CN107069416B - Tunable frequency stabilized laser - Google Patents

Tunable frequency stabilized laser Download PDF

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Publication number
CN107069416B
CN107069416B CN201710313775.8A CN201710313775A CN107069416B CN 107069416 B CN107069416 B CN 107069416B CN 201710313775 A CN201710313775 A CN 201710313775A CN 107069416 B CN107069416 B CN 107069416B
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frequency
rare earth
earth ion
laser
ion doped
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CN107069416A (en
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韩琳
薄勇
杨晶
彭钦军
王小军
许祖彦
林弋戈
李烨
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Technical Institute of Physics and Chemistry of CAS
National Institute of Metrology
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Technical Institute of Physics and Chemistry of CAS
National Institute of Metrology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/1303—Stabilisation of laser output parameters, e.g. frequency or amplitude by using a passive reference, e.g. absorption cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1106—Mode locking
    • H01S3/1112—Passive mode locking

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  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)

Abstract

The invention relates to the technical field of frequency stabilized lasers, and provides a tunable frequency stabilized laser. The tunable frequency stabilized laser adopts a frequency stabilization technology based on crystal spectrum hole burning, and introduces synchronous control crystal tuning transformation, thereby realizing wavelength tuning frequency stabilized laser output. The frequency stabilization crystal unit comprises a plurality of different rare earth ion doped crystals. The different rare earth ion doped crystals have different positions of resonance absorption frequency due to different ion energy levels, ion service lives and crystal lattice environments in which the ions are located, so that through reasonable selection of the rare earth ion doped crystals, non-uniform broadening absorption spectral lines of all the rare earth ion doped crystals can be realized to form a continuous large-range absorption spectral line, and each frequency position in the absorption spectral line can form a spectral hole burning, so that frequency locking reference is provided for frequency stabilization. Therefore, the locking position of the laser frequency can be continuously tuned in the continuous wide-range absorption line formed by all the rare earth ion doped crystals, so that the frequency-stabilized laser output with continuously tuned wide-range wavelength can be realized.

Description

Tunable frequency stabilized laser
Technical Field
The invention relates to the technical field of frequency stabilized lasers, in particular to a tunable frequency stabilized laser.
Background
The tunable laser source can be adapted to different application requirements because the wavelength of the tunable laser source can be tuned and changed within a certain range, so that the tunable laser source has strong flexibility and is widely applied to many fields such as atomic laser cooling, quantum storage, microwave spectrum optical storage and the like. However, a narrow linewidth, wavelength-tunable ultra-frequency stabilized laser source is difficult to realize due to the lack of a frequency-locked reference suitable for multiple wavelengths.
At present, in order to realize frequency stabilization of a laser source, a frequency stabilization method based on atomic absorption spectrum lines is generally adopted, which is only suitable for frequencies meeting the atomic absorption spectrum lines, and although the frequency can be finely adjusted in an absorption spectrum line range or locked after frequency shifting by means of an AOM (acoustic optical modulator), frequency locking of continuous tuning of a large range of wavelengths cannot be realized. The frequency stabilization method based on the ultra-stable F-P (Fabry-Perot) reference cavity can only lock the laser frequency on a limited number of discrete specific frequency positions taking the free spectral path of the F-P cavity as the period, and the achievable frequency adjustable range is smaller as the fineness of the F-P ultra-stable cavity is higher. For different wavelengths with large variations, different F-P reference cavities have to be used, whereby the adjustment of the sets of vacuum temperature control devices and the changing optical path introduced is very complicated.
In the technology, the temperature coefficient of a frequency locking reference is about 20Hz/mK, which is much lower than that of a reference cavity made of U L E (ultra-low expansion) material, and the sensitivity to acceleration is superior to that of an optimized F-P cavity by one order (7 × 10)-12/g) and is therefore more suitable for external field applications, and is expected to break through the thermal noise limit of the F-P cavity and achieve higher frequency stability. This technique also fails to achieve frequency locking for continuous tuning of a wide range of wavelengths.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art or the related art.
One of the objects of the invention is: the tunable frequency stabilized laser is provided, and the problem that the laser in the prior art cannot realize frequency locking of continuous tuning of large-range wavelength is solved.
