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Photonic crystal splits light

28 Aug 2002

For the first time, researchers develop a 2D photonic-crystal Y-splitter that operates near communication wavelengths.

US scientists claim to have developed the first 2D photonic-crystal Y-splitter that operates close to the communication wavelength regime.

With measured losses of 0.5 dB at 1650 nm, the team from Sandia National Laboratories and Massachusetts Institute of Technology says its device looks promising for making integrated photonic-circuits. (Optics Letters 27 1400)

The device uses a 2D photonic bandgap (PBG) to guide and bend light. Based on a triple-line-defect design, the sample comprises one 120° angle splitter and two 60° bends.

"Light is guided by an input ridge waveguide, split into two by the Y-splitter, bent and then guided into two output ridge waveguides," say the authors. "Five linear PBG waveguides connect the splitter and the bends."

The basic photonic crystal structure is a 2D triangular array, with a lattice constant of 440 nm and a hole diameter of 264 . In order to guide the light effectively, the linear PBG waveguides consist of a triple line defect with a hole diameter increased to 352 nm.

As for size, the Y-splitter junction is 3 µm x 3 µm, the bends are 2 µm x 2 µm and the whole sample is 10 µm x 15 µm.

Measurements show that the device has a near 50/50 splitting ratio between 1640 and 1680 nm, however, outside this window this ratio becomes uneven and the total transmitted output power is reduced.

The researchers now plan to minimize the loss for the PBG splitter by introducing an intentional defect at the Y junction.

Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.

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