NL2029573B1 - Edge frequency stabilization system for semiconductor laser - Google Patents

Edge frequency stabilization system for semiconductor laser Download PDF

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Publication number
NL2029573B1
NL2029573B1 NL2029573A NL2029573A NL2029573B1 NL 2029573 B1 NL2029573 B1 NL 2029573B1 NL 2029573 A NL2029573 A NL 2029573A NL 2029573 A NL2029573 A NL 2029573A NL 2029573 B1 NL2029573 B1 NL 2029573B1
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frequency
semiconductor laser
frequency stabilization
constant current
current source
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NL2029573A
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Dutch (nl)
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NL2029573A (en
Inventor
Huang Cao
Chang Qihai
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Univ Xizang Minzu
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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
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687—Stabilising the frequency of the laser
    • 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
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/06832—Stabilising during amplitude modulation
    • 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
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/06821—Stabilising other output parameters than intensity or frequency, e.g. phase, polarisation or far-fields

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Semiconductor Lasers (AREA)

Abstract

The present invention relates to an edge frequency stabilization system for a semiconductor laser. An edge of an atomic or molecular absorption spectral line is used as a reference for expanding a frequency stabilization range according to the present invention. A visible light frequency range of a semiconductor laser can be expanded, and frequency stabilization of an infrared frequency range can be realized by utilizing an edge of a molecular reference, so that a frequency stabilization range of an existing frequency stabilization method for a semiconductor laser is greatly widened. The frequency stabilization achieves a complete electrical feedback, and the manufacturing cost is low. Since a peak value of the atomic absorption spectral line is locked to generate a constant sinusoidal signal amplitude, the frequency stabilization precision can reach the frequenc

Description

P769/NLpd
EDGE FREQUENCY STABILIZATION SYSTEM FOR SEMICONDUCTOR LASER
TECHNICAL FIELD The present invention relates to the technical field of laser spectrum detection, and in particular, to an edge frequency stabi- lization system for a semiconductor laser.
BACKGROUND ART High-brightness monochromatic (single frequency) light output by a semiconductor laser is influenced by a plurality of factors such as whether a drive current is constant or not, whether a sem- iconductor material is stable or not under working conditions, etc. In order to ensure that the semiconductor laser outputs sin- gle-frequency light, an output frequency of the semiconductor la- ser needs to be actively and reliably controlled, and the stabil- ity of the output frequency is ensured. Unlike common laser fre- quency stabilization, semiconductor laser frequency stabilization is divided into internal cavity frequency stabilization or exter- nal cavity frequency stabilization. Regardless of the external cavity frequency stabilization or the internal cavity frequency stabilization, a frequency selection element needs to be placed outside the semiconductor laser structurally. The frequency selec- tive element may also be referred to as a frequency standard ele- ment. The freguency stabilization achieved by an optical feedback of the frequency reference element to an optical cavity of the semiconductor laser is generally referred to as optical feedback frequency stabilization, and the drive of a measurement result of the frequency reference element to the semiconductor laser by an electrical feedback is referred to as electrical feedback frequen- cy stabilization. As an internal cavity of the semiconductor laser directly forms an optical cavity from a cleavage surface of a sem- iconductor crystal, and the structural stability of the optical cavity is controlled by temperature, current, etc. Therefore, the electrical feedback frequency stabilization is also referred to as internal cavity frequency stabilization.
In the internal cavity frequency stabilization, in order to output reliable and stable single-frequency light by the semicon- ductor laser, a frequency standard element is placed in a working light path of the semiconductor laser, laser light passes through the frequency standard element, and is received by a photoelectric detector, converted into an electric signal and processed to drive the semiconductor laser.
Common frequency standard components for internal cavity fre- quency stabilization are divided into a Fabry-Perot (FP) etalon or an atomic reference. The FP etalon is composed of two pieces of optical glass which are arranged in parallel, optical gating of a given frequency is realized by selecting a proper interval dis- tance, and a frequency selection function is realized. The atomic reference realizes frequency selection by utilizing the absorption characteristics of atomic gas to light with a given frequency.
There are generally two locking methods to lock a laser out- put frequency to a reference frequency standard: center locking and edge locking, which respectively mean locking a laser frequen- cy to the center or bevel edge of a standard frequency. In con- trast, the center locking is more widely used.
