CN102967734B - Preparation method of barium metaborate crystal electric field sensor based on angular optical biasing - Google Patents

Abstract

The invention relates to a preparation method of a barium metaborate crystal electric field sensor based on an angular optical biasing, which belongs to the technical field of measurement of a high-voltage field. According to the method, a barium metaborate crystal is used as the sensing material of the electric field sensor, and in the fixed shaft cutting process of the crystal, the optical axis c of the crystal is controlled to form a smaller angle with the normal direction of a light transmission face. The angle is determined according to the wavelength of a laser source, the refractive index of the barium metaborate crystal under the wavelength and the length of the light transmission direction of the crystal. Linear sensing of the electric field is realized by means of static light wave phase biasing generated by natural birefringence of a paraxial beam of the barium metaborate crystal. The electric field sensor prepared by the method can measure the amplitude of the electric field intensity and can further measure information of the electric field such as frequency and phase, so that the sensor is a time domain measurement electric field sensor and has the advantages of higher measuring sensitivity, quick response speed, wide measuring range and frequency range, simpler structure, good stability and small interference to the electric field to be measured.

Description

The preparation method of the BBO Crystal electric-field sensor based on angular optical biasing

Technical field

The present invention relates to a kind of preparation method of the BBO Crystal electric-field sensor based on angular optical biasing, belong to High Voltage electric field measurement technical field.

Background technology

The eighties in 20th century, along with the development of optical technology, optical electric field sensor becomes study hotspot gradually.Optical electric field sensor based on electrooptical effect can be divided into integrated optics type and body material type.Wherein body material type electric-field sensor, based on discrete device, utilizes quarter wave plate that quiescent point is set, and utilizes monoblock electro-optic crystal to realize electric field sensing.Along with the progress of micro-processing technology, such sensor has the advantages such as full dielectric substance, has important Research Significance and practical value.

The performance of body material type electric-field sensor depends on the selection of electro-optic crystal to a great extent.Lithium niobate, lithium tantalate (LiTaO were mainly adopted in the past ₃), bismuth germanium oxide (Bi ₄ge ₃o ₁₂) crystal is as electrooptical material, also adopted in early days bismuth silicate (Bi ₁₂siO ₂₀) crystal.Because bismuth silicate also exists the multiple effects such as photorefractive effect, optical activity and Faraday rotation except electrooptical effect, eliminated gradually in actual applications.Lithium columbate crystal electrooptical coefficient is large, transmittance is high, optical homogeneity is good, and quality is hard, not deliquescence, easily growth and processing, within a very long time, be all considered to relatively be suitable as the sensing material of electric-field sensor, but lithium columbate crystal refractive index under high light and ultraviolet ray irradiation becomes inhomogeneous, is prone to damage, and refractive index varies with temperature greatly, has pyroelectric effect.Lithium tantalate exists and the similar shortcoming of lithium niobate.Bismuth-germanium-oxide crystal is a kind of artificial lens growing out from melt, in theory without natural birefringence, optical activity and pyroelectric effect, in 800 ~ 1500nm wavelength coverage, there is good temperature stability, but it is uncertain under bismuth-germanium-oxide crystal DC Electric Field in any direction, to respond to main shaft, there is inconvenience in the electric-field sensor using bismuth-germanium-oxide crystal as sensing material, the general material using bismuth-germanium-oxide crystal as voltage sensor in the time of measurement space electric field.

On the other hand, traditional body material type electric-field sensor utilizes quarter wave plate to produce the static phase biasing of pi/2, realize the linear sensing of electric field, expand linear measurement range, improve sensitivity, but the actual phase retardation of quarter wave plate is subject to the impact of the factors such as environment temperature, machining precision and extra-stress, and its fast and slow axis also can produce mismatch deviation, the accuracy that reduction is measured in the process of aiming at electro-optic crystal.In the research of former optical voltage sensor, propose to utilize the natural birefringence of lithium columbate crystal paraxial beam to produce the static phase biasing of pi/2, but it adopt crystal x ₁direction pressurization, x ₃the mode of the logical light of direction, under such sensing mode, the main shaft of crystal can rotate, and need produce paraxial beam by rotating crystal, has larger inconvenience in operation, has increased the complicacy of sensor, and has reduced the stability of sensor.

From two aspects above, in the urgent need to seeking a kind of electro-optic crystal, optical activity, thermo-optic effect, pyroelectric effect etc. are as far as possible little, and electrooptical coefficient is large, good in optical property, and physicochemical property are stable, are easy to processing etc.In addition, need to manage to eliminate the adverse effect of quarter wave plate.

