CN111029899A - Laser power stabilization and noise reduction system - Google Patents
Laser power stabilization and noise reduction system Download PDFInfo
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- CN111029899A CN111029899A CN201911251193.7A CN201911251193A CN111029899A CN 111029899 A CN111029899 A CN 111029899A CN 201911251193 A CN201911251193 A CN 201911251193A CN 111029899 A CN111029899 A CN 111029899A
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- 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
- H01S5/06817—Noise reduction
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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
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Abstract
The invention discloses a laser power stabilizing and noise reducing system which comprises a laser, a power stabilizing and noise reducing device and a phase locking device. In the power stabilization and noise reduction system of the laser, after laser emitted from the laser is transmitted by the Mach-Zehnder interferometer in the power stabilization and noise reduction device, the power stability of the laser output by the laser is improved, and meanwhile, the low-frequency intensity noise is inhibited; the transmission output light beam of the Mach-Zehnder interferometer passes through the half-wave plate and the polarization beam splitter, a small part of light enters the phase locking device, and the phase locking device is used for locking the phase of the Mach-Zehnder interferometer, so that the power stabilizing and noise reducing device can stably operate for a long time. The laser power stabilization and noise reduction system is low in cost, simple in structure, high in stability, small in size, simple in operation and suitable for batch production, and plug and play can be realized on an optical path without changing the propagation direction of an original optical path.
Description
Technical Field
The invention relates to the technical field of laser power stability control, in particular to a laser power stability and noise reduction system.
Background
Laser output by a laser has unique advantages of good monochromaticity, directivity, coherence, high brightness and the like, and is widely applied to the fields of information detection, communication, national defense and the like. In particular, high-power narrow-linewidth lasers have become the main light source in scientific research and application fields such as quantum information processing, quantum imaging and precision measurement. In recent years, with the development of quantum technology, the preparation of high-quality non-classical optical fields such as a high-compression-degree compressed optical field and a high-entanglement-degree quantum entangled optical field is an inevitable demand in subsequent applications. Whether the output performance of the laser source is excellent or not is one of the key problems in preparing a high-quality non-classical light field, and the stability of the output power and the noise characteristic of the laser are directly related to the preparation of the non-classical light field, especially the preparation of the low-frequency non-classical light field.
At present, the commonly used scheme for stabilizing the laser power performs laser modulation by an optical feedback method, and further eliminates irregular fluctuation of the laser power by feedback. One of the schemes is to use an acousto-optic modulator and an external feedback circuit, such as "a medium wave infrared laser power stabilizing device and stabilizing method" and literature "the power stabilization research of 397.5nm ultraviolet laser under feedback control of a shifter in chinese patent 201310687652.2, chinese laser 45 (10): in 1001008(2018), the laser generates a bragg diffraction light signal through the acousto-optic modulator, and the signal is fed back to the acousto-optic modulator through an external feedback loop including a photodetector, a lock-in amplifier, a controller and the like to realize stable control of the laser power. The other scheme is to replace the acousto-optic modulator with an electro-optic modulator, for example, the document "research and measurement report of high-precision laser beam power stabilizer", 21(3):0161(2000) ", the method steps are as above, the laser carries the modulation signal after passing through the electro-optic modulator, and the stable control of the laser power is realized by detecting the modulation signal and feeding back the modulation signal to the electro-optic modulator through a photoelectric detector, a controller and the like. In the two schemes, no matter the acousto-optic modulator or the electro-optic modulator is used, firstly a complex feedback loop is needed to realize the stability control of the laser power, secondly the key device in the scheme, namely the acousto-optic modulator or the electro-optic modulator, is expensive, and although the stability of the laser is improved in the scheme, the intensity noise of the laser is not obviously reduced.
In addition, there is also a proposal that a nonlinear crystal is inserted into the output optical path of the laser, and the fluctuation of the laser power is compensated by converting the second-order nonlinear process of the laser into the efficiency of frequency-doubled light, such as "a laser power stabilizing device and method" related in chinese patent 201510492404.1. In the scheme of stabilizing the laser power by inserting the nonlinear crystal, the effect of reducing the intensity noise of the laser is not achieved at the same time, and the nonlinear crystal is expensive and is not the optimal choice.
