We report what is believed to be the first example of structural long-period gratings written in pure silica photonic crystal fibers (PCFs). The gratings are realized by periodic collapse of the holes of the PCF by heat treatment with a ${\mathrm{CO}}_2$ laser. The resulting periodic hole-size perturbation produces core-to-cladding-mode conversion. These results can lead to a new family of structural all-fiber devices that use the unique properties of PCFs.

A focused carbon dioxide laser beam is used to microstructure fibers that have already been narrowed by conventional fiber tapering. We describe three new miniature devices made with this technique: a fused fiber microcoupler with an interaction length of $200 \mu \mathrm{m}$, a long-period grating made from a periodic chain of microtapers, and a new type of prolate whispering-gallery mode microcavity.

We report a new method for making low-loss interfaces between conventional single-mode fibers and photonic crystal fibers (PCFs). Adapted from the fabrication of PCF preforms from stacked tubes and rods, this method avoids the need for splicing and is versatile enough to interface to virtually any type of index-guiding silica PCF. We illustrate the method by forming interfaces to two problematic types of PCF, highly nonlinear and multicore. In particular, we believe this to be the first method capable of individually coupling light into and out of all the cores of a fiber with multiple closely spaced cores, without input or output cross talk.

We report the development of a fiber taper and fused-fiber coupler fabrication rig that uses a scanning, focused, CO₂ laser beam as the heat source. As a result of the pointlike heat source and the versatility associated with scanning, tapers of any transition shape and uniform taper waist can be produced. Tapers with both a linear shape and an exponential transition shape were measured. The taper waist uniformity was measured and shown to be better than ±1.2%. The rig was also used to make fused-fiber couplers. Couplers with excess loss below -0.1 dB were routinely produced.

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We report what we believe is the first example of efficient rocking filter formation in polarization-maintaining photonic crystal fiber. Very high coupling efficiencies (as much as $-23.5‐\mathrm{dB}$ suppression of the input polarization) and loss of $<0.02 \mathrm{dB}$ were achieved for fibers as short as 11 mm. The filters, which we prepared by periodic mechanical twisting and heating with a scanned ${\mathrm{CO}}_2$ laser beam, are highly compact, and they are expected to be temperature stable.