CN101958510B - External-cavity semiconductor laser - Google Patents
External-cavity semiconductor laser Download PDFInfo
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- CN101958510B CN101958510B CN 201010225143 CN201010225143A CN101958510B CN 101958510 B CN101958510 B CN 101958510B CN 201010225143 CN201010225143 CN 201010225143 CN 201010225143 A CN201010225143 A CN 201010225143A CN 101958510 B CN101958510 B CN 101958510B
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Abstract
The invention discloses an external-cavity semiconductor laser, and an optical resonant cavity, an optical isolator and 1/2 wave plates are mainly arranged in a main optical path of an external cavity of the semiconductor laser; and a light beam emitted by a semiconductor laser tube can pass through the optical isolator in the forward direction via the first 1/2 wave plate, and the light beam after transmission of the resonant cavity of the semiconductor laser passes through the optical isolator in the reverse direction via the second 1/2 wave plate, thereby leading the light beam to return into the semiconductor laser tube along a path which is in collineation and reverse direction with the original emergent light beam. The external-cavity semiconductor laser can solve the problem that the spectral line of the conventional external-cavity semiconductor laser is wider through the relatively simple device.
Description
Technical field
The present invention relates to semiconductor laser field, refer to especially a kind of external-cavity semiconductor laser.
Background technology
Semiconductor laser comprises that distributed feed-back (DFB) and external-cavity semiconductor laser are the important LASER Light Source in scientific research and industry.Yet common external-cavity semiconductor laser output spectral line is very wide, generally reaches even several megahertzes of hundreds of kilohertz, and the dfb semiconductor laser usually has wider live width, and the existence of this wide live width and the application requirements of many occasions are far apart.
For addressing this problem, general semiconductor laser commonly used adopts electro-optical feedback and two kinds of methods of bulk of optical feedback to realize pressing the narrow semiconductor live width.Electro-optical feedback is to tell a part with having the wide laser beam of wider threads, incide separately on controlled Fabry-Perot (F-P) chamber, reception is through the F-P of ovennodulation cavity reflection ray laser signal, with obtain error signal after the modulation signal mixing, utilize the PDH locking means, make laser frequency be locked on certain resonance peak in this F-P chamber, thereby the pressure that realizes laser linewidth is narrow.The bulk of optical feedback method makes semiconductor laser tube and outer light path form optical circuit, utilizes the frequency-selecting effect of resonant cavity, realizes the purpose of laser linewidth.
Wherein, what the bulk of optical feedback method was the most often used is Littrow structure and Littman structure, as depicted in figs. 1 and 2.
In Littrow structure shown in Figure 1, the laser that is sent by semiconductor laser tube 1 is incident on diffraction grating 9 after aspheric collimation lens 3 collimations.The first-order diffraction light of diffraction grating 9 along with the path of the reverse conllinear of incident light, turn back in semiconductor laser tube 1 by former road, the incidence angle θ i that incides on diffraction grating 9 of the laser that sends of semiconductor laser tube 1 equals grating diffration angle θ d here.
In Littman structure shown in Figure 2, the laser that is sent by semiconductor laser tube 1 is incident on diffraction grating 9 with the angle of glancing incidence after aspheric collimation lens (AL) 3 collimations.The first-order diffraction light positive of diffraction grating 9 is incident on a plane feedback reflector mirror (M) 5, and after being fed speculum 5 reflections, Yan Yuanlu turns back on diffraction grating 9, again gets back in semiconductor laser tube 1 after diffraction through diffraction grating 9.
In addition, the bulk of optical feedback method also can be used the mode that adds the F-P chamber in light path.The contrary incident light in treated F-P chamber turns back to and forms bulk of optical feedback in semiconductor laser tube, namely forms resonance, utilizes the narrow spectrum light feedback of F-P resonance peak to press narrow linewidth.
For example: B.Dahmani, L.Hollberg, the resonant feedback semiconductor laser that and R.Drullinger proposes, as shown in Figure 3, utilize the confocal F-P cavity that adds in light path to realize that the light path feedback arranges a confocal F-P cavity that is comprised of chamber mirror 306 and chamber mirror 307 in the semiconductor laser exocoel.The divergent beams that sent by semiconductor laser tube 1 converge through aspheric collimation lens 3 and are collimated light beam, incide beam splitter 304, reverberation arrives speculum 300 through variable attenuator 301, diaphragm 302, matched lenses 303, after speculum 300 reflections, incide on the confocal F-P cavity that is formed by chamber mirror 306 and chamber mirror 307, wherein one road light beam in reverberation is returned in semiconductor laser tube 1 after secondary reflection through speculum 300 along the path reverse with former incident beam conllinear again.The transmitted light of chamber mirror 307 enters photodetector 309.Wherein be provided with F-P intonation seamless electroceramics on chamber mirror 307, be provided with laser phase and adjust piezoelectric ceramic on speculum 300, be respectively used to export the physics adjusting of light frequency and phase place.K. in addition
I.Ernsting, R.-H.Rinkleff, S.Schiller, and A.Wicht propose to adopt transmission-type grating and discrete component F-P chamber to consist of semiconductor laser can realize more narrow linewidth, as shown in Figure 4.Add a F-P refrative cavity that is consisted of by coupling mirror 401, speculum 402 and 403 3 discrete eyeglasses of speculum in the chamber of external-cavity semiconductor laser, form the bulk of optical feedback of F-P chamber and semiconductor laser tube, thereby press narrow linewidth.The divergent beams that semiconductor laser tube 1 is sent converge through aspheric collimation lens 3 and are collimated light beam, incide transmission grating 412, diffraction light arrives through 1/2 wave plate 404 the F-P chamber that is comprised of coupling mirror 401, speculum 402 and speculum 403, the contrary incidence reflection light beam in this chamber is returned in semiconductor laser tube 1 after diffraction through transmission grating 412 again along the path reverse with former incident beam conllinear; The mirror reverberation of coupling mirror 401 enters balance polarization detector 405, enters photodiode 406 through transmission grating 412 transmitted lights, so by the feedback electronic system, makes certain resonance peak in this F-P chamber be locked on the frequency of semiconductor outside cavity gas laser.
