Steven R. Montgomery

Fixing the photorefractive soliton

We report the formation of permanent two-dimensional 12-microm waveguides in a bulk strontium barium niobate crystal. The waveguides are made by formation of a photorefractive spatial soliton in which the space-charge field induces ferroelectric domains that are permanently polarized opposite to the crystal c axis. The fixed waveguide propagates light with 80% efficiency. These results make possible the permanent recording of intricate optical circuitry in the volume of a bulk crystal.

Self-pumped phase conjugation in the red in photorefractive Ba 0.5 Sr 1.5 K 0.25 Na 0.75 Nb 5 O 15 and Sr 0.6 Ba 0.4 Nb 2 O 6 with cerium in 9-fold coordinated sites

Self-pumped phase conjugation has been observed at selected laser wavelengths over the range 647–780 nm. Phase-conjugate reflectivities as great as 20% were measured for power levels ranging from 2 to 100 mW. In addition, phase-conjugate and beam-fanning response times were also measured. Our observations were carried out in crystals belonging to the tungsten-bronze family; these crystals were doped with cerium at the 9-fold coordinated lattice sites to give a red photorefractive response.

Intensity profiles of short optical pulses via temporally reversed pulses

A new technique is reported for determining the intensity profile of optical pulses on a subpicosecond timescale. Several examples are presented in order to demonstrate the capability of the technique.

Near IR nonlinear absorption of an organic supermolecule [Invited]

The photophysics of bis(terpyridyl)osmium-(porphinato)zinc-bis(terpyridyl)osmium (OsPZnOs), a D-π-A-π-D symmetric supermolecule, were investigated in the femtosecond and nanosecond regimes. The supermolecule exhibits a two-photon absorption (δpeak ~900 GM) in the near IR (900-1300 nm) and optical pumping by two-photon absorption leads to a broad excited state absorption (σpeak ~1.1 × 10−16 cm2) in the same near IR region. Since the excited state has a long lifetime, OsPZnOs exhibits a strong nanosecond nonlinear absorption in this region. That nonlinear absorption is substantially enhanced when OsPZnOs is incorporated into a multimode waveguide. When two-photon pumping is the dominant mechanism, an additional enhancement of up to ~100 × in the nonlinear absorption is observed in a microchannel waveguide. OsPZnOs is a promising material for photonic applications such as optical noise suppression and optical limiting in the near IR.

Cooperative photorefractive beam fanning in BaSrKNaNb 5 O 15

A multiline laser beam incident upon a BaSrKNaNb5O15 crystal causes rings to form in the beam fan by means of cooperative photorefractive fanning between the different wavelengths. We examine the novel case in which the input beam consists of two lines from an argon-ion laser with independently controlled linear polarizations as well as the single-line case with equal amounts of ordinary and extraordinary light. We compute the expected rings in each case, taking full account of the crystal birefringence, and compare them with the experimental data. Applications of the rings to crystallography and cryptology are presented.

Enhancing the photorefractive effect

Abstract The transient response for beam fanning in photorefractive tungsten bronze crystals with an applied electric field and a focused laser beam is studied. Response times on the order of 1 ms for an incident power of 1 mW observed for incident beams focused to a 30 μm diameter in the crystal. This improved response time is accomplished without the significant reduction in the magnitude of the photorefractive effect normally observed for focused beams.

Optical properties of solid-core photonic crystal fibers filled with nonlinear absorbers

A theoretical and experimental investigation of the transmission of solid-core photonic crystal fibers (PCFs) filled with nonlinear absorbers shows a sharp change in the threshold for optical limiting and in leakage loss as the refractive index of the material in the holes approaches that of the glass matrix. Theoretical calculations of the mode profiles and leakage loss of the PCF are in agreement with experimental results and indicate that the change in limiting response is due to the interaction of the evanescent field of the guided mode with the nonlinear absorbers in the holes.

Optical limiting in solid-core photonic crystal fibers

Optical limiting in solid-core photonic crystal fibers filled with reverse-saturable absorbers has been observed. A sharp change in limiting threshold was found for materials in the fiber holes with refractive indices near n = 1.44.