CN102004284A - Surplus photocarrier delay line - Google Patents

Abstract

The invention discloses a surplus photocarrier-based adjustable delay line which is used for controlling deflection of a galvanometer and intensity of bias voltage and realizing continuous adjustment of delay time. The surplus photocarrier delay line comprises a pump laser 1, a galvanometer 2, a galvanometer driver 3, a convex lens 4, a photoelectric detector 5, a detection laser 6, a positive electrode 7, a semiconductive material 8, a negative electrode 9 and an adjustable voltage source 10, wherein the pump laser 1 sends out exciting light loaded with a signal Si (t), and the exciting light is focused on the semiconductive material 8 by the convex lens 4 after being reflected by the galvanometer 2 so as to generate surplus photocarrier; the detection laser 6 sends out detection light to be irradiated to the photocarrier diffusion range on the semiconductive material 8, and the detection light is reflected and then received by the photoelectric detector 5 so that a delay signal So (t) of the signal Si (t) is obtained; and an adjustable signal W1 controls the galvanometer driver 3 to change the deflection angle of the galvanometer 2, and the W2 controls the adjustable voltage source 10 to change the voltage between the positive electrode 7 and the negative electrode 9 so as to continuously adjust the delay time in a large range.

Description

The excess optical carrier lag line

Technical field

The present invention relates to the delay line technique field, be specifically related to a kind of excess optical carrier lag line.

Background technology

Lag line is element or the device that is used for signal delay a period of time.Lag line should have smooth amplitude versus frequency characte and certain phase shift characteristic (or time-delay frequency characteristic) in passband.Lag line is widely used in radar, robot calculator, vitascan, communication system, and in the surveying instrument (as oscillograph).

Lag line can be divided into three kinds: the one, and the electric signal lag line is delayed time by several nanoseconds to tens microseconds, as charge-coupled device (CCD) and cable etc.; The 2nd, ultrasonic delay line, several microseconds of delaying time are to several thousand microseconds, as mercury delay line, quartz delay-line etc.; The 3rd, the light signal lag line is as optical delay line, light digital synchronous delay line storage etc.They delay time different, have his own strong points, and complement one another.Wherein, optical delay line is widely used in numerous areas such as phased-array radar technology, electronic countermeasure, full light signal processing and all optical communication.With respect to the electric delay device of routine, optical delay line have time delay long, time-bandwidth product is big, frequency of operation is high, loss is little, size is little, light weight, do not have advantages such as electromagnetic interference (EMI).

Because the different application occasion may need different time delay, therefore require delay device can realize that time delay is adjustable.Variable light lag line commonly used at present is that increment is adjustable and discontinuous adjustable, they are made up of many optical fiber or optical waveguide, every optical path length difference, the routing by cascaded optical switch makes light signal pass through the optical fiber or the waveguide of different length, thereby obtains different time delay.Change because path is an increment, thus time delay also can only be increment and discontinuous variation, precision to the hundreds of picosecond magnitude, has limited the range of application of optical delay line in tens psecs so greatly.

How to realize a kind of existing than great dynamic range, but continuous variable and light delay easy to adjust again becomes present research focus.

Summary of the invention

Problem to be solved by this invention is: how a kind of excess optical carrier lag line is provided, it can overcome the defective of prior art, can realize the signal delay of continuous variable, based on excess optical carrier modulation principle of reflection, can realize the variation continuously on a large scale of time delay by the biased adjusting of galvanometer deflection angle and institute.