In order to achieve the object, the present invention provides a tunable stable frequency laser, including:
the tunable laser source is used for outputting laser with set wavelength;
the optical splitter receives the laser output by the tunable laser source and splits the laser into an output optical path and a reference optical path;
the frequency stabilization crystal unit comprises a plurality of rare earth ion doped crystals with different absorption spectral lines, the absorption spectral lines of all the rare earth ion doped crystals form a section of continuous absorption spectral line, and the rare earth ion doped crystals with the absorption spectral lines corresponding to the set wavelength are positioned in the reference light path;
and the frequency locking circuit unit locks the frequency of the reference light path, so that the frequency is locked on the spectral hole burning of the absorption spectrum line of the rare earth ion doped crystal in the reference light path.
Preferably, the method further comprises the following steps:
and the synchronous control unit receives a wavelength selection instruction, controls the position relation between the reference optical path and the rare earth ion doped crystal according to the wavelength selection instruction, and controls the frequency locking circuit unit according to the wavelength selection instruction.
Preferably, the frequency stabilization crystal unit further includes a heat sink for fixing the rare earth ion doped crystal, the heat sink is connected to the driving member, and the synchronous control unit controls the movement of the driving member according to the wavelength selection instruction, so that the rare earth ion doped crystal whose absorption spectrum line corresponds to the set wavelength moves into the reference light path.
Preferably, the driving member is a rotating motor, an output shaft of the rotating motor is fixed with the heat sink, a position sensor is mounted on the output shaft and used for measuring the position of the rare earth ion doped crystal and sending the position to the synchronous control unit, and the synchronous control unit controls the rotation of the output shaft according to the position.
Preferably, the driving part is a conveyor belt, a plurality of heat sinks are fixed in the conveying direction of the conveyor belt, one rare earth ion doped crystal is fixed on each heat sink, a position sensor is mounted on the conveyor belt and used for measuring the position of the rare earth ion doped crystal and sending the position to the synchronous control unit, and the synchronous control unit controls the conveying movement of the conveyor belt according to the position.
Preferably, an optical deflector is connected between the optical splitter and the frequency stabilization crystal unit; and the synchronous control unit controls the deflection angle of the optical deflector according to the wavelength selection instruction, so that the reference light path passes through the rare earth ion doped crystal corresponding to the set wavelength through an absorption spectrum line.
Preferably, the frequency locking circuit unit comprises an electro-optical modulator, a photoelectric detector, a mixer, a signal generator, a frequency stabilization locking servo system and a signal amplifier;
and the synchronous control unit controls the parameters of the signal generator and the frequency stabilization locking servo system.
Preferably, the frequency stabilization crystal unit further comprises a vacuum tank, and the rare earth ion doped crystal is located in the vacuum tank; and a temperature adjusting subunit is also arranged in the vacuum tank and used for adjusting the temperature of the crystal heat sink in the vacuum tank.
Preferably, the number of the tunable laser sources is multiple.
Preferably, the tunable laser source is a Ti sapphire laser and/or a CO2 laser and/or a semiconductor laser.