In described use bulk of optical feedback mode is pressed narrow semiconductor laser prior art, all use the contrary incident light in treated F-P chamber as feedback light.Not directly utilize F-P cavity reflection light to be as the reason of feedback light: when reverberation forms resonance in the chamber, light intensity is the most weak, and light intensity is the strongest when there is no resonance, therefore can't form the light path feedback, not directly the F-P transmitted light is used as feedback light.Simultaneously, reverse due to reverberation and incident light common road if use F-P cavity reflection light as feedback light when using straight chamber, can cause difficulty to catoptrical detection.
Therefore at described B.Dahmani, L.Hollberg, in the scheme of and R.Drullinger, adopting with confocal F-P cavity axis direction has in the mode incident F-P chamber of minute angle, light is come and gone in V-arrangement degeneracy mode in confocal F-P cavity propagate, when forming vibration, in the chamber, transmitted light beam returns along the incident light direction, form feedback, but such scheme causes the optical path adjusting difficulty.Described K.
I.Ernsting, R.-H.Rinkleff in the scheme of the folding F-P of the resolution element that S.Schiller, the people such as and A.Wicht propose chamber, utilizes the contrary incidence reflection light in folding F-P chamber to have the spectral composition opposite with the F-P chamber, thereby can use as feedback light.But the interference that easily is subject to external audio, mechanical oscillation and variations in temperature and the impact in existing discrete component F-P chamber, Systems balanth is poor.If need higher required precision and be designed to integrated single folding F-P chamber, higher to technological requirement.
Summary of the invention
In view of this, the object of the invention is to propose a kind of external-cavity semiconductor laser, solve the wider problem of conventional external-cavity semiconductor laser spectral line in better simply mode.
Based on above-mentioned purpose a kind of external-cavity semiconductor laser provided by the invention, be laid with in the main optical path of semiconductor laser exocoel: optical resonator, optical isolator and 1/2 wave plate;
The laying of semiconductor laser makes the light beam that described semiconductor laser tube is sent to pass through optical isolator through the one 1/2 wave plate forward, and the light beam that described resonant cavity is crossed in transmission can oppositely pass through optical isolator after the 2 1/2 wave plate, makes after this along turning back in semiconductor laser tube with former outgoing beam conllinear reverse path.
Optionally, also lay grating in the main optical path of semiconductor laser exocoel; The zeroth order diffraction light that the light beam process grating of main optical path forms is as output light, and First order diffraction light is as the feedback light of semiconductor laser;
Perhaps also lay other light-splitting devices beyond grating in the main optical path of semiconductor laser exocoel, the light beam of main optical path is incident on the part of telling after this light-splitting device as the output light of semiconductor laser, and remainder is as feedback light.
Optionally, grating described in this semiconductor laser is reflecting grating or transmission grating;
Described other light-splitting devices are partially reflecting mirror or Amici prism, and the feedback light path at main optical path that further coordinates with light-splitting device partly arranges the frequency-selecting device.
Optionally, resonant cavity described in this semiconductor laser is F-P cavity configuration or ring cavity structure.
Optionally, F-P chamber described in this semiconductor laser is straight cavity configuration or refrative cavity structure.
Optionally, resonant cavity described in this semiconductor laser is resolution element structure or en-block construction.
Optionally, when described in this semiconductor laser, resonant cavity is the F-P chamber, before the light beam that described resonant cavity is crossed in transmission enters described the 2 1/2 wave plate, another optical isolator is set further.
Optionally, also comprise following one or more modulating equipments in this semiconductor laser:
To the equipment that resonant frequency is modulated, the equipment that the noise spectra of semiconductor lasers exocoel is regulated is to the equipment of semiconductor laser tube output light frequency adjusting.
Optionally, the equipment of described in this semiconductor laser, resonant frequency being modulated comprises: on resonant cavity bonding piezoelectric ceramic temperature regulating device is set or both the combination;
The equipment that described noise spectra of semiconductor lasers exocoel is regulated comprises following one or more combinations: electrooptic modulator and chamber mirror controller, electrooptic modulator is used for adding modulation signal at the light beam of main optical path, survey light signal in main optical path by detector, being converted to the signal of telecommunication processes by electricity, obtain error signal, feed back to chamber mirror controller, control described outer cavity long, realize that exocoel is to the tracking of F-P chamber frequency or synchronous;
The described equipment that semiconductor laser tube output light frequency is regulated comprises following one or more combinations: by the semiconductor laser tube drive current is added modulation signal, realize the current-modulation equipment to the modulation of laser frequency; Perhaps change the equipment of semiconductor laser tube output light frequency scope by the temperature that changes semiconductor laser tube.
