1. PHOTONICS @ IIT-MADRAS
Current status + Future opportunities
Prof. Anil Prabhakar
Dept. of Electrical Engineering, IIT-Madras

2. Laboratories
Photonics in EE Experimental Optics
Fibre Laser Lab
Grating Fabrication
Integrated Optics
Systems Optical Networks
Hari, Mani
Networks
Anil, Balaji
Subsystems Deepa, Shanti
Instruments
Ananth, Anil
Component Technologies Balaji, Bijoy
Shanti
Activities span across basic laboratory research to commercialization

3. Funding
• Seed – Gururaj Deshpande
• 2.5 Gbps test bed, new lab, new group
• Multiplier Grants
• Telecom Centre of Excellence – Fibre Bragg Grating Facility
• IRDE, Dehradun – Fibre Laser Laboratory
• IRDE, Dehradun – Silicon Photonics
• DST – Nanophotonics Centre
• DIT – Fibre optic sensors
• DBT – Bio-photonics, Metrology
• Opportunities
• Telecom: 100 Gbps test bed, QKD, photonic integrated circuits
• Fibre Lasers for material processing
• Bioengineering and biomedical applications

4. Collaborations
• Indo-Australian, Indo-Swiss, Indo-German
• Optical MEMS, nano-photonics
• Indo-EU (Dublin, Southampton)
• All optical signal processing
• NCBS, Bangalore
• Biophotonics
• INO
• Passive optical network for the India-based Neutrino Observatory
• LIGO – India (MIT, Caltech, others)
• International collaboration to observe gravity waves

5. Silicon photonics
Design Simulation & Analysis Fabrication
Characterization Packaged devices to market
DWDM
channel
interleaver
1X8 power
splitter
Bijoy K. Das / Integrated Optics Lab

6. Directional Coupler on SOI
Asymmetric ridge waveguides
Bar Port
Input port
Cross Port
• Two S-bend waveguides
Bijoy K. Das / Integrated Optics Lab

7. Towards an integrated SoI platform
Ring Resonator Distributed Bragg Reflector
MZI
pin based
MZI
Bijoy K. Das / Integrated Optics Lab

8. Tunable MEMS diffraction grating
• Goal
• To fabricate a diffraction grating whose period can be tuned
during operation.
• Technique
• Surface micromachining
• Electrostatic actuation
Fabricated tunable grating
structure with 24 microns period
Grating structure (a) unactuated state
(b) actuated state 1 (c) actuated state 2
Shanti Bhattacharya / MOEMS

9. All optical wavelength conversion
Four wave mixing between the CW pump and the
pulsed probe result in the transfer of data from probe to
the conjugate.
Conjugate
Probe
Data
Deepa V. / Optical Comm
10 Gbps

10. Fiber Bragg Gratings
• Resonant structures that have wavelength selective reflection
• Make very good sensors 76
Temperature Map
Temperature [oC] 62
48
34
20
Exp. 63 5 63 Deg.
6 Est. 63 5 63 Deg.
0 2 4 6 8 10
Distance(Km)
• Fabricated using a phase mask and an excimer laser at 248 nm
Balajis Srinivasan / Fibre Bragg Grating Faciltiy

