CN110907136B - A temperature-controllable electro-optical amplitude modulator and test method - Google Patents

Abstract

The invention belongs to the technical field of laser modulation, and in particular relates to a temperature-controllable electro-optical amplitude modulator and a testing method. The purpose of the present invention is to improve the linear modulation performance of electro-optical amplitude modulation and reduce the influence of external temperature changes on the performance of the modulator. The present invention includes a No. 1 base on which an insulating gasket is arranged, and the edge pad The sheet is a cuboid structure, and a No. 2 base is arranged on the insulating gasket, and one side of the No. 2 base is fitted with one side of the insulating gasket, and the remaining three sides are left with a gap. The present invention adopts the combination of the device and the test method. The linear working area and signal amplitude of the amplitude modulator are optimized, the linear modulation performance of the amplitude modulation is improved, a better amplitude modulation signal is obtained, and the implementation effect of the modulator is enhanced.

Description

A temperature-controllable electro-optical amplitude modulator and test method

technical field

The invention belongs to the technical field of laser modulation, and in particular relates to a temperature-controllable electro-optical amplitude modulator and a testing method.

Background technique

Electro-optical modulator is a key device for high-speed optical communication. It can modulate the amplitude or phase of the light wave emitted by the laser, so that the input signal is applied to the optical carrier for transmission. The optical modulator can not only change the intensity of the light wave, but also modulate the intensity of the light wave. polarization state. The requirements of the optical fiber communication system for modulation are: (1) high modulation rate and wide modulation bandwidth; (2) low driving voltage; (3) high extinction ratio; (4) low insertion loss. Lithium niobate (LINBO3) crystal, as an excellent lateral electro-optic modulation material, has the advantages of low driving voltage, small insertion loss, wide spectral working range, high extinction ratio and easy mass production. Electro-optic switches and other fields have been widely used.

The existing electro-optical amplitude modulators on the market do not have temperature control facilities. The main reason is that the temperature control settings take up a lot of space, and the cost-intensive products are not effective. In order to facilitate mass production, the exposed crystals are directly added with electrodes. However, in the actual experiment, the temperature fluctuation has a great influence on the electro-optical amplitude modulation, resulting in the instability of the amplitude modulation signal or the introduction of the phase modulator signal, etc., so the amplitude modulation of the optical field signal will introduce additional useless signals, affecting normal use, Especially for the application of quantum communication and quantum state transmission in quantum optics, additional noise will be directly introduced and the transmitted quantum information cannot be effectively extracted. Therefore, the setting of temperature control is very necessary.

Ideally, the light propagates along the optical axis of the lithium niobate crystal, and the influence of natural birefringence is not considered in the theoretical analysis. There is an error between theory and practice. The analysis of the lateral electro-optical effect of lithium niobate crystals in paraxial and non-paraxial conditions has guiding significance for improving its electro-optical properties by adjusting the angle. At the same time, the electro-optic properties of crystals under paraxial and non-paraxial conditions are very important for new electro-optic devices that need to use the birefringence effect of the crystal for beam splitting or beam combination, and also need to use its electro-optic effect to generate additional phase shifts. . The present invention provides a temperature-controlled electro-optical amplitude modulator, wherein the temperature of the crystal is controllable, and the amplitude modulation can be realized by a simple device.