Optionally, be laid with optical resonator, optical isolator, 1/2 wave plate, light-splitting device and etalon in the main optical path of this semiconductor laser; The outgoing beam that sends from described semiconductor laser tube enters described optical isolator through the one 1/2 wave plate, incide light-splitting device from the outgoing beam of optical isolator, enter etalon after the light-splitting device beam splitting, enter described optical resonator through the etalon transmission, the outgoing beam of optical resonator through the 2 1/2 wave plate oppositely by optical isolator, after this along turning back in semiconductor laser tube with former outgoing beam conllinear reverse path.
Optionally, be laid with optical resonator, optical isolator, 1/2 wave plate and grating in the main optical path of this semiconductor laser; The outgoing beam that sends from described semiconductor laser tube enters described optical isolator through the one 1/2 wave plate, incide grating from the outgoing beam of optical isolator, enter described optical resonator after optical grating diffraction, the transmitted light beam of optical resonator through the 2 1/2 wave plate oppositely by optical isolator, after this along turning back in semiconductor laser tube with former outgoing beam conllinear reverse path.
Optionally, be laid with optical resonator, optical isolator, 1/2 wave plate and grating in the main optical path of this semiconductor laser; The outgoing beam that sends from described semiconductor laser tube incides grating, after optical grating diffraction, enter described optical isolator through the one 1/2 wave plate, outgoing beam from optical isolator, enter described optical resonator, the outgoing beam of optical resonator through the 2 1/2 wave plate oppositely by optical isolator, after this along turning back in semiconductor laser tube with former outgoing beam conllinear reverse path.
As can be seen from above, the external-cavity semiconductor laser that strengthens based on the resonant cavity feedback provided by the invention is utilized Faraday magnetooptical effect, uses the optical isolator resonant cavity in semiconductor laser, by bulk of optical feedback, laser linewidth is pressed narrow.
Description of drawings
Fig. 1 is prior art Littrow structure cavity semiconductor structural representation;
Fig. 2 is prior art Littman structure cavity semiconductor structural representation;
Fig. 3 is prior art B.Dahmani, L.Hollberg, the resonant feedback semiconductor aurora device structural representation that the people such as and R.Drullinger propose;
Fig. 4 is prior art K.
I.Ernsting, R.-H.Rinkleff, S.Schiller, the F-P chamber enhancing transmission grating Littman structure cavity semiconductor structural representation that the people such as and A.Wicht propose;
Fig. 5 is the structural representation of first embodiment of grating external cavity semiconductor laser of the present invention;
Fig. 6 is the structural representation of second embodiment of grating external cavity semiconductor laser of the present invention;
Fig. 7 is the structural representation of the 3rd embodiment of grating external cavity semiconductor laser of the present invention;
Fig. 8 is the structural representation that the present invention does not adopt the external-cavity semiconductor laser of grating;
Fig. 9 is that the present invention is with the structural representation of the grating external cavity semiconductor laser embodiment of complete conditioning equipment;
The structural representation in the single folding F-P chamber of Figure 10 embodiment of the present invention;
Figure 11 is the structural representation of the 4th embodiment of grating external cavity semiconductor laser of the present invention;
Figure 12 is the structural representation of the 5th embodiment of grating external cavity semiconductor laser of the present invention.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
External-cavity semiconductor laser provided by the invention mainly is laid with in the main optical path of semiconductor laser exocoel: optical resonator, optical isolator and 1/2 wave plate;
And, the light beam that described semiconductor laser tube is sent can pass through optical isolator through the one 1/2 wave plate forward, the light beam that described resonant cavity is crossed in transmission can oppositely pass through optical isolator after the 2 1/2 wave plate, make after this along turning back in semiconductor laser tube with former outgoing beam conllinear reverse path.
Main optical path described here namely refer to laser in semiconductor laser vibrate in exocoel the light path of process.
The present invention can lay grating in the main optical path of semiconductor laser exocoel; The light beam that described semiconductor laser tube is sent can pass through grating, and the zeroth order diffraction light of grating is as output light, and the First order diffraction light of grating is as the feedback light of semiconductor laser;
Perhaps be laid with light-splitting device in the main optical path of semiconductor laser exocoel, the light beam that described semiconductor laser tube is sent can pass through this light-splitting device, light beam is incident on the output light that the part of telling after this light-splitting device can be used as semiconductor laser, and remainder can be used as feedback light.And in order to guarantee that laser is output as single mode, preferably also need to add the frequency-selecting device in feedback light path, as etalon etc.
Design of the present invention utilizes the magneto optical effect of Faraday polarization apparatus in optical isolator, makes semiconductor laser possess simultaneously stationary field and traveling-wave field.Utilize the standing wave part in semiconductor laser, can use low-cost standing wave type semiconductor laser tube, simultaneously partly add resonant cavity at the main optical path traveling-wave field, utilize the resonant cavity transmitted light to realize that bulk of optical feedback strengthens, substitute numerous and diverse electricity feedback, make feedback light wavelength or frequency selection effect greatly strengthen by the resonance effect of resonant cavity.And the resonant cavity that uses only need have transmitted light, without other specific (special) requirements.Wherein, described traveling-wave field part refers to the light path part of optical isolator outgoing one side in structure of the present invention, be that light is after the transmission plane transmission of the exit end of optical isolator, before entering to inject optical isolator to the polarization splitting prism from the optical isolator exit end, the light path part of process.In addition, use the rear end PBS of first optical isolator to realize that the resonant cavity transmitted light returns in semiconductor laser tube, use the transmitted light of the resonant cavity of any chamber type to realize bulk of optical feedback and linewidth narrowing, just can be applied to this design as long as have transmitted light, make the realization that obtains narrow linewidth semiconductor laser simpler.
