INNOVATIVE OPTICAL PARAMETRIC SOURCES USING ISOTROPIC

SEMICONDUCTORS

E. Rosencher, M. Baudrier, R. Haidar ,A. Godard, M. Lefebvre and Ph. Kupecek*

ONERA

* University PMC

• Why bother?

• Semiconductor (2) properties

• Quasi-phase matching

• Total internal reflection phase matching

• Random phase matching

• Self-difference frequency generation

• Conclusions

SUMMARY

• Why bother?

• Semiconductor (2) properties

• Quasi-phase matching

• Total internal reflection phase matching

• Random phase matching

• Self-difference frequency generation

• Conclusions

Tunability

Laser Diodes vs

OPO

10

4 5 6 7 8 91

2 3 4 5 6 7 8 910

Laser wavelength (µm)

AlGaN

AlGaAs

InGaAsP

InGaAsSb

InAsSb

PbSSe

PbSnTe

QCL

CRYOGENY

Single diodesingle Pulsed OPO

1.0

0.8

0.6

0.4

0.2

0.0

Tran

smis

sio

n

12108642

Longueur d'onde (µm)

Atmospheric transmission (dry weather, sea level, 5 km)

• Why bother?

• Semiconductor (2) properties

• Quasi-phase matching

• Total internal reflection phase matching

• Random phase matching

• Self-difference frequency generation

• Conclusions

SEMICONDUCTORS

• 0.45 µm < cutoff< 20 µm (0.05 eV < Egap < 3 eV)

cutoffE

E

nd

NLOgap

gapP

3

4

3

2

Second Fermi Golden Rule

Harmonic oscillator

• High nonlinear performance (quantum theory of solids) :

• Large transparency region

• Mature technology III-V LiNbO3

4 6 8 10 12 14 16 18 20 2210

20

30

40

50

60

70

(µm)

ZnSe

GaAs

Transmission including Fresnel losses (%)

• Isotropic materials NO possible phase matching scenario

• Low cost

0,1 1 100,01

0,1

1

10

100

1000

10000

100000

AgGaSe2

ZnSe

GaSe

ZnGeP2

GaAs

InAs

InSb

PPNL

NLBBO

LBOFig

ure

de m

érite

d2 /n

3 (pm

/V)2

Longueur d'onde de coupure (µm)

Propriétés optiques non linéaires des matériaux

First order quasi-phase matching

IDFG

k.L

+d +d-d -d

Cohérence

k1

k2

k3

c2

NbLiO3

5000 V

10 kg/cm2

Ferroelectric pollingM. Fejer et al (Standord) Molecular bonding (GaAs, ZnSe)

TRT, ONERA, Stanford

GaAsZnSe…..

Quasi-phase matching techniques

Fresnel birefrigenceR. Haidar et al (ONERA)

Localized growthE. Lallier et al; M. Fejer et al

Ge

Periodical materials breakthrough

2

3

4

5

678

0.1

2

3

Ave

rag

e p

ow

er (

W)

5.04.54.03.53.0

Idler wavelength (µm)

cw

pulsed 20 ns

PPLN

0.01

0.1

1

10

aver

age

po

wer

(W

)

5 6 7 8 91

2 3 4 5 6 7 8 910

2 3 4 5

deff (pm/V)

PPLN

BBO

KTP

POGaAs

2 cm

40 µm f = 10 kHz

20 ns

98% 98%

Precise coherence length (C) determinationexperimental set-up

HgCdTedetector

Filters

Wedge

1.06 µm

1

LiNbO3 OPO

wavelengthcontrol

3 & 2

motorizedtranslation

• Pulse Energy : 1mJ , 15ns

• = 2 cm-1

ZnSe

GaAs

I1 – Fx cos (k.L)

thickness

(a few deg.)

Advantage of large gap semiconductors in the IR:Large coherence length

8 9 10 11 12 13

30

32

34

36

38

40

74

76

78

Line : TheoryScatter : Experiment

ZnSe

GaAs

C (

µm

)

MIR

(µm)

R. Haïdar, A. Mustelier, Ph. Kupecek, E. Rosencher,R. Triboulet, Ph. Lemasson and G. Mennerat, JAP 2002

Adashi

Li

• Why bother?