SUMMARY OF THE INVENTION

The purpose of the present invention is to improve the linear modulation performance of electro-optical amplitude modulation, and to reduce the influence of external temperature changes on the performance of the modulator. As shown in Figure 12, through the analysis of the change of the main axis of the crystal refractive index by applying voltage to different crystal main axes, the lithium niobate crystal with strong modulation performance and convenient and economical is selected as the modulation crystal. There is no natural birefringence effect when an electric field is applied to the Y axis (natural birefringence is the change in the refractive index of the crystal only before the electric field is applied, that is, when no external electric field is applied, the two polarized components o light and e light passing through the crystal There is a phase difference between them), but after the electric field is applied, both the X and Y axes will become biaxial crystals, but the voltage applied to the X axis has two cross terms according to the formula, so it will undergo two coordinate transformations, One is a 45° rotation around the Z axis, and then the transformation is the same as the Y axis. In the actual design of the electro-optical amplitude modulator, lithium niobate crystal is used, voltage is applied to the X axis, the Z axis is light, and there is no natural birefringence, but the X and Z axes will rotate a small angle around the Y axis, that is, In one direction of X', Y', the amplitude will be projected, but the Y-axis will not rotate, so this projection difference can be eliminated by using two crystals side by side and 90° in series with each other. Since the light is passed on the Z axis and voltage is applied to the other axes, the lithium niobate crystal has no natural birefringence. After the coordinate transformation, it is found that when the voltage is applied in the X axis direction of the crystal main axis and the light propagates along the Z axis, the refractive index main axis of the crystal changes. To meet the linear requirement of amplitude modulation, theoretical studies have found that when a voltage is applied in the X-axis direction, the main axis of the crystal refractive index ellipsoid will undergo two transformations, but the transformation useful for amplitude modulation is only the coordinate transformation around the Z-axis of the optical axis, while Although the transformation angle around the Y-axis is small, it is still one of the important factors affecting the amplitude modulation. Therefore, in this invention, the optical axes of two lithium niobate crystals with the same size and performance are arranged in series at 90°. It is used to compensate the amplitude projection along the Y-axis after the crystal is applied with voltage; in the temperature control design part, first use an insulating and thermally conductive material to wrap the crystal, and then wrap the designed insulating copper furnace on the periphery of the material. Material, insert a thermistor on the insulating copper furnace in the middle of the block crystal, and insert the thermistor to monitor the temperature change of the crystal with a temperature controller. The upper and lower cross sections of the insulating copper furnace are all attached for feedback control. Temperature semiconductor cooler (TEC), and the device is designed to fix electro-optic crystal with temperature control device.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A temperature-controllable electro-optical amplitude modulator, comprising a No. 1 base, an insulating gasket is arranged on the No. 1 base, the edge gasket is a cuboid structure, and a No. 2 base is arranged on the insulating gasket , and make one side of the No. 2 base fit with one side of the insulating gasket, and leave a gap on the other three sides, and a plurality of No. 1 semiconductor refrigerators are arranged side by side on the No. 2 base. The refrigerator is provided with a heat-insulating copper furnace, a plurality of No. 2 semiconductor refrigerators are arranged side by side on the heat-preserving copper furnace, and a No. 1 heat-insulating layer and a No. 2 heat-insulating layer are respectively fixed on the front and rear surfaces of the heat-preserving copper furnace. , a No. 3 thermal insulation layer is fixed on the left and right end faces of the heat insulating copper furnace, a plurality of joint holes are arranged on the upper end face of the outer casing, and a plurality of through holes are symmetrically arranged on the left and right end faces of the outer casing. The light hole is provided with an outer casing on the insulating gasket, and the edge of the outer casing is closely attached to the edge of the insulating gasket, and the outer casing is set on the outside of the No. 2 base, and the No. 1 base and the second The insulating spacer placed between the bases is mainly used to place the electric heat exchange between the platform and the second base; the gaps left on the three sides of the insulating spacer are used to place the outer casing, making it a perfect one between the second base and the second base. Cuboid box; by arranging multiple No. 1 semiconductor refrigerators closely side by side on the No. 2 base, one side of the side-by-side is in close contact with the No. 2 base, and the other side is completely glued to the copper furnace, these multiple The No. 1 semiconductor refrigerator connected in series not only completely covers one side of the copper furnace to prevent heat loss, but also can control the temperature of the copper furnace through its own cold and heat regulation capability, and the No. 2 semiconductor refrigerator on the opposite side has the same function; No. 1 The thermal insulation layer is provided with countersunk holes and fixed on the copper furnace with plastic screws, and one of the surfaces is completely covered and placed for heat conduction; the thermal insulation layer No. 2 is similar to the thermal insulation layer No. 1, the only difference is that one is opened for crystals. The hole for the wire between the electrodes and a hole for the thermistor wire are exactly the same as the multiple outlet holes on the sidewall of the copper furnace; It is fixed on the copper furnace to prevent heat conduction, and there is a hole in the middle that is exactly the same as the light-through hole of the outer casing; ---Through this design, the six sides outside the copper furnace are fully covered (two of which are used for semiconductor body refrigeration. The other four surfaces are covered with a thermal insulation layer to prevent heat conduction with the outside, which can achieve better temperature control.

