Tunable optical properties of photonic crystals and semiconductor microdisks using liquid crystals

The combination of semiconductors and liquid crystals is extremely useful in order to fabricate integrated optical devices with tunable properties. The difference between the dielectric constants of the semiconductor and the liquid crystal ('dielectric contrast') is sufficiently high to obtain photonic band gap structures or resonant microcavities with high quality factor. At the same time, the characteristic frequencies can be controlled by temperature changes or external fields due to the thermo-, electro- or magneto-optic sensitivity of the liquid crystal. Here, previous investigations on microcavities embedded in silicon-based photonic crystals are reviewed and new results on integrated GaAs microdisks containing a light emitting layer of InAs quantum dots are presented. The latter show resonant modes with a typical width below 0.4 nm in the near infrared spectral range around 1.24 mu m, which indicates a quality factor of 3500 and larger. By embedding a microdisk in a well-aligned liquid crystal and subsequent heating to the isotropic phase, a spectral shift of about 7 nm was observed. The results indicate a possible way of developing tunable light sources.