In the present invention, for avoiding the semiconductor laser tube shoot laser directly to feed back to semiconductor laser tube after the resonant cavity front surface reflection, cause the infringement to semiconductor laser tube, after generally resonant cavity being arranged at optical isolator, pass through again resonant cavity after the light beam process optical isolator that namely semiconductor laser tube is sent.And the position of described grating in light path can be any, such as: can make the light beam that semiconductor laser tube is sent pass through successively optical isolator, grating resonant cavity; Perhaps pass through successively optical isolator, resonant cavity and grating; Perhaps pass through successively grating, optical isolator resonant cavity etc.And for fear of the impact of resonant cavity on Output optical power, after generally resonant cavity being placed in grating, with the First order diffraction light that guarantees grating only through resonant cavity as feedback light, and do not pass through resonant cavity as the grating zeroth order diffraction of output light, to guarantee that power output is not decayed by resonant cavity.
Wherein, described resonant cavity can be the structures such as F-P chamber or annular chamber.
Referring to accompanying drawing, the embodiment of the present invention is elaborated.
Shown in Figure 5, the grating external cavity semiconductor laser of first embodiment of the invention mainly comprises: semiconductor laser tube (LD) 1, collimating lens (AL) 3,1/2 wave plate (HWP) 5,8, grating (Gt) 9, optical isolator (OI) 7 and F-P chamber 19.the laser that semiconductor laser tube 1 is sent passes through collimating lens 3 successively, the one 1/2 wave plate 5, after optical isolator 7, be incident upon on F-P chamber 19 at the first order diffraction beam on grating 9, F-P chamber 19 transmitted lights are after speculum 504 reflections, by the 2 1/2 wave plate 8, supervision mouth incident from optical isolator 7 outgoing one sides, utilize the magneto optical effect of optical isolator 7, make the transmitted light in F-P chamber 19 through polarization splitting prism 5022 reflections of optical isolator 7 exit ends, oppositely by optical isolator 7, turn back to semiconductor laser tube 1, thereby make transmitted light formation light path loop, F-P chamber.The zeroth order diffraction light of grating 9 is as output light, and the First order diffraction light of grating 9 is as the feedback light of semiconductor laser.As can be seen from Figure 5, from polarization splitting prism 5022 exit facets of optical isolator 7 exit ends to through reaching again polarization splitting prism 5022 reflectings surface of optical isolator 7 exit ends behind F-P chamber etc., this part light path is the traveling-wave field part, the F-P chamber is arranged at this, can utilize F-P chamber transmitted light to realize that bulk of optical feedback strengthens, substitute numerous and diverse electricity feedback.Because the F-P chamber has better frequency-selecting effect, make the frequency-selecting effect of whole grating external-cavity greatly be strengthened, the frequency noise that its effect shows as laser generation is further compressed, thus the pressure that realizes laser linewidth is narrow.Use the optical isolator resonant cavity in semiconductor laser, make laser possess the advantage of stationary field and traveling-wave field when making this laser form bulk of optical feedback.Partly use resonant cavity at the capable ripple of laser, utilize the resonant cavity transmitted light to realize bulk of optical feedback, utilize the stationary field part, use the standing wave type semiconductor laser tube, avoid using expensive travelling-wave type semiconductor laser tube.Make external-cavity semiconductor laser need not feed back the locking electronic system, realize that the breadth of spectrum line of Output of laser is less than 100kHz.Solved the wider problem of conventional external-cavity semiconductor laser spectral line, solved simultaneously when using low-cost standing wave type semiconductor laser tube, utilize resonant cavity to press the difficult problem of bulk of optical feedback in the application of narrow semiconductor laser linewidth, and need not chamber, F-P chamber type is carried out particular design and complicated processing, feedback locking electronic system without the complicated huge costliness in inside and outside of cavity, and the frequency of laser is more stable, easily tuning and control, has avoided using complicated lock-in circuit at a high speed.
Above preferred embodiment of the present invention be grating is arranged at resonant cavity before, the light beam that namely penetrates from semiconductor laser tube first passes through resonant cavity again through grating, can reduce like this loss of light intensity.But other design also is fine, for example:
shown in Figure 6, in the grating external cavity semiconductor laser of second embodiment of the invention, the laser that semiconductor laser tube 1 is sent passes through collimating lens 3 successively, the one 1/2 wave plate 5, after optical isolator 7, be reflected mirror 504 reflection and enter F-P chamber 19, light beam through F-P chamber 19 transmissions is incident on grating 9, first order diffraction beam is by the 2 1/2 wave plate 8, supervision mouth incident from optical isolator 7 outgoing one sides, utilize the magneto optical effect of optical isolator 7, make the transmitted light in F-P chamber 19 through polarization splitting prism 5022 reflections of optical isolator 7 exit ends, oppositely by optical isolator 7, turn back to semiconductor laser tube 1, thereby make transmitted light formation light path loop, F-P chamber.The zeroth order diffraction light of grating 9 is as output light, and the First order diffraction light of grating 9 is as the feedback light of semiconductor laser.
