CN1162684C - Semiconductor side pumped solid laser gyroscope and its electrooptical modulation method - Google Patents

Abstract

The present invention discloses a semiconductor side-pumped solid laser gyroscope and an electro-optic modulation method thereof and relates to a structural design of the semiconductor side-pumped solid laser gyroscope. The semiconductor side-pumped solid laser gyroscope is mainly composed of a ring cavity reflecting mirror assembly, a gain medium, a pumping device, electro-optic crystals, a beam splitting plate, an optical delayer and a read-out circuit. The present invention is characterized in that the pumping device adopts side pumping which is composed of focusing coupling lenses, a semiconductor laser array and a temperature control device of semiconductor lasers. The present invention can favorably overcome the problem of thermal stress; meanwhile, a ring cavity is a triangle cavity without a negative area, and the structure of the triangle cavity is similar to a gas laser gyroscope so as to fully utilize the ready-made technologies. Electro-optic dithering adopts two electro-optic crystals with the same parameters and uses sine wave signals with a phase difference of 180 DEG for respective modulation so as to notably decrease a lock region of the gyroscope. The present invention has the advantages of small size, stable operation, long service life, etc.; the present invention can be widely used in inertial technologies, such as inertial navigation, inertial guidance, inertia measurement, etc.

Description

Semiconductor side pumped solid laser gyroscope and electrooptical modulation method thereof

Technical field

The invention belongs to semiconductor pumped Solid State Laser technology and sensor technical field, particularly a kind of structural design of semiconductor pumped solid-state laser gyro.

Background technology

Gyroscope is the core of inertial navigation and guidance technology as inertia measurement device.Closely during the last ten years, development along with photoelectric technology, optical gyroscope has become traditional mechanical gyro, the strong rival of electro-mechanical gyro, and laser gyro more obtains the widespread use of weapon equipment such as space flight, aviation, navigation and Ground Combat Vehicle with the many characteristics of himself.Laser gyro becomes one of important development direction.

Divide from principle, optical gyroscope can be divided into two big classes: mode of resonance and interfere type.The former representative is to be the laser gyro of core with the He-Ne gas ring laser, and it also is the navigation level optical gyroscope of present widespread use.The latter's representative is to be the optical fibre gyro (Zhang Yanshen etc. of core by the fibre optic interferometer that multi-ring fiber constitutes.Laser gyro technique report and collection of thesis, smart instrument system of Tsing-Hua University, in October, 1999).Although the gas laser gyroscope is that precision is the highest in the present optical gyroscope, but its intrinsic shortcoming is arranged: 1. the gain media of gas laser gyro is the He-Ne mixed gas, for guaranteeing the constant of its gas composition, concentration, need often change, inflate body, so very high to the sealing requirements in chamber; 2. gain for guaranteeing oscillating condition, must guarantee that gas gain has certain limit light path for mixed gas, and promptly the chamber is difficult to miniaturization, and gas discharge needs high pressure simultaneously; 3. the work optical maser wavelength of He-Ne gas laser gyro is lacked (633nm), therefore the coating process that constitutes its ring resonator catoptron is required very high, thereby its cost is increased greatly; 4. for eliminating intrinsic locking, the gas laser gyro has been introduced the optional feature that produces mechanical shaking, has not only increased the complicacy of gyrosystem, and the system that returns has simultaneously brought extra noise; 5. total efficiency is very low, less than＜0.01%.Owing to exist problems, thereby the gas laser precision of gyroscope is difficult to further raising.

Optical gyroscope exists latch-up phenomenon inevitably because transducing signal is a laser, promptly is lower than certain threshold value when the rotating speed of measurand, gyrostaticly is output as non-linear or no-output.The approach that reduces locking traditionally has 3 kinds: the one, to whole gyroscope add a fixing rotating speed (Raytheon Co., USA); The 2nd, to ring cavity add the shake of periodic vibration carry out offset frequency (Honeywell Co., USA); The 3rd, utilize magneto-optic effect.