The technical scheme of the invention has the following advantages: the tunable frequency stabilized laser adopts a frequency stabilization technology based on crystal spectrum hole burning, and introduces synchronous control crystal tuning transformation, thereby realizing wavelength tuning frequency stabilized laser output. The frequency stabilization crystal unit comprises a plurality of different rare earth ion doped crystals, resonance absorption frequency positions of the different rare earth ion doped crystals are different due to different ion energy levels, ion service lives and crystal lattice environments where ions are located, so that through reasonable selection of the rare earth ion doped crystals, non-uniform broadening absorption spectrum lines of all the rare earth ion doped crystals can be formed to form a continuous large-range absorption spectrum line, and each frequency position in the absorption spectrum line can form a spectrum hole, so that frequency locking reference is provided for frequency stabilization. Therefore, the locking position of the laser frequency can be continuously tuned in the continuous wide-range absorption line formed by all the rare earth ion doped crystals, so that the frequency-stabilized laser output with continuously tuned wide-range wavelength can be realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a continuous tuning frequency stabilization method based on rare earth ion doped crystal;
FIG. 2 is a schematic structural diagram of a frequency stabilization experimental device based on rare earth ion doped crystals;
FIG. 3 is a graph of the results of a frequency stabilization experiment based on rare earth ion doped crystals;
fig. 4 is a schematic structural diagram of a tunable frequency stabilized laser according to the first embodiment;
FIG. 5 is a schematic structural diagram of a tunable frequency stabilized laser according to a second embodiment;
fig. 6 is a schematic structural diagram of a tunable frequency-stabilized laser according to a third embodiment;
in the figure: 1. a tunable laser source; 1-1, Ti gem laser; 1-2, CO2A laser; 2. a light splitter; 3. a frequency stabilizing crystal unit; 3-1, heat sink; 3-2, rare earth ion doped crystal; 3-2-1, a first rare earth ion doped crystal; 3-2-2, second rare earth ion doped crystal; 3-2-3, a third rare earth ion doped crystal; 3-2-4, fourth rare earth ion doped crystal; 3-3, a temperature regulation subunit; 4. a frequency-locking circuit unit; 4-1, an electro-optic modulator; 4-2, a photoelectric detector; 4-3, a mixer; 4-4, a signal generator; 4-5, frequency stabilization locking servo system; 4-6, a signal amplifier; 5. a synchronization control unit; 6. an output optical path; 7. an optical deflector.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; can be mechanically or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Please refer to fig. 1, λ1、λ2、λ3、λ4And λ5Is the central wavelength of the non-uniform broadening absorption spectrum corresponding to ions in different rare earth ion doped crystals 3-2, and the non-uniform broadening widths of the corresponding spectral lines areinh1、inh2、inh3、inh4、inh5. And the number of the first and second electrodes,inh1、inh2、inh3、inh4、inh5forming a continuous absorption line.
Therefore, if the frequency stabilization crystal unit 3 simultaneously comprises the five rare earth ion doped crystals 3-2 in the laser frequency stabilization technology based on the rare earth ion doped crystal 3-2, the frequency stabilization crystal unit 3By controlling the five rare earth ion doped crystals 3-2, the tunable frequency-stabilized laser can be enabled to be in lambda1-λ5And relatively stable tunable frequency stabilization is realized.
Among them, the abundant energy level structure of rare earth ions can provide almost all-band absorption lines from infrared to ultraviolet. Therefore, by selecting different rare earth ions and changing parameters such as crystal matrix materials, temperature and the like, a required frequency stabilization range can be obtained, and laser with a set wavelength can be obtained from the tunable laser source 1. Therefore, the number and the types of the rare earth ion doped crystals 3-2 are not limited, and different rare earth ion doped crystals 3-2 can be selected according to the needs.
The structure of the tunable frequency-stabilized laser provided with a single rare earth ion doped crystal 3-2 is explained first.
Referring to fig. 2, the tunable frequency stabilized laser of the present application includes:
a tunable laser source 1 for outputting laser light of a set wavelength;
the optical splitter 2 receives the laser output by the tunable laser source 1 and splits the laser into an output optical path 6 and a reference optical path;
the frequency stabilization crystal unit 3 comprises a rare earth ion doped crystal 3-2 positioned in the reference light path;
and the frequency locking circuit unit 4 locks the frequency of the reference light path, so that the frequency is locked on the spectral hole burning of the absorption line of the rare earth ion doped crystal 3-2.
At Tm3+YAG crystal (yttrium aluminum garnet doped with thulium ions) is used as an example to briefly introduce the laser frequency stabilization working principle based on rare earth ion doped crystal 3-2. The spectral hole burning in the crystal is transient spectral hole burning, the hole burning life is about 10ms at a temperature of 4.2K, the line width is about 10kHz, and the performance of the reference cavity is similar to that of a 10cm F-P reference cavity with fineness of about 150,000. Found through experiments, Tm3+: transient spectrum hole burning in YAG crystal can realize direct locking without pre-stabilization. Since the passage of the laser through the crystal creates a hole burn in the crystal, it can be done anywhere within the non-uniform absorption bandwidth of the crystal (about 20GHz)Now frequency locking is achieved. The width of the initial hole burning is equivalent to the line width of the laser, about several hundred kilohertz, when locking starts, the original hole burning disappears due to the limited service life because the line width of the laser is reduced, the hole re-burned by the narrow line width laser becomes narrow, and finally reaches the limit of about 10kHz crystal, and the laser line width is locked to be narrower on the basis of the line width.
