首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
Frequency differences of up to 900 GHz between two laser lines near 568 nm were measured by mixing laser light and harmonics of 90 GHz microwave radiation. The Schottky point contact diodes used consisted of tungsten tips onn-GaAs bases with different degrees of doping. The formation of the contacts and the sensitivity and frequency limitations of the device are discussed.  相似文献   

2.
It is shown that in thin-film MOM diodes of contact area ~ 2.5 × 10-9 m2 the basic mechanism of infrared and visible laser radiation detection is the tunneling current dependence on contact temperature (thermally enhanced tunneling). Experiments were run on Al—Al2O3—Al MOM diodes.  相似文献   

3.
In recent years, research groups have used metal-metal point contact diodes for frequency mixing and detection of infrared laser radiation. It has been postulated that the mechanism for the nonlinear current-voltage characteristic of the diode is the tunneling of electrons through an intermediate oxide film from the whisker tip to the metal base, i.e., the configuration is considered to be a metal-oxide-metal (MOM) tunneling junction. Several features of the diodes' operation create considerable doubt concerning the applicability of the MOM tunneling mechanism. Analysis of the available data led us to postulate an alternate solid state mechanism, namely a thermally enhanced field emission process. Such emission would be a consequence of the immersion of the whisker in the laser radiation resulting in (1) conduction heating which induces thermionic emission and (2) generation of an electric field at the tip necessary for electron tunneling. In an earlier paper, we calculated the power absorbed by the cylindrical shank of a point contact diode in an infrared radiation field. Using the absorbed power as a source, detailed calculations were made of the laser induced temperature distributions on the diode; more approximate treatments were used to obtain the electric fields developed on the tip. Values of the computed temperature and field parameters for tungsten were found to be consistent with a thermal field emission process. In this paper we present a more rigorous calculation of the voltages and fields induced on different metal whisker tips by the incident laser radiation. Linear antenna theory is used to describe the receiving properties of the diode. The actual pointed geometry of the diode tip has been taken into account using Schelkunoff's theory of the conical antenna. The electric fields at the tip are found to be comparable with those necessary for field emission. The highest fields are established on gold tips, consistent with the experiments of Green et al. who found the best responsivity occurs with gold-gold contacts. Finally we discuss the significance of the experimental results of Young et al. on metal-vacuum-metal tunneling characteristics to the MOM tunneling hypothesis.  相似文献   

4.
The non-linear current-voltage characteristic of thermally enhanced field emission is proposed to explain the operation of a metal-metal point contact diode used for laser harmonic frequency generation and frequency mixing in the infrared region. This mechanism can explain several experimental observations which appear inconsistent with the previous analysis based on a planar metal-oxide-metal tunneling geometry.  相似文献   

5.
We present frequency measurements of 85 Far Infrared (FIR) laser lines ranging from 2 748 GHz to 421 GHz. We use the heterodyne technique of mixing FIR laser transitions and microwave radiation on MIM point contact diodes to determine the FIR frequencies.Work supported by Consiglio Nazionale delle Ricerche -Italia and INFM (Consorzio Interuniversitario di Fisica della Materia)  相似文献   

6.
Frequency differences of up to 170 GHz between a cw dye laser and a krypton laser at 568 nm were measured by mixing laser and microware radiation with a metalinsulator-metal point contact diode. Beat signals are well above noise and there is still great potential for improvement when better microwave oscillators are used. From the measurements reported it follows that the diode can be used for determining still higher frequency differences of visible laser radiation.  相似文献   

7.
Infrared frequency synthesis techniques with metal-insulator-metal (MIM) diodes have been extended to include absolute frequency measurement of a spin-flip Raman laser (SFRL). As a result of this extension, spectroscopy in the 5.3 μm region more readily can be put on a frequency rather than a wavelength metrology basis. Additional observations with the diode are in qualitative agreement with recent wirk relating to non-linear tuning over axial SFRL modes.  相似文献   

8.
In a series of recent experiments, research groups have made absolute frequency measurements with laser beams in the infrared region (μm) using a metal-metal point contact diode for the generation, frequency mixing and detection. At present there are two models which attempt to explain the rectification mechanism of the diode: 1) Tunneling of electrons through an intermediate oxide film from whisker to the metal base, i.e., configuration is considered to be a metal-oxide-metal (MOM) tunneling junction. 2) Rectification and nonlinear processes are the result of a thermal enchanced field emission. Such emission is a consequence of the immersion of the whisker in the laser radiation which results in conduction induced thermionic emission and/or generation of an electric field at the tip necessary for electron tunneling by field emission. The purpose of this comment is: a) to discuss qualitatively the basic difference between MOM and TFE theories as regards the origin of the nonlinearity and rectification properties of the metal point contact junction; b) to review the analyses describing the ultimate frequency response of the device; and 3) to provide a possible explanation for polarity reversal consistent with the TFE mechanism describing the operation of the whisker diode. This research was supported in part by the NATO Research Grants Program, Scientific Affairs, Brussels, Belgium, and under the auspices of the joint projects ESIS (electronic structure in solids) and IRIS (Institute for Research in Interface Sciences) of the Belgian Ministry for Science Policy  相似文献   

9.
A far-infrared laser cavity designed to favor short-wavelength laser lines was used to generate optically-pumped far-infrared laser radiation. New far-infrared laser lines were discovered in hydrazine, heavy water, ammonia, and several short-wavelength lines previously discovered in methanol were observed. Wavelength, frequency, and relative intensity measurements were performed on laser lines in the wavelength range 42.4 to 253.7 m. Each far-infrared frequency measurement was obtained by mixing the far-infrared radiation with radiation from two reference CO2 lasers and from a microwave synthesizer in a metal-insulator-metal diode. The pump laser was a high-Q Fabry Perot resonator oscillating on 275 grating-selected laser lines including regular, sequence, and hot band lines.  相似文献   