FIG. 1 shows a structural diagram of a center locking method in which a general FP etalon serves as a frequency standard. A se- lection transmission frequency (f,) of the FP etalon is equal to a laser output frequency (ff). A modulation-driven semiconductor la- ser outputs monochromatic light, which passes through the FP eta- lon after beam splitting through a beam splitting sheet. A photoe- lectric detector receives the monochromatic light and corrects the drive of the semiconductor laser to output stable light by phase- locking processing. As shown on the right side of the figure, when f=fr, a phase-locked output error signal is 0, and the drive cor- rection is 0. When f is not equal to fr, the drive is corrected, so that the semiconductor laser outputs frequency-stable laser light. In the figure, the FP etalon may be replaced by an atomic gas standard of which an absorption frequency is consistent with a laser working frequency, and the same frequency stabilization function is realized.
FIG. 2 shows a structural diagram of an edge locking method in which a general FP etalon serves as a frequency standard. A se- lection transmission frequency (f,) of the FP etalon is not equal to a laser output frequency (f), but on an edge of a transmittance curve thereof. The semiconductor laser outputs monochromatic light, which passes through the FP etalon and a variable attenua- tion sheet respectively after beam splitting through a beam split- ting sheet. A photoelectric detector receives the monochromatic light and corrects the drive of the semiconductor laser to output stable light by differential processing. As shown on the right side of the figure, when f= f£,, the variable attenuation sheet is adjusted to make Dl equal to D2, and a differential output error signal is 0. When an output frequency of the semiconductor laser is shifted, the differential output is not zero drive correction, so that the semiconductor laser outputs frequency-stable laser light.
Because of an extremely limited specific absorption spectrum required by an atomic reference and the feasibility and high manu- facturing cost of the FP etalon, it is impossible to realize any frequency stabilization for the semiconductor laser outputting any working frequency laser light, and in reality the frequency stabi- lization can be realized only for limited application.
SUMMARY An object of the present invention is to provide an edge fre- quency stabilization system for a semiconductor laser, capable of stabilizing a working frequency of a semiconductor laser on a large scale.
In order to achieve the above object, the present invention provides the following solutions: An edge frequency stabilization system for a semiconductor laser includes: a constant current source module and a frequency stabilization module. The constant current source module includes a reference semiconductor laser, a modulation source, a first con- stant current source, an atomic reference unit, a first photoelec- tric detector, a first phase-locked amplifier, and a first partial wave sheet. The frequency stabilization unit includes a frequency stabilization semiconductor laser, a controlled modulation source,
a second constant current source, a frequency selection reference unit, a second photoelectric detector, a second phase-locked am- plifier, and a second partial wave sheet.
The reference semiconductor laser outputs amplitude-modulated working frequency laser light under the combined drive of the mod- ulation source and the first constant current source.
The laser light passes through the atomic reference unit of which a trans- mittance peak value is consistent with a laser working frequency, is partially intercepted by the first partial wave sheet, is guid- ed to the first photoelectric detector, and is received by the first photoelectric detector.
A received optical signal is con- verted into an electrical signal and then is processed by the first phase-locked amplifier.
The first constant current source is driven to be stabilized so that the reference semiconductor laser outputs laser light with a stable working frequency.
A drive cur- rent for driving the reference semiconductor laser to output the laser light with the stable working frequency forms a standard constant current source.
The standard constant current source is converted into a ref- erence voltage through a sampling circuit.
The reference voltage is output to the controlled modulation source of the frequency stabilization unit for generating a high-precision amplitude si- nusoidal signal to form a zero-crossing second harmonic frequency discrimination signal which is a frequency stabilization frequency discrimination signal of the frequency stabilization semiconductor laser.
The controlled modulation source is superposed with the second constant current source.
The frequency stabilization semi- conductor laser is driven to generate working frequency laser light, which passes through the frequency selection reference unit, is partially intercepted by the second partial wave sheet, is guided to the second photoelectric detector, and is received by the second photoelectric detector.
A received optical signal is converted into an electrical signal and then is processed by the second phase-locked amplifier.
The frequency stabilization semi- conductor laser is driven to output frequency-stable laser light.
Optionally, the frequency selection reference unit is an atomic reference or a molecular reference.
When the frequency se-
lection reference unit is an atomic reference, the edge frequency stabilization system is an edge frequency stabilization system of the atomic reference, and the constant current source module and the frequency stabilization module share one atomic reference.
