First carbon-nanotube-based optical component performs wavelength conversion

The interaction of carbon nanotubes (CNTs) with the evanescent field of light in the core of a silicon planar waveguide is the basis for the first CNT-based integrated optical component developed by researchers at the University of Tokyo and Alnair Labs Corporation.

Jun 1st, 2010

The interaction of carbon nanotubes (CNTs) with the evanescent field of light in the core of a silicon planar waveguide is the basis for the first CNT-based integrated optical component developed by researchers at the University of Tokyo and Alnair Labs Corporation (both in Tokyo, Japan). The CNT material—fabricated using a high-pressure carbon-oxygen conversion process creating nanotube diameters and distribution parameters optimized for strong absorption near 1550 nm—is deposited in a spraying process over the 7-µm-wide core of a cladding-removed waveguide fabricated using standard silicon-based planar lightwave circuit (PLC) techniques. The CNTs are believed to have a nonlinear refractive index several orders of magnitude higher than silica, originating from interband transitions of p-electrons causing nonlinear polarization like other highly nonlinear organic optical materials.

Due to strong CNT nonlinearity, pump and signal wavelengths from tunable laser sources input to the device undergo a four-wave mixing process; in effect, the device is an effective wavelength converter, with a nonlinear coefficient as high as 5.64 × 103 W-1km-1. For a 10 Gbit/s data stream, the power penalty was 3 dB for a bit-error rate (BER) of 10-9. The ability to deposit CNTs on a variety of waveguide patterns makes possible devices such as Mach-Zehnder interferometers, while their fast response time (less than 500 fs) enables the development of ultrahigh-speed structures for all-optical signal processing and optical logic gates. Contact Kin Kee Chow atkkchow@ntu.edu.sg.

More Laser Focus World Current Issue Articles
More Laser Focus World Archives Issue Articles

More in Optics