Intracavity self-phase modulation and pulse compression in mode-locked lasers

We show that in the presence of a bandwidth-limiting component intracavity selfphase modulation in high power mode-locked and Q-switched lasers is accompanied by interesting pulse-shaping phenomena. If the phase modulation is properly controlled the pulse duration can approach the limit given by the frequency bandwidth of the laser. For example, for a Nd: YAG laser our calculations predict an intracavity pulse compression by approximately a factor of ten over the typical pulse duration of conventional mode-locking.     

Picosecond and subpicosecon pulse generation in synchronously pumped mode-locked cw dye lasers

Generation of tunable near-infrared picosecond and subpicosecond pulses in a synchronously pumped cw mode-locked Oxazine-1-perchlorate dye laser has been investigated for different values of the important system parameters. The experimental results confirm the predictions of a simple theoretical model which describes the steady-state pulse duration in terms of gain modulation strength, pump power, intracavity bandwidth, pump pulse length and cavity detuning. For a pump-pulse length of 100 ps and a bandwidth of more than 500 Å for the intracavity tuning element dye-laser pulses as short as 0.35 ps have been obtained. Under these conditions up to 100 mW of average output power were provided. In addition, mode-locking of an Oxazine 750 dye laser by synchronous pumping with the cw train of pulses obtained from the Oxazine-1-Perchlorate laser is reported.     

A new inflationary universe scenario: A possible solution of the horizon,flatness, homogeneity,isotropy and primordial monopole problems

A new inflationary universe scenario is suggested, which is free of the shortcomings of the previous one and provides a possible solution of the horizon, flatness, homogeneity and isotropy problems in cosmology, and also a solution of the primordial monopole problem in grand unified theories.     

A new method for deconvoluting coded aperture images of three dimensional X-ray objects

Three-dimensional objects are coded using a non-redundant distribution of X-ray sources. The deconvolution of the image is performed by means of an incoherent optical processing system using a zoom-lens and a point-hologram. The method is capable of decoding the layers of the original object starting with a self-luminous image generated for example by an X-ray image intensifier tube.     

Generation of femtosecond anti-stokes pulses through phase-matched parametric four-wave mixing in a photonic crystal fiber

Phase-matched parametric four-wave mixing in higher-order guided modes of a photonic crystal fiber is shown to result in an efficient decay of 40-fs 800-nm Ti:sapphire laser pump pulses into an anti-Stokes signal with a central wavelength around 590-600 nm and a Stokes signal centered at 1.25 microm. The photonic crystal fiber is designed in such a way as to minimize the group-velocity dispersion at the pump wavelength, phase match the parametric four-wave-mixing process, and reduce the group delay between the pump and the anti-Stokes pulses. The duration of the anti-Stokes pulse under these conditions, as shown by cross-correlation frequency-resolved optical gating measurements, is less than 200 fs.     

Solution-processed, highly-oriented supramolecular architectures of functionalized porphyrins with extended electronic states

Thin films of aligned supramolecular architectures built from newly synthesized thiophene-substituted porphyrins have been processed from solution on surfaces.     

Regiospecific N‐Arylation of Aliphatic Amines under Mild and Metal‐Free Reaction Conditions

A transition metal‐free N‐arylation of primary and secondary amines with diaryliodonium salts is presented. Both acyclic and cyclic amines are well tolerated, providing a large set of N‐alkyl anilines. The methodology is unprecedented among metal‐free methods in terms of amine scope, the ability to transfer both electron‐withdrawing and electron‐donating aryl groups, and efficient use of resources, as excess substrate or reagents are not required.