CN100585967C - Based on accurate vertical zeeman laser frequency-stabilizing method and the device that separates of luminous power - Google Patents

Abstract

The invention belongs to the laser application technique field, method of the present invention may further comprise the steps: open the laser tube that also preheating places longitudinal magnetic field, utilize the left and right rounding polarised light of quarter-wave plate and the outgoing of polarizing beam splitter initial gross separation laser tube to obtain the pairwise orthogonal linearly polarized light; Utilize low drift high frequency light electric explorer to change linearly polarized light into the signal of telecommunication and measure the amplitude of direct current and alternating current component in the signal of telecommunication, thereby accurately separate and record the luminous power P of two circularly polarized lights _LAnd P _RAdjustment is wrapped in the current value of the electrothermal device on the laser tube, and it is long to change the laser tube temperature resonant cavity, makes optical power difference P _L-P _RBe zero, two polarised light frequencies are all stablized; The inventive system comprises the accurate separation detection circuit of luminous power that is used to obtain luminous power DC component and alternating current component; Characteristics of the present invention are to utilize low drift high frequency light electric explorer can measure the luminous power of two kinds of different frequency laser of aliasing in the linearly polarized light simultaneously, thereby improve the frequency stability of frequency stabilized carbon dioxide laser.

Description

Based on accurate vertical zeeman laser frequency-stabilizing method and the device that separates of luminous power

Technical field

The invention belongs to the laser application technique field, particularly a kind of vertical zeeman laser frequency-stabilizing method and device that accurately separates based on luminous power.

Background technology

One of characteristics of laser are that monochromaticjty is good, and the laser linewidth limit that its spontaneous emission noise causes is very little, but because the influence of various destabilizing factors, the laser optical frequency drift that freely turns round is far longer than the live width limit.In applications such as precise interference measurement, optical frequency standard, optical communication and accurate spectral investigation, laser requires light frequency (wavelength) to have good stability as length standard.In all frequency stabilized carbon dioxide lasers, vertically the zeeman frequency stabilization laser is owing to characteristics such as simple in structure, double frequency emission, the moderate easy processing of frequency difference have obtained extensive use in above-mentioned field.

According to the difference of feedback signal, vertically the zeeman laser frequency-stabilizing method can be divided into frequency difference frequency stabilizing method and difference power frequency stabilizing method.By the characteristic of vertical zeeman laser as can be known, the extreme point of left and right rounding polarised light frequency difference tuning curve, the zero point of power difference signal, all belong to natural reference, be difficult for the influence of change of external conditions such as Stimulated Light tube discharge condition, temperature, magnetic field intensity, the vertical zeeman laser that is locked in frequency difference extreme point or difference power zero point has higher frequency stability.

The propositions such as T.Baer of U.S. laboratory astrophysics Union College (JILA) are locked in vertical zeeman laser frequency stabilization scheme (Baer T of frequency difference extreme point, Kowalski F V, Hall J L.FrequencyStabilization of a 0.633 μ m He-Ne Longitudinal Zeeman Laser.Appl.Opt.1980, (19): 3173～3177).This frequency stabilization scheme as feedback signal, utilizes piezoelectric ceramic tuning cavity length to make laser be locked in the extreme point of frequency difference tuning curve with left and right sides rounding polarised light frequency difference value, obtains 2 * 10 thereby stablize vertical zeeman laser output light frequency ^-9Long-term frequency stability.But this frequency stabilization scheme need adopt high speed responsor spare such as piezoelectric ceramic to lock extreme point as the long tuning actuator in chamber, has not only increased the complex process degree that laser tube is made, and has also reduced the short-term frequency stability of laser.In addition, because the drift and the lagging characteristics of piezoelectric ceramic self are difficult to make chamber length to be controlled in the accuracy rating of expection.

