RU2650430C1 - RECEIVER OF IR AND THz RADIATIONS - Google Patents

Abstract

FIELD: measuring equipment; radio engineering and communication.

SUBSTANCE: invention relates to the radio measurements technique. Proposed receiver is designed to measure the spatial-energy characteristics of laser radiation at wavelengths of 2.08–16.6 mcm, 0.33–0.37 mm. Receiver of IR and THz radiation, containing a flat hermetically sealed glass-metal housing, consisting of a base with leads, which are electrically connected to the corresponding contact areas of the substrate, and a lid with a window transparent to the registered radiations, the substrate is placed in front of the window, on which the thermal-sensitive elements are placed, from the VO_x film, in the form of a mosaic filling the receiver's circular reception area, each element has a signal and common electrodes connected to contact pads located along the perimeter of the substrate, on the back side of the substrate a film compensation element made of VO_x with electrodes is located. At that, on the front surface of a mica substrate with a thickness of 40 mcm a two-dimensional film aluminum array with square cells is located that fills the receiver's circular receiving area, the two-dimensional array period is determined by the relation d=a+b=0.23–0.25, where a is a cell size, a=0.22 mm; b is the width of the jumper between the cells, b=0.03 mm, along the of the substrate perimeter there a film compensation element is located made of a VO_x film, which dimensions are similar to the temperature sensitive elements that are placed on the underside of the substrate under the cells of the two-dimensional array on the receiver receiving area.

EFFECT: technical result of the proposed device is in extension of the spectral range of wavelengths.

1 cl, 6 dwg, 3 tbl

Description

The invention relates to techniques for radio measurements. The proposed receiver is designed to measure the spatial and energy characteristics of laser radiation at wavelengths of 2.08-16.6 microns, 0.33-0.37 mm. The receiver will provide measurement of the parameters of the pulse-modulated signals of the THz range. The presence of domestic receivers will make it possible to ensure the production and operation of electronic systems of military and civilian equipment.

Currently, the most commonly used terahertz radiation detectors are bolometric detectors (superconducting, hot electron) and GaAs Schottky diodes. The indicated bolometers are characterized by high sensitivity and high speed (up to 50 ns), the main disadvantage is the need for their cooling to cryogenic temperatures. The operating temperature of these bolometric receivers is 8-4.2 K. The main advantages of Schottky diode receivers are speed (up to 20 GHz) and the ability to work at room temperature. The disadvantage of Schottky diodes is the non-linear current-voltage characteristic, which makes it difficult to create measurement devices on their basis.

Known uncooled microbolometric receivers based on VO _x RF films [Development and application of uncooled matrix microbolometers for the terahertz range / M.A. Demyanenko [et al.] // Bulletin of NSU. Series: Physics, 2010. V. 5. 4. S. 73-78], which operate at wavelengths of 0.3-10.6 μm, have a time constant of at least 10 ^-6 s and a threshold sensitivity of 1.6 × 10 ^-6 W. The disadvantage of these receivers is the low sensitivity in the THz range of wavelengths.

Currently, the urgent task is to increase the sensitivity of the microbolometer based on VO _x films in the IR range and provide a sharp increase in sensitivity in the THz range.

Closest to the proposed invention is a multi-element thermal receiver based on a VO _x film [patent for utility model RU No. 153286], comprising a flat metal-glass case with a window, a substrate is located inside the case in front of the window. On the plane of the circular receiving platform, 37 heat-sensitive elements are installed, located at an equal distance from each other, while the vertical arrangement of the elements is as follows: on the center line of symmetry - 7 elements, on the nearest lines to the left and right of 6 elements, on the following lines on the left and on the right of 5 elements and on the boundary lines of 4 elements.

The disadvantage of the closest analogue is the low sensitivity to the middle and far infrared, in addition, the extremely low sensitivity to sources of THz radiation.

The technical problem of the present invention is the impossibility of measuring the energy parameters of continuous and pulsed infrared and terahertz radiation at room temperature.

The problem is solved by the fact that the proposed receiver of infrared and THz radiation, containing a flat sealed metal-glass case, consisting of a base with leads that are electrically connected to the corresponding contact pads of the substrate, and a lid with a window that is transparent for the detected radiation, a mica is installed in front of the window 40 μm thick substrate, on the front surface of which a two-dimensional film aluminum lattice with square cells is placed, filling the circular receiving platform of the receiver, period a two-dimensional lattice is determined by the relation d = a + b = 0.50-0.52, where a is the cell size, a = 0.22 mm; b is the width of the jumper between the cells, b = 0.03 mm, and a compensation element made of VO _x film, the dimensions of which are similar to the thermosensitive elements of VO _x , which are located on the back side of the substrate under the grating cells, the heat-sensitive elements are made in the form of a mosaic in the area of the receiving area, each element has a signal and common electrodes connected to the contact pads of the substrate.

