CN201332215Y - DDS acousto-optic modulating wave length locking device - Google Patents

DDS acousto-optic modulating wave length locking device Download PDF

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Publication number
CN201332215Y
CN201332215Y CNU2008201696180U CN200820169618U CN201332215Y CN 201332215 Y CN201332215 Y CN 201332215Y CN U2008201696180 U CNU2008201696180 U CN U2008201696180U CN 200820169618 U CN200820169618 U CN 200820169618U CN 201332215 Y CN201332215 Y CN 201332215Y
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acousto
laser
dds
optic
optic modulator
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Expired - Fee Related
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CNU2008201696180U
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Chinese (zh)
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张璋
林强
徐云飞
王兆英
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Zhejiang University ZJU
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Zhejiang University ZJU
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  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Lasers (AREA)

Abstract

A DDS acousto-optic modulating wave length locking device mainly comprises a laser (1), a beamsplitter (2), a acousto-optic modulator(3), a DDS acousto-optic driver (4), a polarization beamsplitter (5), a convex lens (6), a quarter wave plate (7), a reflecting mirror (8), an atomical vapor pool (9), a photodetector (10) and a phase locking magnifier (11), an integral body of the DDS acousto-optic modulating wave length locking device is formed through adopting a laser light path for connecting, wherein the phase locking magnifier (11) is connected with the photodetector (10), the DDS acousto-optic driver (4) and the laser (1) respectively, and the DDS acousto-optic driver (4) is connected with the acousto-optic modulator(3). The DDS acousto-optic modulating wave length locking device has the advantages of compact light path, easy adjustment, and good stability of the locking frequency, adopts DDS acousto-optic modulator, and is superior to general voltage controlled oscillators.