U.S. Beckman Instruments company (United States Patent (USP): Laser stabilization servosystem, patent No. US884872) and Chinese Shaaxi Mechanical Engineering College (Chinese patent: temperature-stabilized two-frequency laser, patent No. CN85102385) proposed to be locked in the difference power hot frequency stabilization scheme of vertical zeeman laser at zero point respectively.This frequency stabilization scheme exemplary device principle is for being wrapped in the size of current of the outer electric-heating thin film of laser tube by control, regulate the long locked laser in laser tube temperature resonant cavity chamber and work in difference power zero point.Yet, in vertical hot frequency stabilization system of zeeman laser, be subjected to the influence that design, processing and the alignment error of beam split light path and testing circuit are brought, left and right rounding polarised light luminous power aliasing, the asymmetric drift of luminous power testing circuit parameter, make the frequency stabilization system keyed end depart from the difference power zero point of left and right rounding polarised light, output light frequency stability reduces.Shown in Fig. 1 (a), ideally, vertically the left and right rounding polarised light of zeeman laser outgoing changes the orthogonal A in polarization direction, B two-route wire polarised light into by quarter-wave plate, left circularly polarized light is converted to A route polarised light fully, right-circularly polarized light is converted to B route polarised light fully, and PBS separates A, B two-route wire polarised light fully.Yet, shown in Fig. 1 (b), because the normally nonopiate elliptically polarized light of actual laser emergent light, and quarter-wave plate, PBS all exist manufacturing, alignment error, therefore in the two-way laser of PBS output all simultaneously aliasing left and right rounding polarised light, make the frequency stabilization system keyed end depart from real difference power zero point, output light frequency stability reduces.

For solving the asymmetric drifting problem of parameter of left and right rounding polarised light luminous power testing circuit, introducing liquid crystal rotatory polarization light in hewlette-packard HP5501B and the HP5519 series laser opens the light, utilize same optical-electrical converter time-sharing multiplex to detect two circularly polarized light power respectively, eliminated the influence of optical-electrical converter parameter drift.Yet, asymmetric for preventing to introduce the light path that liquid crystal polarized optical switch brings, in this scheme the optics processing and the required precision of installing higher, debug difficulties.In addition, this scheme does not solve left and right rounding polarised light luminous power aliasing problem, and the luminous power aliasing still exists the influence of light frequency stability.

Summary of the invention

In order to overcome the deficiency in the above-mentioned prior art, the present invention proposes a kind of vertical zeeman laser frequency-stabilizing method and device that accurately separates based on luminous power, utilize the left and right rounding polarised light of the vertical zeeman laser negative output terminal of optics initial gross separation outgoing to obtain the two-route wire polarised light, and by low drift high frequency light electric explorer detection signal further detect and the defiber polarised light in the luminous power aliasing, thereby make the luminous power P of the left and right rounding polarised light of laser negative output terminal outgoing _LAnd P _RAccurately separated.Obtain this moment difference power is not subject to influences such as discharging condition, temperature, time variation zero point, when the left and right rounding polarised light difference power of the long locking of frequency stabilization electronic circuit adjustment laser chamber is zero, two polarised light frequencies are symmetrically distributed with respect to the gain curve centre frequency, have very high frequency stability.

Above-mentioned purpose realizes by following technical scheme:

A kind of vertical zeeman laser frequency-stabilizing method that accurately separates based on luminous power, this method may further comprise the steps:

(1) open the coaxial-type laser cavity that also preheating places longitudinal magnetic field, its negative output terminal outgoing frequency is respectively f _LAnd f _R, power is respectively P _LAnd P _RLeft and right rounding polarised light, utilize the left and right rounding polarised light of quarter-wave plate and polarizing beam splitter initial gross separation to obtain the orthogonal A in polarization direction, B two-route wire polarised light, because the luminous power aliasing and the beat frequency interference of the different frequency laser that the non-ideal characteristic of laser and the design of light path and adjustment error are brought, aliasing has power to be respectively P in the A route polarised light _AL=(1-α) P _L, P _AR=β P _RTwo kinds of different frequency laser, aliasing has power to be respectively P in the B route polarised light _VL=α P _L, P _BR=(1-β) P _RTwo kinds of different frequency laser;

