Quasi-Phase-Matched Gallium Arsenide for Mid Infrared Frequency Conversion

Transcription

1 Quasi-Phase-Matched Gallium Arsenide for Mid Infrared Frequency Conversion E. Lallier, A. Grisard Research & Technology Thales Research & Technology, France B. Gerard Alcatel-Thales 3-5 Lab, France

2 2 Mid-IR sources requirements and OPOs Military Environment Medical Industrial Tunability, multi-spectral t l Mid-IR laser sources High energy /peak power CW to short pulses Narrow or broad linewidth Optical Parametric Oscillator (OPO) Pump Multi-wavelength capability NL Cristal χ (2) Wide tunability Suitable MIR nonlinear crystal?

3 3 MWIR quasi-phase-matched crystal Desirable properties for the NL crystal: High nonlinear coefficient Low absorption loss High laser damage threshold Low thermal lensing Non-critical phase matching Transmission (µm) Nonlinear Coefficient (pm/v) PPLN ZGP GaAs QPM vs BPM: High nonlinearities Non-critical interactions Engineering flexibility Thermal Conductivity (W/m.K) α (cm -1 ) (> 2 µm) ,025 0,02 PPLN-like crystal for the mid-ir?

4 Quasi-Phasematching (QPM) in GaAs Periods under 100 µm for near-infrared pump lasers OP-GaAs 60 µm OP-GaAs 50 µm d eff -d eff d eff -d eff d eff Λ = 2π / Δk wavelength (nm) OP-GaAs 40 µm OP-GaAs 30 µm Output The informatio PPLN 30 µm Pump wavelength (nm)

5 5 Quasi-Phasematching (QPM) in GaAs Following Armstrong et al. (1962) π + χ (2) - χ (2) + χ (2) (19 GaAs plates) [110] [-110] [110] ( p ) π π Boyd et al. (1966) Thompson et al. (1976) 0,5 mm (95 GaAs plates) - χ (2) - χ (2) - χ (2) + χ (2) + χ (2) + χ (2) + χ (2) 8 mm kg 9 mm 7 mm GaAs substrate Gordon et al. (1993) Thales/ Stanford (1999)

6 Thales prior written approval. THALES Template trtp 6 Fabrication of Thick Orientation-Patterned GaAs 1) [001] + [001] 2) [001] 0.1 µm [001] 2 GaAs wafer 2 GaAs wafer + etch-stop layer µm GaAs layer regrowth Crystallographic inversion by wafer bonding process 5) - χ (2) 4) 3) - χ (2) [00-1] [001] Lc [00-1] - χ (2) + χ (2) - χ (2) - χ (2) + χ (2) - χ (2) >500 µm - χ (2) - χ (2) - χ (2) + χ (2) + χ (2) 0,1 µm HVPE regrowth Gratings defined by photolithographic process Mechanical & chemical etching

7 7 Growth techniques on QPM GaAs samples 100 µm 100 µm DB GaAs DB GaAs CSVT growth on 212 µm DB-GaAs sample HVPE growth on 212 µm DB-GaAs sample 500 µm 500 µm OP-GaAs template OP-GaAs template HVPE growth on 60 µm 2 OP-GaAs template (Thales) HVPE growth on 60 µm OP-GaAs sample (Stanford/Thales)

8 Hydride Vapour Phase Epitaxy (HVPE) Physics of GaAs growth : GaCl g + ¼ As 4g + ½ H 2g GaAs + HCl g Oven HCl + H 2 H 2 + HCl add AsH 3 Quartz HCl GaCl HCl Gallium source As 2 / As 4 H 2 GaAs substrate Growth Characteristics : Perfect growth selectivity (preserve initial orientations) GaAs growth with low impurity concentration (residual cm 3 ) High frequency desorption of As/GaCl precursors on surface Growth rate up to 35 µm/h 8

9 9 Influences of HVPE growth parameters Examples of HVPE growth anisotropy of GaAs crystal: III/V= 9, T=760 C T= 780 C, III/V = 3 GaAs band // [-110] III/V = 3 T= 760 C GaAs band // [110], III/V = 3,T= 760 C Due to χ (2) /-χ (2) orientations on OP-GaAs template: OP-GaAs template Apparition of a morphology conflict during HVPE regrowth

10 10 HVPE regrowth on OP-GaAs template (1) Gratings period ~30 µm HVPE film 380 µm 100 µm L C OP-GaAs 30 µm Gratings period ~ 60 µm HVPE film 380 µm 200 µm L C OP-GaAs 60 µm Gratings period ~ 212 µm HVPE film 380 µm L C OP-GaAs L C 212 µm