Further, the No. 2 base includes a fixed seat and a baffle, the fixed seat and the baffle are integrally formed into an L shape, a No. 1 protruding rib is arranged in the middle of the fixed seat, and a No. There is a No. 1 heat-conducting inclined surface between them, and the No. 1 heat-conducting inclined surface is inclined downward from the baffle to the No. 1 protruding rib. A platform is provided at the front end of the No. 1 protruding rib. There are No. 2 ridges and No. 2 heat conduction slopes, and the No. 2 heat conduction slopes and No. 2 semiconductor refrigerators are closely attached. On the inclined surface, it is not only convenient to place the polarizer, because only considering the light modulation in the horizontal direction and the vertical direction, the surface of the copper furnace will not be in contact with the outer casing at all, avoiding heat exchange between the two and saving space. .

Still further, the heat-retaining copper furnace includes a copper furnace body and a copper furnace cover, the copper furnace cover is fixedly arranged on the copper furnace body, and the copper furnace body is a groove-shaped structure with openings at the left and right ends. The inner wall and bottom of the groove of the main body are provided with protrusions, the front end surface of the copper furnace body is provided with a wire outlet hole and a thermistor installation hole, and a thermistor is arranged in the thermistor installation hole, and is insulated with heat insulation. The material seals the thermistor mounting hole, which is used to collect the temperature of the thermal insulation copper furnace.

The copper furnace body and the cover can be separated mainly for the convenience of installing crystals and arranging the electrode wires of the crystals. The protrusions on the inner wall and bottom of the groove of the copper furnace body are used to paste the crystals (the position of the protrusions is different because the two The X and Y axes of the crystal are anti-parallel), the outlet hole of the copper furnace body is opened in the middle of the side wall mainly to lead out the wire between the two crystal electrodes, which is the most space-saving and more suitable for the wiring layout.

A test method that a temperature-controllable electro-optical amplitude modulator applies a modulation signal to a light field amplitude component, comprising the following steps:

Step 1, stick two lithium niobate crystals with exactly the same size in the insulating copper furnace respectively, and the temperature of the lithium niobate crystal collected by the thermistor is fed back by the temperature controller to one of the electro-optical amplitude modulators. On the semiconductor refrigerator No. 2 and the semiconductor refrigerator No. 2, the temperature of the lithium niobate crystal is controlled by constant temperature, and the modulation signal is applied by the signal generator to modulate the amplitude of the optical field;

Step 2, assemble the electro-optical amplitude modulator, and collimate a single-frequency laser that operates stably;

Step 3: Insert the No. 1 polarizer/half-wave plate into the collimated laser path, so that the laser beam is transmitted along the center of the polarizer, and rotate the vibration-transmitting direction to ensure that the linearly polarized light in the vertical or horizontal direction is obtained after passing through the polarizer;

Step 4, after obtaining the linearly polarized light in the vertical or horizontal direction in Step 3, place an electro-optical amplitude modulator behind it, and ensure that the light beam is transmitted and output by the central axis of the lithium niobate crystal;

Step 5, passing the laser light passing through the electro-optical amplitude modulator in step 4 through a 1/4λ wave plate to perform a phase delay of π/2;

In step 6, the light that has undergone π/2 phase delay in step 5 is passed through a No. 2 polarizer/polarization beam splitter prism;

Step 7, input the laser transmitted from the No. 2 polarizer/polarization beam splitter prism in step 6 into the photodetector, the optical signal is converted into a photocurrent signal, and the photocurrent signal is input to the oscilloscope to observe the transmission signal; when the output signal is the same as the input The waveform of the signal is exactly the same, that is, if the input is a sine wave signal, and the output is also a complete regular and symmetrical sine wave, the test of the electro-optical amplitude modulation signal is completed.

Through the combined use of the device and the test method, the linear working area and signal amplitude of the amplitude modulator are optimized, the linear modulation performance of the amplitude modulation is improved, a better amplitude modulation signal is obtained, and the implementation effect of the modulator is enhanced.

