This PDF file contains the front matter associated with SPIE Proceedings Volume 1777, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

'If I have seen further it is by standing on the shoulders of giants.' Sir Isaac Newton.It has been rightly pointed out that such has been the expansion of science in the twentiethcentury that well over 50% of scientists known to history are still alive today. Indeed, in awondrously mixed metaphor, one present-day researcher has stated that "In the sciences, we arenow uniquely privileged to sit side by side with the giants on whose shoulders we stand." Andnowhere is that more true than in the field of research covered by this Conference. Those of uswhose far-infrared experience reaches back to the 1950s will remember that virtually the onlysource we had was a mercury arc lamp and the only detector was a Golay. There were no booksand just a handful of relevant papers. Even by 1970 the authors of the introductory paper at theBrooklyn Symposium on Submillimeter Waves were writing "It is appropriate to view thesubmillimeter wave region as a transition region lying between the millimeter wave and infraredportions of the electromagnetic spectrum and possessing as yet no hallmark of its own". Thatwas perhaps a pessimistic summary, as there were nearly sixty papers at that meeting. Now thatwe have an annual conference - this one with over three hundred papers - I think we can say thatwhat used to be called the 'unexplored region' is being fully explored.

The spectrum of the cosmic background radiation (CBR) has been measured using a liquid heliumcooled spectrometer carried to high altitude by a rocket. The spectrum in the frequency band 2 to30 cm-1 is very well fitted by a Planck function of temperature T=2.736K. The estimatedexperimental accuracy of the mean temperature is +1- 17 mK.

Gyrotrons are microwave oscillators based on the Electron Cyclotron Maser (ECM) instability. The free energy isthe rotational energy of weakly relativistic electrons (1 < 'y < 1.2) in a longitudinal magnetic cavity field. A net transfer ofenergy from the gyrating electrons to the electromagnetic field in the interaction circuit occurs due to the azimuthal phasebunching when the wave frequency is somewhat larger than the relativistic electron cyclotron frequency L-2 or itsharmonics. Many other types of microwave sources are also based on the ECM instablility, such as gyro-klystron, gyro- travelling wave amplifier (gyro-TWA) or gyro-backward wave oscillator (gyro-BWO). Cyclotron maser devices operatingin the relativistic Doppler-shifted regime where the axial bunching mechanism can substancially offset the azimuthalbunching are called cyclotron autoresonance maser (CARM).

Reflection and transmission of electromagnetic radiation is governed by the frequency dependent dielectricpermittivity tensor V(w), in some cases with contributions from the magnetic permeability tensor ' (co). These arefundamental linear response functions, so the corresponding spectroscopy occupies a central position in the study ofsolids. Generally speaking, t3 and U) are the natural point of contact between theory and experiment.

Limb sounding radiometers determine the concentrations of atmospheric constituents by measuring thermalemission from the atmospheric limb along a tangent path (fig 1). Microwave limb sounders have the

Changes to atmospheric composition are of central importance to stratospheric ozone depletionand to global climate change and specific measurement requirements can be identified, both forinvestigation of mechanisms and for monitoring. The attributes of heterodyne measurements atmillimetre and sub-millimetre wavelengths appear particularly well suited to these requirements,especially for the important lower stratosphere/upper troposphere region, and certain criticalmolecules can be measured only at these wavelengths. Many of these attributes have already beendemonstrated at microwave and millimetre wavelengths by ground-based, aircraft, balloon and mostrecently space instruments. Technological advances are now providing access to the sub-millimetreregion as well.

Conventional Free Electron Lasers (FELs) suffer from some drawbacks related to the largesize of most electron beam (e-beam) accelerators that implies high costs, system complexity andshielding requirements. In the Far InfraRed (FIR) and Millimetre (MM) wave region the FEL canmeet the demand of compactness following several approaches involving the different sub-systemsof the device. For example the low e-beam energies required (< 10 MeV) allow the use of small sizeaccelerators like Radio-Frequency (RF) Linacs or Microtrons. The increased performance in termsof gain at wavelengths in the FIR and MM also requires a shorter length of the interaction region,thus allowing the use of short period undulators and small number of periods and resulting in abetter efficiency. Following these considerations a compact FEL source in the MM wave range hasbeen realised at ENEA Frascati.