• Semiconductor (2) properties

• Quasi-phase matching

• Total internal reflection phase matching

• Random phase matching

• Self-difference frequency generation

• Conclusions

Quasi Phase Matching by Total Internal Reflexion *

(Fresnel Birefringence)

*Armstrong et al., Phys. Rev. 127, 1918-1939 (1962)

tLL

F

dup ddown

•

totk.LF

if dup . ddown > 0

if dup . ddown < 0

F = - -

Angle tuning

totFresnel phase matching

z

I

Optimum thickness

L(2n+1) c Dispersion phase matching

z

I

L

2

2/sin2/sin2

2/2/sin2

tot

tot

NN

LkLk

dfg LNI

Fresnel QPMFresnel QPM

Haïdar et al., APL

.L + 2Fk Fresnel QPMFresnel QPM

N

non resonant QPM

.Lk

3.L

2k

1.L

3k

.Lk

.Lk

0 2

k.L

resonant QPM

Resonant Fresnel angle allowing (1.9 µm, 2.3 µm) 8 µm

Optimum angle for Fresnel birefringence phase matching

20 30 40 50 60 70 80 90 100

-4

-3

-2

-1

0

1

ZnSe

= 28°

F = -

= 45°

F = 0

spp

pss

Limit Angle

F (

rad

ian

s)

Angle (deg)10 20 30 40 50 60 70 80 90 100

-5

-4

-3

-2

-1

0

1

2

= 20°

F = -

= 45°

F = 0

Angle (deg)

F (

rad

ian

s)

GaAs

spp

pss

Limit Angle

Haïdar et al., JOSA B

Fresnel phase matching Configuration :experimental set-up

HgCdTedetector

Filters

1.06 µmLiNbO3 OPO

wavelengthcontrol

3 & 2

• Pulse Energy : 1mJ , 15ns

• = 2 cm-1

1

ZnSe plate

25,5 26,0 26,5 27,0 27,5 28,0 28,5 29,0

0,0

0,2

0,4

0,6

0,8

1,0

DF

G e

ffici

ency

(a.

u.)

Internal Angle (°)

Theory Experiment

R. Haïdar, A. Mustelier, Ph. Kupecek, E. Rosencher,R. Triboulet, Ph. Lemasson, APL 2002

10 mm

10 mm

ZnSe

20 25 30 35 40

0

100

200

300

400

B

A

IR E

nerg

y (p

J)

Internal Angle (°)

Theory Experiment

9 10 11 12 1318

24

30

36

42

An

gle

(°

)

DFG wavelength (µm)

Photonic yield :

MIR Source :.1 µJ between 9 µm and 13 µm

Pump 3 : 150 µJ

2µm2n

µm10n10

phot

phot

9

10

11

12

25 30 35 40 45

t = 832 µmt = 885 µm

ppppspspp

pss

Mid

-IR

Wav

elen

gth

(µm

)

Internal Angle (°)

Fresnel quasi-phase matching: GaAs

0 20 40 60 80

R = 98%

R = 100% Noptimal

Intensity I3

out

Number of bounces N0 20 40 60 80 100 120 140

0

20

40

60

80

100

R = 99.5%

R = 99%

R = 98%

R = 100%

R = 97%

Effi

cien

t b

oun

ces N

eff

Geometrical Bounces N

Limitations of Fresnel QPM: influence of wafer roughness

)(nm)(

(%)R

ZnSe GaAs

11 4

27 45 25 45

98 98.6 99.4 99.6

R1g c

1µm40104

cm1g3

shift x

Nmax 200

Limitation to Fresnel QPM: Goos-Hänchen shift

Equivalent to walk off

• Why bother?

