THz Components and Systems

THz Components and Systems Serving the global THz community since 1992

Table of Contents Lenses 3 Free-standing wire-grid polarizers.. 5 Mid-IR polarizers.... 7 Quasi-Optical Sources (BWOs)...8 VR-2S BWO Power Supply.10 VR-6M BWO Power Supply.11 VR-6MU BWO Power Supply..12 MS-1.2 Magnetic System.13 Golay Cells.14 Pyro-electric Detector 15 Semiconductor Detector...16 Spectrometers...17 Software Package EPSIL....20

THz Lenses Polished Picarin Lenses focus THz and visible light Picarin is highly transparent in THz and visible spectral ranges (see transmission spectra on the next page). Refractive index of Picarin is almost the same for THz (n=1.56) and visible light (n=1.55). Unpolished Picarin Lenses Offer the best performance at 2-7 THz spectral range (see transmission spectra on the next page) Unpolished surfaces scatter visible and near-ir light Polyethylene Lenses The lenses are manufactured from a purified high-density polyethylene Offer the best performance at frequencies below 1 THz and above 7 THz (see transmission spectra on the next page Polyethylene is not transparent in visible and near-ir spectral ranges, so that the lenses can be used to block light. Ordering Information: Product Model Lens diameter Clear aperture Focal length Polished Picarin PPL-1.5 -XXmm 1.5 30 mm Any > 30 mm Lenses PPL-2 -XXmm 2.0 45 mm Any > 50 mm Unpolished UPL-1.5 -XXmm 1.5 30 mm Any > 30 mm Picarin Lenses UPL-2 -XXmm 2.0 45 mm Any > 50 mm Product Model Holder diameter Clear aperture Focal length Polyethylene Lenses PL-2-60mm 2.75 2 60 mm PL-2-100mm 2.75 2 100 mm PL-2-120mm 2.75 2 120 mm 3

Transmission spectra of Picarin and Polyethylene in THz spectral range 100 Picarin (2 mm slab) 80 Polyethylene (2 mm slab) Transmission (%) 60 40 20 0 0 5 10 15 20 Frequency (THz) Transmission spectrum of Picarin in the visible spectral range 100 80 Transmission (%) 60 40 20 Picarin (3 mm slab) 0 200 300 400 500 600 700 800 Wavelength (nm) 4

Free Standing Wire Grid Polarizers Product description: These polarizers are made of 10 µm or 15 µm tungsten wire wound on a circular frame with spacing ranging from 25 µm to 500 µm. Operating frequency range - up to 3 THz (see transmission and reflection spectra below) Ordering Information: Polarizer Model Wire diameter / Wire spacing (μm) Clear aperture / External diameter (mm) Polarizer Model Wire diameter / Wire spacing (μm) Clear aperture / External diameter (mm) G25-S 10 / 25 40 / 48 G100-S 15 / 100 40 / 48 G25-L 10 / 25 88 / 98 G100-L 15 / 100 88 / 98 G30-S 10 / 30 40 / 48 G130-S 15 / 130 40 / 48 G30-L 10 / 30 88 / 98 G130-L 15 / 130 88 / 98 G45-S 10 / 45 40 / 48 G200-S 15 / 200 40 / 48 G45-L 10 / 45 88 / 98 G200-L 15 / 200 88 / 98 G60-S 15 / 60 40 / 48 G300-S 15 / 300 40 / 48 G60-L 15 / 60 88 / 98 G300-L 15 / 300 88 / 98 G80-S 15 / 80 40 / 48 G500-S 15 / 500 40 / 48 G80-L 15 / 80 88 / 98 G500-L 15 / 500 88 / 98 40 / 48 G100-S 15 / 100 40 / 48 G100-L 15 / 100 88 / 98 G100-L 15 / 100 88 / 98 Wire G130-SGrid Polarizer 15 / 130 Holders: 40 / 48 G130-S 15 / 130 40 / 48 G130-L 15 / 130 88 / 98 G130-L 15 / 130 88 / 98 We G200-S carry 2 types 15 of / 200 rotating holders 40 / 48 for the wire grid G200-S 15 / 200 40 / 48 polarizers. G200-L 15 / 200 88 / 98 G200-L 15 / 200 88 / 98 G300-S 15 / 300 40 / 48 G300-S 15 / 300 40 / 48 Model G300-L RH1 is designed 15 / 300 for 4 diameter 88 / 98 polarizers, G300-L and 15 / 300 88 / 98 enables G500-Sa 360 15 rotation. / 500 Model RH2 40 / 48is designed G500-S for 4 15 / 500 40 / 48 diameter polarizers, and enables 2-axis adjustments and G500-L 15 / 500 88 / 98 G500-L 15 / 500 88 / 98 360 rotation. 5