Description

DDS acoustooptic modulation wavelength locker
Technical field
The utility model relates to a kind of wavelength locking technology of laser, particularly DDS acoustooptic modulation wavelength locker and wavelength locking method.
Background technology
In a lot of fields of communication, industry and scientific research, all need accurate locked laser wavelength.Usually all the output of tunable laser is locked on the spectral line of certain atom vapor sodium for example, rubidium, indium, iodine etc.Generally the method by phase-locked amplification is locked in laser on the peak of spectrum.At first, the output wavelength of laser is carried out the audio frequency modulation, also will be superimposed with modulation signal on the absorption line when laser sees through atom vapor.By phase lock amplifying technology, detect the error between optical maser wavelength and the atomic spectral line then,, make the output wavelength all-the-time stable of laser on atomic spectral line by feedback circuit FEEDBACK CONTROL laser.
Traditional wavelength locking method need be modulated the resonant cavity of laser, makes laser output wavelength modulate thereupon.After the wavelength locking, the output of laser comprises the audio frequency modulation all the time, in order to obtain narrower laser linewidth, can only reduce modulation amplitude like this.Meanwhile, the error signal amplitude between optical maser wavelength and the atomic spectral line is also less, makes locking stable inadequately.When laser linewidth was had relatively high expectations, the contradiction between laser linewidth and the locking stability just can appear.
Summary of the invention
The utility model is in order to solve this contradiction between laser linewidth and the locking stability, and purpose provides a kind of acoustooptic modulation wavelength locking technology based on Direct Digital synthetic (DDS), is used for replacing traditional laser cavity modulation wavelength lock-in techniques.
The utility model provides a kind of acoustooptic modulation wavelength locking technology based on Direct Digital synthetic (DDS).On the basis that conventional method is modulated the resonant cavity of laser, increase an acousto-optic modulator and convex lens, can realize.Light path is succinct, is easy to adjust, and it is few to increase cost; But can significantly press narrow laser linewidth, and obtain enough error signal amplitude to realize stablizing frequency locking; In addition, select different acousto-optic driving frequencies, can regulate the poor of laser output wavelength and atomic spectral line wavelength easily, can also realize frequency scanning, more flexible than directly being locked on the atomic spectral line.Because adopt the DDS acousto-optic modulator, use digital controlly, be convenient to digital industrial control equipment collaborative work.
The utility model provides the wavelength locking technology of laser, comprising: DDS acoustooptic modulation wavelength locker and wavelength locking method.
The utility model provides DDS acoustooptic modulation wavelength locker, (referring to accompanying drawing 1) is mainly by laser 1, beam splitter 2, acousto-optic modulator 3, DDS acousto-optic driver 4, polarization beam apparatus 5, convex lens 6, quarter-wave plate 7, speculum 8, atom vapor pond 9, photodetector 10 and lock-in amplifier 11 are formed, connect by laser optical path, constitute the integral body of DDS acoustooptic modulation wavelength locker, wherein: lock-in amplifier 11 by coaxial cable respectively with photodetector 10, DDS acousto-optic driver 4 is connected with laser 1, and DDS acousto-optic driver 4 is connected with acousto-optic modulator 3 by coaxial cable.
The utility model provides DDS acoustooptic modulation wavelength locker, has used DDS acousto-optic modulator and modulation compensated light path; Described laser 1 is a tunable laser to be locked; Described beam splitter 2 is told a part with the laser of laser 1 output and is entered acousto-optic modulator 3; Described acousto-optic modulator 3 is modulated the laser of input, is divided into ' 0 ' grade and ' 1 ' grade of output laser; Described DDS acousto-optic driver 4 usefulness radio frequency signals drive acousto-optic modulators 3, its output frequency equals the phonon frequency in the acousto-optic modulator 3; Described polarization beam apparatus 5 allows laser-transmitting or reflection according to the polarization direction; Described convex lens 6 equal the focal length of convex lens 6 apart from the light path of acousto-optic modulator 3, and the laser that penetrates from acousto-optic modulator 3 all becomes directional light after by convex lens 6; ' 1 ' level laser of compensation acousto-optic modulator 3 outputs is because the variation of the deflection angle that different modulating frequencies causes; Make ' 1 ' level laser mirror 8 vertical reflections that can be reflected all the time, and former road returns, form incident light and reverberation and propagate in the other direction, in atom vapor pond 9, produce the saturated absorption effect with light path; Described quarter-wave plate 7 will be penetrated the horizontal linear polarization laser that comes from polarization beam apparatus 5 become Left-hand circular polarization, and the reflector laser of the right-hand circular polarization that will reflect from speculum 8 becomes the vertical curve polarization; Described speculum 8 will reflect back from polarization beam apparatus 5 with reflecting next laser vertical; The atom vapor that is used for observing atomic spectral line has been adorned in described atom vapor pond 9; Will be absorbed in atom vapor pond 9 with the laser of atomic spectral line resonance, two bundle laser of correlation the saturated absorption effect can occur in atom vapor pond 9; Described photodetector 10 is placed on the focus place of convex lens 6, and observation sees through the laser in atom vapor pond 9, and light intensity signal is converted into the signal of telecommunication; Described lock-in amplifier 11 is sent modulation signal into DDS acousto-optic driver 4, detects error between optical maser wavelength and the atomic spectral line by phase lock amplifying technology, and gives laser 1 with this Error Feedback.