Technical matters proposed by the invention is to solve like this: a kind of excess optical carrier lag line is provided, device comprises pump laser 1 (photon energy is greater than the energy gap of semiconductor material), galvanometer 2, vibrating mirror driver 3, convex lens 4, photodetector 5, detection laser 6 (photon energy is less than the energy gap of semiconductor material), positive electrode 7, semiconductor material 8, negative electrode 9 and variable voltage source 10, it is characterized in that, input signal Si (t) modulated pumping laser instrument 1 sends exciting light, modulated exciting light is through galvanometer 2 reflections, after focusing on, convex lens 4 converge on the semiconductor material 8 that is placed on convex lens 4 focal plane position, at the semiconductor material 8 local nonequilibrium carriers that produce concentration with the variation of modulation exciting light, and to diffusion (synoptic diagram is seen Fig. 2) all around, in effective range of scatter, the variation of carrier concentration will cause the material change of refractive; Detection laser 6 is sent and is detected light and be radiated at certain in the semiconductor material 8 surperficial charge carrier range of scatters with incident angle β, β 0 and the angle of total reflection between, semiconductor material 8 refractive index herein changes with modulated optical excitation signal, light reflectivity also changes accordingly, change of refractive is the reflection of the modulation optical excitation signal that postponed herein, then detect light is loaded with the optical excitation signal that has postponed through the reflected light of semiconductor material 8 information, it is transformed to signal So (t) by photoelectric detector 5, and then signal So (t) is exactly the time delayed signal of Si (t).

According to excess optical carrier lag line provided by the present invention, its pump laser 1 and detection laser 6 are characterised in that: the photon energy of the exciting light of pump laser 1 is greater than the energy gap of described semiconductor material 8, and the photon energy of the detection light of detection laser 6 is less than the energy gap of semiconductor material 8.

The present invention is based on the lag line of excess optical carrier modulation principle of reflection, its modulation principle of reflection is characterised in that: pump laser 1 sends the exciting light that has loaded modulation signal Si (t) and produces the nonequilibrium carriers that concentration change with the modulation exciting light in semiconductor material 8 parts, detection laser 6 is sent detection light and is radiated in effective range of scatter of charge carrier on the semiconductor material 8 with incident angle β, β 0 and the angle of total reflection between, the variation of carrier concentration can cause the material change of refractive, detecting light changes with modulated optical excitation signal in the refractive index of semiconductor material 8 incidents place, light reflectivity also changes accordingly, change of refractive is the reflection of the modulation optical excitation signal that postponed herein, then detect the light information of optical excitation signal of modulation signal Si (t) that has been loaded with the loading that postponed through the reflected light of semiconductor material 8, it is transformed to signal So (t) by photoelectric detector 5, and then signal So (t) is exactly the time delayed signal of Si (t).

The detection light that detection laser 6 is sent at the incidence point on the semiconductor material 8 in the charge carrier range of scatter, change the deflection angle of galvanometer 2 by adjustable signal W1 control vibrating mirror driver 3, change the incidence point of exciting light on semiconductor material 8 that pump laser 1 sends, realize the adjusting on a large scale of time delay.

Change positive electrode 7 and 9 bias voltages of negative electrode by adjustable signal W2 control variable voltage source 10, change the electric field that is added on the semiconductor material 8, and then change the rate of propagation of charge carrier in the semiconductor material 8, realize the accurate adjusting of time delay.

According to excess optical carrier lag line provided by the present invention, it is characterized in that: on excess optical carrier modulation principle of reflection basis, can realize the adjusting on a large scale of delay time by galvanometer 2, and realize the accurate adjusting of delay time, thereby realize the adjustable continuously of time delay by variable voltage source 10.

The present invention uses photo-generated carrier to cause the variations in refractive index of semiconductor material and the diffusion motion of photo-generated carrier, formed Photocarrier delay line, and carry out changing continuously of time delay on a large scale by the adjusting of galvanometer and electric field, size is little, light weight, simple in structure, the efficient height, time delay is long, and can realize the signal delay of continuous variable.

Description of drawings

Fig. 1 is a structural representation of the present invention.

Wherein, 1, can modulate pump laser, 2, galvanometer, 3, vibrating mirror driver, 4, lens, 5, photodetector, 6, detection laser, 7, positive electrode, 8, semiconductor material, 9, negative electrode, 10, variable voltage source.

Fig. 2 is the synoptic diagram of photo-generated carrier among the present invention.