Disclosure of Invention
The invention aims to provide a laser power stabilization and noise reduction system, which aims to solve the problems that the existing laser power stabilization scheme is complex in structure and high in price, and cannot stabilize laser power and simultaneously realize noise reduction.
In order to achieve the purpose, the invention provides the following scheme:
a laser power stabilization and noise reduction system, the laser power stabilization and noise reduction system comprising: the device comprises a laser, a power stabilizing and noise reducing device and a phase locking device; the power stabilizing and noise reducing device comprises a first plane reflector, a Mach-Zehnder interferometer, a fourth plane reflector, a half-wave plate and a polarization beam splitter; the Mach-Zehnder interferometer comprises a first beam splitter, a second planar mirror, a third planar mirror, a second beam splitter and piezoelectric ceramics;
the first plane reflector is arranged on an emergent light path of the laser; the first beam splitter is arranged on a reflection light path of the first plane mirror; the second plane mirror is arranged on a transmission light path of the first beam splitter; the second beam splitter is arranged on a reflection light path of the second plane mirror; the third plane mirror is arranged on a reflection light path of the first beam splitter; the second beam splitter is also arranged on a reflection light path of the third plane mirror; the fourth plane mirror is arranged on the first transmission light path and the second reflection light path of the second beam splitter; the half-wave plate is arranged on a reflection light path of the fourth plane reflector; the polarization beam splitter is arranged on a transmission light path of the half-wave plate; the phase locking device is arranged on a reflected light path of the polarization beam splitter; the second plane mirror is fixed on the piezoelectric ceramic; the phase locking device is connected with the piezoelectric ceramic.
Optionally, the power stabilizing and noise reducing apparatus further includes: stacking garbage; the garbage pile is arranged on a first reflection light path and a second transmission light path of the second beam splitter.
Optionally, the power stabilizing and noise reducing device is fixed on the invar steel plate.
Optionally, the phase locking device includes a photodetector, a proportional-integral-derivative controller, and a high-voltage amplifier, which are connected in sequence; the photoelectric detector is arranged on a reflected light path of the polarization beam splitter; the high-voltage amplifier is connected with the piezoelectric ceramic.
Optionally, the wavelength of the laser output by the laser is 1560nm, and the output power is 5 watts.
Optionally, the first plane mirror and the fourth plane mirror are 22.5 degree total reflection mirrors.
Optionally, the first plane mirror, the second plane mirror, the third plane mirror and the fourth plane mirror are all plated with a high reflection film for 1560nm laser.
Optionally, the splitting ratios of the first beam splitter and the second beam splitter are the same.
Optionally, the reflectivity of the first beam splitter and the second beam splitter to 1560nm laser is 92%.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a laser power stabilizing and noise reducing system, which comprises a laser, a power stabilizing and noise reducing device and a phase locking device, wherein the laser is connected with the power stabilizing and noise reducing device; the power stabilizing and noise reducing device comprises a first plane reflector, a Mach-Zehnder interferometer, a fourth plane reflector, a half-wave plate and a polarization beam splitter; the mach-zehnder interferometer includes a first beam splitter, a second planar mirror, a third planar mirror, a second beam splitter, and a piezoelectric ceramic. In the power stabilization and noise reduction system of the laser, after laser emitted from the laser is transmitted by the Mach-Zehnder interferometer, the power stability of the laser output by the laser is improved, and meanwhile, the low-frequency intensity noise is inhibited; the transmission output light beam of the Mach-Zehnder interferometer passes through the half-wave plate and the polarization beam splitter, a small part of light enters the phase locking device, and the phase locking device is used for locking the phase of the Mach-Zehnder interferometer, so that the power stabilizing and noise reducing device can stably operate for a long time. The laser power stabilization and noise reduction system provided by the invention is low in cost, simple in structure, high in stability, small in size, free of changing the original light path propagation direction, capable of realizing plug and play on the light path, and has the advantages of being simple in operation and suitable for batch production.
In addition, all elements in the power stabilizing and noise reducing device are integrally fixed on the invar steel plate, so that the deformation coefficient is small, and the mechanical structure is stable.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and 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 provided by the present invention without any creative effort.