(2) utilize the high frequency light electric explorer to change the radiation of A route polarised light into the signal of telecommunication, have DC level component and frequency in the signal of telecommunication to be | f _L-f _R| alternating current component, straight, AC signal are carried out the amplification with equimultiple, record DC component value P ₁Amplitude P with alternating current component ₃, correspondingly B route polarised light is handled equally, detect DC component value P ₂Amplitude P with alternating current component ₄

(3) by P ₁, P ₃Value is obtained $P_{\mathrm{AL}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+{\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="C2008101370810013H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_3}+\sqrt{P_1-P_3})}^2/4,$ $P_{\mathrm{AR}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+P_3}-\sqrt{P_1-P_3})}^2/4,$ Again according to P ₂, P ₄Numerical value is obtained $P_{\mathrm{BL}}={(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C2008101370810015H1.png,C2008101370810016H1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2+P_4}-\sqrt{P_2-P_4})}^2/4,$ $P_{\mathrm{BR}}={(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C2008101370810015H1.png,C2008101370810016H1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2+{\mathrm{<figure-callout\; id="4"\; label="P"\; filenames="C2008101370810013H2.png,C2008101370810015H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_4}+\sqrt{P_2-P_4})}^2/4,$ Then can accurately separate and record the luminous power P of the left and right rounding polarised light of laser tube negative output terminal outgoing _L=P _AL+ P _BLWith _PR=P _AR+ P _BR

(4) laser tube reach set preheat temperature and near thermal equilibrium state after, according to the optical power difference Δ P=P of left and right rounding polarised light _L-P _R, adjust the current value that is wrapped in the electrothermal device on the laser tube, it is long to change the laser tube temperature resonant cavity, constitutes the frequency stabilization control loop.Control loop locking difference power is zero, and left and right rounding polarised light frequency is symmetrically distributed with respect to the gain curve centre frequency, and two light frequencies are all stablized.

A kind of vertical zeeman laser frequency regulator that accurately separates based on luminous power, its composition comprises: magnet ring, laser tube, high voltage source, temperature sensor, electric-heating thin film, quarter-wave plate, polarizing beam splitter, preamplifier, A/D converter, microprocessor, D/A converter, power amplifier, this device also comprises low pass filter, low drift high frequency light electric explorer, rearmounted direct current amplifier, rearmounted AC coupled amplifier and peak detector, and they and preamplifier constitute the accurate separation detection circuit of luminous power jointly; Between polarizing beam splitter and two preamplifiers, dispose a low drift high frequency light electric explorer respectively, the output of preamplifier is connected with rearmounted AC coupled amplifier with low pass filter respectively, disposes rearmounted direct current amplifier and peak detector respectively between low pass filter and rearmounted AC coupled amplifier and the A/D converter.

The present invention has following characteristics and beneficial effect:

(1) adopt low drift high frequency photelectric receiver to receive the linearly polarized light power signal among the present invention, its output signal had both comprised an aliasing left side, the DC component of right-hand circular polarization luminous power, comprise a left side again, the alternating current component that dextrorotation rotatory polarization beat frequency forms, according to low drift high frequency detector gained DC component size and alternating current component amplitude, the present invention isolates the luminous power of the different frequency light of aliasing in the linearly polarized light effectively, thereby accurately detect the luminous power of left and right sides rounding polarised light, and existing method is owing to adopt low frequency photelectric receiver convert light power to obtain DC component, the power aliasing of two kinds of polarised lights that exist among its polarised light power detection result, this is that the present invention distinguishes one of innovative point of prior art;

(2) the accurate separation of luminous power is to realize by the alternating current-direct current information that low drift high frequency light electric explorer is exported among the present invention, it is nonopiate ellipse inclined to one side that the introducing of low drift high frequency light electric explorer can be eliminated laser output light, the luminous power aliasing that quarter-wave plate and polarizing beam splitter error in mounting position etc. bring, therefore allow the installation location error of quarter-wave plate and polarizing beam splitter on the principle of the invention, reduced the parameters precision requirement of frequency stabilization system to device manufacturing and Installation and Debugging, greatly reduce Installation and Debugging difficulty and workload in vertical zeeman frequency stabilization laser course of industrialization, and prior art requires quarter-wave plate and polarizing beam splitter that very high positional precision is arranged, and this is two of the present invention's innovative point of distinguishing prior art;