Further, the rotation and vibration transmission direction of the No. 1 polarizer/half-wave plate in the step 3 is consistent with the X or Y axis direction of the lithium niobate crystal when no voltage is applied.

Still further, in the step 5, the principal axis direction of the wave plate is consistent with the X and Y axis directions in the coordinate system.

Further, in the step 6, the light transmission direction of the No. 2 polarizer/polarizing beam splitter prism is perpendicular to the light transmission direction of the No. 1 polarizer/half-wave plate.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention is provided with an insulating gasket on the No. 1 base, which is mainly used to place the electric heat exchange between the platform and the No. 2 base; the gaps left on the three sides of the insulating gasket are used to place the outer casing to make it. A rectangular box is formed between the No. 2 base and a plurality of No. 1 semiconductor refrigerators are closely arranged side by side on the No. 2 base, and one side of the side is in close contact with the No. 2 base, and the other side is glued or welded. It is glued to the thermal insulation copper furnace, and the multiple serially connected No. 1 semiconductor refrigerators and one side of the thermal insulation copper furnace are completely covered to prevent heat loss, and can control the temperature of the thermal insulation copper furnace through its own cold and heat regulation ability. The semiconductor refrigerator also has the same function; the No. 1 thermal insulation layer has countersunk holes and is fixed on the thermal insulation copper furnace with plastic screws, and one of the surfaces is completely covered and placed for heat conduction; the No. 2 thermal insulation layer is similar to the No. 1 thermal insulation layer. , the only difference is that a lead hole between the crystal electrodes and a thermistor lead hole are opened, which correspond to the multiple outlet holes on the side wall of the thermal insulation copper furnace; The holes are fixed on the heat-insulating copper furnace with plastic screws to prevent heat conduction, and there are holes in the middle that are exactly the same as the light-through holes of the outer casing; The semiconductor body refrigerator is used to control the temperature, and the remaining four surfaces are all covered with a thermal insulation layer on the copper surface to prevent heat conduction with the outside, which can achieve better temperature control.

2. The No. 2 base of the present invention includes a fixed seat and a baffle, the fixed seat and the baffle are integrally formed, and the baffle is arranged at the rear end of the fixed seat, and a No. 1 protrusion is arranged in the middle of the fixed seat. rib, between the baffle and the No. 1 protruding rib is provided with a No. 1 thermally conductive inclined surface, and the No. 1 thermally conductive inclined surface is inclined downward from the baffle to the No. 1 protruding rib, and the front end of the No. 1 protruding rib is provided with The platform is provided with No. 2 rib and No. 2 heat conduction slope on the inner wall of the front panel of the outer casing, so that the No. 2 heat conduction slope and No. 2 semiconductor refrigerator are closely attached, and pass between the baffle plate and the ridge. There is a No. 1 heat conduction slope, so that the heat preservation copper furnace can be set on the slope, which is not only convenient to place the polarizer, because only considering the light modulation in the horizontal and vertical directions, the surface of the copper furnace will not be in contact with the outer casing at all. Avoid heat exchange between the two and help save space.

3. The heat-retaining copper furnace of the present invention includes a copper furnace body and a copper furnace cover, the copper furnace cover is fixedly arranged on the copper furnace body, and the copper furnace body is a groove-shaped structure with openings at the left and right ends. The inner wall and bottom of the groove of the furnace body are provided with protrusions, and a plurality of outlet holes are provided on the side wall of the copper furnace body. The copper furnace body and the cover can be separated mainly for the convenience of installing crystals and arranging the electrode wires of the crystals. The protrusions on the inner wall and bottom of the groove of the copper furnace body are used to paste the crystals (the position of the protrusions is different because the two The X and Y axes of the crystal are anti-parallel), the outlet hole of the copper furnace body is opened in the middle of the side wall mainly to lead out the wire between the two crystal electrodes, which is the most space-saving and more suitable for the wiring layout.

4. The present invention optimizes the linear working area and signal amplitude of the amplitude modulator through the combined use of the device and the test method, improves the linear modulation performance of the amplitude modulation, obtains a better amplitude modulation signal, and enhances the implementation of the modulator. Effect.

