purpose: to compare tear secretion values following lasik (laser in situ keratomileusis) and photorefractive keratectomy (prk). methods: patients referred to aban eye clinic (isfahan, iran) for refractive surgery were randomly assigned to lasik or prk. exclusion criteria were contraindications for refractive surgery, usage of topical ocular drugs, dry eye and reoperation. schirmer test was perf...

Purpose: To evaluate the accuracy of postoperative refraction ,UCVA,BCVA and possible complications after Photorefractive keratectomy (PRK) using mitomycin C in moderate to high myopia in selected refractive cases that are considered unsuitable for lasik.Methods: twenty one eyes (of 14 myopic patients) were subjected to Photorefractive keratectomy (PRK) using the The ALLEGRETTO WAVE EYE-Q 1010 ...

Dipole and quadrupole solitons in a two-dimensional photorefractive optical lattice are investigated both theoretically and experimentally. It is shown theoretically that out-of-phase dipole solitons and quadrupole solitons exist and are linearly stable in the intermediate-intensity regime. In-phase dipole and quadrupole solitons, however, are always linearly unstable, but their instabilities a...

The diffraction of 100-fs pulses from the static gratings of photorefractive quantum wells (QW’s) produces diffracted pulses that are nearly transform-limited, despite the strong dispersion near the quantum-confined excitonic transitions. This quality makes the QW’s candidates for use in femtosecond pulse shaping, although the currently limited bandwidth of the quantum-confined excitonic transi...

The transient behavior of the fundamental amplitude of the photorefractive space-charge field is derived without restrictions within the band transport model. The two-wave mixing pulse excitation regime is simulated in different ranges of the main parameters, especially in the region where the nonlinear processes become important. The formation and decay of the field are analyzed, and for diffe...

We present and numerically solve a model of the photorefractive Gunn effect. We find that high field domains can be triggered by phase-locked interference fringes, as it has been recently predicted on the basis of linear stability considerations. Since the Gunn effect is intrinsically nonlinear, we find that such considerations give at best order-of-magnitude estimations of the parameters criti...

We demonstrate the recording of holograms and their nondestructive readout in a photorefractive polymer, using two-photon absorption. Sensitivity is provided by the excitation of the electroactive chromophore with femtosecond pulses, followed by charge injection into the photoconducting poly(N -vinylcarbazole) matrix. The holograms can be fully erased with a pulsed laser source but are insensit...

The photorefractive effect in photoconductive ferroelectric liquid crystals that contain photoconductive chiral compounds was investigated. Terthiophene compounds with chiral structures were chosen as the photoconductive chiral compounds, and they were mixed with an achiral smectic C liquid crystal. The mixtures exhibit the ferroelectric chiral smectic C phase. The photorefractivity of the mixt...

We report on the operation of the double phase-conjugate mirror (DPCM). Two inputs to opposite sides of a photorefractive barium titanate crystal, which may carry different spatial images, are shown to pump the same four-wave mixing process mutually and are self-refracted without any external or internal crystal surface. This results in the phase-conjugate reproduction of the two images simulta...

We report the observation of steady-state photorefractive vortex-screening solitons. As a singly charged circular vortex nested on a broad beam propagates through a biased strontium barium niobate crystal, it self-traps in both transverse dimensions despite the inherent anisotropy of the photorefractive nonlinearity. When the vortex beam is a doughnut-shaped narrow beam, it breaks up into two e...