JP6872884B2 - Laser frequency measuring device using optical frequency comb - Google Patents

Description

The present invention relates to a laser frequency measuring device using an optical frequency comb, and in particular, an optical frequency comb capable of measuring a laser frequency with higher accuracy (small uncertainty) according to an averaging time (measurement time). Regarding a laser frequency measuring device using.

Frequency measurement measures how many times a wave vibrates within a certain measurement time, and is expressed as the number of vibrations per second. In general, the magnitude of the measurement time (averaging time) is linked to the magnitude of the averaging effect, so that the frequency stability changes depending on the measurement time, and the measurement uncertainty also changes accordingly. Therefore, in the frequency measurement of the laser, it is required to set and price the averaging time according to the purpose.

Recent inventions of optical frequency comb devices (referred to as optical frequency combs or optical combs) have made it possible to measure laser frequencies with high accuracy using a reference frequency oscillator that is traceable to national standards of frequency (referred to as optical frequency combs or optical combs). See Patent Documents 1 and 2). An optical frequency comb is a device that outputs a laser with a comb-shaped spectrum with a vertical mode interval, that is, a repetition frequency of f _{rep , and has the property that f rep} is exactly equal in any wavelength band (Non-Patent Document). 1).

FIG. 1 shows a schematic diagram of the frequency spectra of an optical frequency comb and a laser to be measured (referred to as a laser to be measured).

_{The oscillation frequency ν n} of the nth comb mode in the optical comb can be expressed by the following equation.
ν _n = n · f _rep + f _CEO … (1)

Here, f _CEO is a fractional carrier envelope offset frequency (referred to as CEO frequency), n is a mode order, and indicates which mode the first mode is when the zeroth mode is set.

By measuring the beat frequency f _{B generated by interfering the oscillation frequency ν n of the optical comb with f rep} and f _CEO stabilized on the reference frequency oscillator and the laser to be measured (frequency ν _DUT ), the laser to be measured Absolute frequency ν _DUT can be obtained.
ν _DUT = ν _n + f _B … (2)

Therefore, by synchronizing the reference frequency oscillator with the national standard of frequency and measuring the frequency of the laser, it is possible to measure traceably to the national standard.

JP-A-2007-256365 Japanese Unexamined Patent Publication No. 2016-17892

H.Inaba, Y.Nakajima, FLHong, K.Minoshima, J.Ishikawa, A.Onae, H.Matsumoto, M.Wouters, B.Warrington, and N.Brown, "Frequency Mesurement Capability of a Fiber-Based Frequency" Comb at 633nm, "IEEE Transactions on Instrumentation and Measurement, vol.58, pp.1234-1240, April 2009.

Here, the iodine-stabilized He-Ne laser, which has been used for a long time as a standard for measuring the frequency of the laser, will be described by raising its characteristics and different from the optical frequency comb.

The iodine-stabilized He-Ne laser is a laser stabilized to the molecular absorption line recommended by the International Committee for Weights and Measures CIPM with an uncertainty of 2.1 × 10 ^-11. In addition to the uncertainty of the frequency of the molecular absorption line, the absolute frequency is due to the frequency offset due to the electrical adjustment error when stabilizing the absorption line, the long-term drift, and the frequency fluctuation due to the oscillation reproducibility. It is an uncertain laser at the 11th platform. However, the frequency stability for a relatively short time centered on the offset amount is extremely high, and for example, the averaging time is 1 second, which is 12th power, and 1000 seconds, which is the first half of 13th power.

On the other hand, in the case of an optical frequency comb, the oscillation frequency is stabilized by performing phase synchronization on the microwave reference frequency oscillator. In addition, the reference frequency oscillator can be stabilized by synchronizing with the national standard of frequency by using the measurement of the time interval of the GPS signal and the comparison system of the measurement result by the Internet. As a result, the uncertainty reaches ^{1.1 × 10 -13} when evaluated with an averaging time of 1 day (8640 seconds). However, due to the synchronization mechanism, the stability for a relatively short time is not very good. For example, since the average for 1000 seconds is 12th power, it is an order of magnitude inferior to the iodine-stabilized He-Ne laser. In addition, the stability of the reference frequency oscillator itself is 11th power on average per second in the case of rubidium Rb, which can be obtained at a relatively reasonable price by the user, which is worse than that of the iodine-stabilized He-Ne laser. .. In general, the uncertainty of the measured value is expressed by the bias (offset amount with respect to the true value) and the variation of the measured value. Therefore, if the stability is poor, the uncertainty increases accordingly.

In other words, the optical frequency comb is said to be a high-precision measuring device that is traceable to the national standard of frequency and has low uncertainty, but in reality, the reference frequency oscillator that can be used by general users is limited, so depending on the averaging time. Has a problem of poor stability and increased measurement uncertainty.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to make it possible to measure a laser frequency with higher accuracy (small uncertainty) according to an averaging time (measurement time). To do.

In general, frequency-stabilized lasers are highly stable over short averaging times. On the other hand, the optical frequency comb has the property that the absolute value is accurate, and if the frequency is measured with a long averaging time, the variation becomes small and the value converges to an accurate value. The present invention provides an apparatus capable of measuring a laser frequency with higher accuracy (small uncertainty) at various averaging times required according to an object by combining the advantages of both.