Along with the development of Solid State Laser technology, diode pumped solid state laser (DPSSL) demonstrates the remarkable superiority than lamp pump solid state laser (LDSSL), and the DPSSL total efficiency is than LDSSL height, and is simple in structure, and laser output is stable.Monolithic integrated (monolithic) Solid State Laser development of technology particularly, narrow linewidth, high power laser light output, development such as Frequency Stabilization Technique have promoted Solid State Laser gyro Study on Technology.Compare with present other optical gyroscopes, semiconductor pumped Solid State Laser gyro has the following advantages: 1. be all solid state scheme, guaranteed the suitable long term storage of product, and suitable miniaturization, production cost is low, a little less than the temperature effect; 2. solid state gain medium is the rare earth metal crystalline material of application technology maturation, and its excitation wavelength long (1.064mm) makes that the requirement to the coating process of catoptron decreases, and can reduce the production cost of gyro so greatly; 3. the He-Ne gas laser gyroscope with present is the same, the Solid State Laser gyro of diode-end-pumped also belongs to the active resonant cavity laser gyro, therefore the advantage that had of traditional gas laser gyro also all is embodied in this class gyrosystem, thereby it will be a kind of high-precision lasergyro; 4. in diode-end-pumped solid-state laser gyro system, signals collecting and processing are to utilize two-way light to produce beat frequency after output terminal closes light, and therefore it and the sexual intercourse of system angle speed retention wire can reduce the difficulty of system signal detection technique greatly.Therefore, semiconductor pumped solid-state laser gyro has caused people's attention.(United States Patent such as Halldorsson in 1999, No.5,960,022) the semiconductor pumped solid-state laser gyro of 3DOF that proposes in, use a plurality of semiconductor lasers as pump light source, ring cavity is the rectangular cavity of monolithic glass, and gain media uses the crystal of 3 valency rare earth metals (to mix Nd ³⁺), laser work adopts the acousto-optic frequency shift technique to reduce and measures the lock district at continuous wave mode, and its advantage is to use the solid gain to replace gas gain, and the method that adopts method of optics to replace machinery reduces the lock district.Its shortcoming is to use the acousto-optic frequency shift technique to produce Doppler effect minimizing locking, complex structure.Document " Diels; Jean-Claude et al.Progress toward a compact solid stateactive laser gyroscope Proc.SPIE Vol.3616; proposed a kind of semiconductor pumped pulse mode-locked solid-state laser gyro p.136-142. ", as shown in Figure 4, the ultra-short pulse laser technology is applied to laser gyro technique, adopt semiconductor laser end pumping mode, use catoptron to constitute 8 font ring cavitys, and Multiple Quantum Well saturated absorbing body (MQW) is as the locked mode device.Because laser work is at pulse mode, through rational resonator design, the two-way light pulse of backpropagation in the chamber can not met on the optical element that constitutes resonator cavity, thereby lock district rather than method, magneto-optic effect or the acoustooptic effect of using gases lasergyro machinery have been eliminated in this expropriation of land.But owing to pulsed light produces backscattering inevitably on MQW the energy coupling takes place, this lasergyro is used square-wave modulation signal to carry out electrooptical modulation and is obtained the offset frequency effect, reduces locking.Shortcoming is owing to adopt the pumped at end face of semiconductor mode, thereby ring cavity is difficult to further miniaturization, and because the inevitable 8 font chambeies of adopting of end pumping, exist negative long-pending, gyrostatic calibration factor will reduce, and hold pump mode can cause the thermal stress inequality of crystal gain simultaneously, cause the gyroscope life-span to be reduced, and the more optical element of needs, complex structure.

Summary of the invention

Purpose of the present invention proposes a kind of semiconductor side pumped solid gyroscope and electrooptical modulation method thereof in order to overcome the weak point of above-mentioned optical gyroscope, makes its further simplified structure, overcomes thermal stress issues preferably, improves measuring accuracy, reduces the lock district.

