2. About My Internship
Institute – Indian Institute of Technology, Delhi
Department – Department of Physics (Applied and
Fiber Optics)
Topic – Photonic Crystals
Aim – To study characteristics of 1D photonic
crystal sensor with two defects using
simulation by Crystal Wave
Guide – Prof. Joby Joseph
Book used – “Photonic Crystal – Molding the Flow
of Light” by John D. Johnnopolous
Software used – Crystal Wave by Photon Design
3. What are Photonic Crystals?
Photonic crystals are periodic optical nanostructures that
affect the motion of photons in much the same way that
ionic lattices affect electrons in solids.
The atoms and molecules are replaced by macroscopic
media with differing dielectric constants
The periodic potential is replaced by periodic dielectric
function (or a periodic index of refraction)
The crystal has a complete photonic band gap if for some
frequency range, the photonic crystal prohibits the
propagation of EM waves of any polarization travelling in
any direction from any source.
4. Types of PhC
A 1-D photonic crystal is periodic in one direction
A 2-D photonic crystal is periodic in two directions
A 3-D photonic crystal is periodic in three directions
Different colors show different dielectrics
6. This is the Master Equation
Differentiating eq. (3) and substituting in eq. (2)
Take curl of eq. (4) and substitute
7. 1-D Photonic Crystal Sensor
The unique characteristics of an EM wave when interacting
with photonic crystals can be applied to build an optical
sensor that interacts with certain material
A sensor will work if there is a strong interaction between
sensor and sample material
A sensor based on PhC will have higher sensitivity
We simulate an optical sensor model of 1-D PhC imbedded
with two defects.
8. Model of the Structure
The model consists of a Si slab with R.I. = 3.48
Eleven dielectric rods were inserted with rod no. 4 and 8 considered
to be defected
The slab thickness = 2x103 nm ; length = 17.5x103 nm
Regular rods were SiO2 (n=1.44, radius=400nm)
First defected rod was Al2O3 (n=1.7). R.I. of second defect was varied.
9. Simulation
The software used is Crystal Wave by Photon Design
Numerical simulation were performed by using finite difference time
domain (FDTD) method.
10. Characteristics
Change in time average energy density
w.r.t. variation in the R.I. of the second
defect for a defect radius of 300nm
(solid square) and 800nm (solid circle)
Change in time average energy density
w.r.t. second defect rod radius with R.I.
of 1.40
11. Results and Conclusion
Studied the characteristics of with two defects by means
of FDTD method
Increasing a second defect R.I. with a radius of 800nm will
produce linear dependence of the time averaged energy
density, which can be potentially applied for an optical
based R.I. sensor
A non-linear time averaged energy density for a certain
refactive index is obtained if the radius of the rod of the
second defect is increased from 300nm to 800nm
