THz Transceivers. Mike C. Wanke Sandia National Labs. IEEE, Phoenix Chapter Workshop Apr 27, 2012

Transcription

1 THz Transceivers Mike C. Wanke Sandia National Labs IEEE, Phoenix Chapter Workshop Apr 27, 2012 Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy s National Nuclear Security Administration under contract DE-AC04-94AL IEEE-WAD Workshop 2012 Slide 1

2 Supporting Cast Michael C. Wanke Mark Lee** Christopher D. Nordquist Michael J. Cich** Chuck T. Fuller Eric A. Shaner John L. Reno Greg C. Dyer Erik W. Young** Albert D. Grine Sandia National Laboratories Now at UT-Dallas Now at Soraa Now at Lumileds LMATA Government Services With Support From: IEEE-WAD Workshop 2012 Slide 2

3 The Shrinking THz Gap THz QCLs.01 From Tom Crowe, VDI Electronic sources (transistors, multipliers, diodes) limited by electron transit times.1 Photonic sources limited by electron scattering and bandgaps Frequency (THz) IEEE-WAD Workshop 2012 Slide 3

4 The THz Gap Integration THz QCLs.01 Electronic sources (transistors, multipliers, diodes) limited by electron transit times.1 Photonic sources limited by electron scattering and bandgaps Frequency (THz) IEEE-WAD Workshop 2012 Slide 4

5 Integration examples Antenna Coupling (IEMN/CNRS) Integrated Waveguide (Sandia) Modulator (U. Paris 7) Pulse Amplifier (Ecole Normale Sup.) IEEE-WAD Workshop 2012 Slide 5 Mechanical Tuning (MIT)

6 Coherent Detector: THz receiver Mirror/optics Mixer Block QCL P E 1 E 2 cos(ω 1 -ω 2 ) + f(ω 1 ) + f(ω 2 )+ f(ω 1 +ω 2 ) IEEE-WAD Workshop 2012 Slide 6

7 Outline Monolithically Integrated Transceiver Description Demonstration of Receiver Operation Laser Characterization IEEE-WAD Workshop 2012 Slide 7

8 Monolithically Integrated Transciever Insert diode directly into laser core Benefits Reduces size Eliminate components V bottom V top Ensures constant alignment Enhances laser/diode coupling GND IF GND Bonus : laser diagnostic tool Wanke, Nat. Phot., 4, 565, (2010) IEEE-WAD Workshop 2012 Slide 8

9 Completed QCL/Schottky THz IC 3 mm V top LASER diode V bottom V top air bridges 3mm x 1.5 mm GND IF GND GND IF GND IEEE-WAD Workshop 2012 Slide 9

10 Diode and Laser DC Properties Typical QCL L-I-V Properties 3mm x 1.5 mm Typicial Diode DC I-V Properties R = 144 Ω Current n = 1.94 Current Voltage Voltage IEEE-WAD Workshop 2012 Slide 10

11 Diode Rectified Response Diode responds to QCL power But not linear in power IEEE-WAD Workshop 2012 Slide 11

12 Integrated Diode THz Mixer Laser output to FTIR QCL modes 3mm x 1.5 mm ν (THz) Purposely built a multimoded QCL centered on 2.81 THz QCL emission (FTIR) spectra show Fabry-Perot modes spaced by ~13 GHz IEEE-WAD Workshop 2012 Slide 12

13 Integrated Diode THz Mixer Laser output to FTIR QCL modes 3mm x 1.5 mm Electrical feed to spectrum analyzer ν (THz) Diode outputs IF signal at spacing between QCL modes IEEE-WAD Workshop 2012 Slide 13

14 IF dependence on laser power IF indicates when laser turns multimoded. IF amplitude is fairly independent of diode bias. IEEE-WAD Workshop 2012 Slide 14

15 Outline Monolithically Integrated Transceiver Description Demonstration of Receiver Operation Laser Characterization IEEE-WAD Workshop 2012 Slide 15

16 Integrated THz Receiver Laser output to FTIR 3mm x 1.5 mm Molecular Gas Laser IEEE-WAD Workshop 2012 Slide 16

17 Integrated THz Receiver Laser output to FTIR 3mm x 1.5 mm Electrical feed to spectrum analyzer Hi-res, coherent, reciever IEEE-WAD Workshop 2012 Slide 17