5 When the frequency selection reference unit is a molecular refer- ence, the edge frequency stabilization system is an edge frequency stabilization system of the molecular reference.
Optionally, the modulation source and the controlled modula- tion source adopt a sinusoidal signal generation circuit respec- tively.
Optionally, optical portions of a first constant current source unit are all in a saturated absorption layout.
Optionally, the first phase-locked amplifier performs a 1f frequency multiplication phase-locking process.
Optionally, the second phase-locked amplifier performs a 2f frequency multiplication phase-locking process.
According to specific embodiments provided by the present in- vention, the present invention discloses the following technical effects: An edge of an atomic reference or a molecular reference is used as a reference for expanding a frequency stabilization range according to the present invention. A visible light frequency range of a semiconductor laser can be expanded, and frequency sta- bilization of an infrared frequency range can be realized by uti- lizing an edge of a molecular reference, so that a frequency sta- bilization range of an existing frequency stabilization method for a semiconductor laser is greatly widened. The frequency stabiliza- tion achieves a complete electrical feedback, and the manufactur- ing cost is low. Since the atomic reference is locked to generate a constant sinusoidal signal amplitude, the frequency stabiliza- tion precision can reach the frequency stabilization precision of center locking by the method.
BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the existing tech- nology, the accompanying drawings to be used in the embodiments will be briefly described below. Obviously, the accompanying draw- ings in the following description are only some embodiments of the present invention, and for a person of ordinary skill in the art, without involving any inventive effort, other accompanying draw- ings may also be obtained according to these accompanying draw- ings. FIG. 1 is a structural diagram of a center locking method in which a general FP etalon serves as a frequency standard. FIG. 2 is a structural diagram of an edge locking method in which a general FP etalon serves as a frequency standard. FIG. 3 is a graph of a transmittance and modulated transmit- tance curve. FIG. 4 is a first harmonic diagram of a modulated transmit- tance curve. FIG. 5 is a second harmonic diagram of a modulated transmit- tance curve. FIG. 6 is a schematic structural diagram of an edge frequency stabilization system of an atomic reference. FIG. 7 is a schematic structural diagram of an edge frequency stabilization system of a molecular reference. FIG. 8 is a structural diagram of an edge frequency stabili- zation system for a semiconductor laser.
DETAILED DESCRIPTION OF THE EMBODIMENTS The technical solutions of the embodiments of the present in- vention will now be described more fully hereinafter with refer- ence to the accompanying drawings in the embodiments of the pre- sent invention. It is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present inven- tion, all the other embodiments obtained by those of ordinary skill in the art without involving any inventive effort may fall within the scope of protection of the present invention. In order that the objects, features, and advantages of the present invention will become more apparent, a more particular de- scription of the present invention will be rendered by reference to the accompanying drawings and the specific implementations.
An atomic reference particularly refers to a glass bulb filled with gas in the present invention. The gas in the bulb has an independent special absorption spectral line. A wavelength cor- responding to a peak value of the spectral line is a working wave- length or a working freguency of frequency-stabilized laser light. Whether it is an atomic reference or an FP etalon, the transmit- tance curve is a bell-shaped curve, called the transmittance curve, after being swept through the independent special absorp- tion spectral line with a light wave of continuous frequency. If the atomic reference is used as a frequency standard, the light wave of continuous frequency is modulated at a low frequency and then swept through the atomic reference. The light wave of contin- uous frequency is received by the photoelectric receiver, a first harmonic signal thereof is extracted by phase locking, and a fre- quency discrimination curve required by an internal cavity fre- quency stabilization center locking scheme is obtained. The fre- quency discrimination curve is a zero-crossing curve (as shown in FIG. 4) in which a zero point exactly corresponds to the peak val- ue of the transmittance curve of the frequency standard (as shown in the lower part of the curve of FIG. 3). Therefore, when the output frequency of the frequency stabilization semiconductor la- ser deviates from the peak value of the transmittance curve of the frequency standard, a deviation value may be used to correct laser driving parameters and stabilize the laser output frequency.
The semiconductor laser driven by a continuous scanning cur- rent will output laser light of continuously varying frequency. By superposing a low-frequency sinusoidal modulation signal on the continuous scanning current, the semiconductor laser may be driven to output laser light with laser intensity amplitude modulated.