The objective of the invention is to be achieved through the following technical solutions:

A kind of semiconductor side pumped solid laser gyroscope, mainly by the ring cavity reflector group, gain media, pump arrangement, electro-optic crystal and electrooptical modulating circuit thereof, beam-splitting board, optical time delay device and sensing circuit are formed, it is characterized in that: described ring cavity is that the electro-optic crystal of two equal parameters is positioned on the waist of isosceles triangle symmetrically by two curved mirrors and the isosceles triangle chamber that level crossing is formed; Described pump arrangement adopts profile pump, and profile pump is by focusing on coupled lens, and semiconductor laser array and semiconductor laser attemperating unit are formed.

Described semiconductor laser attemperating unit is made up of semiconductor chilling plate, heat radiator, thermistor, temperature control circuit.

Described level crossing and curved mirror adopt plating wavelength 1064nm reflectivity to be not less than the level crossing and the curved mirror of 99.9% high-reflecting film.

Described electro-optic crystal adopts the end face plating wavelength 1064nm reflectivity not to be higher than the lithium niobate electro-optic crystal of 0.2% high transmittance film.

Gain media is the vanadic acid yttrium (Nd:YVO4) of neodymium-doped 0.5%, geometric configuration is a lath, the plating of input and output end face is not higher than 0.1% high transmittance film to 1064nm wavelength reflectivity, away from the plating of the one side of post lens wavelength 1064nm reflectivity is not less than 98% high-reflecting film, the one side plating of adjacent post lens is not higher than 1% and wavelength 1064nm reflectivity is not less than 98% Double-color film to wavelength 808nm reflectivity.

Described focusing coupled lens adopt plating to wavelength 808nm reflectivity for not being higher than the post lens of 1% high transmittance film.

The present invention also provides a kind of electrooptical modulation method of described semiconductor side pumped solid laser gyroscope, and this method is utilized signal generator, driven lithium columbate crystal (LiNbO ₃) the electrooptical modulating circuit modulation electric luminescent crystal formed of power amplifier, produce the offset frequency effect, reduce the lock district, it is characterized in that: use the sinewave modulation signal of phase differential 180 degree to modulate the electro-optic crystal of two equal parameters that symmetry places respectively.

Advantage of the present invention is owing to adopt semiconductor laser array profile pump device, use semiconductor laser array and focal lens pumping crystal gain medium, gain media sensitive surface energy is more even, can overcome thermal stress issues preferably, ring cavity is a triangular chamber simultaneously, do not have negative long-pendingly, semiconductor laser array is installed in the inboard of ring cavity or is installed on position perpendicular to the plane, chamber, is convenient to realize gyrostatic miniaturization; Structure is similar with the gas laser gyroscope simultaneously, makes full use of the gyrostatic ready-made technology of gas laser; Adopt electro-optic crystal to carry out electrooptical modulation, play the similar effect of mechanical shaking, but chattering frequency can be far above mechanical shaking; For reducing loss electro-optic crystal end face plating high transmittance film; Modulation signal uses the sinewave modulation signal of phase differential 180 degree to modulate respectively, can reduce gyroscope lock district significantly; Sensing circuit adopts sub-circuit, can greatly improve the gyroscope survey precision.

Description of drawings

Fig. 1 is the semiconductor side pumped solid laser gyroscope structural representation that the present invention proposes.

Fig. 2 is a side pumping unit synoptic diagram of the present invention.

Fig. 3 is an electrooptical modulation structural representation of the present invention.

Fig. 4 is the semiconductor pumped pulse mode-locked solid-state laser gyro structural representation that Diels proposes.