FIG. 1 is a schematic diagram of a laser power stabilization and noise reduction system according to the present invention;
fig. 2 is a schematic diagram illustrating a power stability test result of a laser according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating a test result of laser noise suppression according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating the result of implementing laser noise control by phase locking of a mach-zehnder interferometer according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a laser power stabilization and noise reduction system, which aims to solve the problems that the existing laser power stabilization scheme is complex in structure and high in price, and cannot stabilize laser power and simultaneously realize noise reduction.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic structural diagram of a laser power stabilization and noise reduction system provided in the present invention. Referring to fig. 1, the power stabilizing and noise reducing system of the laser of the present invention includes: a laser 1, a power stabilizing and noise reducing device 2 and a phase locking device 3. The power stabilizing and noise reducing device 2 is used for improving the output performance of the laser 1, stabilizing the laser power and inhibiting the intensity noise of the low-frequency laser band. The phase locking device 3 is used for locking the phase of the mach-zehnder interferometer, so that the power stabilization and noise reduction device can stably operate for a long time.
Specifically, the power stabilizing and noise reducing device 2 includes a first plane mirror 201, a mach-zehnder interferometer, a fourth plane mirror 206, a garbage stack 208, a half-wave plate 209, and a polarization beam splitter 210. The mach-zehnder interferometer includes a first beam splitter 202, a second planar mirror 203, a third planar mirror 204, a second beam splitter 205, and a piezoceramic 207. The phase locking device 3 comprises a photoelectric detector 301, a proportional integral derivative controller 302 and a high-voltage amplifier 303. In practical applications, the garbage heap 208 may employ light blocking sheets.
The mach-zehnder interferometer is composed of a first beam splitter 202, a second plane mirror 203, a third plane mirror 204, a second beam splitter 205 and piezoelectric ceramics 207, and is used for stabilizing the power of the laser and reducing the noise of the laser. The first and fourth plane mirrors 201 and 206 prevent the direction of the output optical path from changing after the laser light passes through the mach-zehnder interferometer. The half-wave plate 209 and the polarization beam splitter 210 enable most of laser to be used after transmission, and a small part of laser is injected into the phase locking device 3, specifically, the laser enters the photoelectric detector 301 to convert an optical signal into an electric signal, is input into the proportional-integral-derivative controller 302, passes through the high-voltage amplifier 303, acts on the piezoelectric ceramic 207 to control the second plane mirror 203, and locks the phase of the mach-zehnder interferometer.
Referring to fig. 1, the first plane mirror 201 is disposed on the outgoing light path of the laser 1; the first beam splitter 202 is arranged on the reflected light path of the first plane mirror 201; the second plane mirror 203 is disposed on the transmission light path of the first beam splitter 202. The second beam splitter 205 is disposed on the reflection optical path of the second plane mirror 203. The third plane mirror 204 is disposed on the reflected light path of the first beam splitter 202. The second beam splitter 205 is also disposed on the reflection light path of the third plane mirror 204. The fourth plane mirror 206 is disposed on both the first transmitted optical path of the second beam splitter 205 and the second reflected optical path of the second beam splitter 205. The garbage heap 208 is disposed on the first reflection optical path and the second transmission optical path of the second beam splitter 205. The half-wave plate 209 is disposed on the reflection light path of the fourth plane mirror 206. The polarization beam splitter 210 is disposed on a transmission light path of the half-wave plate 210. The phase lock device 3 is disposed on a reflected light path of the polarization beam splitter 210. The second plane mirror 203 is fixed to the piezoelectric ceramic 207. The phase lock device 3 is connected to the piezoelectric ceramic 207.
A laser beam emitted from the laser 1 is totally reflected by a first plane mirror 201 and then enters a first beam splitter 202; a part of the laser beam reaching the first beam splitter 202 is transmitted and then enters a second plane mirror 203, which is called a first beam a; another part of the reflected light is incident on the third plane mirror 204, which is called a second light beam b. The first light beam a is totally reflected by the second plane mirror 203, enters the second beam splitter 205, and is split into a first transmitted light beam a1t and a first reflected light beam a1 f. The second light beam b is totally reflected by the third plane mirror 204, enters the second beam splitter 205, and is split into a second transmitted light beam b2t and a second reflected light beam b2 f. The first reflected beam a1f and the second transmitted beam b2t are weak light portions, are combined into one beam after interference, and are blocked by the garbage heap 208 and are not used. The first transmitted beam a1t and the second reflected beam b2f are strong light portions, are combined into one beam after interference, are incident on the plane total reflection mirror 206, and are output along the original output direction of the laser 1. The half-wave plate 209 rotates so that most of the output laser light is transmitted and used after passing through the polarization beam splitter 210, and a small part of the laser light is reflected and reflected back to the phase locking device 3 for locking the phase.