A Free Electron Maser is being designed for ECRH applications on future fusion devices. TheFEM will have an output power of 1 MW, a central frequency of 200 GHz and will be adjustableover the complete frequency range of 125 GHz to 250 GHz.

A compact electron beam source now in operation at NCCU will bedescribed and the application of this beam for the production of radiation fromthe microwave to the submillimeter will be reported.

There is an ongoing program at the FOM institute, TheNetherlands, to develop a 1-MW, long-pulse, 200-GHz FreeElectron Maser (FEM) using a DC accelerator system withdepressed collector. We present an extrapolation of thisdesign to more than 4 MW of output microwave power inorder to reduce the cost per kW and increase the power permodule in a plasma heating system.. A 1 A •

A high power (10 MW), ultra-short pulse (10 ps to 1 ns), millimeter-wave (35 GHz to 100 GHz) Free-Electron Laser (FEL) ex- periment is currently underway at UCLA. The device is energized by a 11/2 cell S-band photocathode RF linac which produceselectron bunches in the 3-4 MeV energy range, with pulse FWHMs ranging between 3 and 10 ps and charges up to 1 nC. Thecopper photocathode is driven by a 1 ps HVVHM frequency-quadrupled Nd:YAG laser. The electron bunch is transversally ac- celerated by a 8.4 cm-period, helically polarized wiggler. Because the electron bunch is much shorter than the FEL wavelength,all electrons coherently radiate spontaneously in the free-space limit, where slippage is important. In the TE11 grazing limit,where the axial bunch velocity matches the electromagnetic wave group velocity, the device behaves as a superradiant high- gain Compton FEL amplifier, seeded by the coherent spontaneous radiation produced at the wiggler entrance. Since the beamis prebunched, efficiencies are very high. Detailed studies of the temporal, spectral, power and phase characteristics of the radi- ation produced in both regimes are planned.

The new amplifier of millimeter (MM) and submillimeter (SBMM) wave bands named as orofemitronl is introduced.The fundamentals of the construction are discussed and the most promising designs are pointed out. On the basis of thetheory developed the ultimate output parameters of the orofemitron are estimated.

The effect of the profiled focusing magnetic field on the operation of theorotron is studied. The two-dimensional model of the bearn-wave interactionis described. The decrease of the starting current and efficiency enhancem- ent are possible for chosen theoretical model .

We present the results of development and study of sub mm range vacuum sources, that are carried out in theInstitute of Radiophysics and Electronics of Ukrainian Academy of Sciences (IRE).

Far infrared photoconductors find important applications in astronomy, Earth observation and laboratory spectroscopy.We will review the main performance characteristics of these detectors, and discuss the choice of detector type, readoutelectronics, operating temperature etc., for a given application. The optimisation of two detector systems, one forlow-background space astronomy ( the Long Wavelength Spectrometer - LWS - for the Infrared Space Observatory)and one for a high-background aircraft experiment (SATIRE - Spectroscopy of the Atmosphere using Far InfraredEmission) will be described.

Firstly conceived at Rockwell Science Center byPetroff and Stapelbroek in 1977 (Ref. 1), the BlockedImpurity Band photodetector (BIB) is now recognised toprovide significant improvements in comparison withconventional photoconductors. Because they areepitaxially grown, they are easily developed in arrayconfigurations having quite uniform pixel response. Theyare inherently radiation hard due to their small volume. Inaddition, they have better noise characteristics and theymay give some extension of the spectral response towardslonger wavelengths. This paper presents some results onBIB photodetectors based on antimony doped silicon,which gave a significant spectral responsivity in the30 pm wavelength region.