Embodiment

Describe concrete structure of the present invention, principle of work and embodiment in detail below in conjunction with accompanying drawing:

Fig. 1 is the semiconductor side pumped solid laser gyroscope example structure synoptic diagram that the present invention proposes, it is mainly by reflector group 1,6,8, gain media 2 focuses on coupled lens 3, semiconductor laser array 4, semiconductor laser attemperating unit 5, electro- optic crystal 7,13, beam-splitting board 9, sensing circuit 10, optical time delay device 11, modulation circuit 12 and piezoelectric ceramics (PZT) 14 formed.Semiconductor laser 4 is as pump light source, through focusing on coupled lens 3 coupling back pumping gain medias 2; Reflector group 1,6,8 looping resonator cavitys; Electro- optic crystal 7,13 is used for electrooptical modulation, produces the offset frequency effect; Bi-directional light 15,17 is via catoptron 8 output, produces beat frequency after optical time delay device 11 and beam-splitting board 9 close light, and sensing circuit 10 is read beat signal, can record with resonator cavity and connect firmly together measurand with respect to the rotating speed of inertial space.Described ring cavity is the isosceles triangle chamber of being made up of 1,6 and level crossings 8 of two curved mirrors, and the electro- optic crystal 7,13 of two equal parameters is positioned on the waist of isosceles triangle symmetrically.

Fig. 2 is a side pumping unit synoptic diagram of the present invention.The present invention adopts profile pump (side-pumped) mode, form the side pumping unit by focusing on coupled lens 3, semiconductor laser array 4 and semiconductor laser attemperating unit 5: semiconductor chilling plate 21 is contained on the heat radiator 18, use heat conductive silica gel that semiconductor chilling plate 21 is attached on the semiconductor laser array 4 and dispel the heat, measure the temperature of semiconductor laser array at the inner placement of semiconductor laser array 4 substrates thermistor 19; Thermistor 19 feedback temperature are to temperature control circuit 20.Temperature control circuit 20 drives semiconductor chilling plate 21, thereby makes semiconductor laser array 4 work under steady temperature, has prevented the drift of pumping wavelength.

Fig. 3 is an electrooptical modulation structural representation of the present invention, is made up of electrooptical modulating circuit and electro-optic crystal.When electro-optic crystal did not have external voltage, refractive index was n.On the waist of triangular chamber, place the electro- optic crystal 7,13 of two equal parameters symmetrically, on crystal 7,13, add earlier a constant u ₀, refractive index becomes n ₀The voltage modulated voltage signal uses triangular wave or zigzag wave u (t), also is added on the electrooptical modulation crystal 7,13, and wherein electrooptical modulation crystal 7 is to be-u (t) on u (t), the electrooptical modulation crystal 13, is the opposite modulation voltage of phase place.When light beam 15 arrived electro-optic crystal 7, modulation voltage was added on the electro-optic crystal 7, because electrooptical effect, the refractive index of electro-optic crystal will change, and become n ₀+ Δ n, wherein

$\mathrm{\Δn}=(-\frac{1}{2}{n}_0\·r_{13})u\left(t\right)------\left(1\right)$

The light path of the light beam 15 l Δ n that also will change, light beam 15 parts are through level crossings 8 outputs, a part continues to advance, through electro-optic crystal 13 since the time compole short, the modulation voltage on this moment electro-optic crystal 13 is-u (t). the refractive index of electro-optic crystal is n ₀-Δ n, light beam 15 change in optical path length amount-l Δ n has been got back to initial phase; Similarly, light beam 17 also takes place similarly to change, and different is that light beam 17 is-l Δ n through level crossing 8 output back light path change amounts, and light beam 15 light path change amounts are l Δ n, and being equivalent to ring cavity has an initial speed Ω ₀For

${\mathrm{\&Omega;}}_0\left(t\right)=\frac{n_0\&CenterDot;l\&CenterDot;{\mathrm{<figure-callout\; id="13"\; label="r"\; filenames="C0211667700081.png"\; state="\{\{state\}\}">r</figure-callout>}}_{13}}{2c}u\left(t\right)------\left(2\right)$

Wherein: l is a crystal thickness; r ₁₃Be electrooptical coefficient; C is the light velocity in the vacuum.

