Laser stimulated broadband emission of graphene

Laser stimulated broadbandemission of graphene

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Wiesław Stręk

Institute of Low Temperature and Structure ResearchPolish Academy of Sciences

Graphene foam emission

80 100 120 140 160 180 200

3

4

5

6

0.01 0.1 1 0.01 0.1 1 0.01 0.1 1 0.01 0.1 1

400 500 600 700 800 900

N

1/r2 [1/cm

2]

N = 3.02

a

Inte

nsity [a.u

.]

Power [W]

(a)N = 6.11N = 4.22

b

(b)

Inte

nsity [a.u

.]

Power [W]

N = 4.74

c

(d)(c)

Inte

nsity [a.u

.]

Power [W]

d

Inte

nsity [a.u

.]

Power [W]

0.01032 0.00838 0.00672 0.00532spot area [cm

2]

(f)

inte

nsity [

a.u

.]

wavelength [nm]

(e)

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Graphene foam emission

Photocurrent measurements

Temporal change in the sample resistivity

Single turn on/turn off resistance changes

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Graphene foam emission

Photocurrent measurements + hot electrons generationApplied electric field influence

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Graphene foam emission

Visible and NIR broadband emission

400 500 600 700 800 900

0

500

1000

1500

1000 1200 1400 1600 1800 2000 2200 24000

1000

2000

3000

4000

5000

6000

23000

24000

25000

inte

nsity (

arb

. u.)

wavelength (nm)

lexc = 975 nm

inte

nsity (

arb

. u.)

wavelength (nm)

rexc = 7000 W/cm2

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Coherence of LIWE on Graphene

Graphene bulb

without exc exc 975 nmInterference

exc 975 nm exc 808 nm

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Coherence of LIWE on Graphene

Measurement setupThe registered interference

Registered fringes with and without spectral filter

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Coherence of LIWE on Graphene

• a point-like white light source with a high degree of spatial coherence

• a possibility to obtain a collimated beam of white light with low divergency angle

Point-like source of white light based on graphene excited by a CW laser

Layout of a light source producing broadband collimated beam

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

LIWE mechanism

Inversion of population

Coherence

White laser???

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Broadband fiber light source

• point-like emission area matching the core size of a typicalmultimode fiber

Layout of a potential bradband fiber light source

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Broadband fiber light source

Insights

• emissivity depends on morphology, porous structure of graphene foam is an advantage

• emissivity higher than for an electric lamp with tungsten filament

• decay of light power over time

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Hydrogen generation

Other application of ionization of graphene surface by laser

The generation of hydrogen from alcoholes and water

Online Symposium „Functional Coatings, Manufacturing, Methodology & Application”, 9 March 2021

Thank you for attention !