1. The Technology of High Resolution Terahertz Spectroscopy International Symposium on Molecular Spectroscopy June 19 – 23, 2006 I. Physikalisches Institut Universität zu Köln Frank Lewen

2. The Terahertz Gap a) Orotron 80 – 325 GHz and fundamental Backward Wave Oscillator (BWO) 53 – 1200 GHz b) Laser Sideband Spectrometer 1750 – 2005 GHz c) MoMeD Frequency Tripler 2300 – 2400 GHz d) Superlattice Multiplier Spectrometer 200 - >2700 GHz

3. 0 11.52.52 0.53 Frequency [THz] Herschel (HIFI) Apex Apex 2A500 - 2100 GHz Laboca345 GHz; 295 Pixel Flash 780 - 890 GHz Condor300 -1500 GHz Herschel HIFI 480 - 1250 GHz 1410 - 1910 GHz Resolution ~ 10 7 APEX (Condor), ALMA SOFIA (CASIMIR, GREAT) Cologne THz-Spektrometer ? Motivation

4. New High Resolution Instrumentation for Astrophysics APEX (Atacama Pathfinder EXperiment) in the Chilean Andes with CONDOR, the CO N+ Deuterium Observation Receiver developed in Cologne Star formation in the Orion Nebula. First Apex/CONDOR detection of highly excited carbon monoxide (CO J = 13 → 12) at 1.5 THz

5. Cologne Terahertz High Resolution Spectrometers SpectrometerFrequency RangeAccuracy [GHz] [  m] [kHz]  Backward Wave Oscillators (BWO) 53-1270240 – 57000.5-1010 -8 -10 -9 BWO + Multiplier (Schottky or SL) 240-2700190-50010-1510 -8 FIR Side Band + BWO 1750-2005150-17010-3010 -8 Intracavity (Orotron) 80-325900-4000303*10 -7 IR-Tunable Diode Lasers 15-100THz3-20100010 -7

6. Orotron Spectrometer (D ouble R esonance Setup)

7. Agilent/HP 83650A synthesizer 0.01 to 50GHz, 1mW at 40GHz min. resolution/stepsize 10Hz remote controled Spacek amplifier 18-43GHz 100mW output power level, connected to a new broadband electroformed horn antenna Pump Beam Setup

8. Double Resonance Spectrum Linewidth 210kHz

9. Condition for D ouble R esonance Experiments: Common Energy Level

10. L.A. Surin et al., PhysRevLett.86.2002 Orotron: Two Photon Absorption

11. BWO stabilized with PLL Beamsplitter BWO Absorption Cell Rubidium Reference MM-Wave Synthesizer df/f 10 -11 78 - 118GHz magn. Coils Cologne Terahertz Spectrometer Harmonic Mixer Diff. Pump Rotary Pump Elliptical Mirror PLL PC Digital Lock In IF Amp FM IEEE Interface InSb Detector QFI/4 (2BI) DATA Voltage Controlled Oscillator Power BWO Power Supply R

12. Operation of BWO

13. BWO Characteristics BWO Beam Pattern @600GHz

14. Harmonic Mixer with Planar Diode Colaboration with D. Paveljev, State Univ. of N. Novgorod

15. High Resolution Spectroscopy: Present Status of selected Systems High Resolution Spectrometers with Phase Lock Loop Electronics Zürich ETH 380 GHz High Resolution Submm-wave source, for high Rydberg states measurements (F. Merkt) New Prague mm- and submm-wave spectrometer based on a µW synthesizer with efficent multiplier stages (S. Urban) Cologne THz BWO Spectrometer (G. Winnewisser) The new Cologne Supersonic Jet Spectrometer for Terahertz Applications, SuJeSTA (T. Giesen) AIST BWO Spectrometer Tsukuba/Tokio (K.M.T. Yamada) University of Waterloo BWO Spectrometer (T. Amano) RAD Spectrometer, N. Novgorod (A. Krupnov) Free running devices Ohio FASSST Spectrometer (F.C. DeLucia) Cologne Orotron Spectrometer (S. Schlemmer)

16. COSSTA Cologne Sideband Spectrometer for Terahertz Applications frequency range 1750 - 2100 GHz frequency stability BWO (phase stabilized) <1 Hz frequency stability FIR - laser (frequency stab.) 5 kHz absolute frequency determination  10 8  20-100 kHz output power < 1.5 µW Sensitivity  10 -4 cm -1 0,2 - 0,41,61,2 - 1,41,8 – 2,0 BWO FIR upper sideband lower sideband (filtered) BWO + FIR- gas laser  Sideband Radiation Schottky-Diode