The half-width of the transmission curve of the frequency standard is taken as a reference, the amplitude of a low-frequency sinusoi- dal signal is gradually increased, and two peaks of a first har- monic signal curve are gradually shifted left and right. The transmission curve modulated through an atomic reference is shown in the upper part of the curve in FIG. 3. As shown in FIG. 4, first harmonic curves from top to bottom are demonstrations of modulation amplitudes less than half width, equal to half width,
and greater than half width, respectively. It is apparent that as the amplitude of a modulation signal increases, the left and right peak values of the first harmonic are shifted left and right, re- spectively. Because the first harmonic has a peak value, a second harmonic zero-crossing curve corresponding to the peak value of the first harmonic may be obtained by extracting the second har- monic of the modulated transmittance signal. The zero-crossing point of the second harmonic is completely in one-to-one corre- spondence with the peak value of the first harmonic. FIG. 5 shows a second harmonic curve corresponding to the first harmonic curve of FIG. 4 from top to bottom, respectively, and it is apparent that the zero-crossing point of the second harmonic is completely in one-to-one correspondence with the peak value of the first har- monic. As the amplitude of the modulated signal gradually increas- es, the two peak values of the first harmonic curve of the modu- lated transmittance curve gradually move towards the left end and the right end from the transmittance peak value, and the whole frequency range covered by the whole transmittance curve is scanned. Since the low-frequency modulation broadens the transmis- sion curve of the frequency standard, the frequency range swept by an actual peak value is greater than the frequency range covered by the transmission curve. This principle makes it possible to re- alize the frequency stabilization of the semiconductor laser by using an edge of a molecular vibration-rotation spectral line, which further extends to the realization of the frequency stabili- zation of near-mid infrared semiconductor lasers.
The frequency stabilization of the semiconductor laser needs to use an atomic absorption spectral line or a Fabry-Perot inter- ferometer as frequency discrimination, the peak position of the absorption spectral line or the invariance of the peak value of the transmittance curve of the interferometer is utilized, the working frequency of the semiconductor laser is locked by feed- back, and the frequency stabilization of the semiconductor laser is realized. However, due to the limitation of the atomic absorp- tion spectral line, the relatively high manufacturing cost of the Fabry-Perot interferometer and the limited applicable frequency range, it is impossible to perform frequency stabilization control on the working frequency of the semiconductor laser in a consider- able range. According to the present invention, with reference to an edge of an atomic absorption spectral line, a working frequency of a semiconductor laser can be stabilized on a large scale. Ac- cording to the present invention, an edge of a molecular vibra- tion-rotation spectral line can be further utilized to realize the frequency stabilization of a semiconductor laser of an infrared band. As shown in FIG. 8, an edge frequency stabilization system for a semiconductor laser of the present invention includes: a constant current source module and a frequency stabilization mod- ule. The constant current source module includes a reference semi- conductor laser 11, a modulation source 12, a first constant cur- rent source 13, an atomic reference unit 14, a first photoelectric detector 15, a first phase-locked amplifier 16, and a first par- tial wave sheet 17. The frequency stabilization unit includes a frequency stabilization semiconductor laser 21, a controlled modu- lation source 22, a second constant current source 23, a frequency selection reference unit 24, a second photoelectric detector 25, a second phase-locked amplifier 26, and a second partial wave sheet
27.
The reference semiconductor laser 11 outputs amplitude- modulated working frequency laser light under the combined drive of the modulation source 12 and the first constant current source
13. The laser light passes through the atomic reference unit 14 of which a transmittance peak value is consistent with a laser work- ing frequency, is partially intercepted by the first partial wave sheet 17, is guided to the first photoelectric detector 15, and is received by the first photoelectric detector 15. A received opti- cal signal is converted into an electrical signal and then is pro- cessed by the first phase-locked amplifier 16. The first constant current source 13 is driven to be stabilized so that the reference semiconductor laser 11 outputs laser light with a stable working frequency, and a drive current for driving the reference semicon- ductor laser 11 to output the laser light with the stable working frequency forms a standard constant current source.
