Supervised By: Presented By:

Prof. D.S. Mehta Ajay Singh IIT Delhi 2014JOP2558

Design and Development of

Solar pumped Nd:YAG Laser System

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Wavelength (nm)

Solar spectrumTransmission and Laser emission 1064nm

946nm937nmLaser rod

Mirror

Alignment Screw

Output coupler

Alignment Screw

Laser rod

Alignment screw Mirror

Holding Screw

MirrorOutput coupler

Base plate to

adjust cavity length

https://en.wikipedia.org/wiki/Laser_construction

Laser Rod(Active Media) Pumping source (flashtubes/

continuous gas discharge lamps/Diode lasers

Laser Cavity & output coupler Power Supply

Typical Nd:YAG Laser 1

Laser Rod(Active Media) Pumping source (flashtubes/

continuous gas discharge lamps/Diode lasers

Laser Cavity & output coupler Power Supply

The Sunlight as pumping source

3.5 to 7.0 kWh/m2 per day Broad spectrum Not hazardous like mercury No power supply No dependence on electricity Available everywhere

Source:http://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg)

Typical Nd:YAG Laser

https://en.wikipedia.org/wiki/Laser_construction

1

Basic Requirements:

Collection of solar light

Transportation of the light

Laser cavity design

Laser pumping by the light

Oscillation/Amplification

Optimization !!

Design of Solar pumped Nd:YAG Laser

Motivation:

Focal len

gth

Solar concentrator (Fresnel Lens)

Conversion of naturally available light into laser light

Alternate pumping source for lasers Ecofriendly system System with “No power supply” Low cost, field portable system Green Photonics

2

• Literature

survey

• Theoretic

al

limitations

• Proposed

several

designs

• Final

Design

• Compone

nts

Procurem

ent

• Physical

Design

• Mount

solar

concentrat

or

• Solar

laser

pumping

• Optimizati

on

• Character

ization

• Alignment

• Cavity

length

modificati

on

Plan Literature

Survey

Build Test

Evalua

te

• Laser

Pumping

• Emission

!!!

• Issues

• Horizontal

Cavity

• Variable

Cavity

length

• Measure

ment of

various

spectrum

• What has

been

achieved

• What we

can do

• Light

collection

• Cavity

• Cooling

• Lightguide

• Building

block

• Concentr

ator

• Lightguid

e

• Cooling

• Vertical

Cavity

• Problems

• Redesign

of

selected

compone

nts

• Redesign

light guide

• Modificati

on in

cooling

system

• Planned

Another

design

• Procurem

ent of

compone

nts

• Adjustabl

e mirror /

output

coupler

• Theoretic

al

Calculatio

ns

• Output

Measure

ment

• Correlatio

n with

theory

• LASER

Problem

Resolution Test

New

Design

Experi

mentati

on

The approach/Process flow 3

Lens

(Concentrator)

Light Guide

Water Outlet

Laser rod

Output

Coupler

Electric Motor

80mm 50mm

The Basic design (Vertical Cavity)

Fig. Basic design of the Solar Laser (Drawing work using

Edraw Max)

4

Fig. Basic design of the Solar Laser (Drawing work using

Edraw Max)

Collection of solar light Fresnel Lens concentrator Focal length : 61cm Diameter: 46 cm Focal spot: 7mm (measured)

Fig. The designed solar

concentrator (System

designed at MDIT Lab,

IIT Delhi)

The Basic design (Vertical Cavity) 4

Lens

(Concentrator)

Light Guide

Water Outlet

Laser rod

Output

Coupler

Electric Motor

80mm 50mm

Fig. Basic design of the Solar Laser (Drawing work using

Edraw Max)

Collection of solar light Fresnel Lens concentrator Focal length : 61cm Diameter: 46 cm Focal spot: 7mm (measured)

Fig. The designed solar

concentrator (System

designed at MDIT Lab,

IIT Delhi)

Glass (BK7) Total internal reflection Reflection: Silver coating

Light Guide Fig. The designed

lightguide (System

designed at Glass

blowing Lab, IIT Delhi)

The Basic design (Vertical Cavity) 4

Lens

(Concentrator)

Light Guide

Water Outlet

Laser rod

Output

Coupler

Electric Motor

80mm 50mm

Laser rod: The Active medium

1%Nd:YAG (Nd:Y3Al5O12 ) Diameter: 5mm Length: 50mm, 120mm AR Coating: (R < 0.2% @ 1064 nm) HR coating : (R >99% @ 1064nm) Orientation: <111> +/- 5% Surface Flatness: <λ/10@1064 nm Damage Threshold: 500MW/cm2

Water cooling Attached to Light guide Laser rod submerged into water

Cooling System Light from concentrator

Laser rod

Water

Nd3+:YAG is a four-level gain medium: substantial

gain even for moderate excitation [15]

The gain bandwidth is relatively small, but this

allows for a high gain efficiency and thus low

threshold pump power [15]

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tro

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ter

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un

t (a

.u.)