10.
We synthesized tunable far-infrared radiation at frequencies higher than 9 THz (300 cm (-1)) by mixing CO(2) laser, (15)NH(3) laser, and microwave radiation in a W-Co metal-insulator-metal diode. We used this farinfrared radiation to accurately measure torsion-rotation transitions of CH(3)OH in the 8-9-THz region. We also measured the frequency of the aP(7, 3) (15)NH(3) laser transition.  相似文献   

11.
We demonstrate the generation of cw tunable far-infrared radiation by mixing a quantum cascade laser and a CO>(2) laser in a W-Ni metal-insulator-metal diode. The first known spectroscopic application to the recording of an H(79)Br transition near 4.47 THz is reported.  相似文献   

12.
Metal-semiconductor point contact diodes have proved to be good detectors and mixers for radiation from the far-infrared to visible. Until now GaAs, InSb and InP are the most studied and used semiconductor materials for these devices. In this work we present the performance in the visible and infrared region for metal-semiconductor point-contact diodes with GaSb or InAs as the semiconductor layers. These two new materials have shown good characteristics.  相似文献   

13.
Metal-Insulator-Metal (MIM) and Schottky-barrier diodes have been used extensively in the past years as harmonic generators and mixers for frequency measurements in the spectral range from the far-infrared to the visible. MIM diodes present a very low fabrication cost and are easy to handle, while Schottky diodes are mechanically more stable and long-lived. In the present work we discuss the performance of a metal-semiconductor point-contact diode for the radiation around 1 m. This device, which may be viewed as a hybrid between a MIM and a Schottky diode, combines the simplicity and easiness of fabrication of the MIM diode with the stability and the long contact life typical of the Schottky diode. It proved to be very efficient even for visible light.  相似文献   

14.
We report results of harmonic mixing experiments between millimetric oscillators and FIR laser radiations up to 3 THz, using micrometer-size Schottky-barrier diodes. Signal-to-noise ratios suitable for precise frequency counting have been obtained for harmonic numbers up to 40.  相似文献   

15.
We present preliminary data on the performance of a new fast photodetector based on a W–InSb metal-insulator-semiconductor point contact diode operating at room temperature and with no bias voltage. The device can work either as a video detector or as harmonic mixer for radiation from far–infrared (FIR) to visible. In the FIR region, for wavelengths from 200 to 400 m, the W–InSb point contact diode showed a sensitivity comparable to that of Golay cells. In the visible region the device showed a video and heterodyne detection responsivity much higher with respect to standard M.I.M. point contact diodes. Owing to its ruggedness, low cost and wide band of operation, the W–InSb point contact diode may be very attractive as a general purpose optical sensor.  相似文献   

16.
The role of S mixing in the quantum tunneling of the magnetization in nanomagnets has been investigated. We show that the effect on the tunneling frequency is huge and that the discrepancy (more than 3 orders of magnitude in the tunneling frequency) between spectroscopic and relaxation measurements in Fe(8) can be resolved if S mixing is taken into account.  相似文献   

17.
By making a combination of both point contact and barrier type tunnel junctions on a single sample of the highT c superconductor BSCCO (2212) single crystal, we have shown that as the tunneling tip is slowly retracted from the surface a point contact junction gradually evolves from a N-S short to a high resistance tunnel junction. The scaled dynamic conductance (dI/dV) of this point contact tunnel junction becomes almost identical to that of a conventional barrier type tunnel junction and both show a linear dI/dVV curve. The observation implies that at high resistance a point contact junction behaves in the same way as a barrier type tunnel junction. We suggested that the almost linear tunneling conductance obtained in both the cases most likely arises due to an intrinsic characteristic of the surface of the crystal comprising of a mosaic of superconducting regions of the order of a few nanometers. We also conclude that the barrierless (N-S) point contact obtained by piercing the surface oxide layer of the crystal shows Andreev reflection which we suggest as the origin of the zero bias anomaly often observed in point contact junctions.  相似文献   

18.
Precisely engineered tunnel junctions exhibit a long sought effect that occurs when the energy of the electron is comparable to the potential energy of the tunneling barrier. The resistance of metal-insulator-metal tunnel junctions oscillates with an applied voltage when electrons that tunnel directly into the barrier's conduction band interfere upon reflection at the classical turning points: the insulator-metal interface and the dynamic point where the incident electron energy equals the potential barrier inside the insulator. A model of tunneling between free electron bands using the exact solution of the Schr?dinger equation for a trapezoidal tunnel barrier qualitatively agrees with experiment.  相似文献   

19.
An acousto-optical spectrometer has been constructed using a visible laser diode light source. The advantages of a visible laser diode in this application over the more prevalent infrared laser diodes are discussed. These include increased Bragg cell bandwidth and diffraction efficiency, and easier instrumental alignment, the latter allowing the attainment of much lower scattered light levels.  相似文献   

20.
The S/N ratio of the beat note obtained from the frequency mixing between a 32 THz CO2 laser, a 10.7 THz H2O laser and a 22 GHz klystron is measured as a function of incident power of both lasers and the klystron on the W-Ni point contact diode. A maximum S/N ratio of 36 dB is obtained. It is found that the S/N ratio arises from the product of the contributions due to the incident power and the fifth coefficient of the current-voltage characteristic of the W-Ni diode. These characteristics are discussed qualitatively.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号