The technical result of the proposed device is to expand the spectral range of wavelengths due to the use of a thin mica substrate as an absorbing layer, coated on the front side with a two-dimensional aluminum film grating (frequency-selective surface), and on the reverse side with a mosaic of heat-sensitive elements (from VO _x film ) with a current wiring diagram (this structure performs the function of a converter). The converter provides resonant absorption of infrared and THz radiation. Absorption in the mid-IR range is determined by the crystal structure of the substrate, and in the THz range is determined by the geometric dimensions of the cells and the grid pitch. The low heat capacity of the IR-THz converter causes a small receiver time constant, which allows it to be used to measure pulsed radiation at wavelengths of 2.08–16.6 μm and 0.33–0.37 mm.

The invention is illustrated using the drawings: FIG. 1-6:

in FIG. 1 (a) shows the front side of the substrate, filled with a metal periodic structure in the form of a two-dimensional lattice with square cells, with a compensating heat-sensitive element, electrodes and contact pads;

in FIG. 1 (b) shows the reverse side of the substrate with the topology of the thermosensitive elements in the form of a mosaic filling the receiver receiving area with electrodes and contact pads;

in FIG. 2 shows a General view of the receiver of infrared and THz radiation (a), its view in section (b);

in FIG. Figure 3 shows the transmission spectrum of a mica substrate with a thickness of 40 microns of the CT-1 grade at wavelengths of 2.08-14.28 microns;

in FIG. Figure 4 (a, b, c) shows graphs of reflection, transmission, and absorption with the following geometric dimensions of the square cells of a two-dimensional lattice: a = 0.1 mm, b = 0.03 mm; a = 0.15 mm, b = 0.03 mm; a = 0.2 mm, b = 0.03 mm;

in FIG. Figure 5 shows the hysteresis dependence of the specific surface resistance of a thermosensitive layer based on a 60 nm thick VO ₂ film on temperature;

in FIG. Figure 6 shows the threshold exposure of radiation sources at wavelengths of 0.3–15 μm, 0.33–0.37 mm, leading to a heating of the heat-sensitive layer by 1 ° C.

The positions in the drawings indicate: 1 - mica substrate; 2 - aluminum mesh; 3 - compensation thermosensitive element (VO _x ); 4 - electrodes with pads compensation thermosensitive element (VO _x ); 5 - thermosensitive elements (VO _x ); 6 - electrodes with contact pads of thermosensitive elements (VO _x ); 7 - receiver receiving area; 8 - a common electrode with a contact pad of thermosensitive elements; 9 - contact pads compensation thermosensitive element (VO _x ); 10 - the base of the receiver; 11 - the cover of the receiver; 12 - input window of the receiver; 13 - gold-plated findings; 14 - dielectric gasket; 15 - IR-THz converter.

In FIG. 1 shows the design of an infrared THz converter made on a mica substrate 1 with a thickness of 40 μm. The front side of the substrate is covered with a two-dimensional aluminum film lattice with square cells 2 that fill the area of the circular receiving platform 7. On the free area of the substrate 1 there is a compensation thermosensitive element (VO _x ) 3 with contact pads 4. The configuration of the compensation thermosensitive element 3 is similar to the configuration of thermosensitive elements 5 , while the values of their specific surface resistances are equal. On the opposite side of the substrate 1, under the aluminum mesh 2, there is a mosaic 5, consisting of 37 square heat-sensitive elements with signal electrodes and contact pads 6 and a common electrode with a contact pad 8. The heat-sensitive elements 5 are equidistant from each other on the plane of the receiver’s circular receiving platform 7. Compensation the thermosensitive element 3 is connected to the contact pads by means of conductors 9. The contact pads 4, 6, 8, 9 are connected by means of conductors to the leads of the housing. The distance between the elements 5 relative to each other is the same, therefore, uniform filling of the heat-sensitive elements of the receiving area of the receiver 7 takes place. The grating shields 27% of the incident radiation.

In FIG. 2 shows the design of the receiver, which contains a sealed enclosure consisting of a base 10 and a cover 11 with an input window 12 made of a material transparent to the detected radiation, for example, BaF. The base of the housing 10 has gold-plated leads 13. On the base of the housing 10, a THz-IR converter 15 is mounted using a dielectric strip 14, which is a dielectric substrate, the front surface of which is covered with a two-dimensional aluminum film grating, a compensation thermosensitive element is placed on the free surface of the substrate, the inverse the side of the substrate is filled with a mosaic of 37 thermosensitive elements from a VO _x film with electrodes and contact pads.