Transmission spectra of radiation polarized perpendicular and parallel to the wires 6

Product description: Mid-IR Polarizers MIP polarizers comprise of a metal wire grid manufactured on a thin polyethylene film. High wire density (1200 wires/mm) and high transparency of a 60 μm-thick polyethylene substrate extend operating spectral range of these polarizers to 4000 cm -1 (2.5 μm; 120 THz). Transmission spectra of radiation polarized perpendicular and parallel to the wires 1 IR polarizer. Substrate -polyethylene E wires Transmission Transm. 0,1 0,01 E II wires 1E-3 0 1000 2000 3000 4000 Ordering Information: Frequency (cm -1 ) ν, cm -1 Model Clear Aperture Diameter (mm) External Diameter (mm) Number of wires per millimeter Substrate thickness (μm) MIR-25 25 33 1200 50 MIR-20 20 28 1200 50 7

THz Sources and Detectors Backward Wave Oscillators (BWOs): High power: 1-100 mw Narrow spectral line-width: 1-10 MHz Wide spectral range: 0.035-1.25 THz BWOs are electro-vacuum diodes, where THz emission is generated by electrons decelerating in a periodic electric field. BWO emission wavelength is tuned by a voltage applied to one of the electrodes (cathode). Tables below show tuning ranges for a number of different BWOs. BWO model # QS-260 ov84 QS-300 ov83 QS-350 ov82 QS-400 ov81 Frequency range, THz 1.0-1.25 0.9-1.1 0.7-1.0 0.6-0.9 Output power, mw 0.5-2 1-3 1-3 1-5 Cathode Voltage, kv 1.5-6.0 1.5-6.0 1.5-6.0 1.5-6.0 Cathode current, ma 30-45 30-45 30-45 30-45 BWO model # QS-500 ov80 QS-700 ov32 QS-1000 ov30 QS-1500 ov24 Frequency range, GHz 530-710 370-530 260-370 180-260 Output power, mw 1-5 1-5 1-10 1-10 Cathode Voltage, kv 1.5-6.0 1.0-5.0 1.0-4.0 1.0-4.0 Cathode current, ma 30-45 25-40 25-40 25-40 BWO model # QS-2.1 ov86 QS-3 ov71 QS-4 ov70 QS-6 ov69 Frequency range, GHz 120-180 80-120 50-80 35-55 Output power, mw 6-20 6-30 12-30 15-40 Cathode Voltage, kv 0.5-1.5 0.5-1.5 0.4-1.2 0.4-1.2 Cathode Current, ma 20-25 20-25 20-25 20-25 BWO cooling system: BWOs operating at frequencies above 180 GHz require water cooling. While BWO dissipates only 300 W of heat, the cooling system has to provide for at least 40 psi of water pressure, due to very narrow tubing on BWO. We recommend a Lytron chiller RC006G03, that can be also purchased from Microtech Instruments. 8

