Nano-structured Phoxonic Crystals for MWIR 

Sensing

Anurag Sharma, Dr. Jyoti Kedia, Dr. Neena Gupta

Photonics Research Lab

Punjab Engineering College (Deemed to be University) 

Chandigarh, India-160012
• The low power and multispectral onchip sensing devices are need of the

hour for having maximum utilization

of photonic integrated circuits.

• Detecting Thermal Infrared

radiations of objects at room

temperature and above (≥300 K)

have wavelength spectral peaks ≥

3μm.

MWIR Sensing
THE BIG PICTURE

PhoXonic 

Crystals

Solutions to 

control 

nonlinearities

MWIR Sensors Need to have a low-power and 

multispectral operation

Suspended 

waveguide 

structures, Brillouin 

Nanophotonics with 

Phoxonic crystals

(engineering 

electromagnetic + Elastic 

waves)

Advanced 2DMaterials :

very tedious to 

synthesize
Θsbs= 

Qm

keff

1

c

d neff

dx

2

Brillouin 

Power 

Gain

go

2 = vg2

ħωoΩm

4Lm

Θsbs

Qm

Single 

photon 

brillouin 

coupling 

gain

xzpf =

ħ

2meffLmΩm Zero point 

fluctuation

Quality factor

Stiffness per unit length

Effective refractive index

Group velocity of optical mode

Angular frequency of mechanical 

resonator

Length of the resonator

Effective mass per unit length

Fundamental mechanical 

frequency

Material thickness

Young’s Modulus

ρ Poisson's Ratio

Wm Width of the resonator

fm = 1.03

t

Wm

2

Ey

ρ

keff=meffΩm

2

Fundamental 

mechanical 

frequency
∇ × ∇ × E = μoε ∂t

2

E − μo ∂t

2

(δP)

∇ ∙ c: S − ρ∂t

2U = −F

Coupled mode equations 

For Optical Mode

For Mechanical Mode

ωs = ωp ± Ω

βs ωs = βp(ωp) ± βm(Ω)

ms ωs = mp(ωp) ± Mm(Ω)

(∂t+(iΔp + κpΤ2))ap=-igoasb + κep sp

(∂t+(iΔp + κpΤ2))as=-igo

∗b∗ap +

+ κes ss

(∂t+(iΔm + γΤ2))b=-igo

∗as

∗

ap

Starting Point
Photo-elastic and moving-boundary Gain contributions

This is an attempt to grasp the nature of photo-elastic 

component used in coupling equations:

gpe = gom

pe ∗ xzpf

xzpf =

ħ

2meffLmΩm

gmb = gom

mb ∗ xzpf
Atomistic Simulation Model For Phoxonic Structure

DESIGN 

ENVIRO

NMENT

Physics of optical 

pump mode (p)

Physics of optical 

scattered mode (s)

Physics of 

mechanical mode

Eigen Value 

Bandsolver 

1

Eigen Value 

Bandsolver 

2

Optical field (p)

Optical wavevector 

beta_p

Optical wavevector 

beta_s

Optical field (s)

Phase matching

beta_m = beta_p 

±beta_s

Eigen Value 

Bandsolver 

3

Mechanical field 

Mechanical 

frequency;

Solid. Omega

Post processing, visualization, gain 

calculation, overlap integrands, 

fields, strains etc.

Custom defined 

variables

Input parameters:

geometry, physical, materials, 

domain selection
The simulated back-reflection is lower than 

−10 dB from the wavelength of 2.26 μm to 

the wavelength of 2.4 μm.

Kang, J. et al. Focusing subwavelength grating coupler for mid-infrared 

suspended membrane germanium waveguides. Opt. Lett. 42, 2094 (2017).
Whispering gallery 

mode Flexural mode Dilational mode

Analysing the mechanical mode variation due to thermo-optic effect 
Current Work in Progress:

• The idea is to simulate Brillouin scattering using a 

single integrated platform

• To create a python based Machine learning model 

for this purpose, which could be integrated with 

available simulators.