The detected radiation passing through the cells in a two-dimensional film aluminum lattice heats the mica substrate and the heat-sensitive layer located on it based on a mosaic of thermally sensitive elements VO _x . The nature of heating of thermosensitive elements forms a two-dimensional picture of changes in their resistance.

in FIG. Figure 3 shows the transmission spectrum of a mica substrate with a thickness of 40 microns of the grade ST-1 at wavelengths of 2.08-16.66 microns. At wavelengths of 2.08–2.63 μm, ~ 90% transmission takes place in the length ranges 2.7–2.78 μm and 9.09–16.66 μm, and ~ 100% absorption of the substrate. In the ranges of 2.85–5.26 μm and 5.55–7.69 μm, 80% and 40% transmission of the substrate occurs, respectively.

IR-THz converter made on a mica substrate 2 with a thickness of 40 μm. The front side of the substrate is covered with a thin two-dimensional aluminum lattice in the form of a circle with square cells 1. On the reverse side of the substrate, a mosaic of 37 thermosensitive elements based on a VO _x 3 film is applied under the grid. The topology of the placement of thermosensitive elements is preserved when the diameter of the receiver receiving pad varies in the range of 3 14 mm Table 1 shows the sizes of heat-sensitive elements depending on the diameter of the receiving platform of the receiver.

The introduction of a frequency-selective surface (a two-dimensional film aluminum grating, with a variation in its geometric dimensions) into the converter selects the wavelength range of the recorded terahertz radiation, thus acting as a two-dimensional diffraction grating.

The converter is a resonant structure, the reflection coefficients of the film layers, which on the basis of Al (two-dimensional lattice) and VO _x (heat-sensitive layer) are respectively in the terahertz range of 50% and 95%, and the mica substrate is almost transparent. Diffraction broadening is determined by the minimum angle Θ = λ / α, where λ is the wavelength, α is the cell width. The thickness of the mica substrate is 0.04 mm, and the wavelength of the detected radiation with a frequency of 1 THz is 0.29 mm.

In order to concentrate the diffracted light waves in the volume of the mica substrate, the cell width was varied to achieve the optimal refractive angle of the diffracted beam. In addition, the period of the two-dimensional lattice was varied to additionally provide an increase in the degree of localization of the detected radiation in the bulk of the substrate.

Under the influence of the detected radiation, vibrations of close resonant frequencies are excited in the substrate, which is accompanied by the accumulation of electromagnetic energy and causes the substrate to heat up.

The aim of the study was to determine the optimal lattice spacing d, the size of the square cell and, for a given thickness of a mica substrate h.

The analysis of the metal lattice was performed by the finite element method (FEM) in the frequency domain [Polarization devices of radio waves in the terahertz frequency range. New principles of construction. Monograph / Under. Ed. A.S. Yakunin. - M.: Radio Engineering, 2012. - 256 p.: Ill.].

The reflection, absorption, and transmission coefficients of the IR-THz converter were determined by solving the wave equation in the considered frequency region of the detected radiation by the finite element vector method using port-type boundary conditions [Grigoryev, A.D. Methods of computational electrodynamics / A.D. Grigoryev // M .: FIZMATLIT. 2013.432 p.]. To take into account the electrophysical parameters of the film layers of an infrared THz converter, we used the dielectric loss model in the considered frequency region of the receiver.

We studied the frequency range of working frequencies 0.8-1.2 THz, which is the most common in terahertz radiation power meters of domestic and foreign companies.

In FIG. Figure 4 (a, b, c) shows graphs of the absorption, reflection, and transmission coefficients of the film structure of an aluminum grid - mica - VO _x , with geometric lattice parameters: a = 0.1 mm, b = 0.03 mm (a); a = 0.15 mm, b = 0.03 mm; (b) a = 0.2 mm, b = 0.03 mm (c), where a is the cell size, b is the width of the jumper between the cells.

The absorption, reflection, and transmission coefficients were determined by solving the wave equation in the considered frequency region of the detected radiation by the finite element vector method using port-type boundary conditions. The dependence of the absorption of the substrate (muscovite) and the sensitive layer (VO _x ) on the frequency of the detected radiation was taken into account by interpolating the experimental data for the permittivity. The calculation was performed for the frequency spectrum 0.8-1.2 THz.

The experimental results are shown in table 2.

With a lattice cell size of 0.2 mm and a jumper width of 0.03 mm, a constant value of the converter absorption coefficient is observed in the frequency range of 0.8–0.9 THz and amounts to 60%. The period of a two-dimensional lattice with square cells is determined from the relation d = a + b = 0.23-0.25, where a is the cell size, in mm; b - jumper width between cells, in mm, are optimal for the frequency range 0.8-0.9 THz.

In FIG. Figure 5 shows the temperature dependence of the specific surface resistance of a heat-sensitive layer based on a VO _x film with a thickness of 60 nm. In the temperature ranges of 20-45 ° С and 45-69 ° С, the direct branch of the thermal hysteresis of the VO _x film can be represented with a small error in the form of two straight segments (AB and BC).

