David T. Schaafsma

Fabrication of single-mode chalcogenide optical fiber

Long lengths (>150 m) of single-mode chalcogenide optical fiber were fabricated by a double crucible technique. Single-mode transmission through 10 m of continuous fiber was demonstrated using an F-center laser at 2.7 /spl mu/m. The optical loss of this fiber was measured by a standard cutback technique using an FTIR spectrometer and also using an F-center laser, A minimum loss of less than 1 dB/m was obtained.

Singlemode chalcogenide fiber infrared SNOM probes

We have fabricated and tested infrared scanning near-field optical microscope (IR-SNOM) probe tips made from singlemode chalcogenide fiber. The process used to create the tips was similar to conventional micropipette-puller techniques, with some modifications to allow for the lower melting temperature and tensile strength of the chalcogenide fiber. SEM micrographs, showing tips with sub-micrometer physical dimensions, demonstrate the feasibility of this process. Topographical data obtained using a shear-force near-field microscope exhibits spatial resolution in the range 80-100 nm. Optical data in the infrared (near 3.5 mu m), using the probe tips in collection mode, indicates an optical spatial resolution approximately lambda/15

Fused taper infrared optical fiber couplers in chalcogenide glass

We have fabricated low loss, high coupling ratio bidirectional optical couplers for infrared light using multimode step-index chalcogenide fiber. Using a fusion technique similar to that commonly employed with silica fibers, we have found a temperature regime where fusion can occur while interdiffusion of the core and cladding materials will not. The resultant device has a roughly 3:1 coupling ratio, less than 0.3 dB of excess insertion loss, and preserves the guided modes of the fiber intact.

All-dielectric miniature wideband rf receive antenna

An integrated Mach-Zehnder interferometer made of electro- optic (EO) polymers with a dimension of 331.2 cm was fabricated as a wideband rf receive antenna. When an electric field is applied to the interferometer arm(s) made of EO material, a phase delay is generated that results in a net imbalance in the interferometer, and thus a change in the output intensity. This output intensity change, which contains electric field strength and temporal profile information, is then read by a photo- detector and processed. This antenna was tested in a m-strip traveling wave electromagnetic cell at frequencies from 100 MHz to 1.04 GHz. The test results show the antenna had a good linear response over a 70-dB power range. The lowest possible measured Emin was about 4 mV/m (or 2.1 pW/cm 2 ) at 1-kHz resolution bandwidth with a laser power of 0.4 mW (24 dBm) measured after the sensor. The measured E-field signal increases with increasing laser power, which indicates that signifi- cant sensitivity improvement can be easily obtained by lowering passive losses. The antenna sensitivity can be further improved by lowering the device insertion loss, optimizing the photodetector and detection cir- cuitry, and using EO polymers with higher EO coefficients.

Modeling of Dy/sup 3+/-doped GeAsSe glass 1.3-μm optical fiber amplifiers

We present a model for optical amplification at 1.3 /spl mu/m using Dy/sup 3+/ in fibers made from a low phonon energy glass, based on GeAsSe. This model uses in-band pumping at 1.28 /spl mu/m, takes into account the spectral distribution of amplified spontaneous emission, and allows for bottlenecking of excited ions into the intermediate states in Dy as well as the excited state absorption (ESA) from those levels. Using data obtained from spectroscopic measurements and Judd-Ofelt calculations, our model shows that very high gain (>30 dB) is possible in short lengths (40-100 cm) of fiber. Given the very high quantum efficiency of the radiative transition in this glass, we show that bottlenecking and ESA should not have a significant impact on device performance. We also predict that devices made from this fiber should have a very high tolerance to the passive loss of the fiber.

Fabrication of single-mode chalcogenide fiber probes for scanning near-field infrared optical microscopy

We fabricate scanning near-field optical microscope (IR-SNOM) probe tips made from singlemode chalcogenide fiber and test them using a standard SNOM setup and free-electron laser. SEM micrographs, showing tips with submicrometer physical dimensions, demonstrate the feasibility of the thermal micropipette puller process used to create the tips. Topographical data obtained using a shear-force near-field microscope exhibit spatial resolution in the range of 80 to 100 nm. Optical data in the IR (near 3.5

First experimental results with the free electron laser coupled to a scanning near-field optical microscope

\mu

Evaluation of the IR transitions in rare-earth-doped chalcogenide glasses

m), using the probe tips in collection mode, indicate an optical spatial resolution of approximately

Rare earth doped glass fibers as infrared sources for IRSS

\lambda/15

All-dielectric fiber-optic passive millimeter-wave antenna

.