Ge:Ga far-infrared photoconductors with dimension of 0.5-mm3 cubehave been fabricated for space astronomical applications. The detec- tors have excellent detectivity at 2K operation under low photon- background, and also good characteristics such as almost no spikenoise, small change in responsivity depending on background-photoninflux, almost no hook response, and small amplitude of slow transientresponse. We have found that reponsivity to chopped infrared light issuppressed at higher bias electric field, while the responsivity tostep change in illumination (DC response) increases normally.

Doped germanium photoconductors cooled to temperatures —3 K are the most sensitive detectors for wavelengths >30pm . However under very low far-infrared (FIR.) backgrounds —fW, expected in-flight on the ISO LWS, these detectorscan exhibit non-linear behaviour which can severely compromise the overall sensitivity. These non-linear effects can bebroadly catagorised into two types.

The temperature and the bias current dependence of noise as well asthe noise spectrum for high Tc superconducting infrared bolometer(HTSIB) have been investigated. The influence of the bolometer structureon device noise has been discussed. The responsibility spectrum and thedetectivity D * spectrum for HTSIB has also been obtained. The optimumoperating temperature has been determined,that is between Tco(zero—re- sistance temperature) and Tcm(the temperature at mid transition point). theperformances of our HTSIB are D * (500,10,1) = 3.7 x 109cmHz1 2W-landnoise equivalent power NEP(500,10,1)= 2.4 x 10-11wHz-1/2.

The theory of infrared (IR) and submillimeter radiation detec- tion in direct-gap semiconductors based on "quenching" effect of Ra- man lines due to interaction between free and bound excitons is pro- posed. The first experiments were performed which shows the possibi- lity to obtain NEP = 10-17-10-19 WHz-1/2 at helium temperature.

Point-contact of metal-semiconductor is widely used as a microwave (MW) power detector or harmonic mixer.However, at high frequencies, the application of such contact is problematic due to small size of the waveguide.

Advances in technology of submicron semiconductor structures make it possible to de- velop a great variety of novel non-conventional Ohotoreceivers. Even if consideringthe classical effects only, one can see that various kinds of the effects could takeplace in the structures of that scale. The nature of the effect depends on relationsbetween the device active layer thickness a and the main physical lengths whichdescribe the relaxation processes in a semiconductor. For submicron structures, therelations

We report the development of two 20 atm CO2-laser systems delivering continously tunable mid- infrared radiation with output powers of 250 mJ and 1 J respectively. Using this radiation foroptical pumping a superradiant far-infrared laser we obtain for several molecular gases emissionvia stimulated Raman scattering in the region from 8 cm' to 250 cm'.

As major applications for millimeter and sub- millimeter electromagnetic waves have developedthere has arisen a need for instruments which willallow measurements to be made of the powercarried by free-space propagating beams and of theenergy carried in short pulses. Such instrumentsshould be calibrated absolutely and re-calibrationshould be a straightforward matter. This paperwill report on the power and energy meters wehave developed for the 60-900 GHz range.

Methyl Alcohol is the most prolific and one of the most efficient moleculesfor the production of optically pumped FIR laser lines. We present a review ofnearly 2000 CO2 pumped FIR laser wavelengths, and frequencies of about fifteenpercent of those, measured in CH3OH and its isotopes.

Over the past two decades, a large number of optically pumped far infraredlaser lines have been discovered with a wide variety of lasing gases. Amongstthese C2H3F, C2H3C1, C2H2F2, C2H5F, C2H3CN and CF20 are important examples.They give many strong laser lines which are very useful for far infrared lasermagnetic resonance(FIR LMR) and tunable far infrared(TuFir) laser spectroscopy.Although these gases have been investigated before, we have neverthelessdiscovered over 30 new laser lines between 140 gm and 9881.1m.