Wavelength (nm)

Fig. Typical energy

band diagram of

Nd:YAG [15]

Fig. The solar spectrum (Measured spectrometer RI300511,

on March 20 (12:30 PM)

5

Link

The Mechanical housing design

Fig. The designed

mechanical housing

Including the cooling

system

Fig. 10 Ray diagram for the case when lightguide is

placed in-focus (top), on-focus (middle) and out of focus

Fig: Showing optimization work for positioning the light guide (simulation carried out using Zemax)

6

The Mechanical housing design

Fig. The designed

mechanical housing

Including the cooling

system

Fig. 10 Ray diagram for the case when lightguide is

placed in-focus (top), on-focus (middle) and out of focus

Software work

Fig. Qualitative

analysis of optical

Loss mechanisms in

the Light guide.

(Zemax)

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Fresnel Reflection

Figure. Ray diagram for the case when lightguide is placed (a) 15mm in-focus (b) on-focus (c) 15mm out of focus to the solar concentrator and (d) close view of (c)

(simulation carried out using Zemax): Positive X coordinate in the direction of the length of the lightguide……. (PC-Ravi Chaudhary)

Focus: X=15mm Focus: X=0

Focus: X= -15mm Focus: X= -15mm

7 (a) (b)

(c) (d)

Characterization

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2.8

3.3

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Wavelength(nm)

Absorption Spectra of the Nd:YAG Laser rod

4G5/2

4F7/2

Ab

so

rba

nc

e (

a.u

.) 4F5/2

4F3/2

4G9/2

4G7/2

4F9/2

Diode Laser

808 nm, 3.32W

Specimen/Laser rod

Focusing Lens

Collimating Lens

Jack

Sample holder

InGaAs

Detector

Micrometer

Acton

Spectrometer

Slit Opening

Screen

Output Coupler

Mirror

Transmission Characteristics of the Mirror and output coupler

Fig. Showing experimental set up and, laser rod, mirror and output characteristics (Dr. G.V. Prakash, Nanophotonics Lab, IIT Delhi)

Nanophotonics

Lab, IIT Delhi

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470

550

900 950 1000 1050 1100 1150 1200

Axis

Title

Axis Title

Emission Spectra the laser rod while pumped with 808nm DPSS

Inte

nsit

y (

a.u

.)

4I9/2

4I11/2

4I13/2

Diode laser

Wavelength (nm)

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mis

sio

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Wavelength (nm)

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Link(All)

Solar spectrum

Problem Areas

Fig. Showing

alignment issues in

the Vertical cavity

design

Fig. The initially

designed lightguide (left)

and representation of

guiding issue in the

conical section (R)

Fig. Silver coated light

guide designed to

overcome the guiding

losses in the conical

section (Glass blowing

Lab,IIT Delhi)

Solution

9

Link

Problem Areas

Fig. Showing

alignment issues in

the Vertical cavity

design

Fig. The initially

designed lightguide (left)

and representation of

guiding issue in the

conical section (R)

Fig. Silver coated light

guide designed to

overcome the guiding

losses in the conical

section (Glass blowing

Lab,IIT Delhi)

Solution

• Mirror holder

• Alignment

• Stability

9

Secondary design

Fig. Block diagram of the

designed horizontal cavity

solar laser system

Laser

Beam

10

Secondary design

Fig. Block diagram of the

designed horizontal cavity

solar laser system

Laser rod

Mirror

Alignment Screw

Output coupler

Alignment Screw

Laser rod

Alignment screw Mirror

Holding Screw

MirrorOutput coupler

Base plate to

adjust cavity length

Fig. The designed horizontal solar laser cavity system

Laser

Beam

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ec

tro

me

ter

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un

t (a

.u.)

Wavelength (nm)

Fig. The Solar spectrum Measured by RI spectrometer on 20 March,

2016, (11 am)

Experimental Results 11

Experimental Results

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ectr

om

ete

r C

ou

nts

(a.u

.)