' 0 ' grade of output of acousto-optic modulator 3 described in the utility model and ' 1 ' level laser, ' 0 ' grade of output laser frequency and direction are all constant, ' 1 ' grade of output laser frequency increases a phonon frequency, and direction deflection and deflection tangent of an angle are the phonon frequency and the ratio of laser frequency.
Laser from acousto-optic modulator 3 output described in the utility model is in polarization beam apparatus 5 reflections, the laser transmission on polarization beam apparatus 5 that reflects from speculum 8.
The wavelength locking method of the utility model DDS acoustooptic modulation wavelength locker is: laser 1 emitting laser is through beam splitter 2, and most of transmission is exported, and fraction reflexes to acousto-optic modulator 3.DDS acousto-optic driver 4 is connected to acousto-optic modulator 3 by coaxial cable, drives acousto-optic modulator 3 work.Acousto-optic modulator 3 is launched ' 0 ' grade and ' 1 ' level laser.' 1 ' level laser of acousto-optic modulator 3 outgoing is incident upon polarization beam apparatus 5, reflexed to convex lens 6 laser fully successively through behind convex lens 6 and the atom vapor pond 9, become left circularly polarized light by quarter-wave plate 7, by speculum 8 vertical reflections, former road is returned again.When laser oppositely sees through quarter-wave plate 7, become the vertical curve polarised light, and oppositely atom vapor pond 9 is crossed in transmission, penetrated the laser that comes with forward and form correlation, produce the saturated absorption effect, the spectrum of the hyperfine structure energy level of the Doppler broadening that obtains to disappear.The reverse transmission of laser is crossed and is seen through convex lens 6 behind the atom vapor pond 9 again and enter polarization beam apparatus 5, because the cause of polarization, retroreflection laser will see through polarization beam apparatus 5 fully, and injects photodetector 10 and be converted to the signal of telecommunication.Photodetector 10 is sent the signal of telecommunication into lock-in amplifier 11 by coaxial cable.Lock-in amplifier 11 is sent into DDS acousto-optic driver 4 with modulation signal by coaxial cable, and the error signal after will handling feeds back to laser 1 by coaxial cable.
Laser 1 described in the utility model is the tunable laser of output wavelength to be locked, is subjected to the control of external voltage signal, changes the characteristic of its resonant cavity, can tuning within the specific limits output Wavelength of Laser.
Beam splitter 2 described in the utility model is a kind of optical elements that laser can be divided into two bundles, and is stronger a branch of as output, and more weak is a branch of as surveying light, is used for the detection laser wavelength.
Acousto-optic modulator 3 described in the utility model, the driving radiofrequency signal that will import by transducer is converted into ultrasonic wave, is applied on the acousto-optic crystal, forms the acoustics grating.Diffraction will take place after by grating in the laser of incident.' 0 ' order diffraction optical wavelength and transmission direction are constant; ' 1 ' order diffraction light frequency increases a phonon frequency, and direction deflection and deflection tangent of an angle are the phonon frequency and the ratio of laser frequency.The utility model utilizes ' 1 ' order diffraction light.
DDS acousto-optic driver 4 described in the utility model directly uses the directly synthetic required frequency of digital mode and the waveform of amplitude, and amplifying power drives acousto-optic modulator 3 again.Accept the modulation signal of lock-in amplifier 11, carry out synchronous frequency conversion.On the atomic absorption spectrum of laser, be superimposed with the modulation signal of lock-in amplifier 11 in this way.
Polarization beam apparatus 5 described in the utility model can make the complete transmission of laser of horizontal polarization, and vertically the laser of polarization reflects fully.
Convex lens 6 described in the utility model make any light by its focus become the light of parallel its main shaft.
Quarter-wave plate 7 described in the utility model is placed to major axis from the horizontal by 45 degree, the laser of horizontal linear polarization can be become Left-hand circular polarization, also reverse transfer ground right-circularly polarized light can be become the vertical curve polarised light simultaneously.
Speculum 8 described in the utility model former road, the laser vertical of incident ground is reflected back, and Left-hand circular polarization becomes right-hand circular polarization.
Atom vapor described in the utility model pond 9 is the cavitys that glass is made, and inside is filled with the gas that is used to observe atomic spectral line.
Photodetector 10 described in the utility model uses photodiode to constitute, and light intensity signal can be converted to the signal of telecommunication.The light of injecting is strong more, and the signal of telecommunication is also strong more.
Lock-in amplifier 11 described in the utility model is a kind of general low noise detection instruments.It joins modulation signal in the measured signal and goes, and will come out with the synchronous signal demodulation of modulation signal by coherent detection then.This working mechanism makes it can detect the intensity and the phase place of the faint AC signal under the strong noise environment.In the utility model, when the detection light wavelength was longer than atomic transition spectral line, lock-in amplifier 11 output voltages made laser 1 output wavelength move to the shortwave direction for just; When surveying light wavelength than atomic transition spectral line in short-term, lock-in amplifier 11 output voltages make laser 1 output wavelength move to the long wave direction for negative.Make that by this feedback surveying optical wavelength is stabilized on the atomic transition spectral line.