11. efficiency.
Figure 2. Block diagram of the high-power amplifier in the MOPA
Approach configuration.
Our aim is to generate a high power pulsed laser by
High power pulsed fiber lasers
amplifying the output from a semiconductor laser diode
using a Ytterbium (Yb)-doped double clad fiber. A double-
clad fiber has an additional cladding with lower refractive
index around the conventional cladding, thereby allowing
Exper imental Results
The above setup has been packaged in a rugged, portable
box as shown in Fig. 3. Peak power of up to 500 W has been
achieved for a 40 ns pulse at 25 kHz repetition rate at the
the inner cladding to act as a waveguide for the pump output of 1st stage of MOPA, with a launched pump power
• Compact, rugged multi-KW level pulsed fiber lasers
radiation. The process of amplification in a double-clad fiber of 4.5 W. Preliminary characterization of output powers
is represented in Fig. 1. The core of the fiber is doped obtained from the 2nd stage has indicated that output powers
• Seed followed by single or dual stage amplifiers
with ytterbium. The signal, which is to be amplified is in the order of a few kWs are possible with M 2 <1.5. Work
coupled into the core of the fiber. The pump is absorbed is underway to scale the output power using multiple pump
• Double clad or Large Mode Area (LMA) fibres
in the overlap region of core and inner cladding. The pump
absorption is almost uniform along the length.
lasers for the second stage amplifier.
Figure 1. Process of amplification in a double- clad fiber.
The maximum output power which can be obtained from
a single stage amplifier is limited by amplified spontaneous
emission and nonlinear processes such as stimulated Ra-
man scattering (SRS) and stimulated Brillouin scattering
(SBS).In order to achieve the kilowatt power levels, a dual
stage Master Oscillator Power Amplifier (MOPA) configu-
ration is used which is shown in Fig. 2. The configuration
consists of a stable master oscillator, which is capable of Figure 3. Experimental setup of dual stage MOPA.
generating laser pulses of 40ns with repetition rate of 25
kHz. The first stage of the MOPA setup consists of a single
mode double clad fiber. The limitations in power scaling Publication
due to the above nonlinearities may be overcome by using Y. Panbiharwala, C. S. Kumar, D. Venkitesh, B. Srinivasan,
Balajis S./ Fibre Laser Laboratory double clad fiber in the second
a large mode area (LMA) "Investigation of self pulsing in Ytterbium doped high power
stage. fiber amplifier," to be presented at Photonics 2012, Chennai.

12. Active Mode Locked Fibre Lasers
Regenerative mode locking
Pulse width of 68ps
Optical cavity
Balajis S./ Fibre Laser Laboratory

13. STED Microscopy
Pulsed STED causes less
thermal damage to the
sample
Must get 2 pulsed high
intensity lasers to
synchronize
Anil Prabhakar / Imaging and Flow Facility, NCBS

14. Dark field plasmon coupled fluorescence
Incident laser beam at
532nm
PMMA +
R6G
Gold
Glas
s
Objective
Anath K./ Experimental Optics Lab

15. Label free plasmonic sensor – Reflective
configuration
Reflectivity v/s Incident angle with variation in analyte index
1
0.9
0.8
Reflectivity
0.7 1.32
1.33
1.34
1.35
0.6
1.36
1.37
0.5
0.4
0 10 20 30 40 50 60 70 80 90
Incident angle
Anath K./ Experimental Optics Lab

16. Optical Coherence Tomography
• Experimental Technique (Fourier Domain)
• Low coherence Interferometry
Scotch tape
Cucumber slice (1.5 mm x 8 mm)
Human wrist pulse
Need it for retinal imaging
Healthcare Technology Innovation Centre
Shanti Bhattacharya / Experimental Optics Lab

17. 17
Microfluidic flow analyzer – HIV detection
S
B1 B2
1550 nm CW FR1
modulated fiber 5 deg offset Control Flow rate
laser + 3dB FR2
FBG@635nm
635 nm pulsed F1 F2 Fluorescence
laser Si-APD
400V bias
F3a
F3b
Side Scatter @ 1550nm, 1550 nm pulsed
InGaAs gated APD, 60V bias laser
Anil Prabhakar / Imaging and Flow Facility, CCAMP

18. Competitive Analysis
Detection Miniature flow
Method of HIV BC CyAn Guava BD
method
detection
Parameters analyzer ADP Easy-Cyte FACSCalibur
Price (INR) 1-2 lakhs 30-50 lakhs 30-50 lakhs 30-50 lakhs
Quantity of sample
100-500µl 1-5ml 1-5ml 1-5ml
required
Cost per sample
100 500 500 500
(INR)
Maintenance
Low High High High
cost
Expertise
Low High High High
requirement
Portability High Low Low Low
1 lakh ~ 1,400 Euro

19. Mega Science Projects
• Involving multiple universities
• International collaborations
• Taking on some grand challenges
• What is the role of Photonics?