Fig. 3 is a graph of the frequency stabilization experimental result of the tunable frequency stabilized laser. The curve of the dots in the figure is a noise curve in an open loop state, the curve of the triangles is an electric noise background of the system, the curve of the x shape is a noise curve locked on the crystal spectrum after hole burning, and it can be seen that the noise through locking the laser is greatly compressed and reaches the point noise background of the system at a position close to the side frequency.
The tunable frequency-stabilized laser in the present application is described in several embodiments below.
Example one
In the first embodiment, a tunable frequency stabilized laser is provided, please refer to fig. 4, which includes:
a tunable laser source 1 for outputting laser light of a set wavelength;
the optical splitter 2 receives the laser output by the tunable laser source 1 and splits the laser into an output optical path 6 and a reference optical path;
the frequency stabilization crystal unit 3 comprises a plurality of rare earth ion doped crystals 3-2 with different absorption spectral lines, the absorption spectral lines of all the rare earth ion doped crystals 3-2 form a section of continuous absorption spectral line, and the rare earth ion doped crystals 3-2 with the absorption spectral lines corresponding to the set wavelength are positioned in the reference light path;
and the frequency locking circuit unit 4 locks the frequency of the reference light path, so that the frequency is positioned on the spectral hole burning of the rare earth ion doped crystal 3-2 in the reference light path.
In order to realize frequency locking of continuous tuning of a wide range of wavelengths for the tunable frequency-stabilized laser, the tunable laser source 1 is required to realize tuning of a wide range of wavelengths. The "large range" and the "wide band" correspond to each other, that is, on the premise that the frequency-locked reference crystal is provided, the wavelength tuning band of the tunable laser source 1 is wider, and the range of frequency locking for wavelength continuous tuning of the tunable frequency-stabilized laser is wider.
In addition, in the case where "all absorption lines of the rare earth ion-doped crystal 3-2 constitute a single continuous absorption line", it is not required that all absorption lines of the rare earth ion-doped crystal 3-2 are continuous two by two. For example as in the case of figure 1,inh1andinh2，inh2andinh3and the two are not just continuous but partially overlapped, but finallyinh1、inh2、inh3、inh4Andinh5in combination, obtain ainh1To the left end ofinh5The right break point of (a) is continuously absorbing lines.
In the tunable frequency-stabilized laser of the first embodiment, the frequency-stabilizing crystal unit 3 includes a plurality of different rare-earth ion-doped crystals 3-2. The positions of resonance frequencies of different rare earth ion doped crystals 3-2 are slightly different due to different lattice environments, so that the continuous nonuniform broadening absorption spectrum lines of all the rare earth ion doped crystals 3-2 can be ensured through reasonable selection of the rare earth ion doped crystals 3-2. Therefore, the almost continuous narrow-linewidth non-uniformly-broadened absorption lines of all the rare earth ion doped crystals 3-2 form the non-uniformly-broadened absorption lines of the whole frequency stabilization crystal unit 3. The locking position of the laser frequency can be continuously tuned throughout the non-uniform broadened absorption line range, thereby achieving frequency locking with continuous tuning of a wide range of wavelengths.
On this basis, in order to control the rare earth ion doped crystal 3-2 in the frequency stabilization crystal unit 3, so that the rare earth ion doped crystal 3-2 whose absorption spectrum line corresponds to the set wavelength is located in the reference optical path, and in order to realize the control of the frequency locking circuit unit 4, the tunable frequency stabilization laser of the first embodiment further includes a synchronization control unit 5.
The synchronous control unit 5 receives a wavelength selection instruction, controls the position relationship between the reference optical path and the rare earth ion doped crystal 3-2 according to the wavelength selection instruction, and controls the frequency locking circuit unit according to the wavelength selection instruction.