Description of drawings

Fig. 1 is the front view overall structure schematic diagram of the present invention;

Fig. 2 is the rear view overall structure schematic diagram of the present invention;

Fig. 3 is the exploded structure schematic diagram of the present invention;

4 is a schematic structural diagram of the present invention removing the outer casing;

Fig. 5 is the structural representation of No. 2 base of the present invention;

Fig. 6 is the structural representation of the outer casing of the present invention;

Fig. 7 is the three-dimensional structure schematic diagram of the copper furnace body of the present invention;

8 is a schematic top view of the structure of the copper furnace body of the present invention;

Fig. 9 is the structural representation of the copper furnace cover of the present invention;

FIG. 10 is an actual measurement diagram of the corresponding relationship between the transmittance of the electro-optical amplitude modulator to the optical signal and the modulation voltage in the present invention;

Fig. 11 is the test state diagram of the present invention;

12 is a schematic diagram of the principle of electro-optic amplitude modulation;

Fig. 13 is the test result diagram of the small amplitude sine wave modulation signal that the signal generator of the present invention adds to the electro-optical amplitude modulator;

Fig. 14 is the light intensity modulated wave test result graph that the present invention outputs after passing through the electro-optical amplitude modulator;

In the picture: 1-No.1 base, 2-Insulation gasket, 3-No.2 base, 301-Fixed seat, 302-Baffle plate, 303-No.1 heat conduction slope, 304-Platform, 4-Shell cover, 401-Joint Hole, 402-light hole, 403-No.2 ridge, 404-No.2 heat conduction slope, 5-No.1 semiconductor refrigerator, 6-Insulation copper furnace, 601-Copper furnace body, 602-Copper furnace cover, 603- Bump, 604-outlet hole, 605-thermistor mounting hole, 7-No.2 semiconductor refrigerator, 8-No.1 thermal insulation layer, 9-No.2 thermal insulation layer, 10-No.3 thermal insulation layer, 11- Electro-optical amplitude modulator, 12-No.1 polarizer/half-wave plate, 13-wave plate, 14-No.2 polarizer/polarizing beam splitter, 15-photodetector, 16-oscilloscope, 17-temperature controller, 18- Signal generator.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example

As shown in Figure 1-14, a temperature-controllable electro-optical amplitude modulator includes a No. 1 base 1, an insulating gasket 2 is arranged on the No. 1 base 1, and the edge gasket 2 is a rectangular parallelepiped structure, A No. 2 base 3 is arranged on the insulating gasket 2, and one side of the No. 2 base 3 is fitted with one side of the insulating gasket 2, and the remaining three sides are left with a gap, and are arranged side by side on the No. 2 base 3 There are a plurality of No. 1 semiconductor refrigerators 5, a plurality of No. 1 semiconductor refrigerators 5 are provided with heat-retaining copper furnaces 6, and a plurality of No. 2 semiconductor refrigerators 7 are arranged side by side on the said heat-preserving copper furnaces 6. No. 1 thermal insulation layer 8 and No. 2 thermal insulation layer 9 are respectively fixed on the front and rear surfaces of the thermal insulation copper furnace 6, and a thermal insulation layer 10 No. 3 is fixed on the left and right end surfaces of the thermal insulation copper furnace 6. The upper end surface of the outer casing 4 is provided with a plurality of joint holes 401, the left and right end faces of the outer casing 4 are symmetrically provided with a plurality of light-passing holes 402, and the insulating gasket 2 is provided with the outer casing 4, so that The edge of the outer casing 4 is closely fitted with the edge of the insulating gasket 2 , so that the outer casing 4 is sleeved on the outside of the second base 3 .

The No. 2 base 3 includes a fixing seat 301 and a baffle 302. The fixing seat 301 and the baffle 302 are integrally formed into an L shape. The No. 1 heat conduction inclined surface 303 is arranged between 302 and the No. 1 protruding edge 305, and the No. 1 heat conduction inclined surface 303 is inclined downward from the baffle plate 302 to the No. 1 protruding edge 305. The front end of the No. 1 protruding edge 305 is provided with a The platform 304 is provided with No. 2 protruding rib 403 and No. 2 heat conduction slope 404 on the inner wall of the front panel of the outer casing 4 , so that the No. 2 heat conduction slope 404 and the No. 2 semiconductor refrigerator 7 are closely attached.

