Electrically Tunable Organic Vertical-Cavity Surface-Emitting Lasers
Wendi Chang, Apoorva Murarka, Annie Wang, Vladimir Bulović
Since their invention in the 1950s, laser systems are an example of a ubiquitous technology that enabled a wide range of applications. From Blu-ray to surgeries, lasers also created the foundation of the modern field of photonics and spectroscopy. However, creating a compact, dynamically tunable laser in the visible wavelengths is still an undeveloped problem. A wavelength tunable lasing device would enable many fields of research and technology, including spectroscopy and remote sensing. Laser wavelength tuning using standard nonlinear optics techniques requires high power and large equipments. While small compact lasers with a range of visible emission wavelengths has been fabricated on a single device, the emission is predetermined during fabrication and cannot be dynamically tuned.
Drawing inspiration from developments in micro-electro-mechanical systems (MEMS) of tunable inorganic, infrared lasers, we demonstrate a organic vertical-cavity surface-emitting laser (VCSEL) with dynamic wavelength-tunability in the visible wavelengths. Since standard inorganic semiconductor fabrication methods such as lithography and etching cannot be applied to soft, organic materials, we develop a composite membrane contact-transfer printing technique to fabricate an array of microcavities. Each vertical cavity is formed by a bottom DBR substrate and a suspended top silver mirror. By applying a voltage across top gold contact and bottom indium tin oxide (ITO) electrode, electrostatic pressure deflects the top membrane, changing the cavity length and laser emission wavelength. Beyond tunable lasing, the same device in could enable many applications as an all-optical pressure sensing array, where the cavity length change is correlated with pressure difference across each membrane.
(a) Schematic of device structure; voltage applied between the top gold and bottom ITO allows membrane deflection due to electrostatic force. (b) Optical interferometry difference image between 20V and 0V applied bias on an array of devices as imaged from the top membrane. (c) Comparison of cavity mode emission peak shift with membrane deflection. (d) Difference profile between applied bias and 0V bias show controllable membrane deflection.
VCSEL wavelength shift under applied bias in two consecutive sweeps shows hysteresis below 1 nm. (inset) Normalized spectra of laser emission at various bias.
Related publications and links
- W. Chang*, A. Murarka*, A. Wang*, G. M. Akselrod, C. Packard, J. Lang, and V. Bulovic, “Electrically tunable organic vertical-cavity surface-emitting laser,” Appl. Phys. Lett., 105, 073303 (2014).
- W. Chang*, A. Wang*, A. Murarka*, J. Lang, and V. Bulovic, "Transfer-Printed Composite Membranes for Electrically-Tunable Organic Optical Microcavities,” Micro Electro Mechanical Systems (MEMS), 2014 IEEE 27th International Conference on.