The standard constant current source is converted into a ref- erence voltage through a sampling circuit. The reference voltage is output to the controlled modulation source 22 of the frequency stabilization unit for generating a high-precision amplitude si- nusoidal signal to form a zero-crossing second harmonic frequency discrimination signal which is a frequency stabilization frequency discrimination signal of the frequency stabilization semiconductor laser 21. The controlled modulation source 22 is superposed with the second constant current source 23. The frequency stabilization semiconductor laser 21 is driven to generate working frequency la- ser light, which passes through the frequency selection reference unit 24, is partially intercepted by the second partial wave sheet 27, is guided to the second photoelectric detector 25, and is re- ceived by the second photoelectric detector 25. A received optical signal is converted into an electrical signal and then is pro- cessed by the second phase-locked amplifier 26. The frequency sta- bilization semiconductor laser 21 is driven to output frequency- stable laser light.
The modulation source 12 and the controlled modulation source 22 adopt a sinusoidal signal generation circuit respectively.
Optical portions of the first constant current source unit 13 are in a saturated absorption layout.
The first phase-locked amplifier 16 performs a 1f frequency multiplication phase-locking process.
The second phase-locked amplifier 26 per- forms a 2f frequency multiplication phase-locking process.
The atomic reference is used herein for locking the working frequency of the reference semiconductor laser 11, so that a drive current becomes a high-stability constant current source.
By con- verting into a voltage reference, a high-precision high-stability amplitude sinuscidal signal is generated by driving.
The high- precision high-stability amplitude sinuscidal signal may form a zero-point stable second harmonic frequency discrimination signal, so that the working frequency of the semiconductor laser is locked at a frequency corresponding to a non-absorption center peak value of the atomic reference.
The amplitude value of the sinusoidal signal may be changed by the frequency according to the working requirement, which may be selected in a full range of the absorp- tion curve of the atomic reference.
According to the present in- vention, by molecular vibration rotation of a slope edge of a con- tinuous spectrum, the working frequency of the semiconductor laser is locked in an infrared frequency working range.
The frequency selection reference unit 24 is an atomic refer- ence or a molecular reference. When the frequency selection refer- ence unit is an atomic reference, the edge frequency stabilization system is an edge frequency stabilization system of the atomic reference, and the constant current source module and the frequen- cy stabilization module share one atomic reference. When the fre- quency selection reference unit is a molecular reference, the edge frequency stabilization system is an edge frequency stabilization system of the molecular reference. In the present invention, both the atomic reference and the molecular reference utilize an ab- sorption roll-off edge of atomic or molecular gas as a reference for frequency stabilization. An edge frequency stabilization sys- tem of an atomic reference and an edge frequency stabilization system of a molecular reference are described in detail below.
1. Edge Frequency Stabilization system of Atomic reference: FIG. 6 shows a schematic diagram of edge frequency stabiliza- tion of an atomic reference. An edge frequency stabilization scheme of an atomic reference consists of a constant current source unit and a frequency stabilization unit. The constant cur- rent source unit is located in the upper half of FIG. 6 and con- sists of a reference semiconductor laser 11, a modulation source 12 (a sinusoidal signal generation circuit), a constant current source, an atomic reference, a photoelectric detector, a phase- locked amplifier, and a partial wave sheet. The frequency stabili- zation unit is located in the lower half of FIG. 6, and has con- stituent elements identical to those of the constant current source unit, and the two units share one atomic reference. Under the combined drive of the modulation source 12 and the constant current, the reference semiconductor laser 11 outputs amplitude- modulated working frequency laser light. The laser light passes through the atomic reference of which a transmittance peak value is consistent with a laser working frequency, is partially inter- cepted by the partial wave sheet, and is guided and received by the photoelectric detector. A received optical signal is converted into an electrical signal and then is processed by a 1f frequency multiplication phase-locking process. The constant current source for driving the laser light is stable, so that the reference semi- conductor laser 11 outputs laser light with a stable working fre- quency. A drive current for driving the reference semiconductor laser 11 to output the laser light with the stable working fre- quency forms a standard constant current source. The constant cur- rent source is converted into a reference voltage through a sam- pling circuit and output to the modulation source 12 of the fre- quency stabilization unit for generating a high-precision ampli- tude sinusoidal signal. The high-precision amplitude sinusoidal signal based on the atomic reference forms a zero-crossing second harmonic frequency discrimination signal. The second harmonic fre- quency discrimination signal is a frequency stabilization frequen- cy discrimination signal of the frequency stabilization semicon- ductor laser 21. The frequency stabilization semiconductor laser 21 is driven to generate working frequency laser light by con- trolled modulation and constant current superposition. The laser light passes through the atomic reference, is partially intercept- ed by the partial wave sheet, and is guided and received by the photoelectric detector. A received optical signal is converted in- to an electrical signal and then is processed by a 2f frequency multiplication phase-locking process for stabilizing a constant current to drive the frequency stabilization semiconductor laser 21 to output frequency-stable laser light. In practical applica- tion, in order to further improve the voltage reference precision of generating high-precision amplitude sinuscidal signals, optical portions of the constant current source unit may adopt a satura- tion absorption layout, so that the voltage reference precision is remarkably improved.
