The purpose of this study was to evaluate anterior segment bioeffects of pulsed 35 GHz and 94 GHz microwave exposure in the nonhuman primate eye. Five juvenile rhesus monkeys (Macaca mulatta) underwent baseline anterior segment ocular assessment consisting of slit lamp examination, corneal topography, specular microscopy, and pachymetry. These studies were repeated after exposure of one eye to pulsed 35 GHz or 94 GHz microwaves at varied fluences, with the other eye serving as a control. The mean fluence required to produce a threshold corneal lesion (faint epithelial edema and fluorescein staining) was 7.5 J cm(-2) at 35 GHz and 5 J cm(-2) at 94 GHz. Transient changes in corneal topography and pachymetry were noted at these fluences. Endothelial cell counts remained unchanged. Threshold corneal injury from 35 GHz and 94 GHz microwave exposure is produced at fluences below those previously reported for CO2 laser radiation. These data may help elucidate the mechanism of thermal injury to the cornea, and resolve discrepancies between IEEE C95.1 (1999), NCRP (1986), and ICNIRP (1998) safety standards for exposure to non-ionizing radiation at millimeter wavelengths.

We demonstrate an array of erbium-doped waveguide-distributed feedback lasers on an ultra-low-loss Si(3)N(4) platform. Sidewall gratings providing the lasing feedback are defined in the silicon-nitride layer using 248 nm stepper lithography, while the gain is provided by a reactive co-sputtered erbium-doped aluminum-oxide layer. We observe lasing output over a 12 nm wavelength range (1531-1543 nm) from the array of five separate lasers. Output powers of 8 μW and lasing linewidths of 501 kHz are obtained. Single-mode operation is confirmed, with side-mode suppression ratios over 35 dB for all designs.

Record low optical threshold power and high slope efficiency are reported for arrays of distributed Bragg reflector lasers integrated within an ultra-low-loss Si(3)N(4) planar waveguide platform. Additionally, arrays of distributed feedback laser designs are presented that show improvements in pump-to-signal conversion efficiency of over two orders of magnitude beyond that found in previously published devices. Lithographically defined sidewall gratings provide the required lasing feedback for both cavity configurations. Lasing emission is shown over a wide wavelength range (1534 to 1570 nm), with output powers up to 2.1 mW and side mode suppression ratios in excess of 50 dB.