11 11 HVPE regrowth on the OP-GaAs (2) HVPE regrowth on an OP-GaAs template with intentional Si doping : Gratings period: 60 µm zoom OP-GaAs GA 30 µm [001] [00-1] [001] [00-1] [001] [00-1] [001] [00-1] [001] V(113) V(-112) Intentional GaAs doping OP-GaAs 30 µm L C No GaAs doping The informatio Growth parameters verify the condition: v(113) * sin 55 = v(-112) * sin 65

12 12 Full wafer growth 2 multigrating 500 µm thick OP-GaAs 500 µm Growth characteristics: Growth rates: v(113)= 33 µm/h v(-112)= 30 µm/h 4 growth interruptions P=63.8 µm 500 µm 0 16,6 mm 500 µm 33,3 mm Cross section of a 3 cm-long OP-GaAs sample (63 µm grating period)

13 13 Towards thicker samples Old growth conditions with shorts cycles: 0.5 mm thickness (prior art) 0.8 mm thickness (summer 2009) 1.3 mm thickness (summer 2010) New growth conditions with long cycles: Thickness is limited it by parasitic nucleation Thicker samples will require a new reactor 1.5 mm thickness (winter 2011)

14 Optical transmission 1,2 1 Air 0,8 Transmission (mw) 0,6 Probe 0,4 HVPE Substrate 1 2 λ =1.5 µm ω 0 =50 µm 0,2 0 1cm ,08 Déplacement vertical (µm) 0, ,06 0,05 0,04 0, α < 0.03 cm -1 pertes cm-1 The informatio 0,02 0, Lowest loss measured cm -1 at 2 µm (in resonant cavity)

15 15 Optical Parametric Oscillation First demonstration of GaAs OPO (2004): Stanford University & Thales (K.L Vodopyanov et al., Optics Letters, Vol 29, 16 (2004)) 500 µm HVPE film OP-GaAs sample length: 13 mm HVPE layer thickness: 500 µm PPLN OPO pump

16 Difference Frequency Generation DFG at around 7.8 µm from Er and Tm CW fiber lasers : UoDusseldorf (S. Vasilyev et al., Opt. Lett., 33, 13, 2008, pp ) 33 mm GaAs optional Isolator Er source l th 1.55 μ m 10 W mid-ir detector wavelength measurement and control optional λ/2 mid-ir DFG output Theorical fit Tm source μ 1.93 m 0.25 W Isolator λ/2 L1 Λ= 38.6 μm t= O C L2 L3 DM OP-GaAs Beam separation DFG output, % The informatio Theorical fit X, mm

17 17 High power OPO High power GaAs OPO (2008): Institut t St. Louis (ISL) (C. Kieleck et al., Optics Letters, Vol 34, 3 (2009)) 2.09 µm high rep.rate Ho:YAG pump, 3-5 µm emission. Up to 60% slope efficiency and 2.85 W output Efficiency comparable to ZnGeP mm OP-GaAs 20 mm long 200 µm pump diameter 50% OC (s+i)

18 18 DIRCM module 20 W Tm fiber laser 10 W Q-switched Ho:YAG 3.0 W MWIR at 40 khz M 2 = 1.4 Portable demo A. Grisard et al., Proc SPIE (2010)

19 Parametric amplification of a DFB QCL 3 mw 4.5 µm CW DFB QCL 2.09 µm Ho:YAG 30 ns pulsed pump p at 20 khz 53 db gain with 41 mm long GaAs crystal 600 W peak power M 2 = 1.3, Δλ < 0.5 nm (instr. limited) mm GaAs Tm Fiber Pump Stage 1.9µm AO Ho:YAG 450 µm OP-GaAs Signal Gain (db) The informatio 19 DFB-QCL 4.5µm 2.09µm Pump : 2.09µm Idler : 3.9µm mm GaAs OP-GaAs Signal : 4.5µm Average Pump Power (W) G. Bloom et al., Optics Letters, Vol.35, N 4, (2010).

20 20 Recent results using OP-GaAs 7.7 W average power ns OPO (ISL) Fiber laser pumped ns OPO (ISL) Intracavity ps DFG for THz generation (Stanford) Fs MIR frequency comb (Stanford) CW OPO (BAE US) CLEO 2012

21 21 Aknowledgments C. Kieleck, M. Eichhorn, and A. Hildenbrand (ISL) S. Vasilyev and S. Shiller (UoDusseldorf) Part of this work was supported by the French MoD DGA/UM-TER/CGN Part of this work was/is supported by the European Comission: i VILLAGE ( MIRSURG ( IMPROV (