18 Outline Monolithically Integrated Transceiver Description Demonstration of Receiver Operation Laser Characterization - Current Tuning - Phase / Injection Locking - Feedback Sensitivity IEEE-WAD Workshop 2012 Slide 18

19 Laser Characterization Current Tuning Small redshift with current - Smaller than FTIR resolution - Fairly noisy measurement IEEE-WAD Workshop 2012 Slide 19

20 Current Tuning 13 GHz δ δ 13 δ 13+δ 13 δ 13+δ Current IEEE-WAD Workshop 2012 Slide 20

21 Current Tuning δ δ 13 δ 13+δ Current IEEE-WAD Workshop 2012 Slide 21

22 Current Tuning δ=0 δ= Current IEEE-WAD Workshop 2012 Slide 22

23 Current Tuning δ δ 13+δ 13 δ Current IEEE-WAD Workshop 2012 Slide 23

24 Current Tuning 13 GHz δ δ ~ 6 MHz / ma - + δ δ Current - + Frequency (GHz) IEEE-WAD Workshop 2012 Slide 24

25 Current Tuning QCL Mode Spacing δ δ Current - + Frequency (GHz) IEEE-WAD Workshop 2012 Slide 25

26 Outline Monolithically Integrated Transceiver Description Demonstration of Receiver Operation Laser Characterization - Current Tuning - Phase / Injection Locking - Feedback Sensitivity IEEE-WAD Workshop 2012 Slide 26

27 Frequency/Phase Locked THz IC Use integrated diode s IF output as feedback to lock the QCL modes against differential fluctuations* Spectrum Analyzer µwave synthesizer µwave freq counter QCL/diode DC power amp *Following Betz, Opt. Lett. 30, 1837, (2005) Baryshev, APL, 89, , (2006) IEEE-WAD Workshop 2012 Slide 27

28 Frequency/Phase Locked THz IC 0 Use integrated diode s IF output as feedback to lock the QCL modes against differential fluctuations* Locked IF linewidth ~1 Hz Extremely stable IF frequency and amplitude QCL/diode Spectrum Analyzer DC power amp µwave synthesizer µwave freq counter *Following Betz, Opt. Lett. 30, 1837, (2005) Baryshev, APL, 89, , (2006) Time IF Signal Power (dbm) 8 min db 1 Hz (instrument resolution) 60 Hz Frequency (Hz) IEEE-WAD Workshop 2012 Slide 28

29 Absolute Frequency not Simultaneously Locked... FP 1 FP 2 (FP MHz) IEEE-WAD Workshop 2012 Slide 29

30 ... Partly because of Temp drift Molecular Gas Laser 1.2 GHz IEEE-WAD Workshop 2012 Slide 30

31 What happens when lasers cross? For δ < 23 MHz, the QCL is injection locked. Injection Locked FIRL + QCL Beat Notes FP Beat Note Wanke, Proc SPIE, 7953, (2011) IEEE-WAD Workshop 2012 Slide 31

32 Outline Monolithically Integrated Transceiver Description Demonstration of Receiver Operation Laser Characterization - Current Tuning - Phase / Injection Locking - Feedback Sensitivity IEEE-WAD Workshop 2012 Slide 32

33 Feedback Sensitivity Molecular Gas Laser Some of the QCL emission retroreflects IEEE-WAD Workshop 2012 Slide 33

34 Feedback Sensitivity Some of the QCL emission retroreflects - Another laser facet - Window or lens - External mixers Wanke, Proc SPIE, 7953, (2011) IEEE-WAD Workshop 2012 Slide 34

35 Focal Position Sensitivity Top View Front View What happens when we scan the cryostat to find the FIRL beam? IEEE-WAD Workshop 2012 Slide 35

36 Focal Position Sensitivity Amplitude (dbm) Y=1 mm FP Mode Separation IEEE-WAD Workshop 2012 Slide 36

37 Focal Position Sensitivity Amplitude (dbm) Y=0,,-1 Y (mm) FP Mode Separation -2 FP Mode Separation IEEE-WAD Workshop 2012 Slide 37

38 Focal Position Feedback Sensitivity Strong frequency and amplitude pulling Simple demonstration of Airy diffraction pattern IF Amplitude IF Frequency Y (mm) 40 db Y (mm) 60 MHz X (mm) X (mm) IEEE-WAD Workshop 2012 Slide 38