In addition, before the present invention also can be placed in the optical isolator resonant cavity with grating.
shown in Figure 7, in the grating external cavity semiconductor laser of third embodiment of the invention, after the laser that semiconductor laser tube 1 is sent collimates through collimating lens 3, first incide on grating 9, first order diffraction beam is by the one 1/2 wave plate 5, after optical isolator 7, be reflected mirror 701 reflection and enter F-P chamber 19, light beam through F-P chamber 19 transmissions reflects through another speculum 702, through the 2 1/2 wave plate 8, supervision mouth incident from optical isolator 7 outgoing one sides, utilize the magneto optical effect of optical isolator 7, make the transmitted light in F-P chamber 19 through polarization splitting prism 5022 reflections of optical isolator 7 exit ends, oppositely by optical isolator 7, turn back to semiconductor laser tube 1, thereby make transmitted light formation light path loop, F-P chamber.The zeroth order diffraction light of grating 9 is as output light, and the First order diffraction light of grating 9 is as the feedback light of semiconductor laser.
In the various embodiments described above, described collimating lens 3 converges for the light that semiconductor laser tube 1 is sent and is collimated light beam, and generally aspheric collimation lens commonly used is realized.Described speculum is used for changing radiation direction, preferably adopts the high reflectance level crossing, can pass through piezoelectric ceramic (PZT) change outer cavity long, realizes that exocoel is to the tracking lock in F-P chamber.
Also can not use grating in the exocoel of semiconductor laser of the present invention, embodiment shown in Figure 8, on outer-cavity structure shown in Figure 5 basis, substitute grating 9 with the partially reflecting mirror 801 with part reflection function, light beam is incident on the output beam that transmissive portion after this partially reflecting mirror 801 can be used as semiconductor laser, and the reflecting part can be used as feedback light.Also can use other light-splitting device except adopting partially reflecting mirror, as alternative in Amici prism etc.Certainly the grating in other embodiment semiconductor exocoels also can be with substituting as light-splitting devices such as partially reflecting mirror, Amici prisms, light beam is incident on the output light that the part of telling after this light-splitting device can be used as semiconductor laser like this, and remainder can be used as feedback light.In order to guarantee that laser is output as single mode, also added an etalon (Etalon) 802 between the partially reflecting mirror in feedback light path 801 and F-P chamber 19.
In the embodiment of the present invention, the resonance frequency that described resonant cavity determines can be by bonding piezoelectric ceramic on resonant cavity mirror, drive the long change of resonator by piezoelectric ceramic, and it is long to change resonator by temperature control technique by the effect of expanding with heat and contract with cold, thereby realize respectively fine tuning and coarse adjustment on a large scale among a small circle at a slow speed fast, realize the tuning of laser frequency and control.
Preferred in the present invention, also can add modulation signal in the electric current of semiconductor laser tube, realize the modulation to laser.the transmitted light of described resonant cavity incides optical isolator with the incident light rightabout after grating diffration, magnetic-optics due to optical isolator 7, through optical isolator Faraday part, the polarization state of feedback light is vertical with incident light, after the reflection of the polarization splitting prism of optical isolator exit end, can be used as locking monitoring light, being converted to the signal of telecommunication through the detector detection processes by electricity, obtain error signal, feed back to modulating equipment and realize that exocoel is to the tracking of resonant cavity frequency or synchronous, such as: by changing the voltage of the piezoelectric ceramic (PZT) after described speculum, realize that exocoel is to tracking or the genlocing of resonant cavity frequency.Wherein for embodiment shown in Figure 7, piezoelectric ceramic can be positioned over speculum 701 or other speculums 702,703 after any one.
In addition, also having a kind of scheme is that (preferably in the feedback light part) lays electrooptic modulator (EOM) in main optical path, be used for adding modulation signal at the light beam of main optical path, being converted to the signal of telecommunication through the detector detection processes by electricity, obtain error signal, feed back to modulating equipment and realize that exocoel is to the tracking of F-P chamber frequency or synchronous.
In the present invention, available tuning and control appliance comprise: resonant frequency is carried out tuning equipment with controlling, such as bonding piezoelectric ceramic on resonant cavity is realized fine tuning among a small circle fast, the heat sink temperature regulating device that waits is set on resonant cavity realizes coarse adjustment on a large scale at a slow speed; The equipment that the noise spectra of semiconductor lasers exocoel is regulated, such as: the scheme of the above-mentioned electrooptic modulator of laying in light path; And to the equipment that semiconductor laser tube output light frequency is regulated, such as current-modulation equipment, by the semiconductor laser tube drive current is added modulation signal, realize the modulation to laser frequency.
Be summed up, the conditioning equipment that semiconductor laser provided by the invention arranges mainly comprises following several types:
To the conditioning equipment of resonant cavity, regulate the resonance frequency that resonant cavity determines, such as the described piezoelectric ceramic that arranges, temperature regulating device etc. by the inside light path that changes the F-P chamber on resonant cavity;
Conditioning equipment to exocoel, regulate laser frequency by changing external cavity length, optical property etc., such as: toply describedly electrooptic modulator is set in main optical path and the chamber mirror controller such as piezoelectric ceramic is set that to be used for controlling outer cavity long after outer cavity mirror (speculum 504,701,702,703 etc. all belongs to the outer cavity mirror).Electrooptic modulator adds modulation signal in the light beam of main optical path, by detector, the light signal in main optical path is surveyed, being converted to the signal of telecommunication processes by electricity, obtain error signal, feed back to chamber mirror controller, control described outer cavity long, realize that exocoel is to the tracking of resonant cavity frequency or synchronous.