20. The nearest major
India-based Neutrino Observatory city:
Madurai
 South I ndia,
ne the
ar
te IIT Madras
m city
ple
of Madurai
Madurai
8

21. Iron Calorimeter (ICAL) Modules
Each module has 10,000 detectors
Magnetized iron plates (a very large electromagnet)

22. Large Passive Optical Network
1 Mbps from each detector. 5 Mbps worst case
8 rows x 8 columns on each plane, in each module

23. Resistive Plate Chamber
64 channels from each RPC for x,y localization
Neutrinos ionize the inert gas, and generate an
avalanche pulse picked up by 2” strips

24. PON hardware – corner of each RPC
• Tx at 1310nm, -10 dBm, 1-5 Mbps
• Rx at -35dBm
• We can also look at 1x64 splitter
• Need monitoring, timing, (x,y) and trigger information

25. Gravitational-Wave Detectors
image credit: Luis Calcada

26. Advanced LIGO
x10 better amplitude sensitivity
x1000 rate=(reach)3
1 day of Advanced LIGO
» 1 year of Initial LIGO !
Slides on LIGO are courtesy the LIGO Scientific Collaboration
Source: R. Adhikari, Caltech
26

27. A Global Network
GEO Virgo
LIGO TAMA/LCGT
• Detection confidence
• Locate sources
• Decompose the
polarization of
gravitational waves
INDIGO? 1 2
27

28. Geographical relocation: science gains
Source localization error
Original plan
2 +1 LIGO USA+ Virgo
LIGO-India plan LIGO-Aus plan
1+1 LIGO USA+ Virgo+ LIGO India 1+1 LIGO USA+ Virgo+ LIGO Aus

29. Advanced LIGO detectors
LASER
AEI, Hannover
Germany
Suspension
GEO, UK

30. Advanced LIGO Laser
• Design: Albert Einstein Institute, Germany
• Higher power (reduce photon shot noise)
– 10W  180W
• 10x improvement in intensity and frequency stability
Courtesy: Stan Whitcomb 30

31. 31
Quadruple Suspensions
• Quadruple pendulum:
• ~107 attenuation @10
Hz Magnet Actuator
• Controls applied to
Electrostatic
upper layers; noise
Actuator
filtered from test
masses  Fused silica fiber
 Welded to ‘ears’, hydroxy-
catalysis bonded to optic
• Seismic isolation and
suspension together:
• 10-19 m/rtHz at 10 Hz

32. Advanced LIGO Mirrors
• Larger size
– 11 kg -> 40 kg
• Smaller figure error
– 0.7 nm -> 0.35 nm
• Lower absorption
– 2 ppm -> 0.5 ppm
• Lower coating thermal noise
• All substrates delivered
• Polishing underway
• Reflective Coating process starting up
Courtesy: Stan Whitcomb 32

33. 33
LIGO Scientific Collaboration
~40 institutions, ~550 scientists
Caltech LIGO Laboratory MIT
LIGO Hanford Observatory LIGO Livingston Observatory
University of Adelaide ACIGA Loyola New Orleans
Australian National University ACIGA Louisiana State University
Balearic Islands University (Mallorca !) Louisiana Tech University
Caltech LIGO MIT LIGO
Caltech Experimental Gravitation CEGG Max Planck (Hannover) GEO
Caltech Theory CART Max Planck (Potsdam) GEO
University of Cardiff GEO University of Michigan
Carleton College Moscow State University
Cornell University NAOJ - TAMA
Embry-Riddle Aeronautical University Northwestern University
University of Florida-Gainesville University of Oregon
Glasgow University GEO Pennsylvania State University
NASA-Goddard Spaceflight Center Southeastern Louisiana University
Hobart – Williams University Southern University
India-IUCAA Stanford University
IAP Nizhny Novgorod Syracuse University
Iowa State University University of Texas-Brownsville
INDIGO, India Washington State University-Pullman
University of Western Australia ACIGA
University of Wisconsin-Milwaukee

34. Unilumen Photonics Pvt Ltd
• Incubated by IIT Madras
• Registered in 2012
• High power fibre lasers
• Optoelectronics design

35. Photonics @ IIT Madras
• 8 faculty in EE, 40 post-grad students
• Another 6 in Physics, Engineering Design, Applied
Mechanical
• Growing visibility in international community
• Larger role in developing Photonics in India
• Need to form collaborations and teams
• New opportunities in biophotonics, silicon
photonics, telecommunications, defense
• Organizers for Photonics 2012, in December.