39 Cavity Length Sensitivity Mirror Position 1 mm Amplitude Frequency 9 db 20 MHz Period = 1/2 λ Frequency Mirror Position IEEE-WAD Workshop 2012 Slide 39

40 Feedback Effects on FP mode Not always a single beat frequency Mirror Position 1/2 λ 500 µm IEEE-WAD Workshop 2012 Slide 40

41 Feedback Effects on FP mode Region I - Normal Fabry-Perot Modes 600 MHz Mirror Position Frequency IEEE-WAD Workshop 2012 Slide 41

42 Feedback Effects on FP mode Region II - Fabry-Perot Modes Bifurcate 600 MHz Mirror Position Frequency Stable Spectrum IEEE-WAD Workshop 2012 Slide 42

43 Feedback Effects on FP mode 600 MHz Region III - Chaos Onset Mirror Position Frequency Unstable Spectrum IEEE-WAD Workshop 2012 Slide 43

44 When life gives you lemons peaches use feedback to image the topography IEEE-WAD Workshop 2012 Slide 44

45 Or... ((( )))... use feedback to measure vibration frequency of a reflector Amplitude (dbm) Oscillating Mirror 863 Hz Mirror Freuqency (Hz) FM sidebands ν - 12,927,489.3 (khz) ν - 12,927,489.3 (khz) IEEE-WAD Workshop 2012 Slide 45

46 THz Integrated Transceiver Summary Laser Characterization Injection Locking Vibrometry Phase Locking Imaging Feedback / Chaos 3mm x 1.5 mm IEEE-WAD Workshop 2012 Slide 46

47 Extras IEEE-WAD Workshop 2012 Slide 47

48 Feedback Effects for Locked FP FP Mode Mode Mirror Position 200 µm 50 µm 100 MHz 600 MHz FP frequency is locked (~1 Hz) but amplitude is not. absolute frequency is not. IEEE-WAD Workshop 2012 Slide 48

49 External Coupling to Receiver 3mm x 1.5 mm IEEE-WAD Workshop 2012 Slide 49

50 Integrated Waveguide Performance THz QCLs Merges microwave and optical technology Output beam pattern defined by horn Emission can be moved around on the chip Horn Antennae 6 bends Beam Pattern IEEE-WAD Workshop 2012 Slide 50

51 Mixer Response vs Diode Bias IEEE-WAD Workshop 2012 Slide 51

52 Coherent Detector: THz receiver Heterodyne receivers enable: 1) high sensitivity detection Mirror/optics Mixer Block ~ W/Hz QCL P E 1 E 2 cos(ω 1 -ω 2 ) + f(ω 1 ) + f(ω 2 )+ f(ω 1 +ω 2 ) IEEE-WAD Workshop 2012 Slide 52

53 Phase Locking Bandwidth IEEE-WAD Workshop 2012 Slide 53

54 Diode placement relative to internal field Metal QCL Metal layer Substrate n+ Bottom contact layer Kohler et al., Nature, 417, 2002 IEEE-WAD Workshop 2012 Slide 54

55 Coherent Detector: THz receiver Mirror/optics Heterodyne transceivers enable: 1) high sensitivity detection 2) high spectral resolution -10 QCL Mixer Block IF Signal Power (dbm) db 1 Hz (instrument resolution) 60 Hz Frequency (Hz) P E 1 E 2 cos(ω 1 -ω 2 ) + f(ω 1 ) + f(ω 2 )+ f(ω 1 +ω 2 ) IEEE-WAD Workshop 2012 Slide 55

56 Similar for Temperature Tuning Can see the small shifts at low temperature Can see the FP mode spacing change Can see non-monotonic behavior of the FP mode spacing FP Beat Note FIRL + QCL Beat Notes IEEE-WAD Workshop 2012 Slide 56

57 Feedback Effects for Locked FP FP Mode FP Mode Amplitude Mirror Position 9 db 100 MHz 200 µm FP frequency is locked (~1 Hz) but amplitude is not. IEEE-WAD Workshop 2012 Slide 57

58 Feedback Effects for Locked FP FP Mode Mode Mirror Position 200 µm 50 µm 100 MHz 600 MHz FP frequency is locked (~1 Hz) but amplitude is not. absolute frequency is not. IEEE-WAD Workshop 2012 Slide 58

59 Proof of asymettric splitting of FP modes FP Mode FP Current A B C D Frequency A B C D IEEE-WAD Workshop 2012 Slide 59