To the conditioning equipment of semiconductor laser tube, change semiconductor laser tube output light frequency scope, for example above-mentioned current-modulation equipment by the input current that changes semiconductor laser tube; Perhaps change semiconductor laser tube output light frequency scope by the temperature that changes semiconductor laser tube, for example arrange heat sinkly on semiconductor laser tube, control its temperature.
Referring to shown in Figure 9, the external-cavity semiconductor laser embodiment with conditioning equipment of the present invention is specifically described.
wherein, comprise: semiconductor laser tube 1, semiconductor laser tube is heat sink 2, aspheric collimation lens 3, aspheric collimation lens adjustment rack 4, the one 1/2 wave plate 5, detector 6, optical isolator 7, the 2 1/2 wave plate 8, grating 9, grating fixing bracket 10, the 3 1/2 wave plate 11, lens L1 12, electrooptic modulator 13, lens L2 14, high reflectance chamber mirror M1 15, matched lenses L3 16, diaphragm 17, high reflectance chamber mirror M2 18, F-P chamber 19, F-P chamber vacuum chamber 20, matched lenses L4 21, piezoelectric ceramic 22, high reflectance chamber mirror M3 23, λ/4 wave plates 24, the 4 1/2 wave plate 25, high reflectance chamber mirror M4 26, high reflectance chamber mirror M5 27, high reflectance chamber mirror M6 28, base plate 30.What label 29 was indicated is the zero order diffracted light of grating 9, can be used as the output beam of external-cavity semiconductor laser, and the First order diffraction light of this grating 9 continues to vibrate in exocoel as feedback light.
Wherein, described detector 6 is photodetector, is used for surveying F-P cavity reflection light, realizes that exocoel is to the tracking lock in F-P chamber; Matched lenses L3 16 is used for realizing that the LD output beam is to the coupling in F-P chamber; Diaphragm 17 is used for space filtering; F-P chamber vacuum chamber 20 is for increasing F-P chamber stability (sound insulation and heat insulation); Matched lenses L4 21 is used for realizing the coupling in exocoel and F-P chamber; Grating 9 is fixed on base plate 30 by grating fixing bracket 10, if needs also can be arranged to activity in addition, to regulate grating 9 angles.
In the present embodiment, power 30mW wavelength is the laser beam that the semiconductor laser tube 1 of 689nm is sent, be 4mm through focal length, after numerical aperture is 0.6 aspheric collimation lens, 3 collimations, 689nm30dB optical isolator 7 is crossed in transmission, to be incident on incisure density be 1800g/mm, have suitable diffraction efficiency, the groove size is that 12.5mm * 12.5mm, thickness are on the blazed diffraction grating 9 of 6mm, and for example incidence angle is 20.2 °, and the angle of diffraction is 63.5 °.The zeroth order diffraction light of grating 9 is as the output beam of laser.Grating 9 First order diffraction optical modes incide on the F-P chamber 19 that is made of the materials processing of high-quality optical quartz glass matchingly, with common exocoels that forms such as grating 9, semiconductor laser tube 1, optical isolator 7 and F-P chambeies 19.Optical isolator 7 in light path plays isolation F-P cavity reflection and returns the light of semiconductor laser tube and realize that F-P chamber 19 transmitted lights form the effect of optical circuits.F-P chamber transmitted light oppositely passes through after the polarization splitting prism reflection of optical isolator 7 exit ends by the exit end monitoring mouthful incident of optical isolator 7, turns back in semiconductor laser tube 1.Frequency-selecting effect due to F-P chamber 19 makes the frequency-selecting effect of grating 9 exocoels further be strengthened, and the frequency noise that its effect shows as laser generation is further compressed, thereby the pressure that realizes laser linewidth is narrow, obtains the short-term live width less than 100kHz.
F-P chamber described in the various embodiments described above of the present invention except being straight cavity configuration, can be also the structures such as refrative cavity.In addition, described F-P both can adopt in the chamber isolating construction (as two speculums with certain reflectivity), can be also en-block construction (as the monolithic quartz glass of plated film).For example, can adopt as shown in figure 10 single folding cavity configuration.Wherein the S1 face for the input coupling surface, the S2 face be fully reflecting surface as the fold plane in F-P chamber, the S3 face for output coupling surface.Incident light enters the F-P chamber from the S1 face, after multiple oscillation, exports from the S3 face between three faces.This en-block construction makes resonant cavity stability greatly improve, and is not subject to external interference.
In each embodiment in above-mentioned employing F-P chamber, can increase again another optical isolator in order to reach better effect, be arranged on feedback beam by the position before optical isolator 7, with the light that filters out impurities, prevent undesirable feedback light.Preferred described another optical isolator can be arranged on transmission and cross before the light beam of described resonant cavity enters into the 2 1/2 wave plate 8.
The present invention is preferred, and resonant cavity adopts high-purity and uniformity, and the high-quality optical quartz glass is as material.The F-P chamber is chosen as the straight cavity configuration of flat-concave cavity type, and its two speculum is carefully processed according to ultra-smooth optics processing technology, and the roughness on surface is lower than 0.5nm.Optically coated absorption coefficient is less than 50ppm.Resonant cavity preferably adopts high Q (quality factor) value, and concrete numerical value may be different for different chamber type, material and application etc., and scope can be tens to several ten thousand, for example: for above each embodiment, can select the Q value can select 5000.
In the embodiment of the present invention, except adopting the F-P chamber, also can adopt the resonant cavity of other structures such as annular chamber.