Wavelength(nm)

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Sp

ec

tro

me

ter

Co

un

t (a

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Wavelength (nm)

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30000

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60000

800 850 900 950 1000 1050 1100

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ec

tro

me

ter

Co

un

t (a

.u.)

Wavelength (nm)

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32000

1020 1040 1060 1080 1100

Sp

ec

tro

me

ter

Co

un

t (a

.u.)

Wavelength (nm)

Fig. Output spectrum of designed Solar Laser system (808nm

diode laser pumped) using 900 nm high pass filter, measured

Maya Spectrometer

Fig. The close view of spectra shown abovee in the

range 1000-1100 nm The close view of spectra shown above, in the range 900-

1100 nm

Fig. The spectrum outside (transmission as well as PL) the Laser Cavity_ Measured

by Avantes spectrometer on 30-April-2016, (11 am) Fig. The Solar spectrum Measured by Avantes spectrometer on

30-April-2016, (11 am)

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925 940 955 970 985 1000 1015 1030 1045 1060 1075 1090

Sp

ec

tro

me

ter

Co

un

t (a

.u.)

Wavelength (nm)

4F3/2 4I11/2

4F3/2 4I9/2

Fig. Detailed analysis of various spectrums recorded. Comparison of output spectrum of the designed laser system (Inset) while pumping by solar energy (black) and

808 nm Diode laser

Experimental Results Cont….. 12

Fig. Detailed analysis of various spectrums recorded. Comparison of output spectrum of the designed laser system (Inset) while pumping by solar energy (black) and

808 nm Diode laser

Experimental Results Cont…..

𝑓 =𝜋 𝑅1𝑅2

1/4

1 − 𝑅1𝑅2 1/2

S.No. λ (nm) FSR, Δλ (nm) (Theoretical)

FWHM, δλ (nm) (Theoretical)

FWHM, δλ (nm) (Experimental)

1 946 1.7561 1.1634 1.35

2 1064 2.2215 1.4717 1.67

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Wavelength (nm)

Solar spectrum Transmission and Laser emission

1064nm 946nm

937nm

Experimental Results Cont…..

Fig. The Solar spectrum and The spectrum outside (transmission as well as PL, with baseline correction) the Laser Cavity_

Measured by Avantes spectrometer on 30-April-2016, (11 am)

13

FSR= C/2d

and Finesse

𝑓 =𝛥𝜆

𝛿𝜆

Source: Wiki [19]

Merits and Future scopes of the prototype…….

Optical Optical domain: Efficiency

Temporally constant, broadband, sunlight laser light: Collimated, narrowband, rapidly pulsed, radiation with high brightness and intensity

Nonlinear processes, such as harmonic generation: To obtain broad wavelength coverage, including the ultraviolet wavelengths, where the solar flux is very weak

The direct excitation of large lasers by sunlight: Drastic reduction in the cost of coherent optical radiation for high average power applications

Renewable extreme-temperature material processing

Ocean, earth, and atmospheric sensing from space

Detecting, illuminating, and tracking hard targets in space

Deep space communications

And many more things one can do with a laser !!!!!

14

[1]. J. Almeida, D. Liang, E. Guillot, and Y. Abdel-Hadi, “A 40 W cw Nd:YAG solar laser pumped through a heliostat: a parabolic mirror system,” Laser Phys. 23,

065801 (2013)

[2]. Joana Almeidaa, Dawei Lianga and Emmanuel Guillotb, Improvement in solar-pumped Nd:YAG laser beam brightness, Optics and Laser technology ,Volume

44,Issue 7,October2012

[3]. D. Liang and J. Almeida, Highly efficient solar-pumped Nd:YAG laser, Opt. Express 19 (2011) 26399-26405

[4]. L. Jing, H. Liu, Y. Wang, W. Xu, H. Zhang, and Z. Lu, “Design and optimization of Fresnel lens for high concentration photovoltaic system,” Int. J. Photoenergy

14, 539891 (2014)

[5]. T. Yabe, B. Bagheri, T. Ohkubo, S. Uchida, K. Yoshida, T. Funatsu, T. Oishi, K. Daito, M. Ishioka, N. Yasunaga, Y. Sato, C. Baasandash, Y. Okamoto, and K.

Yanagitani, “100 W-class solar pumped laser for sustainable magnesium-hydrogen energy cycle,” J. Appl. Phys. 104(8), 083104 (2008).