BWO Power Supplies and Magnets Operation of BWO-based THz sources requires a high voltage power supply (e.g. VR-6MU) and a magnetic system (e.g. MS-1.2) that houses a BWO tube. High Voltage Power Supplies: VR-series power supplies provide for highly stabilized cathode voltage ranging from 0 to 6000 V, as well as BWO grid and heater voltages. The software package ( EPSIL ) and digital-to-analog converter (DAC-16) enable user-friendly control of the system via RS- 232 or GPIB interfaces. Model # Max Voltage Application VR-2S 1500 V Low frequency BWOs (<180 GHz) VR-6M 6000 V High Frequency BWOs (>180 GHz) VR-6MU 6000 V All types of BWOs Focusing Magnetic System MS-1.2: MS-1.2 magnetic system includes a 1.2 Tesla permanent magnet designed to house high-frequency BWOs operating in the spectral range 0.18-1.25 THz. The system is equipped with a 3-axis mechanical translation stage for centering BWO in the magnetic field. The system also has inputs for BWO electrical connections and water cooling system. 9

Power Supply VR-2S Product description: VR-2S is designed to power tunable monochromatic quasioptical sources of millimeter and sub-millimeter wavelength radiation based on Backward- Wave Oscillators (BWOs) operating in the frequency range 35-178GHz VR-2S consists of three modules: cathode power supply, grid power supply and heater power supply unit. All the voltages are highly regulated, insuring stable BWO operation with very low level of incidental modulation on the output power. Cathode power supply - Output: 300...1500V at load current 0...40mA. - Polarity: negative (relative to a grounded BWO anode). - Ripple and noise: less than 10mV. - Line regulation (5% voltage change) 0.001%. - Load regulation (100% load change) 0.001%. - Output Voltage Slew rate: 1 V/μs -- Modulation: triangle form 2.5kHz, 0-50 V (peak-to-peak). - Overload and short circuit protection. -- Computer control via RS-232 interface (IEEE-488 (GPIB) - optional) Grid power supply - Voltage DC 200V - Maximum current 7mA - Automatically switched off, if the cathode voltage is less than 200V Heater power supply - Maximum DC current is 2.75A, regulated. - Maximum voltage is 1.4V. - Automatically switched off, if the cathode voltage is less than 200V Input power requirement. - Voltage AC: 110 V or 220 V +/-5% - Power Consumption: 120 W. Mechanical specification.- Height: 150 mm; Width: 380 mm; Depth: 380 mm; Weight: 15 kg. 10

Power Supply VR-6M Product description: VR-6M is designed to power tunable monochromatic quasi-optical sources of terahertz radiation based on Backward-Wave Oscillators (BWOs) operating in the frequency range 0.16 1.25 THz. VR-6M consists of two modules: cathode power supply and heater power supply unit. All the voltages are highly regulated, insuring stable BWO operation with very low level of incidental modulation on the output power. An optional software package and digital-toanalog converter (DAC-16) enable user-friendly computer control of the system. Cathode power supply - Output voltage: 0...6000V DC - Output current at the external load: 0...50mA DC - Output voltage polarity: negative relative to the grounded BWO- anode. - Output voltage ripple and noise: not more than 40mV (pp). - Output voltage change (at 5% line voltage change): 0.002%. - Output voltage change (at 100% load change): 0.002%. - Manual voltage control: Coarse: 0 6000V via 10-turn potentiometer, Fine: ±3V via 1-turn potentiometer. - Automatic voltage control: via the external voltage (+10-10)V using Digital-to-Analog Converter (DAC-16). - Output voltage slew rate: 1 V/μs - Internal modulation: triangle form 2.5kHz, 0...50V(p-p). - Metering: 6kV-voltage panel meter, 60mA-current panel meter. - Protection: overload and short circuit protection. Heater power supply - Output current: 0 2.75A AC, 360Hz (sinusoidal). - Output voltage: 0 8V AC (eff.). - Manual current control: via 3-digit tumblewheel switch. - Automatic current loading/unloading system. - Metering: 3A-current panel meter. Input Power requirements. - Input AC Voltage: 110 V or 220 V +/-5% - Power consumption 500 W (typical). Mechanical specification.- Height: 250 mm; Width: 500 mm; Depth: 500 mm; Weight: 29 kg. 11

