Overlay Filter Research Articles

Continuously tunable single-frequency erbium ring fiber laser

We report on a frequency-stabilized narrow-linewidth continuous-fiber erbium-doped ring fiber laser in which the operating wavelength is defined by an overlay filter. The oscillating frequency is stabilized by a side-of-fringe locking technique, and longitudinal mode hops are inhibited by phase-sensitive detection of the signal rejected from an intracavity all-fiber étalon. With this frequency-stabilization scheme resolution-limited linewidths of 68 kHz with a root mean square frequency jitter of 10 kHz are measured. The oscillating frequency is continuously tunable over 3 GHz.

24] Purification and assay of kinases that interact with Rac/Cdc42

This chapter describes a method to detect a new family of Rho p21 interacting proteins. It also describes the use of the assay for expression screening and in the purification of an abundant Cdc42 and Rac1 target, which is the brain serine/threonine kinase p65-PAK. The GTPase-activating protein (GAP) overlay technique not only detects tissue levels of GAPs after sodium dodecyl sulfate (SDS) electrophoresis but also detects GTPase-inhibitory proteins. For these proteins to exert such an effect on the intrinsic GTPase activity of p21, they must remain bound (that is, they cannot act in a catalytic manner as do GAPs). After autoradiography of the nitrocellulose overlay filter, which holds the image of the nucleotide state of the test p21 within the original filter, some of these proteins can be observed as signals darker than the background. The process of detection of SDS–polyacrylamide-fractionated GTP-p21-binding proteins is described in the chapter.

Tunable erbium fiber laser using a novel overlay bandpass filter

A unidirectional erbium fiber laser incorporating a novel LiNbO(3) overlay fiber-optic bandpass filter is demonstrated. By applying index-matching oils of different refractive indices to the surface of the overlay filter, we could tune the operating wavelength of the laser from 1531 to 1556 nm while maintaining a bandwidth of less than 0.2 nm (resolution limited). Output powers as high as 3 mW for 36 mW of pump power have been recorded.

Reading Disabilities and the Effects of Colored Filters

The efficacy of a controversial treatment, using colored filters to remediate reading disabilities, was measured empirically, with colored overlays placed over reading material on white paper. Irlen's (1983) method is to prescribe specific tinted filters as lenses that she claims filter specific light frequencies and remove a range of perceptual disorders that adversely affect reading and related learning performance. Irlen calls this condition "scotopic sensitivity" and claims it is a significant factor in a high percentage of people with learning disabilities. Ninety-two children with significant reading disabilities were classified as either scotopic or nonscotopic using the Irlen Differential Perceptual Schedule, and were randomly assigned to one of six treatment groups using colored or clear overlays. Reading performance (rate, accuracy, and comprehension) as measured by the Neale Analysis of Reading Ability (Neale, 1987) and the Formal Reading Inventory (Wiederholt, 1986) improved significantly when the scotopic children read with the preferred colored overlay filter compared to clear or different-colored overlay filters. Nonscotopic children showed no change.