60 Focal Position Sensitivity Hi-resolution slice - 3 mm out of focal plane - phase flips every 1/4 λ IEEE-WAD Workshop 2012 Slide 60

61 Feedback over long scan Regions where signal goes away may be single mode IEEE-WAD Workshop 2012 Slide 61

62 Unique Tool to Explore Feedback Sensitivity Found QCL is strongly sensitive to feedback. Difficult to measure other ways. Bad when frequency stability is needed. But possibly useful for vibrometery. Possible reason for odd beampatterns. Demonstrates need for isolators. FM sidebands FP Frequency Mirror Freuqency (Hz) Y (mm) ν (GHz) ν - 12,927,489.3 (khz) X (mm) IEEE-WAD Workshop 2012 Slide 62

63 Integrated THz Receiver Laser output to FTIR 3mm x 1.5 mm Electrical feed to spectrum analyzer High-resolution, coherent detection of incident radiation IEEE-WAD Workshop 2012 Slide 63

64 Mid-scale Integration: QCLs in rectangular waveguides Source: VDI RF horn Why Rectangular Waveguides RWG is a widely used standard Propagation mode structure in RWG known Horns should improve beampatterns and coupling Waveguide elements (couplers, splitters,...) exist Can mate directly to mixers in existing RWG (no optics) Problems with Existing Waveguides Conventional machined split-block RWG doesn t work well with QCLs $$$ QCL Mixer IEEE-WAD Workshop 2012 Slide 64 Source: INAF ISSTT-08

65 Micromachining Rectangular Waveguides 1. Deposit seed metal and pattern photoresist PR substrate 2. Electoplate Au in photoresist openings PR substrate Additive electroplating technique suitable for various substrates 3. Deposit 2 nd seed, pattern 2 nd PR, and plate lids PR substrate Allows waveguide fabrication on QCLs or other devices 4. Remove photoresist and 2 nd seed metal substrate Rowen, Proc. SPIE, 7590, 2010 IEEE-WAD Workshop 2012 Slide 65

66 Micromachined THz Waveguides Photoresist removal holes H-Plane Bends Horn antenna End view of waveguide horn antenna IEEE-WAD Workshop 2012 Slide 66

67 THz Micromachined Waveguide Components Demonstrated THz components (waveguides, bends, tees, and couplers) needed for THz integrated circuits Achieved low propagation and bend losses (at 2.9 THz) / db / mm (.15 db / λ) / db / bend Observed good far-field beam patterns. Transmission through various components Preliminary Antenna Beam Pattern Beam Power Loss Linear Scale Log Scale SEMS of Waveguides Nordquist, JSTQE, 17, 130, (2011) IEEE-WAD Workshop 2012 Slide 67

68 Integrated Lasers with Waveguides Built waveguides on top of lasers Note: parallel assembly advantage Chip Tests H-plane bends E-plane bends Magic-Tees Combiners Horns Insertion position WG length Wanke, Proc SPIE, 7215, (2009) IEEE-WAD Workshop 2012 Slide 68

69 Integrated Waveguide Performance Integrated Far-field beampatterns Low Res High Res Linear Scale Log Scale Improvement over bare laser beampattern IEEE-WAD Workshop 2012 Slide 69

70 Integrated Waveguide Summary Successfully merged of optical and electronic technologies Opens the door for THz on chip routing and integrated circuits IEEE-WAD Workshop 2012 Slide 70

71 Two THz Waveguides Metal-Metal Waveguide Surface Plasmon Waveguide Kumar, Opt. Exp., 15, 113, 2007 Demichel, Opt. Exp., 14, 5335, 2006 IEEE-WAD Workshop 2012 Slide 71

72 QCL Far Field Issues Metal-Metal Waveguide Surface Plasmon Waveguide (Courtesy J. R. Gao, TU Delft) IEEE-WAD Workshop 2012 Slide 72

73 Fixing the beam pattern Amanti, Elec. Lett., 43, p573, 2007 Maineult, Appl. Phys. Lett. 93, (2008) Lee, Opt. Lett., 32, p2840, 2007 IEEE-WAD Workshop 2012 Slide 73

74 Controlling the Beampattern Danylov, Appl. Opt. 46, 5051 (2007) Amanti, Nat. Phot..3, 586 (2009) Yu, J. Opt. Soc. Am. B, 27, B30, 2010 IEEE-WAD Workshop 2012 Slide 74