Summary of the invention

The object of the invention is to propose a kind of BBO Crystal (β-BaB based on angular optical biasing ₂o ₄, hereinafter to be referred as BBO) and the preparation method of electric-field sensor, utilize the electrooptical effect of bbo crystal to realize electric field sensing, and produce static phase biasing by the natural birefringence of bbo crystal paraxial beam, realize the linear sensing of electric field.

The preparation method of the BBO Crystal electric-field sensor based on angular optical biasing that the present invention proposes, comprises the following steps:

(1) adopt molten-salt growth to obtain BBO Crystal;

(2) BBO Crystal is carried out to dead axle cutting, makes the c optical axis direction of crystal and the optical direction of crystal into θ angle:

Wherein, the lasing light emitter wavelength that λ is free space, for the phase delay being produced by uniaxial crystal natural birefringence, n _ofor the ordinary refraction index of BBO Crystal, n _o=1.6680, n _efor the abnormal optical index of BBO Crystal, n _e=1.5310, l is the length of crystal on crystal optical direction;

(3) cut the bonding polarizer of sharp light incident side of the BBO Crystal obtaining at step (2) dead axle, the bonding analyzer of laser emitting end.

The preparation method of the BBO Crystal electric-field sensor based on angular optical biasing that the present invention proposes, has the following advantages:

1, the electric-field sensor that utilizes the inventive method to prepare, not only can measure the amplitude of electric field intensity, can also measure the information such as frequency, phase place of electric field, is a kind of electric-field sensor of time domain measurement.

2, the electric-field sensor that prepared by the inventive method, adopts bbo crystal as sensing material, has the advantages such as highly sensitive, fast response time, bandwidth, good stability.

3, the electric-field sensor that prepared by the inventive method, adopts the natural birefringence of electro-optic crystal itself to produce static phase biasing, has removed quarter wave plate and the adverse effect thereof in traditional structure, has simplified transducing head structure, has improved temperature stability.

4, the electric-field sensor that prepared by the inventive method, for full dielectric, without hardware, very little to the interference of electric field to be measured, and sensor electrical luminescent crystal is small-sized, and the spatial resolution of sensor is high.

Brief description of the drawings

Fig. 1 is the structural representation of the electric-field sensor prepared of the inventive method.

Fig. 2 is the sensing principle schematic diagram of electric-field sensor sensing of the present invention.

Fig. 3 is the schematic diagram of the electric field measurement system of application electric-field sensor composition of the present invention.

In Fig. 1-Fig. 3, x ₃(c) be the c optical axis direction of crystal, x ' ₁and x ₂be respectively Width and the short transverse of crystal, x ₁with x ' ₁, x ₃(c) in same plane, and respectively with x ₂, x ₃(c) vertical, the 1st, bbo crystal, the 2nd, the polarizer, the 3rd, analyzer, the 4th, direction of beam propagation, the 5th, rise folk prescription to, the 6th, analyzing direction, the 7th, extra electric field, with the short transverse x of crystal ₂parallel, the 8th, lasing light emitter, the 9th, polarization maintaining optical fibre, the 10th, electric field sensing head, the 11st, single-mode fiber, the 12nd, photoelectric commutator, the 13rd, radio-frequency cable, the 14th, electrical signal detection device.

Embodiment

The preparation method of the BBO Crystal electric-field sensor based on angular optical biasing that the present invention proposes, as shown in Figure 1, preparation method comprises the following steps the structure of the electric-field sensor of preparation:

(1) adopt molten-salt growth to obtain BBO Crystal 1;

(2) BBO Crystal is carried out to dead axle cutting, making the c optical axis direction of crystal (is the x in Fig. 1 ₃direction) with the optical direction of crystal be that direction of beam propagation 4 in Fig. 1 is into θ angle:

Wherein, the lasing light emitter wavelength that λ is free space, for the phase delay being produced by uniaxial crystal natural birefringence, n _ofor the ordinary refraction index of BBO Crystal, n _o=1.6680, n _efor the abnormal optical index of BBO Crystal, n _e=1.5310, l is the length of crystal on crystal optical direction;

(3) cut the bonding polarizer 2 of sharp light incident side of the BBO Crystal obtaining at step (2) dead axle, the bonding analyzer 3 of laser emitting end.

Bbo crystal is a kind of uniaxial negative crystal, belongs to trigonal system 3m point group, and its optical homogeneity is good, and (189nm ~ 3500nm) is wide for transparency range, electrooptical coefficient (γ ₂₂=2.7pm/V) larger, optic damage threshold value is high, is usually used in the electro-optical Q-switch in the supper-fast laser system of high power.The shortcoming of bbo crystal is to have certain hygroscopy, and this shortcoming can suppress by the method for end face coating.So bbo crystal is the comparatively ideal electrooptical material of body material type electric-field sensor.