2. Edge Frequency Stabilization system of Molecular refer- ence: FIG. 7 shows a schematic diagram of edge frequency stabiliza- tion of a molecular reference. An edge frequency stabilization scheme of a molecular reference consists of a constant current source unit and a frequency stabilization unit. The constant cur- rent source unit is located in the upper half of FIG. 7 and con- sists of a reference semiconductor laser 11, a modulation source 12 (a sinusoidal signal generation circuit), a constant current source, an atomic reference, a photoelectric detector, a phase- locked amplifier, and a partial wave sheet.
The frequency stabili- zation unit is located in the lower half of FIG. 7 and consists of a frequency stabilization semiconductor laser 21, a modulation source 12, a constant current source, a molecular reference, a photoelectric detector, a phase-locked amplifier, and a partial wave sheet.
Under the combined drive of the modulation source 12 and the constant current source, the reference semiconducter laser 11 outputs amplitude-modulated working frequency laser light.
The laser light passes through the atomic reference of which a trans- mittance peak value is consistent with a laser working frequency, is partially intercepted by the partial wave sheet, and is guided and received by the photoelectric detector.
A received optical signal is converted into an electrical signal and then is pro-
cessed by a 2f frequency multiplication phase-locking process.
The constant current source for driving the laser light is stable, so that the reference semiconductor laser 11 outputs frequency-stable laser light.
A drive current for driving the reference semiconduc- tor laser 11 to output the stable frequency forms a standard con-
stant current source.
The constant current source is converted in- to a reference voltage through a sampling circuit and output to the modulation of the frequency stabilization unit for generating a high-precision amplitude sinusoidal signal.
The high-precision amplitude sinusoidal signal based on the atomic reference forms a zero-crossing second harmonic frequency discrimination signal.
The second harmonic frequency discrimination signal is a frequency stabilization frequency discrimination signal of the frequency stabilization semiconductor laser 21. The frequency stabilization semiconductor laser 21 is driven to generate working frequency la-
ser light by controlled modulation and constant current superposi- tion.
The laser light passes through the molecular reference, is partially intercepted by the partial wave sheet, and is guided and received by the photoelectric detector.
A received signal is pro- cessed by a 2f frequency multiplication phase-locking process for stabilizing a constant current to drive the frequency stabiliza- tion semiconductor laser 21 to output frequency-stable laser light.
In practical application, in order to further improve the voltage reference precision of generating high-precision amplitude sinusoidal signals, optical portions of the constant current source unit may adopt a saturation absorption layout, so that the voltage reference precision is remarkably improved.
The absorption spectral lines of the atomic reference are mainly distributed in a visible range, and the independent absorp- tion spectral lines are extremely limited. Therefore, the applica- tion of the semiconductor laser working in the visible light fre- quency range is limited, the frequency stabilization of the semi- conductor laser in an infrared band is very difficult, and the de- fect that the freguency stabilization structure is complex and the manufacturing cost is high exists even if the frequency stabiliza- tion is feasible. The FP etalon has the defects of manufacturing difficulty and high manufacturing cost. For the semiconductor la- ser working at an infrared frequency, the designed FP etalon is large in size and cannot be applied in practical use.
In the prior art, the frequency stabilization range of the working frequency of the semiconductor laser is very limited, so that the use of the semiconductor laser is limited.
An edge of an atomic reference or a molecular reference is used as a reference for expanding a frequency stabilization range according to the present invention. A visible light frequency range of a semiconductor laser can be expanded, and frequency sta- bilization of an infrared frequency range can be realized by uti- lizing an edge of a molecular reference, so that a frequency sta- bilization range of an existing frequency stabilization method for a semiconductor laser is greatly widened. The frequency stabiliza- tion achieves a complete electrical feedback, and the manufactur- ing cost is low. Since the atomic reference is locked to generate a constant sinusoidal signal amplitude, the frequency stabiliza- tion precision can reach the frequency stabilization precision of center locking by the method.
