Segmented high-purity germanium detectors

Segmented planar high-purity germanium detectors were developed. Segmentation of p-n junction was performed by implantation of boron (for the n-type Ge) and mechanical grooving of the Li diffusion layer (for the p-type Ge). The electric and spectrometric characteristics of each individual segment and interactions between segments were investigated. The reliability and stability of the detectors were improved by using special passivation of the crystal surfaces.     

Radiation detectors based on PbSnTe:In films,sensitive in the terahertz range of the spectrum

This paper presents a review of studies of the photoelectric properties of PbSnTe:In films obtained by molecular beam epitaxy and photosensitive structures in the far infrared and submillimeter ranges based on these films. The parameters of photodetector arrays of this type and detectors based on doped semiconductors and superconductors are compared. One-dimensional (2×128 elements) and two-dimensional (128 × 128 elements) PbSnTe:In based arrays with a sensitivity threshold of ~22 μm and an operating temperature of T ≤ 16 K are implemented. Under background-free conditions, the noise equivalent power (NEP) was NEP ≤ ^10?18 W/Hz^0.5 at T = 7 K for a black body radiation source at T_BB = 77 K. In the submillimeter range of the spectrum, sensitivity to laser radiation with a wavelength λ ≤ 205 μm and a value NEP ≤ 10^?12 W/Hz^0.5 was observed without optimization of the design of the photosensitive element and minimization of the measurement circuit noise. The directions of the development of PbSnTe:In based radiation detectors are considered..     

Gas-discharge He–Ne laser with a wavelength of 1.52 <Emphasis Type="Italic">µ</Emphasis>m for telecommunications systems

Results of a detailed study of a gas-discharge He–Ne laser with a wavelength of 1.52 µm for telecommunications systems are reported. Some important parameters of the laser are measured, such as the laser beam divergence (M ²), the laser power as a function of temperature, laser power stability, noise characteristics of laser radiation, etc. A possibility of laser microminiaturization is mentioned, which is of interest for its application under conditions of intense electromagnetic interference.     

A method for measuring spectral and time characteristics of mixed pulsed gamma-neutron fields with scintillation and Cherenkov detectors with nanosecond time resolution

A method for measuring spectral and time characteristics of pulsed mixed (n, γ) fields is described. The essence of this method is that a sequence of signals from individual (n, γ) particles registered by (n, γ) detectors is written in a computer with the subsequent amplitude-time analysis of the signal parameters. Fast scintillation and Cherenkov detectors with FWHM of pulses of ～1.5 and 2.5 ns, respectively, are used as (n, γ) detectors. A TDS-3054 broadband digital oscilloscope records signals and transmits them to the computer through a GPIB-USB interface. The equipment used ensures efficient detection of (n, γ) particles at detector counting rates of up to ～2 × 10⁸ pulses/s. The efficiency of this method has been tested in measurements of characteristics of (n, γ) radiation fields from an ИНГ-031 pulsed neutron generator and from a copper target irradiated with a beam of carbon nuclei with an energy of 200 MeV/amu from the TVN-ITEF acceleration-storage complex.     

Measurement of the internal photoeffect quantum yield in semiconductors

A method for measuring the internal photoeffect quantum yield in various semiconductors is described. It is based on the fact that the dependence of the charge-carrier separation coefficient at a p-n junction on the wavelength of incident radiation in the proposed structure is constant in a wide range of short wavelengths. The results of measurements of the spectral sensitivity at two wavelengths, one of which is chosen in a region where the quantum yield is a priori equal to unity, is calculated for the second wavelength.     

A polarimetric interferential radiometer

A polarimetric interferential radiometer operating in the L band and the procedure for measuring a full set of Stokes polarization parameters are described. It is shown that the interference principle of operation of the measuring system is intended to obtain the Stokes-polarization and polarization-ellipse parameters. Some polarization parameters preliminarily measured in a 1410-to 1420-MHz frequency band for seawater radiation are given.     

Dielectric and Optical Properties of Strontium–Barium Niobate Films in the Range of 0.2–1.3 THz

The knowledge of optical and dielectric properties of ferroelectric films, in particular, strontium–barium niobate films, in the terahertz spectral range is needed to use these films as a basis of active elements and structures for detection and control of terahertz radiation. The properties of strontium–barium niobate films with x = 0.5 grown on oriented sapphire substrates with a deposited electrode are studied by the method of terahertz time-domain spectroscopy in the spectral range of 0.2–1.3 THz. It is found that strontium–barium niobate films can be used to develop devices for detection and control of terahertz radiation.     

Silicon radiation detectors (<Emphasis Type="Italic">Review</Emphasis>)

The modern status of the field of development of silicon detectors of charged particles and x/γ rays is considered. The types and characteristics of spectrometric detectors are briefly described; the predominant attention is given to track devices. The results of studies of the radiation resistance of silicon detectors are presented.     