We revealed many coincidencies of generation lines frequenciesof FIR lasers and absorption lines frequencies of strong lines ofthe rotational spectrum of formic acid molecule. The results arereported in Table 1. We used FIR lasers frequencies which have beenreported in N.G.Douglas handbook MA. And absorption linesfrequencies of fomic acid have been obtained when we investigatedthe rotational spectrum of these molecules in frequency range up to400 GHz. About 8,000 frequencies of absorption lines of HCOOH,DCOOH, H000D, DCOOD, H13000H, D13000H, H13000D, D13000D, HC1800H,HC0180H, DC1800H, DC0180H, DC1800D, DC01801) in ground state and,part icully, in exited vibrational ones were measured. Accuracy ofthese measurements was ± 20 50 kHz. As a result the sets of rota- tional and centrifugal molecular parameters of Watson's Hamilto- nian, 0 representation, have been obtained for each species.

A numerical model of time-dependent simulation of FIR laseris presenti. The model expands the previously reportedsteady-stato soluEion for the !krbitral:y field poiarisationconfiourations in OPFIRL to the time dependent model. Nolimitations on the intensities of the interacting fields areimposed.

It is not an amazement that optically pumped submillimeter laser (OPSML)system can show rich dynamical behaviours of bistability and instability,for it may be taken for a combination of passive and active systems, It isone of the most suitable lasers for laser dynamical research,

Laser dynamical behaviours in both passive and active resonators haveattracted much attention of many laboratories since 1980's. The research cannot only reveal the origin and character of laser dynamics, and give a goodexample for general nonlinear theory, but also provide theoretical andexperimental foundations of practical designing of submillimeter laser withcontinuous-wave (cw), pulsation and chaos outputs.

Open resonators, both of the spherical and hemispherical geometry, have beenused in different sizes and configurations to measure the dielectric loss tangentof tow toss dielectrics at numerous frequency spots between 15 GHz and 300 GHz.Data were obtained at room temperature for Sapphire, Quartz and High Resistivi- ty Silicon.

A measurement system based on the analysis of TEMP modes in a hemispherical Fabry-Perot resonator around 145 GHzhas been optimized to give access to temperatures as low as 25 K and dielectric loss tangents at 106. The extended perfor- mance which relies on refined data acquisition and conversion methods is shown for special grades of CaF2 and Sapphire.

Backward-wave oscillator (BWO) based tunable monochromatic spectrometer equipped withcomputer aided control and data processing means is applied for liquid (ethanol, water, mineral oil)and solid (Si, GaAs, YBaCuO) sample characterization in the frequency range above 200 GHz.

Results of investigations at wavelengths from 6.0 to 0.4 mmofoptical characteristics (complex refractive index, transmic'sionreflection coefficients, including anisotropic characteristics) ofseveral dozens of building and common use materials are presented. Thequasi optical methods and backward-wave tubes were used formeasurements.

A method of measuring the complex dielectric constant of the medium is proposed in this paper. Unlike the usualmethod, this method is based on measurement techniques and the numerical calculation. The simplicity and accuracyof this method is shown.

The frequency dependence of complex refraction index and induced anisotropy in magnetite ferrofluid and itscomponents were evaluated from transmission spectra, measured with BWO-spectrometer, using interference modelof three-layer cell. The value of birefringence of ferrofluid (dielectric nature, cluster model) is greater, frequencyindependent and has opposite sign compared to that of ferrite (magnetic nature) .

This paper describes a method for measuring dielectric complex permittivitybased on an electric-field cross-correlation Fourier-transform spectrometer.The method is a time-domain one, its principle can be extended over the wholemicrowave region. The parameters of Teflon, plexigrass and a kind of sand weremeasured in 8mm-wave region, the accuracy of three or four significant figuresof e r can be achieved, and the relative accuracy of tans is only about 10%.

The quasy-optical two-frequency radiospectrometer was created. Theresults of the electron-nuclear systems investigation of the dynamicnuclear polarization targets are presented. In particular temperaturedependences of the nuclear polarization relaxations were measured.Complex solution of HMBA-Cr" in 1.2-propylene glycol was used as thetarget substance.

