirped mirrors. The prism pair allows for the flexible adjustment of both the duration and the center wavelength of the pulse. The doublechirped mirrors show a high reflectivity better than 99.8% over the full bandwidth of 300 nm and a controlled group delay over more than 250 nm. The choice of a proper output coupler turns out to be critical for ultrashort pulse generation directly from the laser.
We investigate the origin of dynamics of hexagonal pattern formation in a photorefractive single ... more We investigate the origin of dynamics of hexagonal pattern formation in a photorefractive single feedback system[ By introducing an asymmetry\ we induced di}erent complex motion behaviours[ A visualization method is presented and means to control the dynamics in the case of _xed external parameters are discussed[ Þ 0888 Elsevier Science Ltd[ All rights reserved[ 0[ TRANSVERSE STRUCTURES IN PHOTOREFRACTIVE MEDIA
A double-chirped mirror structure with broadband negative dispersion was realized with semiconduc... more A double-chirped mirror structure with broadband negative dispersion was realized with semiconductor technology. The necessary high precision of the fabrication was achieved by using special calibration structures. A single reflection on the obtained low-loss mirror produces sufficient negative dispersion for dispersion compensation in a femtosecond laser cavity. In this way we demonstrate 200 fs pulses from a compact Nd:glass laser without any additional dispersion compensation.
We present a new bistable scattering effect in a filled nematic liquid crystal, and its applicati... more We present a new bistable scattering effect in a filled nematic liquid crystal, and its application to a high resolution laser-addressed display. The filled nematic consists of a small fraction of inorganic particles of nm size in a nematic liquid crystal with positive dielectric anisotropy. The scattering ON state is reached by locally writing with a laser. The transparent OFF state can be obtained by combining a moderate voltage with selective application of the laser to the part to be erased. The key parameters controlling the processes and the possible physical mechanisms involved are discussed.
Theoretical and experimental investigations of electric field multiplexing and selectivity of ref... more Theoretical and experimental investigations of electric field multiplexing and selectivity of reflection volume holograms in LiNbO 3 are reported. Recording of at least five holograms is demonstrated. Equivalent spectral selectivity ∆λ ≈ 4.5 pm for the case of three electrically tunable holograms and ∆λ ≈ 9 pm for the case of five electrically tunable holograms are estimated.
Uploads
Papers by Theo Tschudi