Semiconductor nanostructures, especially self-assembled quantum dots and photonic crystals, are emerging as an important future direction for optoelectronics. Photonic crystals offer a wide range of possibilities, ranging from improved light-emitting diodes to photonic integrated circuits to spontaneous emission control. Semiconductor quantum dots have an atomic-like density of states that offers substantial opportunities for unique and improved devices. These include ultra-low-threshold laser diodes with low temperature dependence, and semiconductor optical amplifiers with reduced cross-gain modulation and large bandwidth. Several fundamental properties of quantum dots, including resonant absorption cross-sections and homogeneous linewidth, set limitations on device operation. For example, high-spectral-resolution measurement of quantum dots is important for quantifying structural homogeneity as well as providing data to model devices to be used in quantum information applications.

The ability to generate and control single photons offers new opportunities to meet customer needs in quantum-based radiometric measurements where optical power is measured by counting photons.  Quantum cryptography is an emerging form of ultrasecure communications that requires an on-demand source of single photons as well as single photon detectors. The single-photon turnstile will allow us to meet the requirements of this new technology. It can be extended to generate pairs of entangled photons. These entangled-photon pairs are useful for a wide range of applications, from fundamental tests of quantum mechanics to reduced dimensions with optical lithography. Semiconductor single photon detectors with reduced timing jitter, higher quantum efficiency, and photoresponse beyond 1000 nm offer advantages in applications such as semiconductor and integrated circuit characterization, LIDAR, and quantum cryptography.