Far infrared surface electromagnetic waves propagation on A3B5 semiconductors

The real and imaginary parts of surface electromagnetic waves (SEW) refraction index n_ef in n-type InSb, GaAs and InP have been measured in FIR region (=85–142 cm^–1). The n_ef measurements allowed to determine plasma frequency _p and plasmon damping . The obtained nonlinear SEW propagation distance L dependence on Te impurity concentration in GaAs (N=10¹⁷–10¹⁹ cm^–3) was explained taking into account the conduction band nonparabolity as well as the presence of isostructural phase transition at N=2×10¹⁰ cm^–3.     

Performance of W-InSb Metal-Semiconductor Point-Contact Diodes as Detectors and Mixers in the Near Infrared

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.     

How to improve transmissive optics in the very far infrared?

Conclusion We have presented the possibility to make optical coatings on quartz in the FIR and we have got a transmission coefficient as high as 97% at room temperature. It will rise probably close to 100% at liquid helium temperature where the quartz two-phonon difference processes are frozen. The use of polyethylene or TPX is also possible to make plates and lenses. The reflectivity losses are smaller because the refractive index is much smaller, but they cannot be further reduced by any coating because there is no transparent material with n1.2 in the FIR. These lenses are very useful in the FIR (except around 60 cm^–1 if they are made of polyethylene). TPX is quite transparent over the whole FIR range, and also in the visible with nearly the same refractive index as in the FIR. Alignments can be made with visible light, and still work in the FIR.     

Direct observation of the differences between Raman scatering and population inversion transition for their emission frequencies and pulse waveforms

In FIR laser emissions optically by a CO₂ laser, it has been reported that there are two different process namely induced Raman scattering and population inversion transition.In this paper, we show that the two different process have clearly different characteristics in emission frequensies and pulse waveforms in the case of a TEA-CO₂ laser excitation.We used in this work an intra-cavity etalon for the study of the emission frequensies and also we used a MOM point contact diode for the detection of the wavaformes.Especially, we show that the FIR pulse waveformes are able to analyze numerically on the concept of rate equations.In conclusion, we indicate that molecules would be classified into two categories with regard to optically pumping by a TEA-CO₂ laser. One of them produce mainly Raman scattered emissions, and other produce only the FIR emissions from population inversion transition in spite of high power intensity excitation.     

Localization and antilocalization in InSb and InAs antidot lattices

We report on the observation of localization, antilocalization and Altshuler–Aronov–Spivak (AAS) oscillations in antidot lattices patterned on high-mobility InSb/InAlSb and InAs/AlGaSb heterostructures. In addition, the antidot lattices display ballistic commensurability features. The strength of the localization peak in InSb antidot lattices decreases exponentially with temperature, with a high characteristic temperature of 25 K between 0.4 and 50 K. Analysis of the AAS oscillations enables the extraction of phase and spin coherence lengths in InAs.     

Calculation of the carrier-induced refractive index change in InSb

We report a theoretical model for an estimate of carrier-induced changes in the refractive index of InSb at room temperature. The dispersion of n within the photon-energy interval of 0.12–0.24 eV is investigated for nonequilibrium carrier concentrations of 10¹⁵–10¹⁸ cm^–3. An analysis of the influence of the initial carrier density on n is performed. The obtained results can help to develop InSb opto-electronic devices.     

Two-proton multiplets in theN=82 nucleus 62 144 Sm82 from in-beamγ-measurements

In a high sensitivity (,2n) in-beam study of ₆₂ ¹⁴⁴ Sm₈₂, with the Kölner Würfel OSIRIS -detector array including a Compton polarimeter, we have identified the complete two-proton multiplets d ₅ ^2/–2 , d ₅ ^2/–1 g ₇ ^2/–1 , g ₇ ^2/–2 , h_11/2d ₅ ^2/–1 and the 9^– to 4^– members of the h_11·/2g ₇ ^2/–1 multiplet.Work partially supported by CICYT (Spain).     

GaSb and InAs: New Materials for Metal-Semiconductor Point-Contact Diodes

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.     

An IR-Radiometer with Internal Signal Modulation

An infrared (IR) radiometer electrical circuit on the basis of photoresistors and photodiodes made of silicon doped with zinc (Si) as well as the narrow bandgap semiconductor alloy Pb_0.78Sn_0.22Te is presented. In the circuit suggested a bridge with the photoreceiver connected to the radiometer input and immediately fed by signal generators functions as a radiation modulator. The threshold sensitivity turned out on a recorder is 2·10^–13 W·Hz^–1/2 (for the n⁺–n–n⁺ structures made of Si, =0.8–l.2m, T=300K); 1.4·10^–15W·Hz^–1/2 (for p⁺–n–n⁺ S-diodes on the basis of Si, =0.8–1.2m, T=300K) and 10^–12W·Hz^1/2 (for photodiodes on the basis of Pb_0.78Sn_0.22Te, =8–13m, T=77K).     