The Mach-Zehnder interferometer designed by adopting the linear optical element has the advantages of low cost, simple device structure and easy operation, and can simultaneously realize the improvement of the power stability of laser output of the laser and the suppression of the intensity noise at a low frequency.
The first plane mirror 201 and the fourth plane mirror 206 are 22.5 degree total reflection mirrors, so that the output laser of the laser 1 is totally reflected by the 22.5 degree plane total reflection mirror and enters the mach-zehnder interferometer. A22.5-degree plane total reflection mirror is also arranged on the strong light output light path, so that laser is output along the propagation direction of the input light path, and the propagation direction of the original light path is not changed.
The wavelength of the laser output by the laser 1 is 1560nm, and the output power is 5W. The first plane mirror 201 and the fourth plane mirror 206 used by the power stabilizing and noise reducing device 2 are plated with high reflective films (reflectivity R > 99.9% @1560nm) for 1560nm light at 22.5 degrees.
The splitting ratios of the first beam splitter 202 and the second beam splitter 205 are the same. The reflectance of the first beam splitter 202 and the second beam splitter 205 with respect to laser light having a wavelength of 1560nm was 92%.
The second plane mirror 203 and the third plane mirror 204 are also coated with a high reflection film (reflectance R > 99.9% @1560nm) for 1560nm light.
The second plane mirror 203 is bonded to a piece of annular piezoelectric ceramic 207 to precisely lock the phase of the mach-zehnder interferometer.
The mach-zehnder interferometer (including the first beam splitter 202, the second plane mirror 203, the third plane mirror 204, the second beam splitter 205 and the piezoelectric ceramic 207) in the power stabilizing and noise reducing device 2, the first plane mirror 201, the fourth plane mirror 206, the half-wave plate 209 and the polarization beam splitter 210 are integrally fixed on an invar steel plate, and the mechanical stability of the device can be improved due to the small deformation coefficient of the invar steel. Preferably, the invar panel is 80mm wide and 150mm long.
The phase locking unit 3 is composed of a photodetector 301, a proportional-integral-derivative controller 302 and a high-voltage amplifier 303, wherein the photodetector 301 is arranged on a reflection light path of the polarization beam splitter 210; the photoelectric detector 301, the proportional-integral-derivative controller 302 and the high-voltage amplifier 303 are connected in sequence; the high voltage amplifier 303 is connected to the piezoelectric ceramic 207.
A small portion of the laser light reflected by the polarization beam splitter 210 enters the photodetector 301, and the photocurrent is converted into an electrical signal as an error signal for locking the phase of the mach-zehnder interferometer. The electrical signal is processed by the proportional integral derivative controller 302, amplified by the high voltage amplifier 303 and fed back to the piezoelectric ceramic 207 to realize phase locking, so that the mach-zehnder interferometer operates to an optimal operating point.
The invention adopts a single-frequency continuous wave fiber laser as a laser light source, the laser 1 outputs laser with the wavelength of 1560nm, and the output power is 5 watts. Laser output by the laser passes through a 22.5-degree plane total reflection mirror and is totally reflected to enter the Mach-Zehnder interferometer. After the laser is transmitted by the Mach-Zehnder interferometer, the stability of the laser power output by the laser and the low-frequency intensity noise are improved and suppressed. The transmitted light is divided into two beams, one beam is a weak light part, and the other beam is a strong light part for output due to low power. And a 22.5-degree plane total reflection mirror is arranged on the strong light output path to ensure that the laser is output along the propagation direction of the input light path. The output light beam passes through the half-wave plate 209 and the polarization beam splitter 210, a small part of light enters the photoelectric detector 301, and the phase of the mach-zehnder interferometer is locked by the phase locking device 3, so that the power stabilizing and noise reducing device 2 can stably operate for a long time. All elements in the power stabilizing and noise reducing device 2 are integrally fixed on an invar steel plate, so that the deformation coefficient is small, and the mechanical structure is stable. Therefore, the laser power stabilization and noise reduction system has the advantages of simple structure, high stability, small size, plug and play on the light path without changing the propagation direction of the original light path, simple operation, suitability for batch production and the like.