Shown in Figure 11, the grating external cavity semiconductor laser of four embodiment of the invention mainly comprises: semiconductor laser tube (LD) 1, collimating lens (AL) 3,1/2 wave plate (HWP) 5,8, grating (Gt) 9, optical isolator (OI) 7 and annular chamber (Cavity) 19a that is comprised of three discrete eyeglasses.the laser that semiconductor laser tube 1 is sent passes through collimating lens 3 successively, the one 1/2 wave plate 5, after optical isolator 7, be incident upon on annular chamber 19a at the first order diffraction beam one diffraction angle d on grating 9, the transmitted light of exporting after process ring oscillation between inner three eyeglasses of annular chamber 19a is after speculum 504 reflects, by the 2 1/2 wave plate 8, supervision mouth incident from optical isolator 7 outgoing one sides, utilize the magneto optical effect of optical isolator 7, make the transmitted light of annular chamber 19a through polarization splitting prism 5022 reflections of optical isolator 7 exit ends, oppositely by optical isolator 7, turn back to semiconductor laser tube 1, thereby make annular chamber 19a transmitted light form the light path loop.The zeroth order diffraction light of grating 9 is as output light, and the First order diffraction light of grating 9 is as the feedback light of semiconductor laser.As can be seen from Figure 11, from polarization splitting prism 5022 exit facets of optical isolator 7 exit ends to through reaching again polarization splitting prism 5022 reflectings surface of optical isolator 7 exit ends after annular chamber 19a etc., this part light path is the traveling-wave field part, annular chamber 19a is arranged at this, can utilize the annular chamber transmitted light to realize that bulk of optical feedback strengthens and linewidth narrowing, substitute numerous and diverse electricity feedback.
In the present embodiment, utilize annular chamber incident light and reverberation (comprising transmitted light in a part of chamber) not to be total to the characteristics on road.Owing to not being normal incidence, even there is laser to incide the rear end face in chamber in the other direction along feedback light, through reflection, this light reflects light path, can't form feedback light, thereby plays buffer action preferably.Even for can reach requirement concerning the highstrung semiconductor laser of feedback light yet, do not need as the various embodiments described above that adopt the F-P chamber, another optical isolator to be set, thereby make system more simple, stable.
Shown in Figure 12, the grating external cavity semiconductor laser of fifth embodiment of the invention mainly comprises: semiconductor laser tube (LD) 1, collimating lens (AL) 3,1/2 wave plate (HWP) 5,8, grating (Gt) 9, optical isolator (OI) 7 and single-block annular chamber (Cavity) 19b.the laser that semiconductor laser tube 1 is sent passes through collimating lens 3 successively, the one 1/2 wave plate 5, after optical isolator 7, be incident upon on annular chamber 19b at the first order diffraction beam one diffraction angle d on grating 9, the transmitted light of exporting after process ring oscillation between inner three eyeglasses of annular chamber 19b is after speculum 504 reflects, by the 2 1/2 wave plate 8, supervision mouth incident from optical isolator 7 outgoing one sides, utilize the magneto optical effect of optical isolator 7, make the transmitted light of annular chamber 19a through polarization splitting prism 5022 reflections of optical isolator 7 exit ends, oppositely by optical isolator 7, turn back to semiconductor laser tube 1, thereby make annular chamber 19b transmitted light form the light path loop.The zeroth order diffraction light of grating 9 is as output light, and the First order diffraction light of grating 9 is as the feedback light of semiconductor laser.As can be seen from Figure 12, from polarization splitting prism 5022 exit facets of optical isolator 7 exit ends to through reaching again polarization splitting prism 5022 reflectings surface of optical isolator 7 exit ends after annular chamber 19b etc., this part light path is the traveling-wave field part, annular chamber 19b is arranged at this, can utilize the annular chamber transmitted light to realize that bulk of optical feedback strengthens, substitute numerous and diverse electricity feedback.The advantages such as the present embodiment is set to the structure of monolithic by annular chamber, make resonant cavity stability greatly improve, and has the external interference of not being subject to, and volume is little, system is simple and easy to use.
In the various embodiments described above of the present invention, the semiconductor laser tube resonant cavity all adopts temperature sensor and semiconductor cooler to realize temperature control.The resonance frequency of this resonant cavity can be by being bonded in the piezoelectric ceramic on this chamber method and resonant cavity precise temperature control technology is done respectively fast fine tuning among a small circle and coarse adjustment on a large scale at a slow speed, realize to the tuning of laser frequency with control.
Semiconductor laser tube in such scheme also can be selected other wavelength, other power output, and optical isolator is selected the respective wavelength isolator, and can select other isolations.Grating also can adopt transmission grating, and other incisure density and big or small thickness consist of, and selects other incidence angle and the angle of diffraction.Grating also can be positioned over the positions such as high reflectance chamber mirror M1, M2 shown in Fig. 7 or Fig. 9.Collimating lens also can adopt other focal length and numerical aperture.The material in F-P chamber also can adopt other material, can adopt other to have the chamber type of transmitted light, as straight chamber (comprising average, plano-concave, concave-concave etc.), refrative cavity, monolithic one body cavity etc., optically coated reflectivity also can adopt other numerical value, and the Q value can be selected other values between tens to several ten thousand.After piezoelectric ceramic also can be positioned over chamber mirror M1, M2, M3 or M4.