As shown in Figure 1, choose bbo crystal x ₂direction inductor electric field, x ₃direction is optical direction, and such benefit is when bbo crystal is at x ₂the extra electric field E of direction ₂under effect, the main shaft of index ellipsoid is substantially constant, and three new principal refractive indexs of direction are:

$\left\{\begin{array}{c}{n}_1^{\′}=n_o+\frac{1}{2}{n}_o^3{\mathrm{\γ}}_{22}{E}_2\\ n_2^{\′}\≈n_o-\frac{1}{2}{n}_o^3{\mathrm{\γ}}_{22}{E}_2\\ n_3^{\′}\≈n_e\end{array}\right.---\left(1\right)$

Wherein, n _oand n _ebe respectively ordinary refraction index and the abnormal optical index of bbo crystal.

If bbo crystal x ₂the length of direction is d, logical light x ₃the length of direction is l, propagates light beam along crystal x ₁and x ₂the phase differential that two eigenmodes of direction produce through Electric Field Modulated is

When bbo crystal incident end and exit end arrange respectively the polarizer and analyzer, and polarization direction be respectively ± 45 °, analyzer output intensity I _owith incident intensity I after the polarizer _iratio be:

If there is static phase biasing can realize the linear sensing of electric field

For this reason, consider to utilize the natural birefringence of bbo crystal paraxial beam to produce static phase biasing the i.e. method based on angular optical biasing.As shown in Figure 2, by bbo crystal 1 around its x ₂axle turns over a small angle theta, makes the c optical axis (x of direction of beam propagation and crystal ₃direction) angled θ.The phase delay now being produced by uniaxial crystal natural birefringence for

Otherwise, produce phase bias, the angle theta of propagating light beam and crystal c optical axis is

In formula, the optical wavelength that λ is free space.By by the c optical axis degree into θ angle of direction of beam propagation and bbo crystal, can produce static phase biasing to realize the linear sensing of electric field.The size of crystal can be chosen according to the scope of electric field intensity to be measured.

In an embodiment of the inventive method, the dimensional parameters of the bbo crystal of use is 3mm × 3mm × 20mm, i.e. length l=20mm on crystal optical direction; Lasing light emitter wavelength X=the 1550nm using, the n of bbo crystal _o=1.6680, n _e=1.5310, so can calculate θ=0.64 °.

Sensor access lasing light emitter 8, polarization maintaining optical fibre 9, single-mode fiber 11, photoelectric commutator 12, radio-frequency cable 13 and electrical signal detection device 14 prepared by the inventive method, form an electric field measurement system as shown in Figure 3, become the BBO Crystal electric-field sensor based on angular optical biasing.

When the electric-field sensor based on angular optical biasing that uses the present invention to propose carries out electric field measurement, the light beam that lasing light emitter 8 produces is transferred to sensing head 10 through polarization maintaining optical fibre 9, first be the polarizer of+45 ° through polarization direction, then incide BBO electro-optic crystal and carry out Electric Field Modulated generation phase delay after it, through analyzer analyzing, light intensity signal utilizes single-mode fiber 11 to be transferred to photoelectric commutator 12 to carry out after opto-electronic conversion, can be by electrical signal detection device 14(as oscillograph) show output waveform.? under less condition, the output power of output terminal is directly proportional to extra electric field.Therefore, measure the luminous power of output terminal, just can obtain electric field to be measured.Analyzer also can replace with polarization beam apparatus, thereby obtains the output of two-way complementation, can eliminate the impact of luminous power fluctuation after being normalized, and improves the accuracy of measurement result.

Claims (1)

1. a preparation method for the BBO Crystal electric-field sensor based on angular optical biasing, is characterized in that the method comprises the following steps:

(1) adopt molten-salt growth to obtain BBO Crystal;

(2) BBO Crystal is carried out to dead axle cutting, makes the c optical axis direction of crystal and the optical direction of crystal into θ angle:

Wherein, the lasing light emitter wavelength that λ is free space, for the phase delay being produced by uniaxial crystal natural birefringence, n _ofor the ordinary refraction index of BBO Crystal, n _o=1.6680, n _efor the abnormal optical index of BBO Crystal, n _e=1.5310, l is the length of crystal on crystal optical direction;

(3) cut the bonding polarizer of sharp light incident side of the BBO Crystal obtaining at step (2) dead axle, the bonding analyzer of laser emitting end.