The laser power stabilization and noise reduction system adopts the Mach-Zehnder interferometer and the phase locking device 3 thereof to improve the power stability of laser output by the laser 1, reduce the intensity noise of low-frequency band of the laser, solve the bottleneck problem of preparing low-frequency band compressed light field and entangled light field, and provide a high-quality light source for the research and application of continuous variable quantum optics.
In the laser power stabilization and noise reduction system, laser output by a laser 1 passes through a first plane total reflection mirror 201 arranged at 22.5 degrees and is totally reflected to enter a Mach-Zehnder interferometer. After passing through the first beam splitter 202, the laser light is partially transmitted and partially reflected, and the transmitted light and the reflected light are incident to the second plane total reflection mirror 203 and the third plane total reflection mirror 204 respectively and are totally reflected. The two light rays are combined at the second beam splitter 205 and are partially transmitted and partially reflected, respectively. The Mach-Zehnder interferometer structure is used for determining, the beam splitting ratio of the beam splitter is irrelevant, and the laser part transmitted by the second beam splitter 205 is weak in power, so that the laser part is not used and is blocked by the garbage pile 208; the laser reflected by the second beam splitter 205 has a relatively high power and is used as a laser source with improved output performance. This part of the laser light passes through a fourth plane total reflection mirror 206 placed at 22.5 degrees and is output along the original propagation direction of the laser 1.
In order for the power stabilizing and noise reducing apparatus 2 to operate stably, the phase of the mach-zehnder interferometer needs to be locked. Therefore, a half-wave plate 209 and a polarization beam splitter prism 210 are placed on the output laser light path, and a small part of the laser light is split for phase locking. Since the laser light output through the second beam splitter 205 is composed of two parts, determined by the interferometer structure, the two outgoing beams include a weak light part and a strong light part. The weak light part is not used due to weak power, and the garbage heap 208 is used for blocking light. The reflected light of the strong light part, which also includes the reflected light of the second plane full-reflection mirror 203, passes through the transmitted light a1t of the second beam splitter 205, and the reflected light of the third plane full-reflection mirror 204 passes through the reflected light b2f of the second beam splitter 205, and the two lights interfere with each other, so that the interference visibility is 85%. A half-wave plate 209 and a polarization beam splitter prism 210 are arranged on the output laser light path, and a small part of laser light is split for phase locking. The photodetector 301 detects the interference signals of the two lights a1t and b2f, and converts the signals into a dc electrical signal as an error signal. After being processed by a proportional integral derivative controller 302, the signal is sent to a high-voltage amplifier 303 for amplification and then fed back to the piezoelectric ceramic 207 which is adhered to the second plane total reflection mirror 203, and the spatial position of the second plane total reflection mirror 203 is controlled, so that the control of the length of the interferometer arm of the Mach-Zehnder interferometer is realized. Locking the interferometer arm length, i.e. locking its phase.
The phase of the mach-zehnder interferometer is locked at different voltages of a transmission curve detected by the photoelectric detector 301 by adjusting the proportional-integral-derivative controller 302 and the high-voltage amplifier 303 in the feedback loop, so that the control of the phase of the interferometer can be realized, and the transmittance of the interferometer corresponds to different values at the moment.
The technical effects of the laser power stabilization and noise reduction system of the invention are verified as follows:
in this embodiment, the fiber laser 1 is used to output a continuous monochromatic laser with a wavelength of 1560nm, and the power stability of the output laser when the fiber laser 1 is free running is first tested, as shown by a curve (i) in fig. 2. FIG. 2 shows the abscissa as Time (Time) in hours (hour); the ordinate is the Power (Power) in watts (w). Then, after placing the power stabilization and noise reduction device 2 at the output end and locking the phase of the mach-zehnder interferometer by the phase locking device 3, the power stability of the output laser is tested at the output end, as shown by a curve (ii) in fig. 2. As shown by curve (i) in FIG. 2, the power fluctuation of the 1560nm laser was. + -. 0.185% when laser 1 was free-running for 5 hours. As shown in curve (ii) in fig. 2, when the phase-locked loop of the herd-gardel interferometer is closed, the power fluctuation of the 1560nm laser operation for 5 hours is only ± 0.016%. Therefore, after the laser power stabilization and noise reduction system is adopted, the power fluctuation of 1560nm laser is obviously improved.
