RU2455753C1 - Oscillator with laser excitation of quartz resonator - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: quartz piezoelectric cell (QPC) is made double-frequency and placed normally to laser diode (LD) beam. On one surface of QPC three interdigital transducers are applied, and on the opposite surface metalized spot is applied. The first interdigital transducer is located adjacent to contact leaf of QPC holder, the second interdigital transducer is located at the angle of 90° to it, the third interdigital transducer is located counterwise to the second interdigital transducer. The first and the second interdigital transducer are connected respectively to the first and the second amplifiers of frequency dynamic factor temperature control scheme the outputs of which are connected to inputs of phase detector (FD). The signal from FD enters the third amplifier the output of which is connected to the first input of voltage comparator the second input of which is connected to output of digital temperature stabilisation microprocessor (DTSMP). Comparator output is connected to input of current amplifier the output of which is connected to the first input of laser diode electronic modulator (LDEM). The output of LDEM is connected to anode of laser diode (LD) the cathode of which is connected with body. To the input of stabilised frequency signal generator oscillations from the first interdigital transducer come. From its output they are fed to multivibrator oscillator input and the second input of DTSMP. To the first input of DTSMP oscillations come from the output of temperature oscillation mode generator to the inputs of which oscillations from the third interdigital transducer are fed selectively.

EFFECT: higher long-term and temperature frequency stability and lower temperature dynamic frequency factor.

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Description

The invention relates to the field of electronics and can be used in frequency stabilization devices.

A known method of laser excitation of a quartz resonator (LHD) [1, 2], in which, using a beam of a helium-neon laser directed to the surface of a piezoelectric element with deposited electrodes, they excite electric vibrations equal to the frequency of natural vibrations of Raman scattering. In this case, an acousto-optic modulator is placed between the laser and the quartz piezoelectric element (KP) along the path of the laser beam, to which a modulating voltage multiple of the harmonic of the Raman frequency and a voltage of 70 MHz are supplied. The heat dissipation of the uncontrolled heat that arises in the CP is ensured by reflecting part of the unmodulated beam from its surface and feeding it to the photodetector, and the maximum of the modulated laser beam is directed to the periphery of the CP, which makes it possible to implement the excitation method most optimally.

However, this method of excitation does not allow to fully realize the generator with laser excitation of the quartz resonator of the LCS due to a number of fundamental disadvantages.

These include: 1. The complexity of the design and construction of an acousto-optic modulator, requiring additional modulation from an external independent 70 MHz oscillator, which complicates its synchronization system via the feedback circuit. 2. A significant uncontrolled part of the heat due to the phonon-phonon conversion of the laser beam energy, causing a drift of the stabilized frequency, and at high powers twinning of the piezoelectric element and evaporation of metallization from its surface can occur. 3. An increase in the noise level on the modes of the quartz resonator due to the uncontrolled local power of heating the KP.

As a result, this method turned out to be most suitable only for measuring the piezoelectric activity characteristics of various CPs.

The closest to the claimed one should be called a generator with laser excitation of a quartz resonator LVCR [3], in which a CP with an electrode coating is placed in an evacuated glass cylinder, shock-excited by a helium-neon laser beam, and a focusing laser is placed between the laser and the CP a system with an optical modulator placed outside a glass container transparent for a given laser-generated wavelength, followed by illumination of a metallized spot sprayed onto a surface CP KP, and the obtained natural vibrations of KP taken from the electrodes of the KP are fed to the amplifier and through the feedback circuit they are again fed to the beam modulator of a helium-neon laser, which ensures the generation of oscillations stabilized by KP.

However, this generator with LHD is not free from the disadvantages that are inherent in both analogues and prototype.

These include: 1. The complexity of the structural and technological design of the optical modulator in the serial production of such generators. 2. The uncontrolled part of the heat in the glass cylinder of the quartz resonator due to the phonon-phonon conversion of the energy of the laser beam causes a significant temperature-dynamic coefficient of frequency instability (TLC), as well as temperature instability of the frequency of the generator as a whole, a significant time to establish the frequency from the moment of switching on. 3. The long-term instability of the generator frequency increases due to the relaxation effect of the electrode film coating of the CP. 4. Low coefficient of use of thermal power dissipated by the laser, because It is located outside the cylinder.