具有亚波长结构的突然自聚焦光束的频谱调控研究

为了提高具有亚波长结构的圆对称艾里光束的自聚焦特性,将光束的工作波长扩大至太赫兹波段,并在频谱空间中分别加入高通和带通滤波进行调控。对两种滤波效果进行对比发现,通过滤波函数的参数变化可以控制空间频谱的分布,从而对光束的传播特性进行调制。当选取合适的参数时,焦斑尺寸减小,焦点强度增加,突然自聚焦特性会大幅增强,同时可实现焦点位置的控制。比较两种调制方法后发现,带通滤波后的光束拥有更好的自聚焦特性。     

Analysis of the Photonic Crystal Power Splitter Based on the Junction Defect Radius for Optimum Resonance

Nano-photonics is an emerging area of optical materials, which would take the optointegrated circuits towards progress. Photonic crystal (PC) based power splitters are useful constituents for the design of photonic integrated circuits (PICs). They are very important devices for connecting different building blocks on an integrated optical chip. In this paper, a two-dimensional PC Y-junction power splitter (21×15 μm) based on the resonance effect with circular air holes etched on a hexagonal lattice with a period a is proposed. The plane wave expansion (PWE) and finite difference time domain (FDTD) techniques are used for analyzing the structure. The simulation results show that the optimum resonance occurs when the radius of the defect hole is 0.3a, leading to the maximum and equal power distribution.     

A diffraction-compensating 0-25 ns free space terahertz delay line for coherent quantum control

Free space delay lines provide pulses of variable time spacing for optical experiments such as pump-probe spectroscopy and coherent quantum control, including spin and photon echo techniques. However, in the terahertz region of the spectrum, beam divergence due to diffraction limits the useful length of traditional free space delay lines. We present a novel double-folded variable delay line for light in the frequency range 0.24-1.2 THz, which incorporates a symmetric arrangement of lenses whose spacing can be adjusted to compensate for diffraction at each delay. Scalable for use in other wavelength regimes, the design relays an input Gaussian beam waist to the output with up to 25 ns ( approximately 8 m) total delay and is enclosed in a desiccated volume of <0.5 m3. The delay line can deliver two or three pulses with relative amplitudes controlled via variable spacing silicon etalon beam splitters. Profiles of a 0.24 THz beam show good agreement with calculations at long delays, with insertion loss per delay stage of approximately 3 dB.     

A versatile and reconfigurable setup for all-terahertz time-resolved pump-probe spectroscopy

A versatile optical setup for all-terahertz (THz) time resolved pump-probe spectroscopy was designed and tested. By utilizing a dual THz pulse generator emitter module, independent and synchronized THz radiation pump and probe pulses were produced, thus eliminating the need for THz beam splitters and the limitations associated with their implementation. The current THz setup allows for precise control of the electric fields splitting ratio between the THz radiation pump and probe pulses, as well as in-phase, out-of-phase, and polarization dependent pump-probe spectroscopy. Since the present THz pump-probe setup does not require specialized THz radiation optical components, such as phase shifters, polarization rotators, or wide bandwidth beam splitters, it can be easily implemented with minimal alterations to a conventional THz time domain spectroscopy system. The present setup is valuable for studying the time dynamics of THz coherent phenomena in solid-state, chemical, and biological systems.     

A pulsed two-channel Nd:YAG laser with an improved spatial structure of IR radiation for prompt recording and development of photothermoplastic holograms

A two-channel Nd:YAG laser for high-speed recording and development of photothermoplastic holograms has been created. In two independent channels, the laser generates monopulse radiation of nanosecond duration (30 ns) at the second harmonic frequency (λ ₂ = 0.532 μm) and IR radiation (λ ₁ = 1.064 μm) produced by quasi-stationary free-running lasing of millisecond duration (4 ms). The radiations with wavelengths λ ₂ and λ ₁ are used, respectively, for exposure and development of photothermoplastic holograms. A method based on the use of a passive resonator is proposed to improve the spatial structure of IR radiation during lasing.     

Error analysis on measurement temperature by means dual-color thermography technique

Dual color thermography is a non-contact measurement temperature technique used mainly when the emissivity of surface is unknown; it is based on ratio of monochromatic emissive power calculated by means Planck’s radiation equation and allows measuring the temperature of gray body surface objects without being assigned their emissivity and without approximations.For real surfaces, the emissivity varies with the temperature of surface as well as the wavelength and the direction of radiation. In this case, the dual color thermometry is executed by equipping the IR camera of two narrow band pass filters, so as to consider the surface emissivity of a quite constant value. This allows calculating the ratio between the radiative fluxes of the two different emission wavelengths that is almost independent to the surface emissivity.One of the crucial factor in this technique is the choice of the two narrow filter wavelengths. In fact the measurement errors depends directly on the two wavelengths and the variation of spectral emissivity related to the wavelength chosen and it also depends inversely on distance between central value of filters.In this paper, the authors have developed and validated a mathematical model of experimental setup to measure object surface temperature by means IR thermo-camera. This mathematical model was used to quantify the temperature measurement error in the dual-color technique. A novel correlation to estimate temperature measurement error was provided.     