The mechanism of DDS acoustooptic modulation wavelength locking technology provided by the utility model is: the output of laser 1 is told sub-fraction as surveying light, 3 pairs of acousto-optic modulators that use DDS acousto-optic driver 4 to drive are surveyed light and are carried out frequency modulation, and the modulation signal of this frequency modulation and lock-in amplifier 11 is synchronous.Detection light after the frequency modulation is done the saturation-absorption spectrum in atom vapor pond 9, and the angular deflection of the detection light that produces during by convex lens 6 compensation acousto-optic modulators 3 frequency modulation that are positioned over one times of focal length place.Enter photodetector 10 through the detection light of saturated absorption and be converted to the signal of telecommunication, make phase-locked processing and amplifying by the lock-in amplifier 11 that is attached thereto again, produce the error signal of surveying between optical wavelength and the atom absorption line.Feed back to the wave length shift of laser 1 compensate for laser with this error signal.
DDS acoustooptic modulation wavelength locking technology provided by the utility model is the output wavelength of direct modulated laser not, therefore can significantly press the output laser linewidth of narrow laser; Can obtain enough error signal amplitude to realize stablizing frequency locking; Light path is succinct, is easy to adjust, and it is few to increase cost; Select different acousto-optic driving frequencies, can regulate the poor of laser output wavelength and atomic spectral line frequency easily, can also realize frequency scanning, more flexible than directly being locked on the atomic spectral line; Adopt the DDS acousto-optic modulator, the frequency stability of locking is good, is better than general voltage controlled oscillator; Adopt digital frequency modulation, flexible, be convenient to digital industrial control equipment collaborative work.
Description of drawings:
Accompanying drawing 1 is the schematic diagram of DDS acoustooptic modulation wavelength locker
Embodiment
Embodiment 1:
Referring to accompanying drawing 1, the device of DDS acoustooptic modulation wavelength locking mainly is made up of laser 1, beam splitter 2, acousto-optic modulator 3, DDS acousto-optic driver 4, polarization beam apparatus 5, convex lens 6, quarter-wave plate 7, speculum 8, atom vapor pond 9, photodetector 10 and lock-in amplifier 11.
Described laser 1 is a tunable laser to be locked; What this embodiment used is the Lynx type external cavity semiconductor laser that a Sachar company produces.The about 150mW of power output, the output wavelength scope be 776nm to 795nm, centre wavelength is arranged on 780.1nm, the scope of can coordinating continuously is greater than 20GHz.In continuous tuning coverage, this laser can come tuning output optical maser wavelength by external control voltage, and voltage raises and moves to the shortwave direction, and the voltage reduction is moved to the long wave direction.
Described beam splitter 2 is told about 1mW with the laser of laser 1 output and is entered acousto-optic modulator 3.
Described acousto-optic modulator 3 is modulated the laser of input, and is divided into ' 0 ' grade and ' 1 ' grade of output laser.' 0 ' grade of output laser frequency direction is all constant, phonon frequency of ' 1 ' grade output laser frequency increase, and direction deflection and deflection tangent of an angle are the phonon frequency and the ratio of laser frequency.What the utility model used is the 3080-122 type acousto-optic modulator of Crystal Technology company.
Described DDS acousto-optic driver 4 usefulness radio frequency signals drive acousto-optic modulators 3, its output frequency equals the phonon frequency in the acousto-optic modulator 3.The DDS acousto-optic driver of this embodiment, its output center frequency is 72MHz, the frequency modulation amplitude is 2MHz.When the modulation signal of lock-in amplifier 11 was high level, DDS acousto-optic driver 4 was output as 74MHz; When the modulation signal of lock-in amplifier 11 was low level, DDS acousto-optic driver 4 was output as 70MHz.
Described polarization beam apparatus 5 can allow laser-transmitting or reflection according to the polarization direction.Will be from the laser of acousto-optic modulator 3 output in polarization beam apparatus 5 reflections, and the laser that reflects from speculum 8 will transmission on polarization beam apparatus 5.
Described convex lens 6 just equal the focal length of convex lens 6 apart from the light path of acousto-optic modulator 3, and the laser that penetrates from acousto-optic modulator 3 all will become directional light after by convex lens 6.' 1 ' level laser that so just can compensate acousto-optic modulator 3 outputs is because the variation of the deflection angle that different modulating frequencies causes.Make ' 1 ' level laser mirror 8 vertical reflections that can be reflected all the time, and former road returns, form incident light and reverberation and propagate in the other direction, in atom vapor pond 9, produce the saturated absorption effect with light path.
Described quarter-wave plate 7 will be penetrated the horizontal linear polarization laser that comes from polarization beam apparatus 5 become Left-hand circular polarization, and the reflector laser of the right-hand circular polarization that will reflect from speculum 8 becomes the vertical curve polarization.
Described speculum 8 will reflect back from polarization beam apparatus 5 with reflecting next laser vertical.
The thin rubidium steam that is used for observing atomic spectral line has been adorned in described atom vapor pond 9.The spectrum of the hyperfine structure energy level of the Doppler broadening that can obtain to disappear the saturated absorption effect can appear, in two bundle laser of correlation in atom vapor pond 9.The D of rubidium atom 2Transition is at the 780.1nm place, and the natural linewidth of hyperfine structure energy level is 6MHz.
Described photodetector 10 also is placed on the focus place of convex lens 6, and observation sees through the laser in atom vapor pond 9, and light intensity signal is converted into the signal of telecommunication.The silicon photoelectric diode that this embodiment uses is as photodetector 10.
Described lock-in amplifier 11 is sent modulation signal into DDS acousto-optic driver 4, detects error between optical maser wavelength and the atomic spectral line by phase lock amplifying technology, and gives laser 1 with this Error Feedback.Lock-in amplifier 11 modulating frequencies are 10KHz, and modulation waveform is a square wave.

