Frankfurt 2006 – scientific programme

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Q: Quantenoptik und Photonik

Q 20: Photonische Kristalle I

Q 20.7: Talk

Tuesday, March 14, 2006, 12:10–12:25, HI

Tunable photonic crystal laser with integrated wavelength monitor — •Christian Ulzhöfer, Helmut Scherer, Martin Kamp, and Alfred Forchel — Technische Physik, Am Hubland, D-97074 Würzburg, Germany

We have investigated the integration of tunable photonic crystal (PhC) lasers with a wavelength monitor. The tunable lasers are based on two coupled PhC waveguides with slightly different length. PhC mirrors are placed at the end, joint and front of the two waveguides. Tuning is achieved by a variation of the injection currents in the two segments. The wavelength monitor, which is placed behind the rear mirror of the laser, consists of a multi-mode PhC waveguide. Mode coupling between the fundamental mode and a higher order mode results in dips in the waveguide transmission (mini-stopband). The operating point of the laser is chosen on either side of the mini-stoband, so that any change of the wavelength will lead to a change of the transmission. An integrated photodiode at the end of the waveguide records the transmitted intensity.

The devices are fabricated from InP laser layers with 1.5 µ m emission wavelength. Electron beam lithography is used to define the PhC patterns, which are then etched through the complete laser structure to a depth of more than 3.5 µ m. The lasers have high sidemode suppression ratios between 30 and 45 dB and output powers above 25 mW. The tuning range of the devices is around 20 nm. The photocurrent of the integrated diode shows a clear dependence on the laser wavelength, in good agreement with simulations of the wavelength monitor transmission.