Observation of thermal-induced optical guiding and bistability in a mid-IR continuous-wave, singly resonant optical parametric oscillator.

We report the observation of thermal-induced optical guiding and bistability in a mid-IR cw, singly resonant optical parametric oscillator (SRO) at approximately 3.2 microm. The SRO employs a MgO:PPLN crystal as the gain medium and a 1-nm-linewidth Yb-fiber laser at 1.064 microm as the pump source. As soon as the pump power reaches the thermal guiding threshold at 16.5 W, the SRO shows a step increase in the parametric efficiency by a factor of 2.5. At 25 W pump power, the SRO generated 5.3 and 1.2 W at 1.58 and 3.23 microm, respectively, with single-longitudinal-mode performance for the 3.23 microm radiation.

Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes.

The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.

Distributed-feedback optical parametric oscillation by use of a photorefractive grating in periodically poled lithium niobate.

We report a demonstration of distributed-feedback (DFB) optical parametric oscillation (OPO) by writing photorefractive gratings in periodically poled lithium niobate (PPLN). The photorefractive DFB structures were fabricated by illumination of PPLN with UV light through a photomask and by writing of PPLN with UV-light gated interfering laser beams at 532 nm. Evidence of OPO was observed from the spectral narrowing at the 1438.8- and the 619.3-nm signal wavelengths from 1064- and 532-nm-pumped PPLN crystals with the DFB grating periods phase matched to the 4084.5- and 3774-nm idler wavelengths, respectively.

CO(2) laser frequency stabilization using the radio-frequency optogalvanic Lamb dip.

The Lamb dip of the CO(2) saturation signal in an extracavity low-pressure CO(2)-N(2) rf glow discharge is detected optogalvanically and used to stabilize the frequency of a CO(2) laser. The frequency stability is estimated to be better than 100 kHz.

Two-mode frequency stabilization of a 543-nm He-Ne laser using current feedback.

An internal mirror 543-nm He-Ne laser is stabilized to a stability of 1 MHz by a two-mode method using current feedback.

Low-cost frequency-stabilized CO(2) laser using 4.3-microm saturated fluorescence.

A frequency-stabilized CO(2) laser using the saturated fluorescence technique was constructed. Stainless-steel rods were used to support the cavity, and a thermoelectrically cooled PbSe detector monitored the 4.3-microm fluorescence from a low-pressure CO(2) absorption cell. Stabilization of the CO(2) laser at the center of the saturation dip was achieved with the absorption cell inside or outside the laser cavity. The frequency stability is estimated to be better than 3.5 x 10(-9).

Enzyme-linked immunosorbent assay for detection of antibodies to Rift Valley fever virus in ovine and bovine sera.

An enzyme-linked immunosorbent assay (ELISA) was developed for the rapid detection of antibodies to Rift Valley fever virus (RVFV) in ovine and bovine sera. Conditions to reduce nonspecific reactions were optimized. The ELISA results correlated with those of a plaque-reduction neutralization test, revealing 100% specificity and 90.7% sensitivity. In sera from sheep and cattle inoculated against RVFV, the hemagglutination-inhibition test in combination with the ELISA provided a better indication of response to killed RVFV vaccine than did either test alone.

Optogalvanic Lamb-dip frequency stabilization of a sequence-band CO(2) laser.

The Lamb dip at the center of sequence-band CO(2) laser transitions is detected optogalvanically by using a low-pressure N(2)-CO(2) discharge. The first derivative of this signal is used to frequency stabilize a sequence-band CO(2) laser to a stability of better than 2 x 10(-9).