The heat-retaining copper furnace 6 includes a copper furnace body 601 and a copper furnace cover 602. The copper furnace cover 602 is fixed on the copper furnace body 601. The copper furnace body 601 is a groove-shaped structure with openings at the left and right ends. The inner wall and bottom of the groove of the copper furnace body 601 are provided with protrusions 603, the front end surface of the copper furnace body 601 is provided with a wire outlet hole 604 and a thermistor mounting hole 605, and the thermistor mounting hole 605 is provided in the copper furnace body 601. There is a thermistor inside, and the thermistor installation hole 605 is sealed with a heat insulating material, which is used to collect the temperature of the heat preservation copper furnace 6 .

A test method that a temperature-controllable electro-optical amplitude modulator applies a modulation signal to a light field amplitude component, comprising the following steps:

Step 1, stick two lithium niobate crystals with exactly the same size in the insulating copper furnace 6 respectively, and the temperature of the lithium niobate crystal collected by the thermistor is fed back to the electro-optical amplitude modulator 11 by the temperature controller 17. On the No. 1 semiconductor refrigerator 5 and No. 2 semiconductor refrigerator 7, the temperature of the lithium niobate crystal is controlled at a constant temperature, and a modulation signal is applied by the signal generator 18 to modulate the amplitude of the light field;

Step 2, assemble the electro-optical amplitude modulator 11, and collimate a single-frequency laser that operates stably;

Step 3: Insert the No. 1 polarizer/half-wave plate 12 into the collimated laser path, so that the laser beam is transmitted along the center of the polarizer, and the direction of vibration transmission is rotated to ensure that the linearly polarized light in the vertical or horizontal direction is obtained after passing through the polarizer; The rotation and vibration transmission direction of the No. 1 polarizer/half-wave plate 12 is consistent with the X or Y axis direction when no voltage is applied in the lithium niobate crystal;

Step 4, after obtaining the linearly polarized light in the vertical or horizontal direction in step 3, place the electro-optical amplitude modulator 11 behind it, and ensure that the light beam is transmitted and output by the central axis of the lithium niobate crystal;

In step 5, the laser light passing through the electro-optical amplitude modulator 11 in step 4 is passed through the 1/4λ wave plate 13 to carry out a phase delay of π/2; the main axis direction of the wave plate 13 is consistent with the X and Y axis directions in the coordinate system. .

In step 6, the light that has undergone π/2 phase delay in step 5 is passed through a second polarizer/polarization beam splitter prism 14; the light transmission direction of the second polarizer/polarization beam splitter prism 14 is the same as / The light transmission direction of the half-wave plate 12 is vertical;

Step 7, input the laser light emitted by the No. 2 polarizer/polarization beam splitter prism lens 14 in step 6 into the photodetector 15, the optical signal is converted into a photocurrent signal, and the photocurrent signal is input to the oscilloscope 16 to observe the transmission signal; The waveform of the signal is exactly the same as that of the input signal, that is, if the input is a sine wave signal, and the output is also a complete regular and symmetrical sine wave, the test of the electro-optical amplitude modulation signal is completed.

The incident light first passes through the polarizer parallel to the X-axis of the coordinate system, and then passes through the lithium niobate crystal that applies a voltage in the direction of the X-axis of the crystal. After passing through the crystal, it passes through a fast axis parallel to the lithium niobate crystal and applies a voltage to the X-axis. Finally, the X' axis passes through the analyzer parallel to the Y axis of the coordinate system. This is the basic principle of electro-optical amplitude modulation. The direction of the applied electric field is parallel to the X axis of the crystal, and the modulated light is outgoing light, and the outgoing light direction is parallel to The Y axis of the coordinate system, the intermediate crystal is an electro-optical modulation crystal, and the size of the intermediate crystal is 3mm × 4mm × 20mm; the size and performance of the two crystals are exactly the same, and the optical axes are arranged in series at 90° to each other, that is, the Y' axis of a crystal and X axes are parallel to the X' and Y axes of the other crystal, respectively.