High power 1.5 μm integrated superluminescent light source with tilted ridge waveguide

In order to further suppress the F–P lasing and increase the superluminescent power, the tilted ridge waveguide was introduced to the integrated superluminescent device [monolithic integration of the superluminescent diode (SLD) with semiconductor optical amplifier (SOA)[. By this means, high power 1.5 m integrated superluminescent light source has been fabricated without anti-reflection (AR) coating. The F–P oscillations between the two cleaved facets were suppressed successfully compared with the device without ridge waveguide. More than 200 mW peak pulsed power was obtained under quasi-CW condition (0.1 ms pulse width, 10% duty cycle) by co-operation of the two integrated sections. The spectral FWHM is 25 nm.     

Primary Matter Creation in a Weyl–Dirac Cosmological Model

In the framework of an integrable Weyl–Dirac (W–D) theory a cosmological model is proposed. It describes a universe that began its expansion from a primary pre-Planckian geometric entity containing no matter. During the pre-Planckian period, from R ₀ =5.58×10 ^–36 cm to R_I=5.58×10 ^–34 cm, this embryonic universe has undergone a very rapid expansion and cosmic matter was created by geometry. At R_I the universe was already filled with matter having the Planckian density _P and being in the state of prematter (P=–), while the Weylian geometric elements were insignificant. This state is the Planckian egg that has served as the initial state of the singularity-free cosmological model ⁽¹⁾ considered in the framework of Einstein's general theory of relativity. The W–D character of the geometry and the cosmological constant are significant in the pre-Planckian period during the matter creation. In the dust-dominated period a relic of the W–D geometry causes a global dark matter effect. In between the pre-Planckian and dust period one has Einstein's framework and is negligible.     

Investigation of GaAs Schottky barrier diodes in the THz range

The properties of GaAs Schottky barrier diodes as video detectors and mixing elements were investigated in the frequency range from 0.8–2.5 THz. For the most sensitive diode, the video responsivity and system noise temperature were measured as a function of incident laser power. The highest video responsivity was 2,000 V/W at 214m and 60 V/W at 118m. For five diodes differing in doping, capacitance, series resistance and anode diameter, the system noise temperature was measured at 214m and 118m. The best single sideband (SSB) values are 12,300 K and 24,200 K at 214m and 118m, respectively. The system noise temperature versus frequency is given over the range from 0.5–3 THz for two specific diodes demonstrating that the sharpness of the I–V characteristics is only of secondary importance for mixer perfomance at such high frequencies.     

Novel mid-IR laser based on hybrid AlGaAsSb/InAs/CdMgSe heterostructure

We report on the development of a novel design of a mid-IR laser combining III–V and II–VI compounds in a “hybrid” double heterostructure. It possesses large (1.5 eV) potential barriers both for injected electrons and holes, suppressing their leakage from the active region, and provides strong optical confinement. An AlGaAsSb/InAs/CdMgSe laser diode with a III–V/II–VI heterovalent interface at the 0.6 μm-InAs active region has been grown by molecular beam epitaxy on an InAs substrate. Despite a far from optimal defect density at the CdMgSe/InAs interface and high losses inherent for bulk active region of the laser, the structure demonstrates lasing at 2.8 μm (up to 100 K) in the pulsed regime with a threshold current density of 3–4 kA/cm². Type II InSb monolayer insertions into an InAs layer show bright photoluminescence at 3.8 μm (77 K), confirming the great potential of the InAs-based nanostructure active region for longer wavelength applications.     

Atomic structure of melts of complex systems with eutectic transformations

The short-range-order structure of complex eutectic In-Sb-Sn, In-Sb, and Al-Sb-Bi melts is examined. The investigations are carried out on a high-temperature x-ray diffractometer. The curves of intensity of coherent x-ray scattering are used to plot the radial atom distribution functions (RADF). The RADF are analyzed for various different models of the structure of the fluids under investigation. It is established that the most acceptable model for the structure of In-Sb-Sn melts is the complex quasieutectic distribution corresponding to atom coordination in fused InSb and in fluid In and Sb. In a eutectic alloy of the Th-Sb system there are microinhomogeneous regions enriched with InSb atom complexes and with pure antimony in the total fusion region. A doped type of structure is characteristic of the Al-Sb-Bi melt. As the temperature rises the melts under investigation have a tendency to form a homogeneous solution.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 88–92, July, 1976.     