The laser intensity noise output by the optical fiber laser 1 adopted in the embodiment is far higher than the shot noise reference, the self-homodyne detection system is placed at the output end of the mach-zehnder interferometer to measure the intensity noise of the laser, the laser output by the laser 1 is divided into two beams by the 50/50 beam splitter and input into the two photoelectric detectors, the sum of the two detector photocurrents is the intensity noise of the laser, and the subtraction of the two detected photocurrents is the corresponding shot noise reference. The intensity noise of the laser light output from the laser 1 is suppressed by the mach-zehnder interferometer, as shown in fig. 3. In FIG. 3, the abscissa is Frequency (Frequency) in kHz; the ordinate is the Noise Power (Noise Power) in decibel-milliwatts (dBm). Curve (i) in FIG. 3 is the intensity noise of the 1560nm laser without free running Mach-Zehnder interferometer; curve (ii) in fig. 3 shows the intensity noise of the output laser light after locking the phase of the mach-zehnder interferometer (MZI) when the beam splitter reflectivity is 91%; curve (iii) in fig. 3 is the shot noise floor. It can be seen that after the laser power stabilization and noise reduction system is adopted, the intensity noise of the laser is suppressed within the range of the analysis frequency of 0Hz to 45kHz, and the intensity noise is reduced by about 10dB at the analysis frequency of 8 kHz. However, the intensity noise of the fiber laser at the low frequency band is far higher than the shot noise reference, so the intensity noise of the suppressed laser is still about 10dB higher than the shot noise reference within the analysis frequency range of 0Hz-30 kHz.
The present embodiment also achieves control of laser noise through phase locking of the mach-zehnder interferometer. And the interferometer is locked at different voltage values of the transmission curve through a feedback loop, so that the arm length and the phase of the interferometer are controlled. When the phases of the interferometers are different, the output power of the transmission ends of the corresponding interferometers is also different. The ratio of the power of the intense light part at the output of the interferometer to the optical power at the input of the interferometer is defined as the transmittance of the interferometer. Fig. 4 is a schematic diagram showing the control result of laser noise by phase locking of the mach-zehnder interferometer according to the present invention, and the specific phase control shows that the intensity noise of the laser changes when the transmittance of the output laser is different and the transmittance is different. In FIG. 4, the abscissa is Frequency (Frequency) in kHz; the ordinate is the Noise Power (Noise Power) in decibel-milliwatts (dBm). Curve (i) in fig. 4 is the intensity noise of 1560nm laser light without mach-zehnder interferometer free-wheeling, and curves (ii), (iii), and (iv) in fig. 4 are the intensity noise of output laser light with mach-zehnder interferometer locked at different phase positions, corresponding to 45%, 65%, and 85% transmission, respectively. It can be seen that the intensity noise of the laser is greatly suppressed with the increase of the transmittance after the interferometer is locked, and the intensity noise is reduced by nearly 10dB in the analysis frequency range of 0Hz to 30 kHz. The intensity noise of the laser in the 0Hz-45kHz analysis frequency range will be closer to the shot noise floor when the transmission value is increased from 45% to 85%. In the case of the transmittance of 45%, the intensity noise of the laser light is higher by about 5dB in the case of the transmittance of 85%, and the upper limit of the range of frequency suppression also extends from 35kHz at the transmittance of 45% to 45kHz at the transmittance of 85%. The present embodiment thus achieves control of laser noise through phase locking of the mach-zehnder interferometer.
Therefore, the laser power stabilization and noise reduction system provided by the invention can inhibit the intensity noise of the low frequency band while improving the stability of the laser output power of the laser, so that the laser power stabilization and noise reduction system can be widely applied to quantum optical research and application for preparing continuous variable non-classical light fields.
The embodiments of the present invention are merely exemplary of how the power stabilization and noise reduction of 1560nm fiber lasers may be performed by the present invention. The laser power stabilizing and noise reducing system can be further expanded to lasers of various types and wavelengths for power stabilizing and noise reducing.