Various embodiments in this description are described in a progressive manner. Each embodiment is described with emphasis up- on differences from the other embodiments. Mutual reference is made to like parts throughout the various embodiments.
The principles and implementations of the present invention are described by using specific examples herein.
The above de-
scription of the embodiments is only used to help understand the system and core ideas of the present invention.
Meanwhile, for a person of ordinary skill in the art, according to the ideas of the present invention, there will be changes in the specific implemen-
tations and the scope of application.
In summary, this description should not be construed as limiting the present invention.

Claims (6)

CONCLUSIESCONCLUSIONS 1. Randfrequentiestabilisatiesysteem voor een halfgeleiderlaser, met het kenmerk, dat deze omvat: een constante stroombronmodule en een frequentiestabilisatiemodule, waarbij de constante stroombron- module een referentiehalfgeleiderlaser, een modulatiebron, een eerste constante stroombron, een atomaire referentieeenheid, een eerste foto-elektrische detector, een eerste fasevergrendelde ver- sterker en een eerste partiele golfplaat omvat, waarbij de fre- quentiestabilisatie-eenheid een frequentiestabilisatiehalfgelei- derlaser, een geregelde modulatiebron, een tweede constante stroombron, een frequentieselectiereferentie-eenheid, een tweede foto-elektrische detector, een tweede fasevergrendelde versterker en een tweede partiële golfplaat omvat; waarbij de referentiehalfgeleiderlaser amplitude-gemoduleerd la- serlicht van de werkfrequentie afgeeft onder de gecombineerde aandrijving van de modulatiebron en de eerste constante stroom- bron, waarbij het laserlicht door de atomaire referentie-eenheid gaat waarvan een transmissiepiekwaarde consistent is met een werk- frequentie van de laser, gedeeltelijk wordt onderschept door de eerste partiële golfplaat, wordt geleid naar de eerste foto- elektrische detector en wordt ontvangen door de eerste foto- elektrische detector, waarbij een ontvangen optisch signaal wordt omgezet in een elektrisch signaal en vervolgens wordt verwerkt door de eerste fasevergrendelde versterker, waarbij de eerste con- stante stroombron wordt aangedreven om te worden gestabiliseerd zodat de referentiehalfgeleiderlaser laserlicht met een stabiele werkfrequentie afgeeft, en een aandrijfstroom voor het aandrijven van de referentiehalfgeleiderlaser om het laserlicht met de sta- biele werkfrequentie uit te voeren een standaard constante stroom- bron vormt; en waarbij de standaard constante stroombron wordt omgezet in een re- ferentiespanning via een bemonsteringscircuit, waarbij de referen- tiespanning wordt uitgevoerd naar de geregelde modulatiebron van de frequentiestabilisatie-eenheid voor het genereren van een zeer nauwkeurig sinusvormig signaal met amplitude om een nuldoorgang tweede harmonische frequentiediscriminatie signaal te vormen dat een frequentiestabilisatie-frequentiediscriminatiesignaal is van de halfgeleiderlaser met frequentiestabilisatie, waarbij de gere- gelde modulatiebron wordt gesuperponeerd met de tweede constante stroombron, de fregquentiestabilisatiehalfgeleiderlaser wordt aan- gedreven om laserlicht van werkfrequentie te genereren, dat door de frequentieselectiereferentie eenheid gaat, gedeeltelijk wordt onderschept door de tweede partiele golfplaat, wordt geleid naar de tweede foto-elektrische detector, en wordt ontvangen door de tweede foto-elektrische detector, waarbij een ontvangen optisch signaal wordt omgezet in een elektrisch signaal en vervolgens wordt verwerkt door de tweede fasevergrendelde versterker, en waarbij de halfgeleiderlaser met frequentiestabilisatie wordt aan- gedreven om frequentiestabiel laserlicht uit te voeren.An edge frequency stabilization system for a semiconductor laser, characterized in that it comprises: a constant current source module and a frequency stabilization module, the constant current source module comprising a reference semiconductor laser, a modulation source, a first constant current source, an atomic reference unit, a first photoelectric detector, a first phase-locked amplifier and a first partial waveplate, the frequency stabilization unit comprising a frequency stabilization semiconductor laser, a regulated modulation source, a second constant current source, a frequency selection reference unit, a second photoelectric detector, a second phase-locked amplifier and comprises a second partial wave plate; wherein the reference semiconductor laser outputs amplitude modulated laser light of the operating frequency under the combined drive of the modulation source and the first constant current source, the laser light passing through the atomic reference unit having a transmission peak value consistent with an