Wherein, 1, exciting light, 2, the photo-generated carrier dispersal direction, 3, photo-generated carrier, 4, photo-generated carrier dispersal direction

Embodiment

Below in conjunction with accompanying drawing the present invention is further described:

Ultimate principle of the present invention is as follows: a branch of exciting light (photon energy is greater than the energy gap of semiconductor material) incides semiconductor material surface, semiconductor material absorbs luminous energy and inspires nonequilibrium carrier (electron hole pair), because this light beam has gone into to cause the variation of nonequilibrium carrier concentration in the semiconductor material, the variation of carrier concentration will cause the material change of refractive.If the exciting light light intensity is modulated by a rf signal, then modulate the signal that optical excitation signal can be converted to the semiconductor material variations in refractive index, this variations in refractive index signal is loaded with the information of modulation optical excitation signal.The nonequilibrium carrier that light beam goes into to cause spreads to the low direction of concentration from the concentration height in life time, certain in the range of scatter of charge carrier (through one period diffusion time) is with a branch of detection light (photon energy is less than the energy gap of semiconductor material), with certain incident angle (0 and the angle of total reflection between) irradiation semiconductor material, because semiconductor material refractive index herein changes with the modulation optical excitation signal, light reflectivity also changes accordingly, then detecting reflection of light light light intensity also changes, detect the variation that reflection of light light light intensity changes reflection modulation exciting light, to detect the reflection of light converting optical signals be rf signal by being placed on photoelectric detector before the semiconductor material, the frequency spectrum of the frequency spectrum of the rf signal of output and the rf signal of input is identical, has just postponed a period of time.Exciting light incoming position difference, then charge carrier is diffused into difference diffusion time that detects light incident place from exciting light incident, it is difference time delay, detect the emergent light of light like this and just represent the different optical excitation signal of time-delay, rf signal by photoelectric detector output is just represented the different former modulated RF electric signal of time-delay, can continuously change the exciting light incoming position by the deflection angle of regulating galvanometer, just can realize variable delay on a large scale, if semiconductor material is in the electric field, then photo-generated carrier is under effect of electric field, rate of propagation can be changed,, accurately variable delay can be realized by the continuous adjusting of electric field.

Photoproduction carrier concentration is directly proportional with the exciting light light intensity in the semiconductor material, so the concentration change of charge carrier has just reflected the variation of exciting light light intensity; Refractive index with carrier concentration change mainly be by can be with filling effect (Burstein-Moss effect), band gap dwindles effect and the free carrier absorption effect causes, semiconductor material change of refractive and carrier concentration are varied to linear relationship, after injecting charge carrier, refractive index reduces, and carrier concentration is big more, and refractive index is more little.Therefore, the variations in refractive index signal just is loaded with the information of modulation optical excitation signal.Can use this formulate by dwindling the change of refractive that effect causes with filling effect and band gap:

Δ α difference in two kinds of effects, wherein N is for injecting electron number, and P is the injected hole number, and Δ α is the changing value of absorption coefficient, and E is an incident photon energy, and c is the light velocity, and e is an electron charge,

Be the Planck constant, P ∫ represents principal value integral; Can use this formulate by the change of refractive that the free carrier absorption effect causes:

$\mathrm{\&Delta;n}=-\frac{{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="HSA00000264692900012.png"\; state="\{\{state\}\}">e</figure-callout>}}^2{\mathrm{\&lambda;}}^2}{8{\mathrm{\&pi;}}^2{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HSA00000264692900012.png"\; state="\{\{state\}\}">c</figure-callout>}}^2{\mathrm{\&epsiv;}}_{0}n}(\frac{N}{m_e}+\frac{P}{m_h}),$

Wherein n is the refractive index of material, and λ is an optical wavelength.The stack of three kinds of effects has just disclosed the relation of the interior injection level of semiconductor and photon energy and variations in refractive index: semiconductor material change of refractive and carrier concentration are varied to linear relationship.

Detect light and incide the semiconductor refractive index region of variation, then detect reflection of light light light intensity and just be loaded with the variations in refractive index signal, the emergent light light intensity signal that detects light so just is loaded with the modulation optical excitation signal.

The nonequilibrium carrier that light beam goes into to cause spreads to the low direction of concentration from concentration height (exciting light incident central point) in life time, and for thick semiconductor material, carrier concentration is roughly exponential form with the variable in distance from the exciting light incidence point and successively decreases; For thin sample, carrier concentration roughly is linear decrease with the variable in distance from the exciting light incidence point.Difference in range of scatter spreads used asynchronism(-nization), so just makes the signal lag asynchronism(-nization).The continuous adjusting of galvanometer deflection angle can make detection light be in the interior difference of charge carrier range of scatter continuously, realizes adjustable delay on a large scale.

