the technology of high resolution terahertz spectroscopy international symposium on molecular...
TRANSCRIPT
The Technology of High Resolution
Terahertz Spectroscopy
International Symposium on
Molecular SpectroscopyJune 19 – 23, 2006
I. Physikalisches InstitutUniversität zu Köln
Frank Lewen
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
0 1 1.5 2.520.5 3
Frequency [THz]
Herschel (HIFI)
Apex Apex 2A 500 - 2100 GHz Laboca 345 GHz; 295 Pixel Flash 780 - 890 GHz Condor 300 -1500 GHz
Herschel HIFI 480 - 1250 GHz
1410 - 1910 GHz Resolution ~ 107
APEX (Condor), ALMA
SOFIA (CASIMIR, GREAT)
Cologne THz-Spektrometer
?
Motivation
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 detectionof highly excited carbon monoxide (CO J = 13 → 12) at 1.5 THz
Cologne Terahertz High Resolution Spectrometers
Spectrometer Frequency Range Accuracy
[GHz] [m] [kHz]
Backward Wave Oscillators (BWO)
53-1270 240 – 5700 0.5-10 10-8-10-9
BWO + Multiplier(Schottky or SL)
240-2700 190-500 10-15 10-8
FIR Side Band + BWO
1750-2005 150-170 10-30 10-8
Intracavity (Orotron)
80-325 900-4000 30 3*10-7
IR-Tunable Diode Lasers
15-100THz 3-20 1000 10-7
Agilent/HP 83650A synthesizer0.01 to 50GHz, 1mW at 40GHzmin. resolution/stepsize 10Hzremote controled
Spacek amplifier 18-43GHz100mW output power level,connected to a new broadbandelectroformed horn antenna
Pump Beam Setup
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
PCDigital Lock In
IF Amp
FM
IEEE Interface
InSb DetectorQFI/4 (2BI)
DATA
Voltage Controlled Oscillator
Power
BWO Power
Supply
Supply
R
e
Magnetic FieldH
Window
Radiation Out
Filament Filament + Cathode
Slow Wave Structure
Operation of BWO
Backward Wave Oscillator OB-44U/f characteristic
Slow Wave Structure Voltage U [kV]
f [THz]
BWO Characteristics
Slow Wave Structure Voltage [V]
RF Power[mW]
Frequency[GHz]
Backward Wave Oscillator OB5-0
ISTOK, 141120 Fryazino, Moscow Region
*
*
BWO Beam Pattern @600GHz
Harmonic Mixer with Planar Diode
IF Matching Unit
HEMT Port
Z=50 Ohms
BIAS Port
Harmonic Mixer
Planar FilterParabolic Mirror
(Waveguide Input e.g. 53-178 GHz)
mm Wave Synthesizer BWO or FIR 200 - 1650 GHz
RFC
IF & DC
L
C
HMIX Diode
Colaboration with D. Paveljev,State Univ. of N. Novgorod
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)
COSSTACologne 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 108 20-100 kHz
• output power < 1.5 µW Sensitivity 10-4 cm -1
0,2 - 0,4 1,61,2 - 1,4 1,8 – 2,0
BWO
FIR
upper sidebandlower sideband(filtered)
• BWO + FIR- gas laser Sideband Radiation Schottky-Diode
COSSTA
PermanentMagnet
PolarizingFilter
IF
Harmonic Mixer125-385GHz
BWO phase stabilization Evacuated Optics with Mixer Stabilized FIR - Laser
THz-Sideband-Mixer
BWO-
Radiation
Grating
Upper Sideband
1.75-2.01THz
Parabolicmirror
Absorption Cell InSb-Detector
Laserbeam
EllipticalMirror
Si-beamsplitter
Harmonic Mixer1.626THz
ZF
GunnAFC
FIR-Ringlaser
CO2 - PumplaserFilterBWO
PLL
MoMeD Tripler 2300 – 2700 GHz
• Monolithic Membrane Diode, MoMeD• SEM Image courtesy F. Maiwald / P. Siegel JPL
MoMed Mux Spectrum
2333840 2333860 2333880 2333900 2333920 2333940
-200
0
200
400
2.33 THz Tripler, BWO x 3
calc.: 2333887.400(36)obs.: 2333887.446(52)Line width 6.36(16) MHz
D2O 8
2 6 - 7
3 5
Inte
nsity
[ar
b. U
nits
]
Frequency [MHz]
HiRes THz Spectrometer:Superlattice Multiplier
THz-SLMultiplier
SL Input80 – 118GHz5-8mW
SL Output234 – >1060GHz
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)
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
BWO1.9 THz633 GHz
- dB
DC Bias
T
GUNNfrequency
power
DC Bias
X 3
PLL 2Ref 2
PLL 1Ref 1
BWO
Prot. GUNN
HM
X
Synth.
HV ffcc
336 MHz
24 MHz
6-7GHz 80-90GHz
8-10 V
±10 V
BS
Phase Lock Loop 1.9THz LO
Breadboard Construction SOFIA LO
GREAT Heterodyne Receicer TP D1
Heat Sink
Bias
GUNN
QO Harmonic Mixer
Pump
Chopper
optics
PLL protectBWO
Locked !