Photonic Crystal Lasers

Nanobeam Photonic Crystal Lasers

Tom Mahony, Parag Deotare, Vladimir Bulović

It goes without saying that lasers are an incredibly useful piece of technology to our modern world. Over the past half century, as lasers matured, they enabled new techniques for sensing, communicating, manufacturing, and measuring in many settings. Though lasers have been miniaturized in the form of semiconductor diode lasers, these lasers operate mostly in the infrared regime without additional optics, and are non-trivial to integrate with silicon-based electronic circuits. We are designing lasers to address both of these challenges.

To design a laser that operates in the visible regime, we use organic molecules and colloidal quantum dots as gain materials. These materials are deposited as thin films using thermal evaporation or solution processing, which allows them to be used on nearly any substrate. We then find ways of building optical cavities that incorporate these materials.

The optical cavities we use are called nanobeam photonic crystal cavities. They are essentially waveguides with one dimensional photonic crystals patterned along their length to trap light and build up a population of photons that enables lasing. Due to their very small mode volume and high quality factor, they have large Purcell enhancements and can enable low lasing thresholds. 

We have demonstrated lasing using organic lasers of this geometry. For more information about those devices, see our paper below. We now hope to demonstrate nanobeam photonic crystal lasers using quantum dots.

 

SEM of an organic nanobeam photonic crystal laser.

Photoluminescence spectrum taken from a quantum dot nanobeam cavity. We see amplified spontaneous emission through the cavity mode at 605 nm. Fitting to a lorentzian lineshape, we conclude the cavity has a quality factor of around 2000.

Related publications:

  • P. B. Deotare, T. S. Mahony, and V. Bulović, “Ultracompact Low-Threshold Organic Laser,” ACS Nano, vol. 8, no. 11, pp. 11080–11085, Sep. 2014.