In future fusion reactors as well as in intermediate machines, such as ITER or NET, there will bea new dimension when compared with actual machines, and that is the presence of a high radiation field,both ionizing and displacement. This requires the design and development of radiation resistant systemswhich may be operated under radiation. In the case of heating systems the measurements of radiofrequency window materials has been started only recently to be performed under radiation'. Thesemeasurements should be made with special attention due to the perturbation induced by the ionization ofthe filling gases. This effect could also be important in high power heating systems based in pressurizedwaveguides due to the presence of ionizing radiation2. Here the radiation effects on the dielectricproperties of different gases at atmospheric pressure are presented.

Experimental evidence of millimeter-wave phase conjugation by resonantly enhanced degenerate four-wave mixing(DFWM) is presented for the first time. Nonlinear millimeter-wave interaction was caused by saturation of transitionbetween rotational levels of gaseous carbonyl sulfide (OSC). For radiation with A = 1.64 mm phase-conjugatereflectivity of about 0.4 % has been observed at the gas temperature 200 K, and under optimal pressure.

The results of recent studies of SO2 pressure broadened by H2, He, 02, and N2will be presented. This is part of the variable temperature pressure broadening studies ofvarious molecules between 90 K and 600 K. The 4(2,2)-3(1,3), 13(1,13)-12(0,12), and26(4,22)-26(3,23) transitions of the ground vibrational state of SO2 are studied between236 and 500 K. Measurements at other temperatures are in progress at this time. Resultsfor the temperature dependence of the pressure broadening parameters will be discussedand compared with the results of previous studies on other molecules. Any trend in the 300K broadening parameters and temperature coefficient as a function of their quantumnumbers will be noted.

The basic scaling relations governing the production of Smith-Purcell radiation in the relativistic limit are introduced.

The problem of designing an amplifier of powerful electromagnetic radiation in millimeter and submil- limeter wavelength band is one of the most important problem today. To solve this problem considerableefforts are being made in developing gyro-resonant TWT's as well as 0-type electron-wave systems withrelativistic beams and oversized electrodynamic structures. In realizing such devices a number of difficultiesoccur. For gyro-resonant TWT it is a necessity to set up more and more powerful magnetic fields whilemoving into the short-wave band. For relativistic electron-wave systems it is a strong dependence of theoutput radiation structure on the electron beam parameters and in consequence this dependence is unstable.

A code of 3—D FEL amplifier with single mode was developed on a PC-386. Using this code, thesimulation results are: 1.emittance causes the exponential reduction of output power. 2.the geometry of electronphase space has important influence on output power. 3.nonideal incidence of e—beam beyond some regioncauses the exponential reduction of output power.

A nonlinear self-consistent theory of two-stream electron-wave FEL has been created. The meth- ods of averaged kinetic equation and slowly varying amplitudes was used. A system of nonlinearequation for amplitudes waves and values of generating electric and magnetic fields has been obtained.The analyses of isochronic and non isochronic model has been carried out.

Numerical computations of the entropylike quantity are given to the equilibrium electrons in a collective free- electron laser. Results show that a reversed guide field may present better beam quality than a positive guide field.The conclusions from the comparison of the entropylike quantities principally coincide with the experimentalphenomena observed by the MIT researchers.

We have observed Cherenkov radiation from gasses in the millimeter wave and visible regions, which was emittedby electron beams from inear accelerators. The radiation is observed only when a path length of the electrons, or theemission length, is longer than the formation zone.

The measurement conducted in order to develop a precise beam diagnostics based on far-infrared (FIR)transition radiation is described. Coherent transition radiation produced by a high current single bunch of L- band electron linac at Osaka University is observed while the bunch width is tuned. Performance of the beamdiagnostics using the spectrometry of FIR radiation from the single bunch is studied.

Results of experiments to produce lighlover microvave radiation of given vavelength bythe tuning of a selective external feedback system are presented. Considered also are theadvantages of this system for obtaining a narrower spectral line of radiation in the millimeterand submillimeter vavebands. The generator has a helical undulator and operates in a free- electron maser regime vith an electron beam energy of up to 1 MeV and total current of upto 1 kA.