17. COSSTA Permanent Magnet Polarizing Filter IF Harmonic Mixer 125-385GHz BWO phase stabilization Evacuated Optics with Mixer Stabilized FIR - Laser THz-Sideband- Mixer BWO - Radiation Grating Upper Sideband 1.75-2.01THz Parabolic mirror Absorption Cell InSb- Detector Laserbeam Elliptical Mirror Si-beamsplitter Harmonic Mixer 1.626THz ZF Gunn AFC FIR-Ringlaser CO 2 - Pumplaser Filter BWO PLL

18. CCC Lowest Bending Transitions measured with COSSTA Gendriesch et al. (2003)

19. ortho-CH 2 at 1955 GHz

20. MoMeD Tripler 2300 – 2700 GHz Monolithic Membrane Diode, MoMeD SEM Image courtesy F. Maiwald / P. Siegel JPL

21. MoMed Mux Spectrometer Power BWO 765 – 900 GHz 3- 12mW

22. MoMed Tripler

23. MoMed Mux Spectrum

24. S uper L attice Structure

25. S uper L attice : Symmetric I/V Curve

26. HiRes THz Spectrometer: Superlattice Multiplier THz-SL Multiplier SL Input 80 – 118GHz 5-8mW SL Output 234 – >1060GHz

27. Microwave Synthesizer Generator Unit AMC + SL Spectrometer 80 – 118 GHz 5 - 8 mW BWO Sweeper

28. Multiplication x 3 rd, x 5 th, x 7 th, x 9 th First Record > 1THz! CH 3 OH

29. S uper L attice Broadband Scan

30. HiRes THz Spectrometer: Superlattice Multiplier C. Endres et al. in prep.

31. HiRes THz Spectrometer: Superlattice Multiplier C. Endres et al. in prep.

32. HiRes THz Spectrometer: Superlattice Multiplier C. Endres et al. in prep.

33. HiRes THz Spectrometer: Superlattice Multiplier C. Endres et al. in prep.

34. Conclusions The Gap is closed! Orotron-Spectrometer, sensitivity higher than FTMW, first 2 photon absorption / double resonance spectra (80 -325 GHz) BWO in fundamental mode, Sub-Doppler capability (53 to 1.2 THz) Schottky Frequency Tripler for HiRes Spectroscopy up to 2.4 THz Introduction of Superlattice devices for broadband HiRes Terahertz Spectroscopy (0.2 - 2.7 THz)

35. Acknowledgement Sandra Brünken, Christian Endres, Holger Spahn, Leonid Surin, Dimitri Fourzikov, Holger S.P. Müller, Frank Maiwald (JPL), Hideta Habara, Hiroyuki Ozeki, Martin Philip, Bernd Vowinkel and G. Winnewisser Thomas Giesen and Michael Caris (Chain Molecules) D.G. Paveliev, K. Renk (Superlattice) Gen. Dir. A.N. Korolev and A.A. Negirev (both ISTOK, BWOs) Deutsche Forschungsgemeinschaft Grant SFB 494 Grant GI 319/1-1 within the Laboratoire Européen Associé ( LEA) HiRes. Humboldt Foundation and State of NRW Russian Science Foundation for Basic Research Acknowledgement

36. BWO 1.9 THz633 GHz - dB DC Bias T GUNN frequency power DC Bias X 3 PLL 2 Ref 2 PLL 1 Ref 1 BWO  Prot. GUNN HM X Synth. HV f fc c 336 MHz 24 MHz 6-7GHz 80-90GHz 8-10 V ±10 V BS Phase Lock Loop 1.9THz LO

37. Breadboard Construction SOFIA LO GREAT Heterodyne Receicer TP D1 Heat Sink Bias GUNN QO Harmonic Mixer Pump Chopper optics PLL protect BWOBWO Locked !

38. L.A. Surin et al., PhysRevLett.86.2002 Orotron

39. SL Spectrometer

40. DCN Subdoppler

41. The Methylene Radical CH 2 Ozeki & Saito Lovas, Suenram Evenson Cologne 1955 GHz 943 GHz