Historically, safety analyses for radio frequency emission and optical laser exposures have been designed to define the threshold level for tissue damage. To date, no experimental studies have documented damage thresholds to living tissues in the terahertz (THz) range of electromagnetic frequencies (0.1 - 10 THz). Exposure limits exist as extrapolated estimates at the extreme bounds of current occupational safety standards for lasers and radio frequency sources. Therefore, due to the lack of published data on the safety of terahertz emissions, an understanding of the bioeffects of tissue exposures to terahertz beams is necessary. The terahertz frequency band represents an intermediate range in which both optical and radiofrequency methods of theory and experimentation can be selectively employed and compared for consistency. We report on work recently completed to reconcile the theoretical methods of optical and radio-frequency radiative transport modeling, while additionally discussing preliminary theoretical estimates of damage thresholds to skin tissue from terahertz energy and work planned to validate these findings experimentally.
In this paper, we first review the working principle of grating-base wavelength division (de)multiplexers (WD(D)M) for optical networks. Then key device parameters for WDM multiplexers, including insertion loss, isolation, channel passband, wavelength accuracy, polarization-dependent loss and temperature sensitivity are provided to evaluate the performance for the devices. After that, issues regarding optical design of grating-based WD(D)Ms for commercial uses are addressed. Next, several grating-based WD(D)M structures are analyzed with the procedures to optimize design of grating-based wavelength division (de)multiplexers. Based on these designs and analyses, we give the procedures of optimal design of devices with experimental data.
Due to the lack of supply of wavelength division multiplexer components and emerging communications protocols, single- mode fiber coarse wavelength division multiplexers (WDMs), multimode fiber WDMs, and single-mode fiber dense WDMs are being considered in the metropolitan core and metropolitan access networks. This paper describes the evolving specifications for WDMs placed in metropolitan transport equipment. Comparisons of WDM components from various technologies such as arrayed waveguides, bulk grating, thin film filters, and fiber bragg gratings will be presented.
We construct a passive grating-based wavelength-division (de)multiplexer (MUX/DMUX) for single-mode-fiber networks. The MUX/DMUX has almost identical bi-directional filtering characteristics on optical signals at wavelengths around 1550 nm. With total insertion loss less than 3 dB and an enlarged passing band of each channel, the encapsulated device exhibits very stable performance under temperature variation and is immune from mechanical vibration. The insertion loss of this device changes about 1 dB at temperatures from 25 degree(s)C to 60 degree(s)C, while the enter wavelength of each channel drifts about 8.3 X 10-4 nm/(nm(DOT) degree(s)C). Better results are expected with further optimization on the design. The device successfully demultiplexes 231 -1 PRBS signals up to 3.5 Gb/s per channel in an emulated amplifier-free local- area networks (LAN's) and metropolitan-area networks transmission. It is plausible the cost-effective MUX/DEMUX is an excellent candidate to meet 10 Gb/s all-optical multi- wavelength short-link applications.
We describe the design and performance of a multimode 8- channel, 200 GHz-spaced dense wavelength division demultiplexer using a high order blazed grating. The mean insertion loss of this DEMUX is 1.95 dB. Adjacent crosstalk is measured to be better than -45 dB. The temperature test cycling from 20 to 60 degree(s)C indicates that the wavelength thermal drift is less than 0.00033 nm/ degree(s)C. The device has multi-mode fibers for both input and output, which is good for the optical networks in both metropolitan and local areas. The device is not sensitive to the disturbance of temperature and environment, so no temperature controller is needed.
The design, packaging, and performance of a novel 32 channel, 100GHz dense wavelength division
demultiplexer (DWDM) using the 22w' diffraction order of an Echelle grating is described. A fully
packaged prototype operating in the 1 .54 to 1 .57-rim spectral range is built and tested. The insertion losses
of all 32 channels are within -3.0±0.2 dB. The crosstalk between adjacent channels for all the 32 channels
is in the neighborhood of -30dB, and average 1dB optical pass band is O.256nm.
Key words: Wavelength division demultiplexing, Echelle grating, dispersion ability, DWDM packaging
This paper reports our efforts to develop an optical True- Time-Delay line module for Phased Array Antenna applications using optical polymeric waveguides. We first give a brief description of a targeted phased array antenna, having chosen a 16-element sub-array as our demonstration system. Then we address the design considerations of the True-Time- Delay lines pattern based on the sub-array antenna's parameters, including simulations we have done to optimize the building blocks of the pattern: splitters, arcs' curvature, and crossings. Finally, we describe the steps of a modified fabrication process and present the primary result. Our experiment shows that the polyimide-based waveguide has a promising future because it has high fabrication precision and packaging density.
A 32-channel wavelength-division demultiplexer has been designed and tested. Intended for commercial use, the instrument is designed to be rugged, stable, and insensitive to temperature variations. Operating in the 1.54-1.57-micrometers spectral range, the unit uses single-mode fiber input and multi-mode fiber output. The optics consists of a Littrow plane-grating spectrograph that uses the same lens for collimation and for focusing. In order to reduce the size of the device, the gratin is used at a large diffraction angle. A coarse ruling is used in a high diffraction order, which results in a device that has a low polarization-dependent loss. The mean insertion loss for all channels was 3.1 dB, and the standard deviation of the insertion loss was 0.23 dB. The mean channel bandwidth was 0.26 dB.
A miniaturized, handheld biosensor for identification of hazardous biowarfare agents with high specificity is being developed. An innovative biological recognition system based on bacteriophage displayed peptide receptors will be utilized in conjunction with the miniature biosensor technology being developed. A bacteriophage library has been constructed to provide the artificial receptors. The library can contain millions of bacteriophage with randomly displayed peptide sequences in the phage outer protein coat which act as binding sites for the agents of interest. This library will be used to 'bio-pan' for phages that bind to a number of toxins and infectious agents and can, thus, provide an endless supply of low cost, reliable, specific, and stable artificial receptors. The biosensor instrument will utilize evanescent wave, planar waveguide, far-red dyes, diode laser and miniature circuit technologies for performance and portability.
McDonnell Douglas Electronic Systems Company (MDESC) approach to developing 1.5X micron lasers have been to either diode pump Er:Glass or to use Nd hosts to pump optical parametric oscillators (OPOs). A 1.57 micron Optical Parametric Oscillator (OPO) from a multimode 1064 nm Nd:YAG slab laser has been demonstrated. Using KTP as the nonlinear crystal, 39 mJ of 1.57 micron has been achieved with 1064 nm pump input of 200 mJ. The system had a wall plug efficiency > 1%.
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