The purpose of this invention is to solve the problem and create a generator with LHD, devoid of the disadvantages inherent in the prototype. The technical result that the implementation of the invention provides is to reduce long-term frequency instability due to the absence of an electrode coating on the surface of the KP, to reduce the temperature dynamic frequency coefficient (TKCH) due to the correction of the frequency of stabilized oscillations by spraying on the periphery of the KP two IDTs, one of which is located in the area of the mounting lobe of the gearbox, and the second IDT is located relative to the first at an angle of 90 °, as well as in reducing the time for reaching the generator operating mode due to the placement a laser diode (LD) and controlling its luminous flux inside the Raman cylinder, increasing the temperature stability of the generator frequency due to the dual-frequency design of the KP and arranging at its periphery normal to the first or second IDT, the third IDT tuned to the frequency of the temperature mode of oscillation supplied to the circuit controlling the temperature of the gearbox and in the Raman cylinder by controlling the intensity of the radiation of the LD along the feedback circuit, and reducing the energy dissipated into the surrounding environment is achieved by coating the inside the first surface of the Raman cylinder with a mirror film of metal and placement of the KP - LD structure on a support base with high thermal resistance.

This goal is achieved by the fact that to increase the long-term and temperature stability of the frequency, to reduce the TDKCH, an LD, a temperature oscillation mode generator (GTMK), a temperature compensation circuit of the TDKCH, a digital temperature stabilization microprocessor (MPTCS), an electronic laser diode modulator (EMLD) are introduced into it, a voltage comparator, a current amplifier, a stabilized frequency signal generator (RNG), a multivibrator, and three IDTs are applied to the free surface of the gearbox, on the back side of which there is a metal lysed coating with a diameter of about 1.5 mm, and the first IDT is located next to the contact tab of the gearbox holder, and the second IDT is located at an angle of 90 ° to it, the third IDT is opposite to the second, while the first and second IDTs are connected to the first and second, respectively amplifiers of the compensation circuit of the TDKCH, the outputs of which are connected to the inputs of the phase detector (PD), and the signal from the output of the PD goes to the input of the third amplifier, the output of which is connected to the first input of the voltage comparator, to the second input of which the MP output is connected PZTS, the output of the voltage comparator is connected to the input of the current amplifier, the output of which is connected to the first EMLD, the output of the multivibrator is connected to the second input, and the LD anode is connected to the output of the EMLD, the cathode of which is connected to the housing, while the oscillations from the first IDT, from the output of which they are fed to the input of the multivibrator and the second input of the MPTsTS, and the first input of the MPTsTS receives oscillations from the output of the GTMK, the input of which is fed selectively to the oscillations from the third IDT, moreover, the LD together with contact the petals holding the KP and the focusing lens are mounted on a metal plate that is held by metal rods passing through the dielectric insulators of the metal support ring, while the KP is double-frequency and is normal to the LD beam, and the focusing lens is fixed between the LD beam exit and the metallized coating on KP surface.

New in the invention is the design of the heater and the exciting device, combined in a laser diode, the implementation of a two-frequency quartz piezoelectric element without electrode coating. The above technical result is provided by the entire combination of essential technological and circuit features.

Drawings, which depict:

- figure 1 - design of the resonator (without internal connections) and the structural diagram of the generator;

- figure 2 is a view of the design of the lens quartz piezoelectric element - a laser diode (enlarged);

- figure 3 is a view A of the structure (without housing) from above for a lens quartz piezoelectric element with interdigital transducers.