Above-described specific embodiment is only specific embodiments of the invention, is not limited to the present invention, and is within the spirit and principles in the present invention all, any modification of making, is equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (12)
1. an external-cavity semiconductor laser, is characterized in that, is laid with in the main optical path of semiconductor laser exocoel: optical resonator, optical isolator and, the one 1/2 wave plate and the 2 1/2 wave plate;
The laying of semiconductor laser makes the light beam that semiconductor laser tube is sent to pass through described optical isolator through described the one 1/2 wave plate forward, and the light beam that described optical resonator is crossed in transmission can oppositely pass through described optical isolator after described the 2 1/2 wave plate, makes after this along turning back in described semiconductor laser tube with former outgoing beam conllinear reverse path.
2. semiconductor laser according to claim 1, is characterized in that, also lays grating in the main optical path of semiconductor laser exocoel; The zeroth order diffraction light that the described grating of light beam process of main optical path forms is as output light, and First order diffraction light is as the feedback light of semiconductor laser;
Perhaps also lay other light-splitting devices beyond described grating in the main optical path of semiconductor laser exocoel, the light beam of main optical path is incident on the part of telling after this light-splitting device as the output light of semiconductor laser, and remainder is as feedback light.
3. semiconductor laser according to claim 2, is characterized in that, described grating is reflecting grating or transmission grating;
Described other light-splitting devices are partially reflecting mirror or Amici prism, and the feedback light path at main optical path that further coordinates with light-splitting device partly arranges the frequency-selecting device.
4. semiconductor laser according to claim 1, is characterized in that, described resonant cavity is F-P cavity configuration or ring cavity structure.
5. semiconductor laser according to claim 4, is characterized in that, described F-P chamber is straight cavity configuration or refrative cavity structure.
6. semiconductor laser according to claim 4, is characterized in that, described resonant cavity is resolution element structure or en-block construction.
7. semiconductor laser according to claim 4, is characterized in that, when described resonant cavity is the F-P chamber, before the light beam that described resonant cavity is crossed in transmission enters described the 2 1/2 wave plate, another optical isolator is set further.
8. semiconductor laser according to claim 1, is characterized in that, this semiconductor laser also comprises following one or more modulating equipments:
To the equipment that resonant frequency is modulated, the equipment that the noise spectra of semiconductor lasers exocoel is regulated is to the equipment of semiconductor laser tube output light frequency adjusting.
9. semiconductor laser according to claim 8, is characterized in that, the described equipment that resonant frequency is modulated comprises: on resonant cavity bonding piezoelectric ceramic temperature regulating device is set or both the combination;
The equipment that described noise spectra of semiconductor lasers exocoel is regulated comprises following one or more combinations: electrooptic modulator and chamber mirror controller, described electrooptic modulator is used for adding modulation signal at the light beam of main optical path, survey light signal in main optical path by detector, being converted to the signal of telecommunication processes by electricity, obtain error signal, feed back to described chamber mirror controller, control described outer cavity long, realize that exocoel is to the tracking of F-P chamber frequency or synchronous;
The described equipment that semiconductor laser tube output light frequency is regulated comprises following one or more combinations: by the semiconductor laser tube drive current is added modulation signal, realize the current-modulation equipment to the modulation of laser frequency; Perhaps change the equipment of semiconductor laser tube output light frequency scope by the temperature that changes semiconductor laser tube.
10. according to claim 1-9 described semiconductor lasers of any one, it is characterized in that, be laid with described optical resonator, described optical isolator, described the one 1/2 wave plate, described the 2 1/2 wave plate, light-splitting device and etalon in the main optical path of described semiconductor laser; The outgoing beam that sends from described semiconductor laser tube enters described optical isolator through described the one 1/2 wave plate, incide described light-splitting device from the outgoing beam of described optical isolator, enter described etalon after described light-splitting device beam splitting, enter described optical resonator through described etalon transmission, the outgoing beam of described optical resonator through described the 2 1/2 wave plate oppositely by described optical isolator, after this along turning back in described semiconductor laser tube with former outgoing beam conllinear reverse path.
11. according to claim 1-9 described semiconductor lasers of any one, it is characterized in that, be laid with described optical resonator, described optical isolator, described the one 1/2 wave plate, described the 2 1/2 wave plate and grating in the main optical path of described semiconductor laser; The outgoing beam that sends from described semiconductor laser tube enters described optical isolator through described the one 1/2 wave plate, incide described grating from the outgoing beam of described optical isolator, enter described optical resonator after described optical grating diffraction, the transmitted light beam of described optical resonator through described the 2 1/2 wave plate oppositely by described optical isolator, after this along turning back in described semiconductor laser tube with former outgoing beam conllinear reverse path.
12. according to claim 1-9 described semiconductor lasers of any one, it is characterized in that, be laid with described optical resonator, described optical isolator, described the one 1/2 wave plate, described the 2 1/2 wave plate and grating in the main optical path of described semiconductor laser; The outgoing beam that sends from described semiconductor laser tube incides described grating, after described optical grating diffraction, enter described optical isolator through described the one 1/2 wave plate, outgoing beam from described optical isolator, enter described optical resonator, the outgoing beam of described optical resonator through described the 2 1/2 wave plate oppositely by described optical isolator, after this along turning back in described semiconductor laser tube with former outgoing beam conllinear reverse path.
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| CN106877168B (en) * | 2017-03-07 | 2019-08-02 | 中国科学院国家授时中心 | A kind of locking device of the optical cavity based on EOM and PZT |
| CN110429472A (en) * | 2019-09-10 | 2019-11-08 | 微源光子(深圳)科技有限公司 | A kind of high-power dual output exocoel narrow linewidth laser of easy volume production |
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