Power Supply VR-6MU Product description: VR-6MU is designed to power tunable monochromatic quasioptical sources of terahertz radiation based on Backward-Wave Oscillators (BWOs) operating in the frequency range 0.03 1.25 THz. VR-6MU consists of three modules: cathode power supply, grid power supply and heater power supply unit. All the voltages are highly regulated, insuring stable BWO operation with very low level of incidental modulation on the output power. An optional software package and digital-to-analog converter (DAC-16) enable user-friendly computer control of the system. Cathode power supply - Output voltage: 0...6000V DC - Output current at the external load: 0...50mA DC - Output voltage polarity: negative relative to the grounded BWO- anode. - Output voltage ripple and noise: not more than 40mV (pp). - Output voltage change (at 5% line voltage change): 0.002%. - Output voltage change (at 100% load change): 0.002%. - Manual voltage control: Coarse: 0 6000V via 10-turn potentiometer, Fine: ±3V via 1-turn potentiometer. - Automatic voltage control: via the external voltage (+10-10)V using Digital-to-Analog Converter (DAC-16). - Output voltage slew rate: 1 V/μs - Internal modulation: triangle form 2.5kHz, 0...50V(p-p). - Metering: 6kV-voltage panel meter, 60mA-current panel meter. - Protection: overload and short circuit protection. Grid power supply - Voltage DC: 200V - Maximum current: 7mA - Automatically switched off, if the cathode voltage is less than 200V Heater power supply - Output current: 0 2.75A AC, 360Hz (sinusoidal). - Output voltage: 0 8V AC (eff.). - Manual current control: via 3-digit tumblewheel switch. - Automatic current loading/unloading system. - Metering: 3A-current panel meter. Input Power requirements. - Input AC Voltage: 110 V or 220 V +/-5% - Power consumption 500 W (typical). Mechanical specification.- Height: 250 mm; Width: 500 mm; Depth: 500 mm; Weight: 29 kg. 12

Magnetic System MS-1.2 Product description: MS-1.2 magnetic system includes a 1.2 Tesla permanent magnet designed to house a high-frequency BWO operating in spectral range 0.18-1.25 THz. The system is equipped with a 3-axis mechanical translation stage for centering BWO in the magnetic field. The system also has inputs for BWO electrical connections and water cooling system. Mechanical specifications: Height: 300 mm; Width: 300 mm; Depth: 300 mm; Weight: 42 kg. 13

THz Detectors Golay Cells Product description: Golay Cell is an opto-acoustic detector designed for operation in the spectral range 0.2-20 THz It is equipped with a 6 mm diameter polyethylene input window that provides for high transparency at frequencies up to 20 THz. Black polyethylene input windows are available as an option to cut off optical radiation. Golay Cell includes a build-in preamplifier. Operation of a Golay Cell requires a three-unit power supply delivering the following: +15 V, - 15 V and 32 ma. Such a power supply is also available as an option Performance of Golay Cells is detrimentally affected by mechanical vibrations. Addressing this problem, our Golay Cells are mounted on proprietary vibration-isolating bases. Technical Specifications: Parameter Value Responsivity at 12.5 Hz modulation, V/W 1.5 x 10 5 Sensitivity at 12.5 Hz modulation, W/Hz 1/2 10-10 Maximum modulation frequency 50 Hz Dynamic range 0.1 nw- 10 μw Rise time, ms 25 Maximum output voltage, V 0.5 Input window diameter, mm 6 Dimensions, mm 135x115x120 Operating Conditions: Parameter Value Temperature, o C +15 to +25 Pressure, Pa 8.4x10 4 to 10.7 x 10 4 Humidity, % 45-80 14

