Fullerene-assisted electron-beam lithography for pattern improvement and loss reduction in InP membrane waveguide devices.

In this Letter, we present a method to prepare a mixed electron-beam resist composed of a positive resist (ZEP520A) and C60 fullerene. The addition of C60 to the ZEP resist changes the material properties under electron beam exposure significantly. An improvement in the thermal resistance of the mixed material has been demonstrated by fabricating multimode interference couplers and coupling regions of microring resonators. The fabrication of distributed Bragg reflector structures has shown improvement in terms of pattern definition accuracy with respect to the same structures fabricated with normal ZEP resist. Straight InP membrane waveguides with different lengths have been fabricated using this mixed resist. A decrease of the propagation loss from 6.6 to 3.3 dB/cm has been demonstrated.

Tolerant polarization converter for InGaAsP-InP photonic integrated circuits.

We report the fabrication and characterization of a new polarization converter for InGaAsP-InP photonic integrated circuits. The converter consists of two right trapezoidal sections with the angled sidewalls etched wetly. The converters show a greatly improved tolerance to variations of the fabrication, an averaged efficiency of polarization conversion of 99.8% and a loss of about 0.7 dB at a wavelength of 1.535 µm.

Improved fabrication process of low-loss and efficient polarization converters in InP-based photonic integrated circuits.

We show an improved fabrication process of trapezoidal polarization converters for InP-based photonic integrated circuits. The new process has reduced complexity, and the fabricated converters have loss two times lower than reported previously. The measurements of the converters show an efficiency of polarization conversion of 97.9% at a wavelength of 1.535 µm and loss below 0.5 dB.

High-efficiency ultrasmall polarization converter in InP membrane.

An ultrasmall (<10 µm length) polarization converter in InP membrane is fabricated and characterized. The device relies on the beating between the two eigenmodes of chemically etched triangular waveguides. Measurements show a very high polarization conversion efficiency of >99% with insertion losses of <-1.2 dB at a wavelength of 1.53 µm. Furthermore, our design is found to be broadband and tolerant to dimension variations.