In free electron laser with a long, linear wiggler,the magnetic field at the entrance of wiggler and theexternal focusing required to keep the electron beam fromdiapering can determine the character of the electronorbits and seriously influence the FEL gain. To obtain goodresults in FEL experiments, it is necessary to investigatethe linearly polarized wiggler with good magnetic field atthe entrance and self-focusing.

In recent years, a great deal of attention has been focused on the free - electron laser with anelectromagnetic wiggler (EM -FEL) due to the potential .of shorter wave length operation than the free -electron laser with a magnetostatic wiggler with electron beams of relatively modest energy. In 1983 and1984 , Y. Carmel et al. and G. G. Denisov et al. observed the powerful r:Ldiation at millimeter wavelengthswith a relativistic backward wave oscillator (BWO) at 3-cm as the electromagnetic wiggler ,respectively.In 1985, Bratman et al. reported the general theory on stimulated emission of the powerful relativisticelectron beam.

The sharp variation of wiggler entrance regionmagnetic field in result of lowering the electron beamcurrent quality is able fully to be removed by ultilizationof stagged terminal loops with carefully design, themagnetic field profile without any information generated bythis device exactly fits the desirable requirement ofadiabatic change of the field amptitute from zero touniform region value, the axial magnetic field expressionof the entrance region and the fabricating technique of thedevice have been presented in the paper, the experimentmeasurement results show a good agreement with numericalsimulation and provide a verification for rationality ofthe design techique. For another possible application, thebifilar helical wiggler with stagged loops will be expectedto operate in experiment of variable parameter FEL.

In this paper,A new type of linearly polarized wiggler, withthe ability that its magenet field amplitude and period canbe varied conveniently,has been investigated in details.This device consisted of many loops which seperatedly fixon the drifting tube. Changing the raduis and period, we canobtain the magenetic field profile which we expect. Thetheory about the magnetic field profile in the device hasbeen derived and stimulted resuts of computer show that itcan produce any magnetic profile that we desire by vergingloops radius or periods or period and radius together.

A superconducting (SIS) tunnel junction heterodyne receiver has been constructed and tested over the frequency range450 to 540 GHz. The receiver uses a reduced height waveguide mount and a Pb alloy tunnel junction as the detectingelement. Performance measurements made with the receiver installed on the James Clerk Maxwell Telescope, Hawaii,show a noise temperature (DSB) of 165 K at 460 GHz and 220 K at 490 GHz, measured in a 1 GHz instantaneous IFbandwidth centred at 4 GHz. The receiver demonstrates that Pb alloy junctions are sufficiently stable and reliable toallow use at a remote observing site at sub-millimetre wavelengths.

Physical limitation of response time of a superconducting bolometer as well asthe nature of non-equilibrium detection of radiation have been investigated forAl, Nb and NbN thin films in spectral range from submillimeter to near-infraredwavelengths [1,2]. In the case of ideal heat removal from the film with the f_`. 100A thickness the detection mechanism is an electron heating effect that is notselective to radiation wavelength in a very broad range. The response time ofan electron heating bolometer is determined by an electron-phonon interactiontime. This time is of about 10 ns, 0.5 ns and 20 ps for Al, Nb, and NbNcorrespondingly near the critical temperature of the superconducting film. Thesensitive area of the bolometer consists of a number of narrow strips (with awidth of 1µm) connected in parallel to contact pads; these pads together witha sapphire substrate and a ground plate represent the microstrip transmissionline with an impedance of 50 Q.

Picosecond nonequilibrium and slow bolometric responses from a patterned high-Tc superconducting (HTS) film due toinfrared radiation were investigated using both modulation and pulse techniques. Measurements at A, = 0.85 [tm andA, = 10.6 lim have shown a similar behaviour of the response vs modulation frequency f. The responsivity of the HTS filmbased detector at f ..- 0.6-1 GHz is estimated to be 10-2 - 10-1 V/W.