Thereby produce the electric light flutter effect.For reducing loss, the plating of electro-optic crystal end face is not higher than the lithium niobate of 0.2% high transmittance film to wavelength 1064nm reflectivity.

The semiconductor pumped pulse mode-locked solid-state laser gyro structural representation that Fig. 4 proposes for Diels, by semiconductor laser, collimation lens, shaping prism, curved mirror, gain crystal, ring cavity level crossing, lens, saturated absorbing body, electrooptical modulation crystal.Adopt 8 font chambeies, use Multiple Quantum Well (MQW), be used to produce mode locking pulse laser as saturated absorbing body.Semiconductor laser is that excitation wavelength is the GaAlAs/GaAs laser instrument of 808nm, and crystal has been selected Nd:YVO for use ₄, electro-optical efficiency is greater than 50%.Because the backscattering of MQW causes locking,, adopt electro-optic crystal LiNbO in order to reduce locking ₃Modulate, produce offset frequency.Bi-directional light is exported from catoptron, and one road light closes light again through the light path time-delay.

This side pump gyroscope principle of work is as follows: as shown in Figure 1, and the pump light λ that sends by semiconductor laser array 4 ₁=808nm, through focusing on coupled lens (adopt plating to wavelength 808nm reflectivity for not being higher than the post lens of 1% high transmittance film), collimation focuses on the vanadic acid yttrium (Nd:YVO4) of crystal gain 2[neodymium-doped 0.5%], geometric configuration is a lath, the plating of input and output end face is not higher than 0.1% high transmittance film to 1064nm wavelength reflectivity, away from the plating of the one side of post lens wavelength 1064nm reflectivity is not less than 98% high-reflecting film, the one side plating of adjacent post lens to wavelength 808nm reflectivity be not higher than 1% and wavelength 1064nm reflectivity is not less than 98% Double-color film); Crystal gain absorbs λ ₁, send the fluorescence of serial wavelength; The ring cavity that catoptron 1,6,12 forms constitutes travelling-wave cavity, because mode competition resonant cavity modeling, wavelength is that the light wave of 1.06 μ m will form bi-directional oscillating in the chamber; Through output reflector 8 outputs; Bi-directional light is through beam-splitting board 9, and optical time delay device 11 produces resonance on sensing circuit 10, can obtain the beat signal of two-way lightwave, along direction 16 mobile optical chronotrons 11, can regulate the phase differential of two-way lightwave; Electrooptical modulation crystal 7,13 is used to produce the electric light shake, reduces gyrostatic latch up effect.