The wavelength selection command can be input through some special devices, for example, a wavelength selection button can be arranged on the tunable stable laser, so that when the button representing a specific wavelength is pressed, a wavelength selection command is issued. Alternatively, an operation panel may be provided so that a wavelength selection instruction or the like is input through the operation panel.
The frequency stabilization crystal unit 3 further comprises a heat sink 3-1 for fixing the rare earth ion doped crystal 3-2, the heat sink 3-1 is connected with a driving piece, and the synchronous control unit 5 controls the movement of the driving piece according to the wavelength selection instruction, so that the rare earth ion doped crystal 3-2 is set to move into the reference light path.
On this basis, the driving member may be a rotating electrical machine, an output shaft of the rotating electrical machine is fixed to the heat sink 3-1, and a position sensor is mounted on the output shaft and used for measuring the position of the rare earth ion doped crystal 3-2 and sending the measured position to the synchronous control unit 5. In this case, the rare earth ion doped crystal 3-2 is distributed along the rotation direction of the heat sink 3-1. Therefore, the synchronous control unit 5 controls the rotation of the output shaft according to the position of the rare earth ion doped crystal 3-2, so that the specific rare earth ion doped crystal 3-2 on the heat sink 3-1 moves to a reference light path to serve as a frequency stabilization locking reference standard, and finally the tunable laser source 1 outputs laser with a set wavelength.
Of course, the form of the driving member is not limited. The drive element may also be a conveyor, such as a conveyor belt or a conveyor chain, for example. Therefore, a plurality of heat sinks 3-1 are fixed along the conveying direction of the conveying device, one rare earth ion doped crystal 3-2 is fixed on each heat sink 3-1, and a position sensor is mounted on the conveying device and used for measuring the position of the rare earth ion doped crystal and sending the position to the synchronous control unit 5. The synchronous control unit 5 controls the movement of the transmission device according to the position of the rare earth ion doped crystal 3-2, so that a certain heat sink 3-1 drives the specific rare earth ion doped crystal 3-2 to move to a reference light path, and finally the tunable laser source 1 outputs laser with a set wavelength.
Wherein, the rare earth ion doped crystal 3-2 is fixed on the heat sink 3-1, mainly because the heat conduction of the heat sink 3-1 is good, thereby being convenient for controlling the temperature of the rare earth ion doped crystal 3-2. A copper heat sink 3-1 with very good thermal conductivity is preferably, but not necessarily, used.
Further, the frequency stabilization crystal unit 3 further comprises a vacuum tank, and the rare earth ion doped crystal 3-2 is positioned in the vacuum tank; and a temperature adjusting subunit 3-3 is also arranged in the vacuum tank and is used for adjusting the temperature in the vacuum tank. Because the frequency positions of the non-uniform broadening absorption spectral lines of each rare earth ion doped crystal 3-2 at different temperatures are different, and the frequency position of the absorption spectral line is the frequency-locking reference, the tuning of the frequency-locking reference frequency can be realized by adjusting the temperature of the rare earth ion doped crystal 3-2.
The vacuum tank is generally controlled in a low-temperature environment, so that the temperature control range of the rare earth ion doped crystal 3-2 is adjustable from 1.6K to 30K, and the absorption line of the single rare earth ion doped crystal 3-2 is as narrow as possible. Wherein, the vacuum tank can be refrigerated by liquid helium continuous flow circulation or a compressor to reduce the temperature of the heat sink 3-1, and then the low-temperature rare earth ion doped crystal 3-2 is obtained.
On the basis, by utilizing the different frequency positions of the non-uniform broadening absorption spectral lines of different crystals at different temperatures, a plurality of rare earth ion doped crystals 3-2 with different components are placed in the same vacuum tank, and the broadband tunable frequency-stabilized laser can be realized by tuning and converting the rare earth ion doped crystals 3-2 and the temperature thereof and synchronously tuning the frequency locking parameters of the frequency locking circuit unit 4.
For example, the frequency stabilization crystal unit 3 comprises a plurality of rare earth ion doped crystals 3-2, and the doped rare earth ions may include thulium Tm3+Er, Er3+Praseodymium Pr3+Holmium Ho3+Tb, Tb3+Europium Eu3+Nd, Nd3+Plasma rare earth ions; the crystalline host material may include Y3Al5O12(YAG) crystal, L iNbO3Crystal, Y2Si2O7Crystals, etc.; the ion doping concentration range can be between 0.001% and 5%.
