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3. High frequency modulation for injection locking of mid-infrared QCL Maria Amanti A.Calvar, M. Renaudat Saint-Jean, S. Barbieri, C. Sirtori, A. Bismuto, J. Faist, G. Beaudoin, I. Sagnes In collaboration with:

4. 1) QCLs are unipolar devices based on intersubband transitions Transition energy depends only on layer thickness Ultrafast carrier lifetime (ps) Photon energy is fixed by chemistry Carrier lifetime of ≈ 100 ps Laser diode

5. a  up =  3 Photon population Current modulation

6. a  up =  3 Photon population Current modulation

7. Diode lasers vs QCL  3 ≈ 1 ns  3 ≈ 0.3 ps  tot = 10 cm -1  photon ≈ 10 ps j/j th =1.3

8. Motivations Stabilization and control of the laser modes via direct modulation Time Mode locking for mid infrared non linear optics Nature Photonics 6,440–449,(2012). Frequency Combs for spectroscopy Molecular absorption in the MIR

9. Optical spectrum Microwave spectrum Stabilization of the laser cavity modes: toward frequency combs  nn  n-1  n+1 Laser Bias Optical Intensity Frequency FWHM give an insight on the noise of the cavity modes ωBωB

10. Optical spectrum Modulation at ω inj : Stabilization of the laser cavity modes: toward frequency combs Laser Bias Optical Intensity  nn  n-1  inj  n+1  inj Frequency

11. Optical spectrum Microwave spectrum Modulation at ω inj =ω B Stabilization of the laser cavity modes: toward frequency combs Laser Bias Optical Intensity  nn  n-1  inj  n+1  inj Frequency ωBωB

12. Optical spectrum Microwave spectrum ωBωB Modulation at ω inj close to ω B Stabilization of the laser cavity modes: toward frequency combs Laser Bias Optical Intensity  nn  n-1  inj  n+1  inj ω inj

13. Direct modulation of a QCL @ 9  m 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Buried QCL @ 9 µm in InGaAs/AlInAs

14. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Modulation Beat note of the cavity modes FWHM= 1.2MHz Direct modulation of a QCL @ 9  m

15. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Direct modulation of a QCL @ 9  m

16. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Direct modulation of a QCL @ 9  m

17. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Locking of the optical modes to the external RF source Direct modulation of a QCL @ 9  m

18. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Tuning of the cavity modes with the external modulation Direct modulation of a QCL @ 9  m

19. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Tuning of the cavity modes with the external modulation Direct modulation of a QCL @ 9  m

20. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Direct modulation of a QCL @ 9  m

21. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Direct modulation of a QCL @ 9  m

22. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Direct modulation of a QCL @ 9  m

23. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Direct modulation of a QCL @ 9  m

24. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer Direct modulation of a QCL @ 9  m

25. 65 GHz band QWIP detector QCL Modulation Experimental set-up Spectrum analyzer ModulationBeat note of the cavity modes Injected power : 20 dBm Direct modulation of a QCL @ 9  m  m ≈1MHz

26. Buried QCL @ 9 µm in InGaAs/AlInAs Evolution of the locking with the emitted optical power

27. @ 1.7 kA/cm 2 Buried QCL @ 9 µm in InGaAs/AlInAs Evolution of the locking with the emitted optical power

28. @ 1.7 kA/cm 2 Buried QCL @ 9 µm in InGaAs/AlInAs Evolution of the locking with the emitted optical power @ 2.0 kA/cm 2

29. @ 1.7 kA/cm 2 Buried QCL @ 9 µm in InGaAs/AlInAs Evolution of the locking with the emitted optical power @ 2.4 kA/cm 2 @ 2.0 kA/cm 2 No locking

30. Laser oscillations Microwave modulation Coupled oscillators Theory Cavity field Modulated signal  nn  n-1  inj  n+1

31. Laser oscillations Microwave modulation Cavity field Modulated signal  nn  n-1  inj  n+1 Microwave losses (propagation losses, impedence mismatch) Coupled oscillators Theory

32. Laser oscillations Microwave modulation Cavity field Modulated signal  nn  n-1  inj  n+1 Siegman, A. (1986). Lasers. University Science Book Razavi, B. (2004). Solid-State Circuits, IEEE, 39(9):1415-424. Locking range Coupled oscillators Theory

33. Laser oscillations Microwave modulation Cavity field Modulated signal  nn  n-1  inj  n+1 Siegman, A. (1986). Lasers. University Science Book Razavi, B. (2004). Solid-State Circuits, IEEE, 39(9):1415-424. Locking range Optical power Modulation power Coupled oscillators Theory

34. Coupled oscillators theory mm mm mm

35. MIR QCL guide

36. Microwave lineMIR QCL guide

37. Microwave lineMIR QCL guide Design: Control of the losses in the MIR Good overlap of the microwave with the active region Width of the top contact Thickness of the InP claddings

38. Drude model for the calculation of the complex refractive index Finite element 2D simulation in the plane of the facet MicrostripStandard Losses @ 33 THz (cm -1 )3.5 Losses @ 13 GHz (cm -1 )5590 Overlap AR @ 13 GHz (%)1.50.6 Figure of merit @ 13 GHz (cm) 0.030.006 Simulations of the optical and microwave modes

39. Microstrip vs Standard Buried heterostructure ≈ 15 GHz Improvement of the bandpass up to ~ 15 GHz Calvar et al Applied Physics Letters 102, 181114 (2013) Modulation response

40. Calvar et al Applied Physics Letters 102, 181114 (2013) Microstrip vs Standard Buried heterostructure Similar performances

41. FWHM 100 kHz dBm FWHM 1,2 MHz dBm Similar performances Calvar et al Applied Physics Letters 102, 181114 (2013) Microstrip vs Standard Buried heterostructure

42. Direct modulation of a microstrip QCL @ 9  m 65 GHz band QWIP detector QCL Modulation

43. Renaudat Saint-Jean et al Laser & Photonics Reviews 8, 443-449 Direct modulation of a microstrip QCL @ 9  m

44. Beatnote (Δω) Signal at the modulation frequency ω m Renaudat Saint-Jean et al Laser & Photonics Reviews 8, 443-449 Locking over more than 1.5 MHz Direct modulation of a microstrip QCL @ 9  m

45. 7 Broadening of 40 % (13 cm -1 ) of the spectrum width Renaudat Saint-Jean et al Laser & Photonics Reviews 8, 443-449 Direct modulation of a microstrip QCL @ 9  m

46. 20 dBm Microstrip laser Standard laser No effect on the beatnote Microstrip vs Standard Buried heterostructure

47. Coupled oscillators theory

48. Microwave losses for the microstrip reduced of a factor 10 respect to standard buried

49. Injection locking of QCL emitting in the mid infrared via direct modulation Design and realization of waveguide embedded in a microstrip line: Reduction of a factor 10 of the microwave losses Locking over more than 1.5 MHz with 10 dBm modulation Power Conclusion: THANK YOU FOR YOUR ATTENTION

51. Injected signal

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