Embodiment: the structural representation of this system as shown in Figure 1.The detailed description step is as follows: used semiconductor laser array 4 is GaAlAs/GaAs double heterojunection laser array 6W, and peak wavelength is 810 ± 5nm, is fixed on the semiconductor cooler, and uses the temperature control system temperature control.The crystal that gain media 2 adopts absorbing wavelength and semiconductor laser peak wavelength to be complementary, we select very ripe Nd:YVO for use ₄, do not select Nd:YAG for use.Nd:YVO ₄The doping content ≈ 0.5% of crystal, geometric configuration is a lath, size 10 * 5 * 5mm, input and output end face (i.e. the face of 25 * 5mm) plating is not higher than 0.1% high transmittance film to 1064nm wavelength reflectivity, away from the plating of the one side of post lens wavelength 1064nm reflectivity is not less than 98% high-reflecting film, the plating of the one side of adjacent post lens is not higher than 1% and wavelength 1064nm reflectivity is not less than 98% Double-color film to wavelength 808nm reflectivity, crystal is inserted in the copper billet with indium foil parcel (to reach good thermo-contact), and this copper billet cools off and controllable temperature with semiconductor cooler.Cylindrical mirror is focal length 500um, length 13mm.Ring cavity is by two curved mirrors and the isosceles triangle chamber that level crossing is formed, waist is long to be 150mm, the base is 200mm, catoptron 1,6 for diameter 20mm, radius-of-curvature 200mm, be coated with the curved mirror of R＞99.9%@1064nm (24 ° of incident angles) film system, level crossing 8 is diameter 20mm, is coated with R＞99.9%@1064nm (42 ° of incident angles) film system, forms ring cavity.11 platings of optical time delay device are used for optical time delay and close light the high anti-film of wavelength 1.06 μ m system.Beam-splitting board 9 plating λ=1.06 μ m, T=50% also is used to close light.Sensing circuit 10 is used for read output signal.The used electro-optic crystal of electrooptical modulation is the electro-optic crystal of two equal parameters, adopt the end face plating wavelength 1064nm reflectivity not to be higher than the lithium niobate electro-optic crystal of 0.2% high transmittance film, physical dimension 3 * 3 * 5mm (with length 5mm on the y optical axis that row ripple traffic direction overlaps) is positioned on the waist of isosceles triangle symmetrically.This system can Measuring Object with respect to the rotating speed of inertial space, and can reduce the lock district significantly.

Claims (7)

1. semiconductor side pumped solid laser gyroscope, mainly by the ring cavity reflector group, gain media, pump arrangement, electro-optic crystal and electrooptical modulating circuit thereof, beam-splitting board, optical time delay device and sensing circuit are formed, it is characterized in that: described ring cavity is that the electro-optic crystal of two equal parameters is positioned on the waist of isosceles triangle symmetrically by two curved mirrors and the isosceles triangle chamber that level crossing is formed; Described pump arrangement adopts profile pump, and profile pump is by focusing on coupled lens, and semiconductor laser array and semiconductor laser attemperating unit are formed.

2. semiconductor side pumped solid laser gyroscope according to claim 1 is characterized in that: described semiconductor laser attemperating unit is made up of semiconductor chilling plate, heat radiator, thermistor, temperature control circuit.

3. semiconductor side pumped solid laser gyroscope according to claim 1 is characterized in that: described level crossing and curved mirror adopt plating wavelength 1064nm reflectivity to be not less than the level crossing and the curved mirror of 99.9% high-reflecting film.

4. according to claim 1, the described semiconductor side pumped solid laser gyroscope of 2 or 3 arbitrary claims, it is characterized in that: described electro-optic crystal adopts the end face plating wavelength 1064nm reflectivity not to be higher than the lithium niobate electro-optic crystal of 0.2% high transmittance film.

5. according to the semiconductor side pumped solid laser gyroscope of right 4, it is characterized in that gain media is the vanadic acid yttrium (Nd: YVO4) of neodymium-doped 0.5%, geometric configuration is a lath, the plating of input and output end face is not higher than 0.1 high transmittance film to 1064nm wavelength reflectivity, away from the plating of the one side of post lens wavelength 1064nm reflectivity is not less than 98% high-reflecting film, the one side plating of adjacent post lens is not higher than 1% and wavelength 1064nm reflectivity is not less than 98% Double-color film to wavelength 808nm reflectivity.

6. semiconductor side pumped solid laser gyroscope according to claim 1 is characterized in that: described focusing coupled lens adopt plating to wavelength 808nm reflectivity for not being higher than the post lens of 1% high transmittance film.

7. electrooptical modulation method that adopts semiconductor side pumped solid laser gyroscope as claimed in claim 1 is by signal generator, drive lithium columbate crystal (LiNbO ₃) the electrooptical modulating circuit modulation electric luminescent crystal formed of power amplifier, produce the offset frequency effect, reduce the lock district, it is characterized in that: use the sinewave modulation signal of phase differential 180 degree to modulate the electro-optic crystal of two equal parameters that symmetry places respectively.

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