According to the reported Tm3+:Y3Al5O12(Tm3+YAG) crystal has non-uniform spread full width at half maximum of about 20GHz and center wavelength of 793.374nm, and the rare earth ion doped crystal 3-2 is used as frequency locking reference to realize a frequency-stabilized laser with continuously tunable wavelength in the range of 20GHz near 793.374 nm.
Moreover, the change of the central wavelength corresponding to the non-uniform broadening of the same ion in different crystal matrix materials can be utilized to further realize a wavelength continuous tunable frequency-stabilized laser source with a wider range. In combination with the schematic diagram given in FIG. 1, the Tm of the rare earth ion-doped crystal 3-2 can be selected to be 0.1% doped3+:Y2Si2O7Crystal, unevenly broadening a central wavelength of 790.427 nm; tm of 0.1% doping3+YAG crystal with central wavelength of 793.374nm stretched unevenly; tm of 0.1% doping3+:LiNbO3Crystal, unevenly broadening a central wavelength of 794.22 nm; tm of 0.1% doping3+:LaF3Crystal, non-uniformly broadened central wavelength of 796.521 nm. Therefore, when the frequency stabilization crystal unit 3 comprises the rare earth ion doped crystal 3-2, the tunable frequency stabilization laser can basically realize continuous tunable frequency stabilization of the wavelength in the range of 790nm to 796 nm. Of course, the choice of rare earth ion doped crystal 3-2 here does not constitute a limitation on the frequency stabilization crystal unit 3.
For the transmission optical device and the reflection optical device which have requirements on the wavelength in the light path, the coating parameters can be selected to be located between 790nm and 796nm wave bands, or the coating parameters can be selected to cover 790nm to 796nm wave bands.
The tunable frequency-stabilized wavelength range of the tunable frequency-stabilized laser of the first embodiment can be further expanded on the basis. The central wavelength of the crystal doped with different rare earth ions can be unevenly broadened by Pr3+:LaF3477.75nm to Er3+:Y2SiO51536.47nm, and can be adjustedThe non-uniform broadening center wavelength of the crystal is adjusted by crystal parameters such as ion doping concentration, matrix atomic ratio and the like. Such a great deal of wavelength selectivity undoubtedly makes the laser frequency stabilization technology based on the rare earth ion doped crystal 3-2 the first choice for realizing the wavelength tuning super frequency stabilization laser source.
In the first embodiment, if the tunable laser source 1 needs to be locked, the set wavelength is λ1A specific rare earth ion doped crystal 3-2 suitable for this wavelength locking standard is selected, for example, a first rare earth ion doped crystal 3-2-1. Under the control of the synchronous control unit 5, the specific rare earth ion doped crystal 3-2 is made to enter the reference optical path. Meanwhile, the synchronous control unit 5 controls the frequency locking circuit unit 4, so that the frequency locking circuit unit 4 realizes synchronous adjustment of specific experimental parameters. Finally realizing the tunable laser source 1 at the wavelength lambda1Stable, narrow linewidth laser output.
If the tunable laser source 1 needs to be locked with a set wavelength λ2A specific rare earth ion doped crystal 3-2 suitable for this wavelength locking criterion is selected, for example, a second rare earth ion doped crystal 3-2-2. Under the control of the synchronous control unit 5, the specific rare earth ion doped crystal 3-2 is made to enter the reference optical path. Meanwhile, the synchronous control unit 5 controls the frequency locking circuit unit 4, so that the frequency locking circuit unit 4 realizes synchronous adjustment of specific experimental parameters. Finally realizing the tunable laser source 1 at the wavelength lambda2Stable, narrow linewidth laser output. The tuning and frequency stabilization of other wavelengths can correspondingly control the third rare earth ion doped crystal 3-2-3 or the fourth rare earth ion doped crystal 3-2-4 to enter the reference light path.