Figure 12 is a schematic diagram of the principle of electro-optic amplitude modulation. Lithium niobate crystals (two optical axes are arranged at 90° between two orthogonal polarizers, and the polarization direction of the polarizer is parallel to the coordinate axis shown in the figure. The X axis of the analyzer, the polarization direction of the analyzer is parallel to the Y axis of the coordinate axis shown in the figure, and a λ/4 glass slide is inserted between the crystal and the analyzer. When an electric field is applied to the crystal in the X axis direction, the crystal The induction main axes X' and Y' are respectively rotated to an angle of 45° with the original main axes X and Y. Therefore, the light beam incident along the Z axis passes through the polarizer and becomes linearly polarized in the X axis direction of the coordinate system shown in the figure. After entering the crystal, the light is decomposed into two components in the X' and Y' directions, and the amplitude and phase are the same; from the relationship between the transmittance and the modulation voltage as shown in Figure 2, in general, the output characteristics of the modulator The relationship with the applied voltage is nonlinear; if the modulator works in the nonlinear region, the modulated light intensity will be distorted; in order to obtain linear modulation, a fixed π/2 phase delay can be introduced to make the voltage offset value of the modulator At a working point with a transmittance of 50%; a λ/4 glass slide is inserted into the optical path of the modulator, and its fast and slow axes are at an angle of 45° to the X-axis of the main axis of the crystal, so that a π/2 difference is generated between the two components. Fixed phase difference.

The electro-optic amplitude modulation can be realized by using the lateral electro-optic effect of the electro-optic crystal. As shown in Figure 12, the incident light becomes linearly polarized light parallel to the X-axis after passing through the polarizer. Its projection and phase on the crystal are equal, and they are set as:

E _x′ =E _y′ =Acosδ (1)

Or using the method of complex amplitude, the light wave incident on the surface of the crystal Z=0 can be expressed as:

E _x′ (0)=E _y′ (0)=A (2)

So the intensity of the incident light is:

I _i =|E _x′ (0)| ² +|E _y′ (0)| ² =2A ² (3)

When light passes through two lithium niobate crystals with a total length of l, the phase difference δ is generated between X' and Y':

E _x' (l)=A,E _y' (l)=Ae ^iδ (4)

The light exiting the analyzer when ignoring the λ/4 glass is the sum of the projections of the two components on the Y axis:

Its corresponding output light intensity _It can be written as:

The light intensity transmittance T is:

And also:

It can be seen that δ is related to the voltage applied to the crystal. When the voltage increases to a certain value, the polarized light in the X' and Y' directions can generate a phase difference δ=π after passing through the crystal. At this time, the light intensity transmittance T =100%, the voltage applied to the crystal at this time is called half-wave voltage, usually expressed by V _π , V _π is an important parameter describing the electro-optical effect of the crystal,

Where V ₀ is the DC voltage applied to the crystal, V _m sinωt is the AC modulation signal applied to the crystal at the same time, V _m is its amplitude, and ω is the modulation frequency. It can be seen from the above formula that changing V ₀ or V _m , the output characteristics will change accordingly. For monochromatic light and a definite crystal, V _π is constant, so T will vary only with the voltage applied to the crystal.

The next step is to consider the effect of DC bias on the output characteristics:

V_m<<V_π时，将工作点选择在线性工作区的中心可以获得较高效率的线性调制，把

带入(9)式得：when

When V _m <<V _π , selecting the operating point at the center of the linear working area can obtain a higher efficiency linear modulation, and set the

Bring in (9) to get:

Since V _m << V _π

which is

T∝sinωt (12)

At this time, although the amplitude of the signal output by the modulator and the modulation signal are different, the frequencies of the two are the same, and the output signal is not distorted, that is, linear modulation.

The test results of this device are shown in Figure 13 and Figure 14, in which Figure 13 is the small amplitude sine wave modulation signal added by the signal generator to the electro-optical amplitude modulator, and Figure 14 is the light intensity modulated wave outputted by the electro-optical amplitude modulator ; It can be seen that the frequency and waveform fidelity of the light field modulation signal are high, which proves that the modulator works in the linear region described in Figure 10, and the modulation effect fully meets the application needs.

