Photonic bandpass filters with high skirt selectivity and stopband attenuation

A new photonic signal processor topology that simultaneously achieves both a high-Q and a high skirt selectivity and stopband attenuation filter response is presented. It is based on a novel dual-cavity bandpass optical structure in which two pairs of active fiber Bragg grating cavities are used with an optical gain offset to control the poles and stopband attenuation characteristics of the filter. This concept enables a large improvement in the filter stopband attenuation, rejection bandwidth, and skirt selectivity to be realized. Measured results demonstrate both a narrow bandpass bandwidth of 0.4% of center frequency and a skirt selectivity factor of 16.6 for 40 dB rejection, which corresponds to a 6.5-fold improvement in comparison to conventional single cavity high-Q structures. To our knowledge, this is the best skirt selectivity reported for a photonic bandpass filter to date. The new photonic filter structure has been experimentally verified and excellent agreement between measured and predicted responses is shown.     

Effect of oblique light incidence on magnetooptical properties of one-dimensional photonic crystals

We have investigated the magnetooptical properties of one-dimensional magnetic photonic crystals for the case of oblique light incidence. We developed a theoretical model based on the transfer matrix approach. We found several new effects such as transmittance resonance peak shift versus external magnetic field and the Faraday effect dependence on the incidence angle. We discuss several possible one-dimensional magnetic photonic crystals applications for the optical devices.     

A Tunable Multiwavelength Laser Employing a Semiconductor Optical Amplifier and an Opto-VLSI Processor

We propose and experimentally demonstrate a stable tunable multiwavelength laser employing a semiconductor optical amplifier (SOA) in conjunction with an opto-very-large-scale-integration (VLSI) processor. By uploading digital phase holograms onto the opto-VLSI processor, the amplified spontaneous emission of the SOA is arbitrarily sliced and injected back into the SOA to generate multiple lasing wavelengths with a linewidth of 0.5 nm. Experimental results demonstrate a tunable multiwavelength laser with a tuning range from 1528 to 1533 nm with power fluctuations of less than 0.5 dB.     

Design and Characterization of CMOS/SOI Image Sensors

The design, operation, and characterization of CMOS imagers implemented using: 1) "regular" CMOS wafers with a 0.5-mum CMOS analog process; 2) "regular" CMOS wafers with a 0.35-mum CMOS analog process; and 3) silicon-on-insulator (SOI) wafers in conjunction with a 0.35-mum CMOS analog process, are discussed in this paper. The performances of the studied imagers are compared in terms of quantum efficiency, dark current, and optical bandwidth. It is found that there is strong dependence of quantum efficiency of the photodiodes on the architecture of the image sensor. The results of this paper are useful for designing and modeling CMOS/SOI image sensors     

High capacity optical beam forming for phased arrays with fiber gratings and frequency conversion for beat noise control

A new wavelength division multiplexing grating-based beam-forming architecture for phased arrays that can achieve the minimum possible number of optical interconnects is presented. A reduction in interconnect hardware of 99.6% is obtained for a 512-beam array, which is, as far as we know, the lowest number of interconnects reported to date. Analysis of the ultimate beam capacity limit of the beam former shows that the beat noise interference limitation is the most important factor. We present a new hybrid frequency-converting optical beam former that removes the fundamental beat noise limitation. This frequency downconverts the rf signal to an intermediate frequency before performing the true-time-delay equalization in the optical domain. The resulting advantage of reduced optical bandwidth per channel enables more wavelengths to be used for a given wavelength span, resulting in an increased beam capacity. A greater than sevenfold increase in beam capacity is demonstrated through the use of the frequency conversion technique, with 960 beams synthesized at 12.4 GHz, showing a 99.8% reduction in required interconnects.