Referring to fig. 4, the frequency locking circuit unit 4 of the first embodiment further includes an electro-optical modulator 4-1, a photodetector 4-2, a mixer 4-3, a signal generator 4-4, a frequency stabilization locking servo system 4-5, and a signal amplifier 4-6. Wherein, the electro-optical modulator 4-1 is connected between the optical splitter 2 and the frequency stabilization crystal unit 3. The laser light enters the frequency stabilization crystal unit 3 after passing through the electro-optical modulator 4-1. In the frequency stabilization crystal unit 3, a rare earth ion doped crystal 3-2 is arranged on a heat sink 3-1, and the heat sink 3-1 is connected with a temperature regulation subunit 3-3. After being emitted from the frequency stabilization crystal unit 3, the laser enters a mixer 4-3 through a photoelectric detector 4-2; the signal generator 4-4 sends out signals to the electro-optical modulator 4-1 and the mixer 4-3 at the same time, and the signals are mixed with the laser which enters the mixer 4-3 before, and then the signals are returned to the tunable laser source 1 after passing through the frequency stabilization locking servo 4-5 and the signal amplifier 4-6.
The synchronous control unit 5 controls the parameter settings of the signal generator 4-4, the frequency stabilization locking servo system 4-5 and other links in the frequency locking circuit unit 4, so that the optimal frequency locking under each frequency is realized.
The frequency locking parameter setting in the frequency locking circuit unit 4 can be manually adjusted, or a matched database can be set and stored, and the parameter setting is automatically adjusted by the synchronous control unit 5 according to the frequency stabilizing wavelength, so that the frequency locking with the best effect is realized.
Of course, the specific form of the frequency locking circuit unit 4 in the first embodiment does not limit the tunable frequency-stabilized laser in the present application. Obviously, the tunable frequency-stabilized laser can also adopt any other existing mode to lock frequency.
Example two
The difference between the first embodiment and the second embodiment is that, in the tunable frequency-stabilized laser of the second embodiment, referring to fig. 5, an optical deflector 7 is connected between the optical splitter 2 and the frequency-stabilizing crystal unit 3. Specifically, the optical deflector 7 is located after the electro-optical modulator 4-1, and the reference optical path is made to pass through the optical deflector 7 before entering the frequency stabilization crystal unit 3.
In this case, in order to position the rare earth ion doped crystal 3-2 having the absorption spectrum line corresponding to the set wavelength in the reference light path, the required rare earth ion doped crystal 3-2 can be selectively passed through by controlling the optical deflector 7 to deflect at a small angle without moving the rare earth ion doped crystal 3-2.
In the second embodiment, the optical deflector 7 may be an acousto-optic deflector 7 or an electro-optic deflector 7 for controlling deflection of light beams. The specific form of the optical deflector 7 is not limited, for example, to use AOM, but the light beam can be guided to a desired direction by this form of the optical deflector 7 by an adjustable spectral combining device such as a prism, a grating, or the like.
EXAMPLE III
The tunable frequency-stabilized laser of the third embodiment is different from the first and second embodiments in a tunable laser source 1.
Referring to fig. 6, a tunable frequency stabilized laser provided with an optical deflector 7 is shown. Of course, the tunable frequency stabilized laser of the third embodiment may not be provided with the optical deflector 7, so as to move into the reference optical path through the rare earth ion doped crystal 3-2.
In the tunable frequency-stabilized laser of the third embodiment, the tunable laser source 1 is a Ti sapphire laser 1-1 and/or a CO2 laser 1-2. When the two tunable laser sources 1 of the third embodiment are respectively a Ti sapphire laser 1-1 and a CO2 laser 1-2, the Ti sapphire laser 1-1 and the CO2 laser 1-2 have different wave bands and are independent of each other.
Wherein, the Ti gem laser 1-11-1 can directly emit laser to enter the electro-optical modulator 4-1; the laser emitted by the CO2 laser 1-21-2 enters the electro-optical modulator 4-1 after being reflected by a mirror M1 and a mirror M2; the Ti gem laser 1-1 and the CO2 laser 1-2 may be turned on alternately.