In the existing laser power stabilizing device scheme, no matter an acousto-optic modulator or an electro-optic modulator is used, firstly a complex feedback loop is needed to realize the stability control of the laser power, secondly the key device in the scheme, namely the acousto-optic modulator or the electro-optic modulator, is expensive, and although the stability of the laser is improved in the scheme, the intensity noise of the laser is not obviously reduced. In the scheme of stabilizing the laser power by inserting the nonlinear crystal, the reduction of the intensity noise of the laser is not achieved at the same time, and the nonlinear crystal is expensive and is not the optimal choice. The Mach-Zehnder interferometer designed by adopting the linear optical element has the advantages of low cost, simple device structure and easy operation, and can simultaneously realize the improvement of the power stability of laser output of the laser and the suppression of the intensity noise at a low frequency.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
The principles and embodiments of the present invention have been described herein using specific examples, which are presented solely to aid in the understanding of the apparatus and its core concepts; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (9)
1. A laser power stabilization and noise reduction system, comprising: the device comprises a laser, a power stabilizing and noise reducing device and a phase locking device; the power stabilizing and noise reducing device comprises a first plane reflector, a Mach-Zehnder interferometer, a fourth plane reflector, a half-wave plate and a polarization beam splitter; the Mach-Zehnder interferometer comprises a first beam splitter, a second planar mirror, a third planar mirror, a second beam splitter and piezoelectric ceramics;
the first plane reflector is arranged on an emergent light path of the laser; the first beam splitter is arranged on a reflection light path of the first plane mirror; the second plane mirror is arranged on a transmission light path of the first beam splitter; the second beam splitter is arranged on a reflection light path of the second plane mirror; the third plane mirror is arranged on a reflection light path of the first beam splitter; the second beam splitter is also arranged on a reflection light path of the third plane mirror; the fourth plane mirror is arranged on the first transmission light path and the second reflection light path of the second beam splitter; the half-wave plate is arranged on a reflection light path of the fourth plane reflector; the polarization beam splitter is arranged on a transmission light path of the half-wave plate; the phase locking device is arranged on a reflected light path of the polarization beam splitter; the second plane mirror is fixed on the piezoelectric ceramic; the phase locking device is connected with the piezoelectric ceramic.
2. The laser power stabilization and noise reduction system of claim 1, wherein the power stabilization and noise reduction device further comprises: stacking garbage; the garbage pile is arranged on a first reflection light path and a second transmission light path of the second beam splitter.
3. The laser power stabilization and noise reduction system of claim 1 or 2, wherein the power stabilization and noise reduction device is fixed on invar.
4. The laser power stabilization and noise reduction system according to claim 1, wherein the phase locking device comprises a photodetector, a proportional-integral-derivative controller and a high voltage amplifier, which are connected in sequence; the photoelectric detector is arranged on a reflected light path of the polarization beam splitter; the high-voltage amplifier is connected with the piezoelectric ceramic.
5. The laser power stabilization and noise reduction system of claim 1, wherein the laser output laser has a wavelength of 1560nm and an output power of 5 watts.
6. The laser power stabilization and noise reduction system of claim 1, wherein the first planar mirror and the fourth planar mirror are 22.5 degree total reflection mirrors.
7. The laser power stabilization and noise reduction system of claim 1, wherein the first, second, third and fourth planar mirrors are coated with a high reflective film for 1560nm laser light.
8. The laser power stabilization and noise reduction system of claim 1, wherein the splitting ratios of the first beam splitter and the second beam splitter are the same.
9. The laser power stabilization and noise reduction system of claim 1, wherein the first beam splitter and the second beam splitter have a reflectivity of 92% for 1560nm laser light.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113483880A (en) * | 2021-08-17 | 2021-10-08 | 广东电网有限责任公司 | Vibration sensing system based on few-mode optical fiber |
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| CN105022606A (en) * | 2015-06-30 | 2015-11-04 | 中国科学技术大学先进技术研究院 | Ultra-high-speed quantum random number generator and generation method based on laser phase fluctuation |
| CN108007572A (en) * | 2017-11-23 | 2018-05-08 | 南京大学 | A kind of rotation disturbance measuring system based on vortex beams and Sa Ge clarke interferometers |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105022606A (en) * | 2015-06-30 | 2015-11-04 | 中国科学技术大学先进技术研究院 | Ultra-high-speed quantum random number generator and generation method based on laser phase fluctuation |
| CN108007572A (en) * | 2017-11-23 | 2018-05-08 | 南京大学 | A kind of rotation disturbance measuring system based on vortex beams and Sa Ge clarke interferometers |
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Application publication date: 20200417 |