Pyro-electric detectors Product description: The pyro-electric detectors based on LiTaO3 crystal, are designed to operate in spectral range 0.02-1.0 THz. At square wave modulation of radiation the saw-tooth signal voltage from the detector is proportional to the intensity of radiation. A filter is mounted on the detector input to prevent parasitic illumination by visible and infrared light. Detector is equipped with a standard BNC connector. Technical Specifications: Parameter Value Operating spectral range, cm -1 3-30 Responsivity V/W 1000 Optimal modulation frequency, Hz 5-30 Noise level, mv 1.0 Power supply voltage (2 AA batteries), V 2x1.5 Power supply current, mv 0.14 Operating battery lifetime, hours >10,000 Dimensions, mm 135x40x30 15

Semiconductor THz detectors Product description: Semiconductor THz detectors based on GaAs Schottky diode are designed to operate in spectral range 0.2-1.0 THz. We offer three different models: SD-200, SD-400, SD- 750. However, most of our semiconductor THz detectors are custom made. Technical Specifications: Parameter/Model SD-200 SD-400 SD-750 Operating frequency range, GHz 100-300 300-500 500-1000 Responsivity V/W 500 200 10-50 Sensitivity W/Hz 1/2 < 8x10-11 < 2x10-10 < 1.6x10-9 Maximum modulation frequency 20 GHz 20 GHz 20 GHz Dynamic range 80 pw 1 μw 640 pw - 1 μw Input waveguide WR-3 WR-2.2 0.25x0.25 Dimensions, mm 60x20x20 60x20x20 28x19x19 16

0 2 Microtech Instruments, Inc THz Spectrometers THz spectrometers offered by Microtech Instruments enable high-resolution spectroscopic measurements in the spectral range from 30 GHz to 1.25 THz. These systems employ frequency tunable Backward Wave Oscillators (BWOs) as sources of THz radiation and Golay Cells as detectors. Key features include: Wide spectral range: 30 GHz - 1.25 THz High spectral resolution: 1-10 MHz Wide Dynamic Range: 10 5 THz spectrometer is a user friendly, computer controlled system used in leading research institutions worldwide. Block-diagram of THz transmission spectrometer: 1 3 sample 7 8 9 11 7 7 12 7 10 2 HIGH VOLTAGE 1 2 34 kv 5 6 OVERLOAD 10 20 3 0 40 MA 50 60 0 0.5 1 1.5 POWER CATHODE VOLTAGE CATHODE CURRENT HEATER CURRENT CTROL GRID VOLTAGE MAN COMP MODULATI Vp-pGRID 6 4 2 CHOPPER MODULATOR PHASE ANALOG METER DETECTOR PHASE SHIFTER 4 5 6 1. Set of high frequency BWOs. 2. Set of low frequency housing BWOs. 3. Focusing magnetic system. 4. Power supply. 5. Digital to analog converter. 6. Data acquisition unit. 7. Polyethylene Lens 8. Thin film attenuator. 9. Chopper. 10. Golay cell detector. 11. Wire grid polarizer. 12. Wire grid analyzer. 17

2 Microtech Instruments, Inc Transmission measurements is the best method for characterization of highly transparent materials. In particular, transmission spectra of plane parallel plates exhibit a periodic transmission pattern caused by interference (Fabry-Perot etalon fringes). Real and imaginary parts of the dielectric constant can be determined from these measurements, as the period and amplitude of the etalon fringes depend on the material refractive index and absorption, respectively. Characterization of semi-transparent materials requires a THz Mach-Zehnder interferometer (shown below), since no etalon fringes can be observed in the transmission spectra of such materials. The Mach-Zehnder setup enables measurements of a phase shift induced by the sample as a function of frequency. Combining this data with transmission spectrum, real and imaginary parts of the dielectric constant can be calculated. Block-diagram of THz Mach-Zehnder interferometer: Sample 5 14 10 5 8 13 1 5 6 7 9 14 5 5 12 11 HIGH VOLTAGE 1 2345 6 kv OVERLOAD 10 20 30 40 50 0 60 MA CATHODE VOLTAGE CATHODE CURRENT FINE CTROL MODULATI Vp-p MAN COMP 0 0.5 1 1.5 HEATER CURRENT POWER PHASE CHOPPER MODULATOR ANALOG METER DETECTOR PHASE SHIFTER 4 6 COARSE 2 3 4 1. Source of radiation: backward-wave oscillator (BWO) in a magnet 2. BWO power supply 3. Digital to analog converter 4. Data acquisition unit 5. Polyethylene lens 6. Thin film attenuator 7. Chopper 8. Golay cell detector 9. Wire grid polarizer. 10. Wire grid analyzer 11. Rail 12. Phase modulator 13. Phase shifter 14. Wire grid beamsplitter 15. Removable absorber 18

