On submillimeter laser lines from optically pumped12CH3OH

Several “new” submillimeter laser lines have been observed in a CH₃OH submillimeter laser, optically pumped by CO₂—laser radiation in a low power pulsed mode. Assignments have been suggested for a number of the lines. A few lines have wavelengths close to atmospheric water vapor absorption peaks, and can be observed only when the air path from the submillimeter resonator exit mirror to the detector is kept short or flushed with dry nitrogen.     

Assignment of laser lines in optically pumped submillimeter lasers: HDCO, D2CO

Respectively, three and eight laser lines have been precisely measured and assigned in asymmetric-top molecules HDCO and D2CO. Frequency calculations of rotational transitions use parameters obtained from microwave studies. For frequency calculations of rovibrational transitions, vibrational energies derived from infrared band analysis have been also taken into account. The assignment is confirmed by infrared radio frequency double resonance experiments inside the submillimeter laser cavity.     

Assigment of the CH2F2laser lines associated with the 9R(34) CO2pumping transition

Two new submillimeter laser transitions are reported for CH2F2optically pumped by the 9R(34) CO2line. The new transitions allow us to assign molecular transitions to the complete group of laser lines observed with that pump transition.     

CH3F submillimeter laser using a new type of resonator

A new type of resonator for the CH3F submillimeter laser was proposed and a successful operation was achieved. The theory of the resonator and experiments including tuning characteristics, pressure dependency, and Stark shift properties are described.     

Submillimeter-wave detection with superconducting tunnel diodes

The review presents a theoretical framework for understanding submillimeter detection using an optical photodiode theory. Both gain and noise in the superconductor-insulator-superconductor (SIS) mixer are described in terms of mixing on a photodiode. The role of impedance matching in the proper design of an SIS mixer is described. A variety of methods for achieving good impedance match at submillimeter frequencies are presented. The state of the submillimeter SIS mixer art as practiced in a variety of laboratories is described and summarized     

Millimeter-Wave and Submillimeter-Wave Imaging for Security and Surveillance

Passive equipments operating in the 30-300 GHz (millimeter wave) band are compared to those in the 300 GHz-3 THz (submillimeter band). Equipments operating in the submillimeter band can measure distance and also spectral information and have been used to address new opportunities in security. Solid state spectral information is available in the submillimeter region making it possible to identify materials, whereas in millimeter region bulk optical properties determine the image contrast. The optical properties in the region from 30 GHz to 3 THz are discussed for some typical inorganic and organic solids. In the millimeter-wave region of the spectrum, obscurants such as poor weather, dust, and smoke can be penetrated and useful imagery generated for surveillance. In the 30 GHz-3 THz region dielectrics such as plastic and cloth are also transparent and the detection of contraband hidden under clothing is possible. A passive millimeter-wave imaging concept based on a folded Schmidt camera has been developed and applied to poor weather navigation and security. The optical design uses a rotating mirror and is folded using polarization techniques. The design is very well corrected over a wide field of view making it ideal for surveillance and security. This produces a relatively compact imager which minimizes the receiver count.     

Synthetic spectrum of the stratosphere in the submillimeter region

A line-by-line and layer-by-layer optimized method is used for the fast computation of new high resolution spectra in the submillimeter region for the stratospheric medium. The results are shown as synthetic spectra between 10 and 40 cm^?1 and the presence of lines of minor gaseous constituents in the stratospheric medium is indexed. The purpose of the calculations is to determine better the spectral emission (better than 1 %) with a minimum computation time (less than 1’/cm^?1). The high resolution spectra (5.10^?4 cm^?1) show excellent submillimeter emission lines; this opens a wide field of investigation for stratospherical studies.     

光泵亚毫米波激光器双稳自脉冲运转特性

研究了光泵亚毫米波激光器的双稳和自脉动等动力学行为.结果表明泵浦光能产生双稳效应,导致输出光的一部分定态不存在,脉动输出较易产生,脉动频率随着泵浦光强的增大而增大.     

Microwave Type Bolometer for Submillimeter Wave Measurements

An approach to the problem of submillimeter wave measurement through the extension of microwave techniques has led to the development of a submillimeter bolometer with the sensitivity requisite to calibration with a thermal source. The sensor employs conventional components, horn, waveguide and coaxial line, with a novel coax-to-guide transition consisting of part of the bolometer element, the rest of which serves as a center conductor of the coaxial lines. The entire set of submillimeter components is contained in a 1/4-inch block of metal. Fundamental problems of detection in this band are discussed with application to the sensor. Calibration techniques and data taken with the instrument are reported.     

新型圆形槽波导定向耦合器

圆形槽波导是一种新型的高功率毫米波、亚毫米波传输线.为了实现圆形槽波导之间的耦合,本文根据双槽波导的耦合机理,设计出了新型圆形槽波导走向耦合器,并计算了3dB圆形槽波导定向耦合器的频率特性.     