Claims (4)

1, a kind of DDS acoustooptic modulation wavelength locker, mainly by laser (1), beam splitter (2), acousto-optic modulator (3), DDS acousto-optic driver (4), polarization beam apparatus (5), convex lens (6), quarter-wave plate (7), speculum (8), atom vapor pond (9), photodetector (10) and lock-in amplifier (11) are formed, it is characterized in that: connect by laser optical path, constitute the integral body of DDS acoustooptic modulation wavelength locker, wherein: lock-in amplifier (11) by coaxial cable respectively with photodetector (10), DDS acousto-optic driver (4) is connected with laser (1), and DDS acousto-optic driver (4) is connected with acousto-optic modulator (3) by coaxial cable.
2, DDS acoustooptic modulation wavelength locker according to claim 1, it is characterized in that: described device has used DDS modulator and modulation compensated light path; Described laser (1) is a tunable laser to be locked; Described laser optical path connects: the laser of laser (1) output enters beam splitter (2), and beam splitter (2) is told part and entered acousto-optic modulator (3); Described convex lens (6) equal the focal length of convex lens (6) apart from the light path of acousto-optic modulator (3); Described photodetector (10) is placed on the focus place of convex lens (6).
3, DDS acoustooptic modulation wavelength locker according to claim 1 is characterized in that: described quarter-wave plate (7) is placed to major axis from the horizontal by 45 degree.
4, DDS acoustooptic modulation wavelength locker according to claim 1 is characterized in that: atom vapor pond (9) are cavitys that glass is made, and inside is filled with the gas that is used to observe atomic spectral line.
CNU2008201696180U 2008-12-02 2008-12-02 DDS acousto-optic modulating wave length locking device Expired - Fee Related CN201332215Y (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103178437A (en) * 2013-02-27 2013-06-26 中国科学院武汉物理与数学研究所 Intelligentialized laser locking device and locking method
CN103746285A (en) * 2013-12-27 2014-04-23 中国科学院国家授时中心 Acoustic optical modulator-based high-stability laser frequency scanning device
CN103760135A (en) * 2013-12-30 2014-04-30 浙江大学城市学院 Speed transfer laser spectrum measuring device and method of V-type energy level structure atoms
CN103783016A (en) * 2013-04-07 2014-05-14 北京志光伯元科技有限公司 Laser disinsectization equipment
CN109473864A (en) * 2018-12-19 2019-03-15 武汉六九传感科技有限公司 A kind of high-precision laser with fixed wavelength

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103178437A (en) * 2013-02-27 2013-06-26 中国科学院武汉物理与数学研究所 Intelligentialized laser locking device and locking method
CN103178437B (en) * 2013-02-27 2015-04-01 中国科学院武汉物理与数学研究所 Intelligentialized laser locking device and locking method
CN103783016A (en) * 2013-04-07 2014-05-14 北京志光伯元科技有限公司 Laser disinsectization equipment
CN103783016B (en) * 2013-04-07 2016-03-16 北京志光伯元科技有限公司 A kind of laser vermin exterminating apparatus
CN103746285A (en) * 2013-12-27 2014-04-23 中国科学院国家授时中心 Acoustic optical modulator-based high-stability laser frequency scanning device
CN103746285B (en) * 2013-12-27 2016-09-21 中国科学院国家授时中心 A kind of high stability laser frequency scanning means based on acousto-optic modulator
CN103760135A (en) * 2013-12-30 2014-04-30 浙江大学城市学院 Speed transfer laser spectrum measuring device and method of V-type energy level structure atoms
CN109473864A (en) * 2018-12-19 2019-03-15 武汉六九传感科技有限公司 A kind of high-precision laser with fixed wavelength

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