The results of the calculated and experimental data on the absorption coefficient of the converter at wavelengths of 2.08–16.66 μm and 0.33–0.37 mm and the value of the energy exposure providing heating of the converter by 1 ° C from a radiation pulse duration of ^1–10–8 s are given in Table 3.

In FIG. Figure 6 shows the dependence of the energy exposure of radiation at wavelengths: 2.08-2.63 microns; 2.7-2.78 microns; 2.85-5.26 microns; 5.55-7.69 microns; 9.09-16.6 microns; 0.33-0.37 mm; from the pulse duration, providing heating of the thermally sensitive layer VO _x by 1 ° C. The range of variation of the radiation pulse duration was chosen for a receiver with an aperture of 3 mm and a thermosensitive element with a size of 0.2 × 0.2 mm. The speed of the measuring channel of the receiver is determined by the ratio of the effective heat capacity of a part of the volume of the converter, which consists of the irradiated surface of the mica substrate, covered with an aluminum grating and located under the substrate of the thermally sensitive element of VO _x , to the thermal loss constant of the substrate. The receiver performance in the IR and millimeter ranges is ~ 10 ^-8 and ~ 10 ^-7 s, respectively.

To manufacture the receiver of IR and THz radiation, a small-sized metal-glass case was used, consisting of a base 1210.29-5Н and a cover 155.15-2 with a transparent window, manufactured by MARS Plant, Torzhok with gold-plated terminals, size 39 × 29 × 4 , 5 mm, with a window made of FBS-I material, transparent for the recorded radiation. The case has 42 gold-plated terminals with a diameter of 0.3 mm and a height of 6 mm, this is the maximum number of conclusions for this type of case. The dielectric substrate is made of mica grade ST-1 size 36 × 24 × 0.04 mm The converter is a mica substrate with a thickness of 0.04 mm, on the front surface of which there is a two-dimensional aluminum film grating with square cells 0.2 × 0.2 mm and a grating period of 0.23 mm. On the reverse side of the substrate there are 37 square-shaped thermosensitive elements, 0.2 × 0.2 mm in size, which fill a circular receiving area with a diameter of 3 mm. The compensation element is made of VO _x film.

The film layers of the converter were deposited using the thermal vacuum deposition method at the URM3.279.060 vacuum deposition unit. The manufacture of the aluminum lattice was carried out according to the technology of classical liquid etching of the aluminum layer according to the pattern of the photoresist mask [RF patent No. 2393512 (13)]. Thermosensitive elements based on VO _x , where x = 1.5-2.02 are applied to a dielectric substrate using the two-stage method described in [Oleinik A.S. Registration of laser radiation by film reversing media based on vanadium dioxide / A.S. Oleinik, A.V. Fedorov // Russian Nanotechnology, 2011. V. 6, No. 5-6. S. 120-129].

To adjust the configuration and dimensions of the lattice, as well as thermosensitive elements, the method of dimensional processing of metal and semiconductor films using laser radiation, for example, using a 4222F2 CNC laser machine, can be used.

The advantage of the proposed multi-element receiver of infrared and THz radiation is the parallel registration of radiation by all 37 measuring channels, while the time constant of the receiver is determined by one measuring channel. The receiver control circuit is given in [Oleinik, A.S. Thermal receivers of laser radiation based on VO _x films / А.S. Oleinik, R.N. Salikhov // Sensors and systems. - 2015. No. 7. S. 19-25]. The design of an IR-THz receiver with a time constant of ~ 10 ^-8 s in the IR range and ~ 10 ^-7 s in the THz wavelength range has been developed. The given characteristics significantly exceed the characteristics of domestic and foreign analogues.

Claims (1)

A receiver for IR and THz radiation, comprising a flat sealed glass-metal case, consisting of a base with terminals that are electrically connected to the corresponding contact pads of the substrate, and a lid with a window transparent to the detected radiation, a substrate is installed in front of the window, on which the thermosensitive elements are placed, of VO _x film as a mosaic filling circular reception area of the receiver, each element has a signal and common electrodes connected to the contact pads disposed on ne imetru substrate on the reverse side of the substrate is film expansion element of VO _x with electrodes, characterized in that located dimensional film aluminum lattice with square mesh, fill a circular reception area of the receiver, the period of the two-dimensional lattice is defined by the relation d on the front surface 40 microns mica substrate = a + b = 0.23-0.25, where a is the cell size, a = 0.22 mm; b is the width of the jumper between the cells, b = 0.03 mm, along the perimeter of the substrate there is a film compensation element made of VO _x film, the dimensions of which are similar to heat-sensitive elements that are placed on the back of the substrate under the cells of the two-dimensional grating on the receiver receiving area.

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