Interphase interactions in a Pd-GaAs system and their effect on electrical properties of schottky-barrier structures I. effect of heat treatment on characteristics of GaAs-Pd/Ni contacts

The electrical characteristics of surface-barrier GaAs-Pd/Ni structures and the physicochemical interaction processes at the metal-semiconductor boundary were comprehensively investigated in relation to heat treatment in various atmospheres. X-Ray structural analysis showed that in the investigated system metallurgical reactions begin at 300–350C: Unstable intermediate phases (presumably Pd₂Ga) are formed. At 400–550C all the palladium is converted to the bound state and the intermetallic compound PdGa is formed. The phase changes have no significant effect on the properties of diode structures fired in a hydrogen atmosphere. Heating in vacuum leads to degradation of the contact parameters at 300C or more. This effect is attributed to penetration of oxygen to the interface during formation of the intermediate phases.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 3–7, April, 1981     

Submillimeter laser action of CW optically pumped CF2Cl2 (Fluorocarbon 12)

Eleven new CW far infrared (FIR) laser lines have been observed in the 600 m–1200 m range from the CF₂Cl₂ (Fluorocarbon 12) molecule optically pumped by a CO₂ laser. A 510^–4–10^–3 accuracy is achieved in the measurement of the FIR wavelengths.The frequency offset between the CO₂ pump center and the absorption line centers are measured using the transferred Lamb dip technique. Owing to a recent spectroscopic study of the CF₂ ³⁵Cl₂ molecule three lines may be assigned with great confidence as rotational transitions in thev ₆ vibrational band 923 cm^–1 of this main isotope.     

Characterization of Carbon- and Alumina-Supported NiW and CoW Sulfided Catalysts

Sulfided NiW and CoW catalysts supported on activated carbon and alumina were characterized with ⁵⁷Co Mössbauer emission spectroscopy (MES) and EXAFS at the W–L_III edge. NiW catalysts were studied with MES by probing the Ni atoms with ⁵⁷Co. MES results demonstrate that the Ni–W–S phase is present in sulfided NiW catalysts. Formation of Co₉S₈-type phases could be related to the lower thiophene HDS activity of CoW catalysts. W EXAFS showed that addition of Co or Ni to a W/Al₂O₃ catalyst results in a higher W sulfidation degree. No structural differences were found for carbon- and alumina-supported catalysts, in spite of the two times larger thiophene HDS activity of carbon-supported NiW.     

Thepin structure employed as current amplifier

Injection of excess carriers into thei region of a forward biasedpin diode diminishes proportionally its resistivity (primary circuit). Resistivity variations in thei region are used to control higher currents and powers in the secondary circuit. This basic idea is developed quantitatively for a simplified symmetrical model of thepin structure in a stationary regime and then generalized for the asymmetrical case. The frequency characteristics of the electronic device are studied. For demonstration of the theoretical results thepin structure in silicon with known parameters is used.Notation 2d [m] length ofi region - D [m² s^–1] ambipolar diffusion constant - e [C] electron charge - E ₂ [Vm^–1] electric field strength iny direction - i ₁ [Am^–2] current density inx direction - i ₂ [Am^–2] current density iny direction - i _m [Am^–2] current density due to recombination of carriers ini region - i _1ef ,i _2ef [Am^–2] effective values of currentsi ₁,i ₂ - i _ns ,i _ps [Am^–2] saturated current densities from the heavily dopedn, p regions - i intrinsic region - I [A] total current throughp-n junction - I ₁ [A] total current in pin diode - I ₂ [A] current in secondary circuit - k[J grad^–1] Boltzmann's constant - L=(D) [m] ambipolar diffusion length of carriers in middle region - n(x) [m^–3] excess electron concentration in middle region - ¯n [m^–3] average value of electron concentration in middle region - n _i [m^–3] intrinsic electron concentration - n _A [m^–3] acceptor concentration inp region - n _D [m^–3] donor concentration inn region - p(x) [m^–3] excess hole concentration in middle region - q [m²] area of electrodes 3 and 4 - Q [C] charge stored ini region - R [m^–3 s^–1] recombination rate - s [m] width of diode - t [m] thickness of diode - T [K] absolute temperature - U [V] voltage acrossp-n junction - U ₁ [V] voltage acrosspin diode - U ₂ [V] voltage across terminals of secondary circuit - U _m [V] voltage drop acrossi region - V _D [V] voltage drop acrossn — i andp — i junctions at zero load - W ₁ [W] power inpin diode circuit - W ₂ [W] power in secondary circuit - x [m] distance from center of diode - coefficient in current amplification factor - [rad] phase shift of diode current with respect to applied voltage - [s] life time of excess carriers ini region - [m² V^–1 s^–1] carrier mobility ini region in the symmetrical model - _n [m² V^–1 s^–1] electron mobility ini region - _p [m² V^–1 s^–1] hole mobility ini region - [^–1 m^–1] conductivity     

Frequency Measurements of Optically Pumped Laser Emissions from the CHD2OH Methanol Isotope

A threelaser heterodyne system was used to measure the frequencies of eleven optically pumped laser emissions from CHD₂OH in the farinfrared (FIR) region. These frequencies, reported with fractional uncertainties of the order ± 2 × 10^–7, are for emissions ranging from 102.9 to 212.4 m. To our knowledge, these measurements are the first reported FIR laser frequencies for the CHD₂OH methanol isotope when used as an optically pumped laser medium.