Submillimeter wave generation through optical four-wave mixingusing injection-locked semiconductor lasers

This paper presents a comprehensive analysis of submillimeter wave generation through optical four-wave mixing (FWM) in an injection-locked semiconductor laser. The probe wave introduces pump-probe difference frequency amplitude modulation (AM) and phase modulation (PM) of the slave laser injection locked to the pump wave. The AM and PM indexes of the locked laser output lightwave modulated at the submillimeter wave frequency have been calculated. The submillimeter wave power generated through this technique has also been calculated theoretically. The analysis predicts a submillimeter wave power of -3.7 dBm at 300-GHz frequency for a free-running slave laser output power of 30 mW. In the presence of amplitude modulation of the probe wave, the same modulation is transferred to the submillimeter wave. The suppression of output lightwave amplitude noise relative to the pump, probe, or free-running slave laser amplitude noise has also been estimated in this analysis. At a submillimeter wave frequency of 300 GHz and a probe power equal to the pump power, typical amplitude noise reduction occurs by 7 dB     

Submillimeter wave communication versus millimeter wave communication

This paper studies the performance of a submillimeter wave antenna operating between frequencies 0.1 THz and 10 THz with a 4-cyano-4-pentylbiphenyl [5CB] substrate. Since the size and shape of the antenna impact its gain/directivity, resonant frequency, bandwidth, and efficiency, the two antenna types considered in this paper are: (a) Rectangular Patch Antenna (RPA), and (b) Cylindrical Dielectric Resonator Antenna (CDRA). Here a submillimeter wave antenna is compared with a millimeter wave (a few GHz to 100 GHz) antenna. These popular mm-wave antennas are chosen for the submillimeter wave antenna in order to understand changes in their performance as the result of changes in their geometrical shape. FEldberechnung bei Korpern mit beliebiger Oberflache (FEKO) software is used for the design and calculation of the Three-Dimensional (3D) ElectroMagnetic (EM) patterns. This paper also concentrates on the design and analysis of a massive submillimeter wave Multiple-Input Multiple-Output (MIMO) (8 by 8) RPA and CDRA.     

Microwave system for free electron masers based on a curved open waveguide

A new microwave system for free electron masers of millimeter and submillimeter wavelength ranges on the basis of an open quasi-optical waveguide in the form of two slightly deformed metallic planes is discussed. The system gives the possibility to control the wavebeam trajectory and, in particular, to separate wave and electron beams. Some basic solutions and results of demonstration experiment are presented.     

Densification of Alumina Ceramics Sintered by Using Submillimeter Wave Gyrotron

The sintering of high purity alumina, by using a very high frequency in range sub-millimeter waves, is presented in this paper. The sintering was performed by using a 300 GHz material processing system. Achieving homogeneous and volumetric heating on submillimeter wave sintering was confirmed by the grain size distribution analysis. The densification curves were obtained for submillimeter wave (300 GHz), millimeter wave (28 GHz), and conventional processing. The enhancement of densification and early shrinkage were observed on submillimeter wave sintering. However, compared with millimeter wave method, the densification of sub-millimeter wave sintering is lower at all sintering temperatures. The grain coarsening was analyzed using SEM photographs of fracture surfaces. The grain sizes of submillimeter wave sintered samples were smaller than those of the millimeter wave sintered samples. The effect of cold isostatic pressing, was also evaluated on submillimeter wave sintering. It suggests that the cold isostatic pressing method is quite effective for densification of SMMW sintering alumina.     

Reliable measurement of the optical and dielectric parameters of liquid carbon tetrachloride in the wavelength region

The power absorption coefficient, the refractive index and the loss tangent data for carbon tetrachloride are presented in the region 3 mm–50 μm (3 cm^?1–200 cm^?1). The data are compared with microwave and submillimeter wave literature values. The integrated band intensity and the integrated absorption intensity of the millimeter and submillimeter wave band and octopole moment are calculated and compared.     

Submillimeter astronomy [heterodyne spectroscopy]

Some of the aspects of submillimeter-wave astronomy which are relevant to the field of heterodyne spectroscopy are reviewed. Most of the discussion concerns the dense interstellar medium where stars are forming, with some work presented on nearby galaxies. Extremely sensitive receivers, large accurate telescopes, and high-mountain, airborne, or space platforms are gradually being developed, so that information is steadily improving in quality and scope. Examples are given of line surveys of heavy molecule spectra, extending from millimeter wavelengths well into the submillimeter, of light molecule spectroscopy, and of atomic fine-structure spectroscopy. The importance of the spatial information on atomic and ionized carbon is discussed. The gas cooling process which allows clouds to collapse to form stars by means of the submillimeter line emission is discussed. Also covered are regions suffering shocks, photodissociation regions, and stellar outflow regions. Work on the submillimeter spectrum of nearby galaxies is briefly described     

Frequency synthesizers up to 370 GHz

A new generation of frequency synthesizers up to 370 GHz is described. The main parts of them are microwave frequency synthesizer covering 11–15 GHz band, effective frequency multipliers-mixers using an opposite pair of planar Shottky diodes and a lock-in loop of a backward-wave oscillator tube covering millimeter and longer part of submillimeter wave bands with tens of milliwatts of output power. The ways of further increase in the operating frequency of such synthesizers are discussed.