The generator (Figs. 1-3) contains a vacuum case 1, in which a base 2 is fixed with an LD 3 placed on it with leads 9 and a horizontally mounted lens 10 in the path of the laser beam 11 mounted on a metal plate 4, and contact tabs 5, of which KP 6 is installed with IDT 7.1, 7.2, 7.3 applied to its surface. The base 2 is made in the form of a metal support ring with attachment points located in it in a vacuum housing 1. The attachment points of the support metal ring in the housing and the attachment points of the metal plate 4 on the support ring are made in the form of dielectric (for example, glass) insulators in which metal rods. The evacuated casing 1 is equipped with metallization of the inner surface 8. The terminals of IDT 7.3 are connected to GTMK 13, and the terminals of IDT 7.1, 7.2 are connected to amplifiers 14, 15 and RNG 16. The terminals of LD 3 are connected to the output of the EMLD 17 and the case. Phase detector 18. Amplifier of the output signal of the phase detector 19. Current amplifier 20. MPTsTS 21. Multivibrator 23. Voltage comparator 22. Metallized spot KP 12. Compensation circuit TDKCH 24, including amplifiers 14, 15, 19 and phase detector 18.

A laser-excited oscillator of a quartz resonator operates as follows. When applying voltage to the terminals 9 of the LD 3 using a beam focused by a lens 10 to a point on a metallized spot KP 12, shock excites volumetric ultrasonic vibrations KP 6 in two modes: stabilized and temperature. In this case, the generated surface waves arrive at the IDT, resonantly tuned to the frequencies of the stabilized (IDT 7.2 and 7.3) and temperature (IDT 7.1) modes of KP oscillations. With IDT 7.1, the fluctuations of the temperature mode are fed to the input of GTMK 13, from the output of which the vibrations are fed to the first input of MPCTS 21. From IDT 7.2, the oscillations of the stabilized mode are fed to the input of the RNG 16, from the output of which the vibrations are fed to the second input of MPCTS and the synchronization input of the multivibrator 23. From the output of the multivibrator 23, the pulsed oscillations of the resonant frequency are fed to the first input of the EMDL 17. Oscillations from the IDT 7.2 and 7.3 are fed to the circuit 24 and, accordingly, are fed to the inputs of the amplifiers 14 and 15 of the phase detector 18, at the output of which a voltage is generated proportional to the emerging TDKCH, fed to the input of the third amplifier 19, and, being amplified amplifier 19, from its output are fed to the first input of the voltage comparator 22. From the output of the MPCTS 21, the temperature stabilization voltage is supplied to the second input of the voltage comparator 22. From the output of the voltage comparator, the resulting the voltage goes to the input of the regulating current amplifier of the LD, the output of which the signal goes to the second input of the EMLD 17. Thus, the LD performs at the same time the function of the excitation element of the KP oscillations and its force vannogo heating by the directed beam of LD 11 to 12 metalized spot located on the surface of CP. Moreover, so as not to overheat the KP or evaporation of the metallization of the spot, an LD 20 current amplifier is included between the EMLD 17 and the voltage comparator 22, which limits the power of the luminous flux of the LD 11, especially during forced heating of the KP, at which the optimum heat pressure through the substrate 4 should be observed. fixed on the support ring 2 and the light flux of the LD 11 focused by the lens 10. The resulting TDKCH is compensated by means of IDTs 7.2 and 7.3 spatially spaced at an angle of 90 °, which makes it possible to obtain signals of stabilized vibrations quadrature, thereby compensating for the difference influx of heat to the CP via the locking tabs 5 and the metal rods. In fact, at the output of the voltage comparator 22, a total-differential signal of temperature compensation is formed both of the thermostabilization circuit and the regulation of the TDCC. Introduction to the stabilization circuit of the multivibrator 23 allows you to implement pulsed modulation of the spatial beam of the LD 11 by modulating EMLD 17, as well as the minimum dependence on changes in the voltage supplying the generator with the LCRS. The metallized coating 8 of the inner side of the Raman cylinder provides minimal heat dissipation into the external environment.

A special place is occupied by the MPCTS 21 generator with the LCRM, which today is a programmable microcontroller device that takes into account not only the temperature stabilization functions according to the set temperature frequency characteristics (CTX) of the generator as a whole, but also a number of its technological temperature characteristics of products and elements in serial production, providing a minimum time for the readiness of the generator with LCR for operation and maximum stability of its frequency.