(3) among the present invention vertically the zeeman frequency stabilization laser separate the keyed end of difference power zero point of the left and right sides rounding polarised light that obtains by twice luminous power as frequency stabilization control, be difficult for the influence that extraneous factors such as Stimulated Light device discharging condition, temperature change, improved the long and short phase frequency stability of laser greatly, and prior art only utilizes zero point of difference of the linearly polarized light power that initial gross separation obtains as the keyed end of frequency stabilization control, be subject to the influence that extraneous factor changes, laser frequency stability is lower, and this is three of the present invention's innovative point of distinguishing prior art;

Description of drawings

Fig. 1 is desirable beam split of existing vertical zeeman laser and actual beam split schematic diagram

Fig. 2 is the theory diagram of apparatus of the present invention

Fig. 3 is the structural representation of apparatus of the present invention

Fig. 4 is a temperature closed loop control system schematic diagram in the warm of the present invention

Fig. 5 is a not constant amplitude polarised light beat frequency light intensity schematic diagram of the present invention

Fig. 6 accurately separates schematic diagram for frequency stabilization process luminous power of the present invention

Fig. 7 locks the closed-loop control system schematic diagram zero point for difference power in the frequency stabilization process of the present invention

Frequency stabilization process optical power difference delta data curve before and after Fig. 8 power of the present invention accurately separates

Among the figure, 1 magnet ring, 2 laser tubes, 3 high voltage sourcies, 4 temperature sensors, 5 electric-heating thin films, 6 quarter-wave plates, 7 polarizing beam splitters, 8 and 9 low drift high frequency light electric explorers, 10 and 11 preamplifiers, 12 and 13 low pass filters, 14 and 15 rearmounted direct current amplifiers, 16 and 17 rearmounted AC coupled amplifiers, 18 and 19 peak detectors, 20A/D transducer, 21 microprocessors, 22D/A transducer, 23 power amplifiers, 24 and 25 frequency stabilization status indicator lamps

Embodiment:

Embodiments of the present invention is described in detail below in conjunction with accompanying drawing.

A kind of vertical zeeman laser frequency-stabilizing method that accurately separates based on luminous power, this method may further comprise the steps:

(1) open high voltage source 3, preheating places the coaxial-type laser cavity 2 of longitudinal magnetic field that magnet ring produces, and its negative output terminal outgoing frequency is respectively f _LAnd f _R, power is respectively P _LAnd P _RLeft and right rounding polarised light, utilize the left and right rounding polarised light of quarter-wave plate 6 and polarizing beam splitter 7 initial gross separations to obtain the orthogonal A in polarization direction, B two-route wire polarised light, because the luminous power aliasing and the beat frequency interference of the different frequency laser that the non-ideal characteristic of laser and the design of light path and adjustment error are brought, aliasing has power to be respectively P in the A route polarised light _AL=(1-α) P _L, P _AR=β _PRThe laser of two kinds of different frequencies, aliasing has power to be respectively P in the B route polarised light _BL=α P _L, P _BR=(1-β) P _RThe laser of two kinds of different frequencies.

(2) utilize low drift high frequency light electric explorer 8 and preamplifier 10 to change the radiation of A route polarised light into voltage signal, have DC level component and frequency in the voltage signal to be | f _L-f _R| alternating current component, respectively straight, AC signal are carried out the amplification with equimultiple by rearmounted direct current amplifier 14, rearmounted AC coupled amplifier 16, record DC component value P ₁Amplitude P with alternating current component ₃Correspondingly utilize low drift high frequency light electric explorer 9 and preamplifier 11 rearmounted direct current amplifiers 15,17 pairs of B routes of rearmounted AC coupled amplifier polarised light to handle equally, detect DC component value P ₂Amplitude P with alternating current component ₄