Designing and studying waveguide filters of terahertz and subterahertz frequency ranges

A unit for filtering terahertz and subterahertz electromagnetic radiation, based on using selective frequency properties of an evanescent waveguide and quasi-optical (optic-waveguide) methods for matching to the environment, are presented. The design of the filtering unit, radiated in a frequency band of 100 GHz to several terahertz, and the measurement results of the amplitude-frequency characteristics of test filters in a range of 100?C700 GHz, are given. The principle of the filter construction and design allows one to obtain a sharp and predicted transmission cutoff with an insignificant attenuation in the passband and a significant suppression of low-frequency radiation in the stop region. The experimentally measured attenuation is at a level of 6?C12 dB in the filter transmission band and at a level of 30?C60 dB out of the transmission band; in this case, the obtained result is determined by noises of the test setup. It is shown that the theoretical attenuation value beyond the passband may reach more than 60 dB, when the frequency is only 10% smaller than the critical one. The designed filter can be used for determining and studying spectra in the subterahertz and terahertz bands, especially in the cases, which call for a sharp spectral cutoff and exclusions of long-wave radiation components.     

A Position-Sensitive Photodetector for Studying the Spatial–Time Radiation Intensity Distribution in a Laser Beam

A position-sensitive nine-sectional photodetector for studying the spatial–time distribution of the radiation intensity in a laser beam is described. The photodetector was developed according to the technology used in the production of silicon surface-barrier detectors of nuclei fission fragments. Its sensitivity at a wavelength of 1.06 m is 0.1 A/W, and the mutual interference of its sections is within 10%. The device was used in studies of the spatial–time evolution of the optical characteristics of an active medium based on an uranium-containing liquid during nuclear pumping on a pulsed reactor.     

Application of a new detector for cathodoluminescence measurements in the wavelength range to 1.8 μm

The energetic gap structure of semiconductors or insulators can strongly be influenced by the local appearance of inhomogenities, impurities, dopants or vacancies. A high spatial resolution cathodoluminescence (CL) measuring technique makes it possible to investigate this gap structure via spectral analysis of the emitted CL. This can lead to a detailed knowledge of the local defect distribution. The wavelength range which could be detected by CL measurements has, up to the present, been limited to values less than 1 μm, because no detectors were available for higher wavelengths. By use of a new germanium detector, the measuring range could be extended to 1.8 μm. This makes it possible to analyse the CL properties, both of materials with small gap energies and of deep impurities. The detector properties which are important for CL measurements are presented. The efficiency of the detector is demonstrated by CL investigations of barium titanate ceramics and silicon. The results are discussed and compared to results obtained using conventional detectors.     

Application of uncooled microbolometer detector arrays for recording radiation of the terahertz spectral range

The mechanism of occurrence of sensitivity of microbolometer detector arrays based on vanadium oxide to terahertz radiation are analyzed. Experimental data are given showing the possibility of increasing the sensitivity of microbolometer detectors in the terahertz range by using an additional thin metal absorbing layer applied on the microbolometer membrane. A polarization dependence of the sensitivity of microbolometers in the terahertz and far infrared spectral ranges is found. It is shown that the sensitivity of microbolometers in the terahertz range is due to the absorption of radiation in the narrow metal runs placed on the support legs of the microbolometers and playing the role of an ohmic contact between the heat-sensitive layer and the processing curcuit.     

Silicon diffractive optical elements for high-power monochromatic terahertz radiation

This paper presents a fabrication technique and results of studies of silicon binary diffractive optical elements (DOEs): a diffractive lens and a 1 : 2 diffractive beam splitter with an aperture diameter of 30 mm for the terahertz spectral range. The elements were fabricated in two versions: with and without an antireflection coating of parylene C. The DOE characteristics were investigated in the beam of the Novosibirsk free electron laser at a wavelength of 141 μm. The results are given of a study of the radiation resistance of the coating, which remained intact upon exposure to an average radiation power density of 4 kW/cm²; the peak power in a 100 ps pulse was almost 8 MW/cm². Experimental estimates of the diffraction efficiency of the elements coated with the antireflection coating are in good agreement with theoretical estimates.     

Detectors on the Basis of High-Purity Epitaxial GaAs Layers for Spectrometry of X and Gamma Rays

The characteristics of detectors of soft-X and γ rays based on high-purity epitaxial GaAs layers are discussed. The characteristics of detectors with different rectifying contacts are compared, that is, those with a Schottky barrier and a p–n junction. The spectral characteristics of the manufactured detectors that were obtained under the irradiation by ⁵⁷Co and ²⁴¹Am sources at different bias voltages and in a photovoltaic mode and the simulation results using the Geant 3.21 software package are presented.