Highly absorptive materials can only be characterized in a reflection geometry, illustrated below. Block-diagram of THz reflection spectrometer: 1 7 22 8 18 21 15 9 13 11 20 2 15 7 10 15 14 OVERLOAD HIGH POWER VOLTAGE MA kv CATHODE VOLTAGE CATHODE CURRENT HEATER CURRENT CTROL GRID VOLTAGE MAN COMP MODULATI Vp-p GRID 6 4 2 1234 56 0 1020304050 60 00.5 1 1.5 2 PHASE CHOPPER MODULATOR ANALOG METER DETECTOR PHASE SHIFTER 4 5 6 1. Set of high frequency BWOs. 2. Set of low frequency housing BWOs. 3. Focusing magnetic system. 4. Power supply. 5. Digital to analog converter. 6. Data acquisition unit. 7. Polyethylene Lens 8. Thin film attenuator. 9. Chopper. 10. Golay cell detector. 11. Wire grid polarizer. 13. Sample holder. 14. Indicator head. 15. Optical rail. 18. Wire grid beamsplitter. 20. Parabolic mirror 21. Cone absorber 22. Absorbing diaphragm The transmission, Mach-Zehnder and reflection spectrometers are supported by EPSIL software, enabling automated data acquisition and analysis. One spectral scan takes 15-30 min for each of the BWOs employed in the system. Please refer to EPSIL datasheet for a detailed description of the software package capabilities. 19

Software Package EPSIL EPSIL software offers a user-friendly Windows-based interface for THz spectrometer operation and data analysis. The program is compatible with Windows-95/98/NT/2000/XP. It enables the following functions: Control of THz spectrometer equipment, including sources, detector and data acquisition unit. Data acquisition, analysis and storage of measured spectra Interactive graphics representation and processing of the spectra Calculation of dielectric parameters of a sample based on its transmission spectrum THz source calibration using a set of standard samples and/or Fabry-Perot interferometer. Storage of calibration parameters. BWO selection and calibration window: This window enables selection of a specific BWO source and calibration of this source using a set of standard samples of Fabry-Perot Interferometer. 20

THz spectrometer tuning window: This window controls THz spectrometer operation by: Setting spectrometer scanning range in terms of power supply voltage or BWO output frequency (in GHz or cm -1 ). Real-time monitoring of the detected signal Adjusting mirror position in Mach-Zehnder configuration Monitoring communication with the data acquisition unit. In addition to the control windows shown above, EPSIL also includes: Transmission measurements window Phase transmission measurements window Reflection measurements window Complete description of EPSIL software package and pricing information are available on request at sales@mtinstruments.com 21

2 Microtech Instruments, Inc Microtech Instruments offers full customer support including: Installation and service of all our products, technical training and contract research. THz Spectrometers HIGH VOLTAGE 1 2 3 4 5 6 kv OVERLOAD 10 20 30 40 50 0 60 MA CATHODE VOLTAGE CATHODE CURRENT FINE CTROL MAN COMP MODULATI Vp-p 0 0.5 1 1.5 HEATER CURRENT POWER CHOPPER PHASE MODULATOR ANALOG METER DETECTOR PHASE SHIFTER 4 6 COARSE Committed to innovation, Microtech collaborates with research institutions worldwide in developing THz technologies and applications. 132 East Broadway, Eugene, OR 97401, USA Tel: (541) 683-6505 Fax: (541) 610-1825 E-mail: sales@ mtinstruments.com