(3) by P ₁, P ₃Numerical value is obtained $P_{\mathrm{AL}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+{\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="C2008101370810013H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_3}+\sqrt{P_1-P_3})}^2/4,$ $P_{\mathrm{AR}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+P_3}-\sqrt{P_1-P_3})}^2/4,$ Again according to P ₂, P ₄Numerical value is obtained $P_{\mathrm{BL}}={(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C2008101370810015H1.png,C2008101370810016H1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2+P_4}-\sqrt{P_2-P_4})}^2/4,$ $P_{\mathrm{BR}}={(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C2008101370810015H1.png,C2008101370810016H1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2+{\mathrm{<figure-callout\; id="4"\; label="P"\; filenames="C2008101370810013H2.png,C2008101370810015H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_4}+\sqrt{P_2-P_4})}^2/4,$ Then can accurately separate and record the luminous power P of the left and right rounding polarised light of laser tube 2 negative output terminal outgoing _L=P _AL+ P _BLAnd P _R=P _AR+ P _BR

(4) laser tube 2 reach set preheat temperature and near thermal equilibrium state after, according to the optical power difference Δ P=P of left and right rounding polarised light _L-P _R, adjust the current value that is wrapped in the electric-heating thin film 5 on the laser tube, the temperature resonant cavity that changes laser tube 2 is long, constitutes the frequency stabilization control loop.Control loop locking difference power is zero, and left and right rounding polarised light frequency is symmetrically distributed with respect to the gain curve centre frequency, and two light frequencies are all stablized.

Utilize the luminous power of quarter-wave plate 6, the left and right rounding polarised light of polarizing beam splitter 7 initial gross separation lasers, and pass through to hang down the luminous power aliasing of different frequency laser light in drift high frequency light electric explorer 8 and the further defiber polarised light of 9 detection signals, thereby make the luminous power P of the whole left and right rounding polarised light of laser tube negative output terminal outgoing _LAnd P _RAccurately separated.

Low drift high frequency light electric explorer 8 and 9 output informations had both comprised the DC component that the luminous power aliasing brings, and comprised the high-frequency ac component that different frequency photo-beat frequency band comes again.

Utilize low drift high frequency light electric explorer 8 output DC component value P ₁Amplitude P with alternating current component ₃Obtain the optical power value of two kinds of frequency laser of aliasing in the A route polarised light $P_{\mathrm{AL}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+{\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="C2008101370810013H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_3}+\sqrt{P_1-P_3})}^2/4,$ $P_{\mathrm{AR}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+P_3}-\sqrt{P_1-P_3})}^2/4,$ Utilize the DC component value P of another low drift high frequency light electric explorer 9 outputs ₂Amplitude P with alternating current component ₄Obtain the optical power value of two kinds of different frequency laser of aliasing in the B route polarised light $P_{\mathrm{BL}}={(\sqrt{P_1+P_3}-\sqrt{P_1-P_3})}^2/4,$ $P_{\mathrm{BR}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+{\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="C2008101370810013H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_3}+\sqrt{P_1-P_3})}^2/4.$

Utilize low drift high frequency light electric explorer 8 and 9 and the P that obtains of the accurate separated light power of testing circuit _AL, P _AR, P _BLAnd P _BR, the luminous power of obtaining the left and right rounding polarised light of laser tube negative output terminal outgoing is P _L=P _AL+ P _BLAnd P _R=P _AR+ P _BR

With keyed end at difference power zero point of separating the left and right sides rounding polarised light that obtains through twice luminous power as frequency stabilization control.

A kind of vertical zeeman laser frequency regulator that accurately separates based on luminous power, its composition comprises: magnet ring 1, laser tube 2, high voltage source 3, temperature sensor 4, electric-heating thin film 5, quarter-wave plate 6, polarizing beam splitter 7, preamplifier 10 and 11, A/D converter 20, microprocessor 21, D/A converter 22, power amplifier 23, frequency stabilization status indicator lamp 24 and 25, it is characterized in that: this device also comprises low pass filter 12 and 13, low drift high frequency light electric explorer 8 and 9, rearmounted direct current amplifier 14 and 15, rearmounted AC coupled amplifier 16 and 17 and peak detector 18 and 19, they and preamplifier 10 and the accurate separation detection circuit of 11 common formation luminous powers.Between polarizing beam splitter 7 and two preamplifiers 10 and 11, dispose a low drift high frequency light electric explorer 8 or 9 respectively, preamplifier 10 or 11 output are connected with rearmounted AC coupled amplifier 16 or 17 with low pass filter 12 or 13 respectively, low pass filter 12 or 13 and rearmounted AC coupled amplifier 16 or 17 and A/D converter 20 between dispose rearmounted direct current amplifier 14 or 15 and peak detector 18 or 19 respectively.

