Photonic crystals ??Crystals composed of periodic dielectric or metallo- dielectricnanostructure that affect the propagation of photon in the sameway as the periodic potential in a semiconductor crystal affectsthe electron motion by defining allowed and forbidden electronicenergy bands.
Why Photonic crystals ?? Give us a control over photon flow and an even greater control over material properties. Quantum dots that provide mode confinement and density of optical state structures for feedback to take place By using 2-D photonic crystals the dimensions of micro- resonators can be greatly reduced. Tuning of cavity, by changing refractive index. Easy to control spontaneous emission, bend light sharply, trap photons and make devices that provide other important advances regarding lasers. Artificially defect states can be introduced .
Design To evaluate the use of quantum dots within the active region of laser, a separate confinement heterostructure laser with 7 layers of quantum dots is fabricated Patterned on two crossing waveguides. The top GaAs waveguide contains a quantum dots-in-a-well structure, which serves as the active material for the laser. The nanocavity, located at the two waveguide’s intersection, creates a high-Q optical resonator with the 1-D photonic crystals acting as highly reflective mirrors.
Confinement and Control Electrical confinement via the energy band structure and Optical confinement is achieved by means of ridge waveguides and index contrast. By removing some of the holes in one of the photonic crystals, one can control the direction of the emitted light Higher powers can be produced by fabricating nanocavities in arrays. Coherent coupling of the cavities generates a single-mode beam from a small array.
What is special in pc laser Ultralow threshold (667 A/cm2 for Lateral cavity PC laser) High Quality factors (>1x10^6) Optical as well as electrical pumping (now) can be used. Both in the CW and pulsed mode of operation at a variety of temperatures (@ room temp. in CW) Flexibility in shape and size. PC nanocavities are an ideal platform for low- power laser sources because strong light- matter interaction can be obtained.But Power ~µw
Applications As low jitter sources of single, indistinguishable photons in quantum information processing and related areas. Low threshold spectroscopy sources and operation of photonic crystal laser in ambient organic solutions Used to perform spectroscopic tests on femtoliter volume of analyte and for high resolution spectroscopy with single molecule sensitivity Advantageous for optical interconnects which require speed of the high-speed communications(order of terahertz).