1. Ajay Singh
IIT Delhi

2. Photonic crystals ??
Crystals composed of periodic dielectric or metallo- dielectric
nanostructure that affect the propagation of photon in the same
way as the periodic potential in a semiconductor crystal affects
the electron motion by defining allowed and forbidden electronic
energy bands.

3. 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 .

4. 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.

5. 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.

6. 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

7. 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).

8. References
http://en.wikipedia.org/wiki/Photonic_crystal
http://web.mit.edu/cbegroup/www/index.html
www.cmu.edu/physics/research/nano-physics/index.html
http://ieeexplore.ieee.org
http://apl.aip.org/resource/1/applab/v93/i22/p221102_s1
http://www.opticsinfobase.org/view_article.cfm?gotour
http://ab-initio.mit.edu/book/
http://www.stanford.edu/group/nqp/jv_files/papers/hatice-
laser.pdf

9. !