Preamplifier 10 and 11 can be with the alternating current component of DC component and MHz magnitude frequency in the amplification faint light current signal of equimultiple.

The course of work of whole device is divided into preheating and two stages of frequency stabilization.

When embodiment device was started working, microprocessor 21 (ATML89C52) drove preheat mode lamp 24 (LED), and display unit enters preheat mode; Microprocessor 21 is opened high voltage source 3 and is lighted laser tube 2; In pre-thermal control, microprocessor 21 is an input signal with the preheating target temperature, the laser tube temperature that temperature sensor 4 (HTS206) records is output signal and feedback signal, this is applicable to the control algolithm of delay system according to MPC, the output digital signal obtains aanalogvoltage by D/A converter 22 (AD420) digital-to-analogue conversion, this aanalogvoltage is delivered to power amplifier 23 (OPA544T) obtain high-power voltage signal, with the electric current I size of control, to laser tube 2 heating by electric-heating thin film 5 (the precious pottery of promise).

Laser tube 2 reach set preheat temperature and near thermal equilibrium state after, microprocessor 21 turn-offs preheat mode lamp 24 (LED), drive frequency stabilization status lamp 25 (LED), microprocessor 21 switches whole device and begins frequency stabilization control: the left and right sides rounding polarised light that laser tube 2 negative output terminals send is converted to orhtogonal linear polarizaiton light according to its polarization characteristic by quarter-wave plate 6, is divided into A, B two-route wire polarization by polarizing beam splitter 7 (PBS) again; Low drift high frequency light electric explorer 8 (PIN) and preamplifier 10 (ICL7650) change A road light into voltage signal, and low pass filter 12, rearmounted direct current amplifier 14 (ICL7650), rearmounted AC coupled amplifier 16, peak detector 18 carry out signal condition and output DC component value P to straight, alternating current component in this voltage signal respectively ₁Amplitude with alternating current component _P3, same, low drift high frequency light electric explorer 9 (PIN), preamplifier 11 (ICL7650), low pass filter 13, rearmounted direct current amplifier 15 (ICL7650), rearmounted AC coupled amplifier 17, peak detector 19 receive B road light and output DC component value P ₂Amplitude P with alternating current component ₄Microprocessor 21 utilizes A/D converter 20 (AD7738) to gather P simultaneously ₁, P ₂, P ₃And P ₄Value, and accurately isolate the luminous power P of the left and right rounding polarised light that laser tube 2 negative output terminals send by computing _L, P _RAnd then draw its difference power Δ P=P _L-P _RWith the null value is input signal, difference power Δ P=P _L-P _RBe feedback signal, this is applicable to the control algolithm of thermal capacitance non linear system to microprocessor 21 according to Smith-PI, the output digital signal obtains aanalogvoltage by D/A converter 22 digital-to-analogue conversions, this aanalogvoltage is delivered to power amplifier 23 obtain high-power voltage signal, long to adjust by the electric current I resonant cavity big or small and laser tube 2 of electric-heating thin film 5 (the precious pottery of promise), make left and right rounding polarised light frequency about gain curve centre frequency symmetry, optical power difference levels off to zero; In the time of near optical power difference is stable at null value, microprocessor 21 turn-offs frequency stabilization status lamps 24 (LED), shows that frequency stabilization work finishes.