Apply an electric field on charge carrier transverse dispersion direction, then charge carrier drifts about on direction of an electric field, and this just makes the rate of propagation of nonequilibrium carrier change, and by regulating electric field intensity, can realize accurately adjustable delay.

According to continuity equation, (suppose that electric signal S (t) is that angular frequency is the simple signal of ω, excitation light irradiation is at the x=0 place, hole concentration Δ p with being changed to of bias voltage for the hole concentration in the semiconductor _{| x=0}=Ae ^{I ω t}):

Wherein

$\mathrm{\&zeta;}(E,\mathrm{\&omega;})=\frac{\mathrm{\&tau;}}{\sqrt{2}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000264692900012.png"\; state="\{\{state\}\}">n</figure-callout>}}^2+4m+\sqrt{{({\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000264692900012.png"\; state="\{\{state\}\}">n</figure-callout>}}^2+4m)}^2+16{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HSA00000264692900012.png"\; state="\{\{state\}\}">m</figure-callout>}}^2{\mathrm{\&omega;}}^2{\mathrm{\&tau;}}^2}}}$

M=D _nτ, n=μ _nE τ, B are constant

Obviously, (E ω) is time delay to Δ t=x ζ.

For example, semiconductor material 8 is the not high silicon of impurity concentration, then D under the room temperature _n=35cm ²(VS), μ _n=1400cm ²/ S records τ=10 μ s.Galvanometer 2 is 10cm to the vertical range of semiconductor material 8, and galvanometer 2 resolution are 2.65 μ rad, and adjustable extent is 5 degree.Get ω=2 π * 10 ³Rad obtains the value of x in the formula by galvanometer 2 to the deflection angle of the vertical range of semiconductor material 8 and galvanometer 2, then

$\mathrm{\&Delta;t}=\frac{7.071067812\&times;{10}^{-6}x}{\sqrt{\sqrt{{(1.96\&times;{10}^{-12}{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="HSA00000264692900012.png"\; state="\{\{state\}\}">E</figure-callout>}}^2+1.4\&times;{10}^{-7})}^2+7.73776985\&times;{10}^{-15}}+1.96\&times;{10}^{-12}{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="HSA00000264692900012.png"\; state="\{\{state\}\}">E</figure-callout>}}^2+1.4\&times;{10}^{-7}}}$

E=0, Δ t=0.01279652869x when added electric field not regulate galvanometer 2, can realize that time delay, resolution was 3.39108ns, and range of adjustment is about 0.1ms, can realize regulating on a large scale.

On this basis, add the electric field of 10V/m, Δ t=0.01278895007x, time-delay reduces to be about 2ps, can realize accurate adjusting.Applied field is big more, and time-delay reduces big more, and when electric field was increased to 3000V/m, time-delay reduced to be about 90% of the resolution sizes of delaying time on a large scale.

Input signal Si (t) modulated pumping laser instrument 1 sends exciting light, modulated exciting light is through galvanometer 2 reflections, after focusing on, convex lens 4 converge on the semiconductor material 8 that is placed on convex lens 4 focal plane position, at the semiconductor material 8 local nonequilibrium carriers that produce concentration with the variation of modulation exciting light, and to diffusion all around, in effective range of scatter, the variation of carrier concentration will cause the material change of refractive, range of scatter certain a bit, the concentration of charge carrier is to change with the exciting light that radio frequency electric signal Si (t) modulates, detection laser 6 send detect light with incident angle β (β 0 and the angle of total reflection between) be radiated at certain in the semiconductor material 8 surperficial charge carrier range of scatters, semiconductor material 8 refractive index herein changes with modulated optical excitation signal, light reflectivity also changes accordingly, change of refractive is the reflection of the modulation optical excitation signal that postponed herein, then detect light is loaded with the optical excitation signal that has postponed through the reflected light of semiconductor material 8 information, it is transformed to signal So (t) by photoelectric detector 5, and then signal So (t) is exactly the time delayed signal of Si (t).The detection light that detection laser 6 is sent at the incidence point on the semiconductor material 8 in the charge carrier range of scatter, change the deflection angle of galvanometer 2 by adjustable signal W1 control vibrating mirror driver 3, change the incidence point of exciting light on semiconductor material 7 that pump laser 1 sends, realize the wide variation of time delay.Change positive electrode 7 and 9 bias voltages of negative electrode by adjustable signal W2 control variable voltage source 10, change the electric field that is added on the semiconductor material 8, change the rate of propagation of charge carrier in the semiconductor material 8, realize the accurate variation of time delay.