operating frequency of the laser, is partially intercepted by the first partial waveplate, is conducted to the first photoelectric detector and is received by the first photoelectric detector, converting a received optical signal into an electrical signal and then processed by the first phase-locked amplifier, the first constant current source being driven to be stabilized so that the reference semiconductor laser outputs laser light at a stable operating frequency, and a drive current for driving the reference semiconductor laser to output the laser light at the stable operating frequency constitutes a standard constant current source; and wherein the standard constant current source is converted to a reference voltage via a sampling circuit, the reference voltage being output to the regulated modulation source of the frequency stabilization unit to generate a highly accurate amplitude sinusoidal signal to perform a zero-crossing second harmonic frequency discrimination form a signal which is a frequency stabilization frequency discrimination signal of the semiconductor laser with frequency stabilization, superimposing the regulated modulation source with the second constant current source, driving the frequency stabilization semiconductor laser to generate laser light of operating frequency, which passes through the frequency selection reference unit, partially is intercepted by the second partial wave plate, passed to the second photoelectric detector, and received by the second photoelectric detector, converting a received optical signal e converted into an electrical signal and then processed by the second phase-locked amplifier, and driving the semiconductor laser with frequency stabilization to output frequency stable laser light. 2. Randfrequentiestabilisatiesysteem voor de halfgeleiderlaser volgens conclusie 1, met het kenmerk, dat de frequentieselectiere- ferentie-eenheid een atomaire referentie of een moleculaire refe- rentie is; wanneer de frequentieselectiereferentie-eenheid een atomaire referentie is, is het randfrequentiestabilisatiesysteem een randfrequentiestabilisatiesysteem van de atomaire referentie, en delen de constante stroombronmodule en de frequentiestabilisa- tiemodule één atomaire referentie; en wanneer de frequentieselec- tiereferentie-eenheid een moleculaire referentie is, is het rand- frequentiestabilisatiesysteem een randfrequentiestabilisatiesys- teem van de moleculaire referentie.The semiconductor laser edge frequency stabilization system according to claim 1, characterized in that the frequency selection reference unit is an atomic reference or a molecular reference; when the frequency selection reference unit is an atomic reference, the edge frequency stabilization system is an edge frequency stabilization system of the atomic reference, and the constant current source module and the frequency stabilization module share one atomic reference; and when the frequency selection reference unit is a molecular reference, the edge frequency stabilization system is an edge frequency stabilization system of the molecular reference. 3. Randfrequentiestabilisatiesysteem voor de halfgeleiderlaser volgens conclusie 1, met het kenmerk, dat de modulatiebron en de geregelde modulatiebron respectievelijk een sinusvormige signaal- opwekkingsschakeling aannemen.The semiconductor laser edge frequency stabilization system according to claim 1, characterized in that the modulation source and the regulated modulation source respectively adopt a sinusoidal signal generating circuit. 4. Randfrequentiestabilisatiesysteem voor de halfgeleiderlaser volgens conclusie 1, met het kenmerk, dat optische delen van een eerste constante stroombroneenheid zich alle in een verzadigde ab- sorptie lay-out bevinden.The semiconductor laser edge frequency stabilization system according to claim 1, characterized in that optical parts of a first constant current source unit are all in a saturated absorption layout. 5. Randfrequentiestabilisatiesysteem voor de halfgeleiderlaser volgens conclusie 1, met het kenmerk, dat de eerste fasevergren- delde versterker een 1f frequentievermenigvuldigings- fasevergrendelingsproces uitvoert.The semiconductor laser edge frequency stabilization system according to claim 1, characterized in that the first phase-locked amplifier performs a 1f frequency multiplication phase-locked process. 6. Randfrequentiestabilisatiesysteem voor de halfgeleiderlaser volgens conclusie 1, met het kenmerk, dat de tweede fasevergren- delde versterker een 2f frequentievermenigvuldigings- fasevergrendelingsproces uitvoert.The semiconductor laser edge frequency stabilization system according to claim 1, characterized in that the second phase-locked amplifier performs a 2f frequency multiplication phase-locked process.
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