[6]. C. G. Young, “A sun-pumped cw one-watt laser,” Appl. Opt. 5(6), 993–997 (1966).

[7]. D. Graham-Rowe, “Solar-powered lasers,” Nat. Photonics 4(2), 64–65 (2010).

[8]. H. Arashi, Y. Oka, N. Sasahara, A. Kaimai, and M. Ishigame, “A solar-pumped cw 18 W Nd:YAG laser,” Jpn. J. Appl. Phys. 23(Part 1, No. 8), 1051–1053 (1984).

[9]. M. Lando, J. Kagan, B. Linyekin, and V. Dobrusin, “A solar-pumped Nd:YAG laser in the high collection efficiency regime,” Opt. Commun. 222(1-6), 371–381

(2003).

[10]. T. Yabe, T. Ohkubo, S. Uchida, K. Yoshida, M. Nakatsuka, T. Funatsu, A. Mabuti, A. Oyama, K. Nakagawa, T. Oishi, K. Daito, B. Behgol, Y. Nakayama, M. Yoshida,

S. Motokoshi, Y. Sato, and C. Baasandash, “Highefficiency and economical solar-energy-pumped laser with Fresnel lens and chromium co-doped laser medium,”

Appl. Phys. Lett. 90(26), 2611201 (2007).

[11]. T. Ohkubo, T. Yabe, K. Yoshida, S. Uchida, T. Funatsu, B. Bagheri, T. Oishi, K. Daito, M. Ishioka, Y. Nakayama, N. Yasunaga, K. Kido, Y. Sato, C. Baasandash, K.

Kato, T. Yanagitani, and Y. Okamoto, “Solarpumped 80 W laser irradiated by a Fresnel lens,” Opt. Lett. 34(2), 175–177 (2009).

[12]. Nature Photonics 4, 64 - 65 (2010) doi:10.1038/nphoton.2009.272

[13]. O. Graydon, “Solar power: a sunny solution,” Nat. Photonics 1(9), 495–496 (2007).

[14]. P.J.Harris, carbon nanotubes and related structures, Department of chemistry, Cambridge University press.

[15]. MC. Rao, “Applications of Nd: YAG Lasers in material processing: Fundamental approach” IJAPBC-2(3), (2013)

[16]. http://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg)

[17]. https://en.wikipedia.org/wiki/Laser_construction

[18]. https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3482

[19]. https://en.wikipedia.org/wiki/Fabry%E2%80%93P%C3%A9rot_interferometer

References: 15

Time for

Time for

!

Property Value

chemical formula Nd3+:Y3Al5O12

crystal structure cubic

mass density 4.56 g/cm3

Moh hardness 8–8.5

Wavelength (μm) Index n (25 °C)

1.0 1.8197

1.2 1.8152

1.4 1.8121

1.5 1.8121

Laser rod: Nd:YAG Comments: FSR, FWHM in terms of frequency

Confocal cavity: Only even (TEM) modes

Plane mirrors: All modes with same frequencies

Combination: all different modes

Paraffin sheet ho hold laser rod

Spectroscopic notation:

Longitudinal modes number for 1064 nm = 2x258.04 mm/ 1064 nm (for 1064 nm) = 485037 The free spectral range (FSR) of a cavity = C/2d (where d is optical length of the cavity) = 580898300 Hz =~ 580 MHz

Critical angle condition: Half angle= Sin-1(n1

2-n22)1/2= 63.44o for Glass

= 57.83o for Water

Fig: Representation of guiding losses in the conical section of the lightguide, while light is coupled from fiber Back

-0.7

-0.2

0.3

0.8

1.3

1.8

2.3

2.8

3.3

210 310 410 510 610 710 810 910 1010

Wavelength(nm)

Absorption Spectra of the Nd:YAG Laser rod

4G5/2

4F7/2

Ab

so

rba

nc

e (

a.u

.) 4F5/2

4F3/2

4G9/2

4G7/2

4F9/2

Back

0

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0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

583 614 644 675 705 736 767 795 826 856 887 917 948 979 1009 10401070 1101

No

rma

lize

d in

ten

sit

y

Wavelength (nm)

Solar spectrumTransmission and Laser emission

1064nm

946nm937nm

Back

300 400 500 600 700 800 900 1000 1100 1200 1300 14000

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200

250

300

350

400

450

Wavelength (nm)

Inte

nsit

y (

a.u

.)Solar Spectrum

Absorption of Nd:YAG

Emission of Nd:YAG

Back

Source:http://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg)

Characterization