Claims (6)

1. excess optical carrier lag line, comprise pump laser (1), galvanometer (2), vibrating mirror driver (3), convex lens (4), photodetector (5), detection laser (6), positive electrode (7), semiconductor material (8), negative electrode (9) and variable voltage source (10), it is characterized in that, input signal Si (t) modulated pumping laser instrument (1) sends exciting light, modulated exciting light is through galvanometer (2) reflection, convex lens (4) converge on the semiconductor material (8) that is placed on convex lens (4) focal plane position after focusing on, at the local nonequilibrium carrier that produces concentration with the variation of modulation exciting light of semiconductor material (8), and to diffusion all around, in effective range of scatter, the variation of carrier concentration will cause the material change of refractive; Detection laser (6) is sent detection light and is radiated at interior certain of the effective range of scatter of the surperficial charge carrier of semiconductor material (8) with incident angle β, β 0 and the angle of total reflection between, semiconductor material (8) refractive index herein changes with modulated optical excitation signal, light reflectivity also changes accordingly, change of refractive is the reflection of the modulation optical excitation signal that postponed herein, then detect light is loaded with the optical excitation signal that has postponed through the reflected light of semiconductor material (8) information, it is transformed to signal So (t) by photoelectric detector (5), and then signal So (t) is exactly the time delayed signal of Si (t).

2. the described excess optical carrier lag line of claim 1, its pump laser (1) and detection laser (6) are characterised in that: the photon energy of the exciting light of pump laser (1) is greater than the energy gap of described semiconductor material (8), and the photon energy of the detection light of detection laser (6) is less than the energy gap of semiconductor material (8).

3. the described excess optical carrier lag line of claim 1 is based on the lag line of excess optical carrier modulation principle of reflection, its modulation principle of reflection is characterised in that: pump laser (1) sends the exciting light that has loaded modulation signal Si (t) and produces the nonequilibrium carrier that concentration changes with the modulation exciting light in semiconductor material (8) part, detection laser (6) is sent detection light and is radiated in effective range of scatter of the last charge carrier of semiconductor material (8) with incident angle β, β 0 and the angle of total reflection between, the variation of carrier concentration can cause the material change of refractive, detecting light changes with modulated optical excitation signal in the refractive index of semiconductor material (8) incident place, light reflectivity also changes accordingly, change of refractive is the reflection of the modulation optical excitation signal that postponed herein, then detect the light information of optical excitation signal of modulation signal Si (t) that has been loaded with the loading that postponed through the reflected light of semiconductor material (8), it is transformed to signal So (t) by photoelectric detector (5), and then signal So (t) is exactly the time delayed signal of Si (t).

4. the incidence point of detection light on semiconductor material (8) that send of detection laser (6) is in the charge carrier range of scatter, change the deflection angle of galvanometer (2) by adjustable signal W1 control vibrating mirror driver (3), change the incidence point of exciting light on semiconductor material (8) that pump laser (1) sends, realize the adjusting on a large scale of time delay.

5. change bias voltage between positive electrode (7), negative electrode (9) by adjustable signal W2 control variable voltage source (10), change the electric field that is added on the semiconductor material (8), and then the rate of propagation of the middle charge carrier of change semiconductor material (8), realize the accurate adjusting of time delay.

6. according to claim 1,2,3,4,5 described excess optical carrier lag lines is characterized in that: on excess optical carrier modulation principle of reflection basis, can realize the adjusting on a large scale of delay time by galvanometer (2), and realize the accurate adjusting of delay time, thereby realize the adjustable continuously of time delay by variable voltage source (10).

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