Fig. 4 is a temperature closed loop control system schematic diagram in the warm of the present invention, temperature closed loop control system input signal preheating target temperature T _SetBe set at fixed value, bring the gain curve central frequency deviation, promptly reduced the frequency drift of frequency stabilization keyed end, improved laser frequency stability with the ambient temperature, the laser tube air pressure change that reduce laser frequency stabilizing system under the different preheating condition.

Fig. 5 has provided the not amplitude and the light intensity schematic diagram of constant amplitude polarised light beat frequency.Because the non-ideal characteristic of the laser shown in Fig. 1 (b) and the design of light path and adjustment error, the luminous power aliasing that has different frequency laser in A, the B two-route wire polarised light, wherein the left and right rounding polarised light luminous power of aliasing is respectively P in the A route polarised light _AL=(1-α) P _L, P _AR=β P _R, the left and right rounding polarised light luminous power of aliasing is respectively P in the B route polarised light _BL=α P _L, P _BR=(1-β) P _R, then rounding polarised light in the left and right sides all forms beat frequency interference in A, B two-way polarised light.With A road polarised light is example, and its aliasing light signal is respectively as Fig. 5 (a), 6 (b), and by relevant beat frequency theory as can be known, photo-beat back frequently forms new optical generation signal, and as Fig. 5 (c), its amplitude maximum is

Minimum value is Therefore, obtain in the optical power signals with the square-law detection through photoelectric device, as Fig. 5 (d), its luminous power mean value is DC component P ₁Be P _AL+ P _BL, luminous power alternating current component peak-to-peak value is ${(\sqrt{P_{\mathrm{AL}}}+\sqrt{P_{\mathrm{AR}}})}^2-{(\sqrt{P_{\mathrm{AL}}}-\sqrt{P_{\mathrm{AR}}})}^2=4\sqrt{P_{\mathrm{AL}}\&times;P_{\mathrm{AR}}},$ Amplitude P ₃For

So there is the Left-hand circular polarization luminous power of aliasing in the polarised light of A road to be:

$P_{\mathrm{AL}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+{\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="C2008101370810013H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_3}+\sqrt{P_1-P_3})}^2/4---\left(1\right)$

The right-hand circular polarization luminous power of aliasing is in the polarised light of A road:

$P_{\mathrm{AR}}={(\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C2008101370810016H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_1+P_3}-\sqrt{P_1-P_3})}^2/4---\left(2\right)$

In like manner, the right-hand circular polarization luminous power of aliasing is in the polarised light of B road:

$P_{\mathrm{BL}}={(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C2008101370810015H1.png,C2008101370810016H1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2+P_4}-\sqrt{P_2-P_4})}^2/4---\left(3\right)$

The Left-hand circular polarization luminous power of aliasing is in the polarised light of B road

$P_{\mathrm{BR}}={(\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="C2008101370810015H1.png,C2008101370810016H1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2+{\mathrm{<figure-callout\; id="4"\; label="P"\; filenames="C2008101370810013H2.png,C2008101370810015H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_4}+\sqrt{P_2-P_4})}^2/4---\left(4\right)$

Fig. 6 has provided and has realized the circuit diagram that luminous power is accurately separated, and utilizes low drift high frequency light electric explorer 8 and preamplifier 10 to change the radiation of A route polarised light into voltage signal, has DC level component and frequency in the voltage signal to be | f _L-f _R| alternating current component, respectively straight, AC signal are carried out the amplification with equimultiple by rearmounted direct current amplifier 14, rearmounted AC coupled amplifier 16, record DC component value P ₁Amplitude P with alternating current component ₃Correspondingly, low drift high frequency light electric explorer 9 and preamplifier 11 rearmounted direct current amplifiers 15,17 pairs of B routes of rearmounted AC coupled amplifier polarised light are handled equally, detect DC component value P ₂Amplitude P with alternating current component ₄Microprocessor 21 utilizes A/D converter 20 to gather P simultaneously ₁, P ₂, P ₃And P ₄Value, and accurately isolate the luminous power P of the left and right rounding polarised light that laser tube 2 negative output terminals send by computing _L, P _R

