Short Period PPLN and its

Potential Applications

P. Baldi, M. De Micheli, E. Quillier LPMC, Nice

L. Guilbert, J.-P. Salvestrini LMOPS, Metz

S. Tascu Iasi, Romania

V. Shur Ekaterinburg, Russia

Outline   Interest of PPLN: example of Optical Parametric

Interactions (OPI)   Phase Matching and Quasi-Phase Matching (QPM)   Materials for co-propagating OPI   PPLN and Integrated Optics

  Short Period PPLN   Counterpropagating OPI   Phase-Matching   Other Applications (Bragg gratings…)

  Towards Short Period on PPLN   Conclusion

PPLN (Periodically Poled Lithium

Niobate)

Co-propagating OPI: Phase Matching

  Generalities ωp = ωs + ωi

kp = ks + ki

Pump, ωp

Idler, ωi χ(2)

Signal, ωs

Co-propagating OPI: Phase Matching

  Colinear case ωp = ωs + ωi

np ωp = ns ωs + ni ωi

Pump, ωp

Idler, ωi χ(2)

Signal, ωs

Co-propagating OPI: Phase Matching

  Colinear case ωp = ωs + ωi

np ωp = ns ωs + ni ωi

Problem with dispersion!

Pump, ωp

Idler, ωi χ(2)

Signal, ωs

Co-propagating OPI: Phase Matching

  Colinear case ωp = ωs + ωi

np ωp = ns ωs + ni ωi

  Use of birefringence. It works, but   Limited choice of materials   Restricted range of available wavelengths   Non-optimum nonlinear coefficient   Possibly high operating temperature, walk-off…

Pump, ωp

Idler, ωi χ(2)

Signal, ωs

Co-propagating OPI: Phase Matching

  Colinear case ωp = ωs + ωi

np ωp = ns ωs + ni ωi

  Use of birefringence. It works, but   Limited choice of materials   Restricted range of available wavelengths   Non-optimum nonlinear coefficient   Possibly high operating temperature, walk-off…

  Quasi-Phase Matching

Pump, ωp

Idler, ωi χ(2)

Signal, ωs

Λ

Co-propagating OPI: Quasi-Phase Matching

  Colinear case ωp = ωs + ωi

kp = ks + ki+2mπ/Λ

Pump, ωp

Idler, ωi

Signal, ωs

χ(2)

Λ

Co-propagating OPI: Quasi-Phase Matching

  Colinear case ωp = ωs + ωi

kp = ks + ki+2mπ/Λ

 Advantages of QPM:   Free choice of wavelengths   Optimized efficiency   Phase Matching engineering

Pump, ωp

Idler, ωi

Signal, ωs

χ(2)

Materials for QPM co-propagating OPI

 Polymers (like DR1/PMMA)

χ(2)

Materials for QPM co-propagating OPI

 Polymers (like DR1/PMMA)  Semiconductors (GaAs, GaN)

χ(2)

(images from CRHEA)

Materials for QPM co-propagating OPI

 Polymers (like DR1/PMMA)  Semiconductors (GaAs, GaN)  Dielectrics (KTP, Lithium Tantalate…

χ(2)

(LT-From Oxyde) (KTP-From BrightCrystals)

Materials for QPM co-propagating OPI

 Polymers (like DR1/PMMA)  Semiconductors (GaAs, GaN)  Dielectrics (KTP, Lithium Tantalate… … and Lithium Niobate)

χ(2)

Periodically Poled Lithium Niobate

  Transparency range from 0.4 to 4 µm   Large nonlinear coefficient (d33= 33pm/V)

  QPM by ferroelectric domain poling   Λ ~ 6 µm over 3’’ φ, 500 µm thick   Down to 3 µm on smaller and thinner sample

  Good quality waveguides on PPLN over L= 8cm

Λ=12.1µm Λ=12µm

Integrated Optics on PPLN ωp = ωs + ωi

βp = βs + βi + 2π/Λ

Pump, ωp

Idler, ωi χ(2) Λ

Signal, ωs

From LPMC, Nice

Soft Proton Exchange: -  ≤ 0.5 dB/cm losses -  PDC efficiency of 10-6 compared to 10-9 for bulk

Short Period PPLN

Counter-propagating OPI   Configuration

Pump, ωp

Idler, ωi χ(2) Signal, ωs

Counter-propagating OPI

  Configuration

  Particular interests relative to co-propagating OPI   Natural spatial separation of signal et idler beams   Narrow spectral PDC bandwidth   Mirrorless OPO   Single-channel amplification and conversion   All-optical signal processing

Pump, ωp

Idler, ωi χ(2) Signal, ωs

Counterpropagating quasi-phase matching   Phase matching

kp = - ks + ki with ks ~ ki : almost impossible !

Counterpropagating quasi-phase matching   Phase matching

kp = - ks + ki with ks ~ ki : almost impossible !

  Quasi-phase matching kp = - ks + ki + 2mπ/Λ : possible with Λ ~ mλp / np

Counterpropagating quasi-phase matching   Phase matching

kp = - ks + ki with ks ~ ki : almost impossible !

  Quasi-phase matching kp = - ks + ki + 2mπ/Λ : possible with Λ ~ mλp / np

But Λ ~ 300 to 350 nm ! (over L ≥ 1 cm)

=> Technological bottleneck (high resolution AND large field)

COPI: «old» idea, few realizations   Theoretical proposition

Harris, Appl. Phys. Lett. 1966   Phase matching

DFG: Chemla et al., Opt. Com. 1974 PDC: Chemla and Batifol, Appl. Phys. Lett. 1976 in Sodium Nitrite (high birefringence ~ 20%) far from degeneracy (455nm, 495nm and 5.63µm) low efficiency (10-12 for PDC)

COPI: «old» idea, few realizations   Theoretical proposition

Harris, Appl. Phys. Lett. 1966   Phase matching

DFG: Chemla et al., Opt. Com. 1974 PDC: Chemla and Batifol, Appl. Phys. Lett. 1976

  Quasi-phase matching OPO: Canalias et al., Nature Photonics 2007 first order PPKTP with Λ = 800 nm far from degeneracy (821nm, 1.14µm and 2.94µm) threshold: 1.6 GW cm-2

Bragg Gratings on SpPPLN

x y

On PPLN z – cut

x

z

On PPLN y – cut

Required periods in band C : order m 1 : 0,36 à 0,37 µm 3 : 1,08 à 1,11 µm 5 : 1,81 à 1,86 µm 7 : 2,51 à 2,58 µm

LMOPS, Metz

PPLN: advances on and directions to short periods   State-of-the-art of short periods PPLN

  Backswitching   Direct e-beam   Local e-field using AFM   Calligraphy… All unsufficient (quality, depth, area…)

PPLN: advances on and directions to short periods   State-of-the-art of short periods PPLN

PPLN: advances on and directions to short periods   State-of-the-art of short periods PPLN

LPMC: 2 µm period

PPLN: advances on and directions to short periods   State-of-the-art of short periods PPLN

Vladimir Shur, Ekaterinburg

PPLN: advances on and directions to short periods   State-of-the-art of short periods PPLN

  Towards SpPPLN at LPMC   Λ = 2 µm (7th order QPM) : classical photolithography   Λ = 900 nm (3rd order QPM) : direct optical writting   Λ = 300 nm (1st order QPM) : direct electronic writting

Conclusion on Short Period PPLN

  High scientific interest

  Many applications

  New experimental field of interest

  Importance of the material aspects

  Technological bottleneck

Conclusion on Short Period PPLN

… and many thanks to the CMDO+ for the

support and for the invitation !