Studies of the characteristics of quartz resonators with pulsed excitation by a monochromatic beam of a laser diode in order to obtain the characteristics of the possible future implementation of precision quartz oscillators with high long-term frequency stability and minimal noise were carried out in [4]. Particular attention was paid to the study of two-mode quartz resonators SC and IT sections, which have the best metrological characteristics of aging in comparison with the AT section, to create precision generators. The significant frequency distance of the temperature mode from the stabilized one in double-rotated sections of the CP allows one to simply provide separate generation of oscillations with a minimum relationship between the temperature and stabilized frequencies. The implementation of the working models of such generators allows the use of power sources up to 3.5 V and elements implemented at the nanotechnology level.

Literature

1. Dieulesaint E., Royer D., Rakouth H. Optical excitation of quartz resonators // Electronics Letters. 29 th, April, vol. 18. N-9, 1982. - pp. 381-382.

2. Dieulesaint E., Royer D., Bonniefoy C. Mechanical excitation of a membrane by an optical beam // Ultrasonics symposium, vol. 2. N.Y., 1981. - pp. 802-805.

3. Pat FR No. 2520566, 28 jaenuiar, 1982, H03H 3/02, H03H 3/04, G02F 2/00. / E. Dieulesaint, D. Royer, R. Guedj // Procede d * excitation resonateur piezoelectrique.

4. Ivanchenko Yu.S. Multi-frequency quartz stabilization. - Novorossiysk: Moscow State University named after Admiral F.F. Ushakov, 2007 .-- 506 p.

Claims (1)

A generator with laser excitation of a quartz resonator, containing a vacuum case of a quartz resonator, inside of which a quartz piezoelectric element (CP) is mounted with exciting electrodes deposited on it and a metallized spot in its central part, a laser, a laser beam modulator, a focusing lens, and fasteners for these devices, and also an amplifier of stabilized oscillations taken from the exciting electrodes and fed through the feedback circuit to the input of the laser beam modulator, characterized in that for To enhance the long-term and temperature stability of the frequency, reduce the dynamic temperature coefficient of frequency (TDKCH), a laser diode (LD), a temperature oscillation mode generator (GTMK), a temperature compensation TDDC circuit, a digital temperature stabilization microprocessor (MPTSTS), an electronic laser diode modulator ( EMLD), a voltage comparator, a current amplifier, a stabilized frequency signal generator (RNG), a multivibrator, and three IDTs are applied to the free surface of a quartz piezoelectric element, with reverse the torons of which in its central part a metallized coating is applied with a diameter of about 1.5 mm, the first IDT is located next to the contact lobe of the quartz piezoelectric element holder, and the second IDT is located at an angle of 90 ° to it, the third IDT is opposite to the second, while the first and the second IDT are connected respectively to the first and second amplifiers of the TDKCH compensation circuit, the outputs of which are connected to the inputs of the phase detector (PD), and the signal from the output of the PD goes to the input of the third amplifier, the output of which is connected to the first input of the voltage comparator, to the second input of which the MPCTS output is connected, the output of the voltage comparator is connected to the input of the current amplifier, the output of which is connected to the first input of the EMD, the second input of which is connected to the output of the multivibrator, and the LD anode is connected to the output of the EMLD, the cathode of which is connected to housing, while the input of the RNG receives selectively oscillations from the first IDT, from the output of which they are fed to the input of the multivibrator and the second input of the MPCTS, and the first input of the MPCTS receives oscillations from the output of the GTMK, to the input of oscillations from the third IDT are selectively applied, and the LD together with the contact petals holding the KP and the focusing lens are mounted on a metal plate that is held by metal rods passing through the dielectric insulators of the metal support ring, while the KP is double-frequency and is normal to the LD beam and the focusing lens is fixed between the exit of the LD beam and the metallized coating on the surface of the CP.

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