Fig. 7 has provided in the frequency stabilization process of the present invention difference power and has locked the closed-loop control system schematic diagram zero point.With the null value is input signal, accurately separates the luminous power P of left and right rounding polarised light gained with microprocessor 21 _L, P _RDifference Δ P=P _L-P _RBe feedback signal, this is applicable to the control algolithm of thermal capacitance non linear system according to Smith-PI, the output digital signal obtains aanalogvoltage by D/A converter 22 digital-to-analogue conversions, this aanalogvoltage is delivered to power amplifier 23 obtain high-power voltage signal, long to adjust by the electric current I of electric-heating thin film 5 resonant cavity big or small and laser tube 2, make left and right rounding polarised light frequency about gain curve centre frequency symmetry, optical power difference levels off to zero.

Fig. 8 has provided power and has accurately separated optical power difference delta data in the front and back frequency stabilization process, and wherein Fig. 8 (a) is the difference power data of conventional power difference frequency stabilization process, and Fig. 8 (b) accurately separates the difference power data of back frequency stabilization process for power.Difference power among two figure through frequency stabilization can be controlled at ± the 3mV scope in, but the frequency stabilization keyed end of Fig. 8 (a) is not real difference power zero point.Be also shown in after overpower accurately separates by Fig. 8, compare with Fig. 8 (a) data, the data of Fig. 8 (b) distribute and have more symmetry, and are consistent with the power symmetry of the left and right rounding polarised light of laser tube, and the authenticity at difference power zero point this moment has been verified in the side.

Claims (2)

1, a kind of vertical zeeman laser frequency-stabilizing method that accurately separates based on luminous power is characterized in that this method may further comprise the steps:

(1) open the coaxial-type laser cavity that also preheating places longitudinal magnetic field, its negative output terminal outgoing frequency is respectively f _LAnd f _R, power is respectively P _LAnd P _RLeft and right rounding polarised light, utilize the left and right rounding polarised light of quarter-wave plate and polarizing beam splitter initial gross separation laser to obtain the orthogonal A in polarization direction, B two-route wire polarised light, aliasing has power to be respectively P in the A route polarised light _AL=(1-α) P _L, P _AR=β P _RTwo kinds of different frequency laser, aliasing has power to be respectively in the B route polarised light _PBL=α P _L, P _BR=(1-β) P _RTwo kinds of different frequency laser;

(2) utilize low drift high frequency light electric explorer to change the radiation of A route polarised light into the signal of telecommunication, have DC level component and frequency in the signal of telecommunication to be | f _L-f _R| alternating current component, straight, AC signal are carried out the amplification with equimultiple, record DC component value P ₁Amplitude P with alternating current component ₃Correspondingly B route polarised light is handled equally, detect DC component value P ₂Amplitude P with alternating current component ₄

(3) by P ₁, P ₃Numerical value is obtained $P_{\mathrm{AL}}={(\sqrt{P_1+P_3}+\sqrt{P_1-P_3})}^2/4,$ $P_{\mathrm{AR}}={(\sqrt{P_1+P_3}-\sqrt{P_1-P_3})}^2/4,$ Again according to P ₂, P ₄Numerical value is obtained $P_{\mathrm{BL}}={(\sqrt{P_2+P_4}-\sqrt{P_2-P_4})}^2/4,$ $P_{\mathrm{BR}}={(\sqrt{P_2+P_4}+\sqrt{P_2-P_4})}^2/4,$ Then can accurately separate and record the luminous power P of the left and right rounding polarised light of laser tube negative output terminal outgoing _L=P _AL+ P _BLAnd P _R=P _AR+ P _BR

(4) laser tube reach set preheat temperature and near thermal equilibrium state after, according to the optical power difference Δ P=P of left and right rounding polarised light _L-P _R, adjust the current value that is wrapped in the electrothermal device on the laser tube, it is long to change the laser tube temperature resonant cavity, constitutes the frequency stabilization control loop.

2, the vertical zeeman laser frequency-stabilizing method that accurately separates based on luminous power according to claim 1 is characterized in that: with the keyed end as frequency stabilization control at difference power zero point of separating the left and right sides rounding polarised light that obtains through twice luminous power.

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