No. 1 base 1, insulating gasket 2, No. 2 base 3, fixing base 301, baffle 302, No. 1 heat conducting slope 303, platform 304, outer casing 4, joint hole 401, light-passing hole 402, No. 2 Protruding ribs 403, No. 2 heat conduction slope 404, No. 1 semiconductor refrigerator 5, insulation copper furnace 6, copper furnace body 601, copper furnace cover 602, protrusions 603, outlet holes 604, thermistor mounting holes 605, No. 2 semiconductor Refrigerator 7, No. 1 thermal insulation layer 8, No. 2 thermal insulation layer 9, No. 3 thermal insulation layer 10, Electro-optic amplitude modulator 11, No. 1 polarizer/half-wave plate 12, Wave plate 13, No. 2 polarizer/ The polarization beam splitter prism 14, the photodetector 15, the oscilloscope 16, the temperature controller 17, and the signal generator 18 are all common standard parts or components known to those skilled in the art, and their structures and principles are known to the skilled person through the technical manual Or known by conventional experimental methods.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above, and it will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but without departing from the spirit or essential aspects of the present invention. In the case of the characteristic features, the present invention can be implemented in other specific forms. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and scope of the equivalents of , are included in the present invention. Any reference signs in the claims shall not be construed as limiting the involved claim.

In addition, it should be understood that although this specification is described in terms of embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (2)

1. A temperature-controllable electro-optic amplitude modulator, characterized by: comprises a first base (1), an insulating gasket (2) is arranged on the first base (1), the insulating gasket (2) is of a cuboid structure, a second base (3) is arranged on the insulating gasket (2), one side of the second base (3) is attached to one side of the insulating gasket (2), gaps are reserved on the other three sides, a plurality of first semiconductor refrigerators (5) are arranged on the second base (3) side by side, a heat preservation copper furnace (6) is arranged on the first semiconductor refrigerators (5), a plurality of second semiconductor refrigerators (7) are arranged on the heat preservation copper furnace (6) side by side, a first heat insulation layer (8) and a second heat insulation layer (9) are respectively and fixedly arranged on the front end surface and the rear end surface of the heat preservation copper furnace (6), a third heat insulation layer (10) is fixedly arranged on the left end surface and the right end surface of the heat preservation copper furnace (6), an outer shell (4) is arranged on the insulating gasket (2), the edge of the outer shell (4) is tightly attached to the edge of the insulating gasket (2), the outer shell (4) is sleeved outside the second base (3), a plurality of joint holes (401) are formed in the upper end face of the outer shell (4), and a plurality of light through holes (402) are symmetrically formed in the left end face and the right end face of the outer shell (4);

base No. two (3) are including fixing base (301) and baffle (302), fixing base (301) and baffle (302) integrated into one piece are the L shape the middle part of fixing base (301) is equipped with abrupt edge (305) No. one be equipped with heat conduction inclined plane (303) between baffle (302) and abrupt edge (305), and make heat conduction inclined plane (303) from baffle (302) to abrupt edge (305) orientation downward sloping No. one the front end of abrupt edge (305) is equipped with platform (304) the front panel inner wall of outer shell (4) is equipped with No. two abrupt edges (403) and No. two heat conduction inclined planes (404), and makes No. two heat conduction inclined planes (404) and No. two semiconductor refrigerator (7) closely laminate.

2. A temperature controllable electro-optic amplitude modulator as claimed in claim 1, characterized in that: the heat preservation copper furnace (6) comprises a copper furnace body (601) and a copper furnace cover (602), wherein the copper furnace cover (602) is fixedly arranged on the copper furnace body (601), the copper furnace body (601) is of a groove-shaped structure with openings at the left end and the right end, protrusions (603) are arranged on the inner wall and the bottom of a groove of the copper furnace body (601), a wire outlet hole (604) and a thermistor mounting hole (605) are arranged on the front end face of the copper furnace body (601), a thermistor is arranged in the thermistor mounting hole (605), and the thermistor mounting hole (605) is sealed by heat insulation materials and used for collecting the temperature of the heat preservation copper furnace (6).

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