• Semiconductor (2) properties

• Quasi-phase matching

• Total internal reflection phase matching

• Random phase matching

• Self-difference frequency generation

• Conclusions

Few lines of trivial theory

mk

1em23

N1

m

1jjXki

mXkiedEEE *

322Xk222N

1 IINcXdI sin

Very predictive:- conversion yield proportional to sample length- independant on polarisation- resonant for - N/Neff easily measurable and compared with materials

cX

Non depletion approximation

3 processes independant

coh1eff IN

2Xk2

d

deff cNN

2

2 sinwith

nX 1nX

nd

RANDOM PHASE MATCHING

0 20 40 60 80 100 1200.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

norm

alis

ed e

ffic

iency

G 0

grain diameter (µm)

experiment theory

Résonance pour taille de grain = longueur de cohérence

110 axis

NE

NEpolycristalline

Non linear diffusion inpowder liquid and gas

Phase mismatch

cE

(a)

(b)

Quasi-phase matching(c)

(d)

-100 0 100 200 300 400 500 600 700 800

-2

0

2

4

6

8

10

12

14

16

18

20

0 3 6 9 12 15 18 2100 -- --Thickness (mm)

Eff

ective

nu

mb

er

of

gra

ins N

eff

Number of grains

Polycrystalline ZnSe ZnSe Single crystal

0.0 0.5 1.0

0.0

0.2

0.4

0.6

0.8

1.0

No

rma

lise

d I

nte

nsity

Thickness (mm)

Baudrier, Haidar, Kupecek, Rosencher (Nature, 2004.)

• Why bother?

• Semiconductor (2) properties

• Quasi-phase matching

• Total internal reflection phase matching

• Random phase matching

• Self-difference frequency generation

• Conclusions

Cr2+-doped ZnSe

0.510 µm

VB

CB

High optical cross-sectionHigh solubilityLarge bandwith

Good ONL materials

Good lasing materialsSelf OPO

S

T2.1 2.3 µm

Cr2+

1.9 µmPompe: 1.9 µmLaser: 2.3 µmDFG-OPO: 10 µm

ZnSe:Cr X

WiFi collapse !

Self-DFG Cr:ZnSe laser—set-up

50% single-pass absorption of the 1.9-µm pump energy

45° internal phase-matching angle (spp), 13 internal reflections

Simple design: easy alignments, but high losses

1.9 µm pump

2.4 µm laser

9 µm DFG

Cr:ZnSesingle-crystal (uncoated)

OPO

Nd:YAG1.06 µm10 ns30 Hz

Tmax @ 1.9 µmR = 95% @ 2.4 µm

Rmax @ 1.9 µmR = 95% @ 2.4 µmTmax @ 9 µm

Laser (2.4 µm)5% yield (/absorbed energy)

Small coupler transmission to maximize the 2.4-µm intracavity electric field

Self-DFG Cr:ZnSe laser – first results

First demonstration of self-DFG in Cr:ZnSe laser

9-µm DFG preliminary resultsNote: thresholdless emission !

0.4 0.6 0.8 1.0 1.2 1.4 1.6

0

5

10

15

20

0.31 0.46 0.61 0.76 0.92 1.07 1.22

Laser energy (2.4µm) Linear fit

Absorbed pump energy (mJ)

Lase

r en

ergy

(µ

J)

Incident pump energy (mJ)

Small temporal overlap of pump and laser pulses Limited DFG efficiency

45 50 55 60 65 70

0.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity (

arb

. u

nit)

Time (ns)

Pump Laser

Solution: longer pulse pump source

Emitted DFG spectrumBroad line (no intracavity spectral filter)

Fixed central wavelength

9.0 9.5 10.0 10.5

0.0

0.2

0.4

0.6

0.8

1.0

DF

G I

nte

nsity (

arb

. u

nit)

Wavelength (µm)

Possible tuning schemes: pump or laser tuning + crystal rotation

Self-DFG Cr:ZnSe laser – discussions

• Why bother?

• Semiconductor (2) properties

• Quasi-phase matching

• Total internal reflection phase matching

• Random phase matching

• Self-difference frequency generation

• Conclusions

Conclusions

• Isotropic semiconductors are becoming viable solutions fornon linear optical sources in the mid-infrared

• Fresnel phase matching allows very large tunability from the mid-IR to the terahertz

•Cr2+ doped ZnSe allows thresholdless self DFG generation

which greatly simplify source architectures: first realisation presented!

•Surface roughness principal limitations to Fresnel QPM

Next step: electrical pumping of OPO !

•Random phase matching works in poly ZnSe and allows very large samples