Biomedical subjects

Ray T Chen

Publications and source records attributed to Ray T Chen.

5 recordsLinked to original sources

PubMed2007

Phase error corrected 4-bit true time delay module using a cascaded 2 x 2 polymer waveguide switch array.

A fully integrated 4-bit true time delay device using polymer optical switches and waveguide delay lines is demonstrated. The fabricated device, which contains five 2x2 thermo-optic switches, has a maximum power consumption of 143 mW and a switching time less than 3 ms. The rf phase error, which is affected by the optical switch cross talk, is also theoretically analyzed and proved to be negligible by experimental results.

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PubMed2006

Rigorous analysis of diffraction gratings of arbitrary profiles using virtual photonic crystals.

A new approach is developed to calculate diffraction efficiency for a dielectric grating with an arbitrary refractive index profile. By treating a one-dimensional grating as a segment of a virtual two-dimensional (2D) photonic crystal, we exploit a rigorous theory of photonic crystal refraction and calculate the diffraction efficiencies. We expand, analytically in many cases, the dielectric function of the grating into 2D Fourier series. We find the eigenmodes for the virtual photonic crystal, and then use these eigenmodes to match the boundary conditions by solving a set of linear equations. In two such simple steps, the diffraction efficiencies can be computed rigorously without slicing the grating into thin layers.

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PubMed2003

Multichannel optical add-drop processes in symmetrical waveguide-resonator systems.

Multichannel optical add-drop processes are studied in a class of symmetric waveguide-resonator systems. With insight gained from group theory, we analyze these systems and show that they can add or drop multiple wavelengths simultaneously, with 100% efficiency. A new mechanism is presented to reduce the remnant light at the dropped wavelengths in the pass-through port. High-order Butterworth filters can also be achieved in these systems. Built upon conventional or photonic-crystal based structures, these systems can be used in optical communication applications.

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PubMed2002

Two-step K(+)-Na+ and Ag(+)-Na+ ion-exchanged glass waveguides for C-band applications.

A two-step K(+)-Na+ and Ag(+)-Na+ ion-exchange technique is introduced to fabricate single-mode channel waveguides in BK7 glass for the telecom-wavelength region. The dependencies of insertion loss, polarization-dependent loss (PDL), end bending loss of curved waveguides on channel width, diffusion time, and annealing time are investigated. Results show that postannealing is a required process for improving waveguide properties and an optimal annealing time exists. Although relatively narrow mask openings are used in most one-step ion-exchange processes, a wider channel width, to as wide as 10 microm, is preferred for this two-step method. The minimum coupling loss to/from single-mode fiber and the propagation loss is found to be 0.4 dB and 0.3 dB/cm, respectively. For 5-cm-long waveguides the PDL is less than 0.1 dB. For the S-bend structure the cosine curve exhibit apparently a lower bending loss than the double-arc curve.

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PubMed2002

Athermalized low-loss echelle-grating-based multimode dense wavelength division demultiplexer.

A high-density wavelength division demultiplexer (DEMUX) capable of demultiplexing eight-channel 200-GHz optically spaced signals into a 62.5-microm multimode-fiber array is reported. The wavelength range of operation is from 1549.32 to 1560.61 nm within the International Telecommunication Union grid. The measured wavelength accuracy is within 0.04 nm. The mean insertion loss of this DEMUX is 1.95 dB. Thermal analysis and temperature testing results are reported. The temperature test cycling from 20 degrees C to 60 degrees C indicates that the wavelength thermal drift is less than 0.8 pm/degrees C. Adjacent cross talk is measured to be better than -45 dB. The measured data transmission bit rate of this device is higher than 3.5 Gb/s.

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