Thereafter, the laser light enters the frequency stabilization crystal unit 3 after passing through the optical deflector 7. In the frequency stabilization crystal unit 3, a rare earth ion doped crystal 3-2 is connected with a temperature regulator subunit 3-3. After being emitted from the frequency stabilization crystal unit 3, the laser enters a mixer 4-3 through a photoelectric detector 4-2; the signal generator 4-4 sends signals to the electro-optical modulator 4-1 and the mixer 4-3 simultaneously, the signals are mixed with the laser which enters the mixer 4-3 before, and then the signals return to the Ti gem laser 1-1 and the CO2 laser 1-2 after passing through the frequency stabilization locking servo 4-5 and the signal amplifier 4-6.
The above embodiments are merely illustrative of the present invention and are not to be construed as limiting the invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications or equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and the technical solution of the present invention is covered by the claims of the present invention.

Claims (8)

1. A tunable frequency stabilized laser, comprising:
the tunable laser source is used for outputting laser with set wavelength;
the optical splitter receives the laser output by the tunable laser source and splits the laser into an output optical path and a reference optical path;
the frequency stabilization crystal unit comprises a plurality of rare earth ion doped crystals with different absorption spectral lines, a heat sink for fixing the rare earth ion doped crystals and a vacuum tank for placing the heat sink; the vacuum tank is also internally provided with a temperature regulating subunit which is used for regulating the temperature of the crystal heat sink in the vacuum tank so as to control the temperature of the rare earth ion doped crystal and regulate the frequency position of the non-uniform broadening absorption spectrum line; the absorption spectral lines of all the rare earth ion doped crystals form a section of continuous absorption spectral line, and the rare earth ion doped crystals with the absorption spectral lines corresponding to the set wavelength are positioned in the reference light path;
the frequency locking circuit unit locks the frequency of the reference light path, so that the frequency is locked on the spectral hole burning of the absorption spectrum line of the rare earth ion doped crystal in the reference light path;
and the synchronous control unit receives a wavelength selection instruction, controls the position relation between the reference light path and the rare earth ion doped crystal according to the wavelength selection instruction, drives the heat sink to move so that the rare earth ion doped crystal with an absorption spectrum line corresponding to the set wavelength moves to the reference light path, and controls the frequency locking circuit unit according to the wavelength selection instruction.
2. The tunable stable frequency laser of claim 1, wherein the heat sink is connected to a driving member, and the synchronization control unit controls the driving member to move according to the wavelength selection command, so that the rare earth ion doped crystal with an absorption line corresponding to the set wavelength moves into the reference optical path.
3. The tunable stable-frequency laser device according to claim 2, wherein the driving member is a rotating motor, an output shaft of the rotating motor is fixed to the heat sink, a position sensor is mounted on the output shaft and used for measuring a position of the rare-earth ion doped crystal and sending the measured position to the synchronous control unit, and the synchronous control unit controls rotation of the output shaft according to the position.
4. The tunable stable-frequency laser device according to claim 2, wherein the driving member is a conveyor belt, a plurality of heat sinks are fixed along a conveying direction of the conveyor belt, each heat sink is fixed with one rare-earth ion doped crystal, a position sensor is mounted on the conveyor belt and used for measuring a position of the rare-earth ion doped crystal and sending the measured position to the synchronization control unit, and the synchronization control unit controls a conveying movement of the conveyor belt according to the position.
5. The tunable frequency-stabilized laser according to claim 1, wherein an optical deflector is connected between the optical splitter and the frequency stabilization crystal unit; and the synchronous control unit controls the deflection angle of the optical deflector according to the wavelength selection instruction, so that the reference light path passes through the rare earth ion doped crystal corresponding to the set wavelength through an absorption spectrum line.
6. The tunable frequency-stabilized laser according to any one of claims 1 to 5, wherein the frequency-locking circuit unit comprises an electro-optical modulator, a photodetector, a mixer, a signal generator, a frequency-stabilized locking servo system and a signal amplifier;
and the synchronous control unit controls the parameters of the signal generator and the frequency stabilization locking servo system.
7. The tunable frequency-stabilized laser according to any one of claims 1 to 5, wherein the number of the tunable laser sources is plural.
8. The tunable frequency-stabilized laser according to claim 7, wherein the tunable laser source is a Ti sapphire laser and/or CO2A laser and/or a semiconductor laser.
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