That is, the present invention comprises an optical frequency comb, a frequency stabilizing laser, and a first frequency counter that measures a first beat frequency generated when the optical frequency comb and the frequency stabilizing laser interfere with each other. , The frequency of the measurement target laser is calculated based on the second frequency counter for measuring the second beat frequency generated between the frequency stabilization laser and the measurement target laser and the first and second beat frequencies. By measuring the frequency of the measurement target laser using the second beat frequency or the first and second beat frequencies according to the averaging time at the time of frequency measurement. , The problem is solved.

Here, with respect to the averaging time at the time of frequency measurement, the frequency of the measurement target laser can be measured using only the second beat frequency in the region of the predetermined averaging time.

Further, the region of the predetermined averaging time can be an averaging time region in which the stability of the frequency-stabilized laser is higher than the stability of the optical frequency comb.

Further, the region of the predetermined averaging time can be an averaging time region in which the uncertainty of measurement by the frequency-stabilized laser is smaller than the uncertainty of the optical frequency comb.

Further, the region of the predetermined averaging time is a region in which the variation of the second beat frequency is smaller than the variation of the values obtained by adding or subtracting the first beat frequency and the second beat frequency. Can be done.

Further, in the region of the predetermined averaging time, the uncertainty in consideration of the variation of the second beat frequency and the deviation of the oscillation frequency of the frequency stabilization laser is the uncertainty of the first beat frequency and the second beat. The region can be set to be smaller than the uncertainty considering the variation of the value obtained by adding or subtracting the frequency and the deviation of the oscillation frequency of the optical frequency comb.

The present invention also comprises an optical frequency comb, a frequency stabilizing laser, and a first frequency counter that measures a first beat frequency generated when the optical frequency comb and the frequency stabilizing laser interfere with each other. , A second frequency counter that measures the second beat frequency generated between the frequency-stabilized laser and the measurement target laser, and a second frequency counter that is generated when the optical frequency comb and the measurement target laser interfere with each other. A third frequency counter for measuring the beat frequency of 3 is provided, and the first beat frequency generated when the optical frequency comb and the frequency stabilizing laser interfere with each other, the frequency stabilizing laser, and the measurement target. By measuring the third beat frequency generated when the optical frequency comb and the measurement target laser interfere with each other in addition to the second beat frequency generated between the lasers, the frequency fluctuation can be changed. it is obtained to be able to determine the difference.

In the frequency evaluation of a laser, frequency measurement at various averaging times is required depending on the purpose, but according to the present invention, higher accuracy (small uncertainty) is required for each averaging time (measurement time). It is possible to measure the frequency with.

The figure which shows typically the frequency spectrum of an optical frequency comb and a laser to be measured. The figure which shows the structure of 1st Embodiment of the laser frequency measuring apparatus which concerns on this invention. Schematic diagram of stability of optical frequency comb and frequency stabilization laser The figure which shows the example of the stability evaluation method Diagram outlining measurement uncertainty Explanatory diagram of the magnitude relationship between the reference frequency and the uncertainty of the frequency-stabilized laser Schematic diagram of uncertainty of optical frequency comb and frequency stabilization laser The figure which shows the example of the method of measuring the deviation of the oscillation frequency of a frequency-stabilized laser. Diagram showing an example of frequency fluctuation assumed in simulation The figure which shows the example of the simulation result in the case of FIG. Diagram showing other examples of frequency fluctuations assumed in the simulation The figure which shows the example of the simulation result in the case of FIG. Diagram showing yet another example of frequency fluctuation assumed in the simulation The figure which shows the example of the simulation result in the case of FIG. The figure which shows the structure of the 2nd Embodiment of the laser frequency measuring apparatus which concerns on this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments and examples. Further, the constituent requirements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, that is, those in a so-called equal range. Further, the components disclosed in the embodiments and examples described below may be appropriately combined or appropriately selected and used.

FIG. 2 shows a schematic diagram of a first embodiment of the laser frequency measuring device according to the present invention. The basic configuration is an optical frequency com 20 that emits output light of _{frequency ν Comb,} a frequency stabilizing laser 30 that emits output light of _{frequency ν Laser , an output light ν Comb} of optical frequency com 20, and an output of a frequency stabilizing laser 30. The first frequency counter 41 that measures the first beat frequency f _LC generated when the light ν _{Laser interferes, the output light ν Laser} of the frequency stabilization laser 30, and the output light ν _{DUT of the measurement target laser 10. The frequency ν DUT of the} laser 10 to be measured is calculated based on the measurement by the second frequency counter 42 for measuring the second beat frequency f _DL generated between the two and the frequency counters 41 and 42 of the beat frequency measuring unit 40. It is composed of a computer (PC) 51 of a calculation unit 50.

In the figure, 11 is a reflection mirror that reflects the output light of the laser 10 to be measured, 31 is a beam splitter (for example, a half mirror) that reflects the output light of the frequency stabilization laser 30, and 21 is a beam splitter 31. A beam splitter (for example, a half mirror) that combines the light reflected by the light frequency com 20 with the output light of the optical frequency com 20, 32 is a beam splitter (for example, a beam splitter) that combines the light reflected by the reflection mirror 11 with the output light of the frequency stabilization laser 30. (For example, half mirror), 24 is a first photodetector that detects the intensity of the light synthesized by the beam splitter 21, and 34 is a second photodetector that detects the intensity of the light synthesized by the beam splitter 32.

In the present invention, when the averaging time T _Gate in the frequency measurement is in the predetermined time region T _Range , the measurement target is measured using the measurement results _{of the second beat frequency f DL} of the measurement target laser 10 and the frequency stabilization laser 30. Calculate the frequency ν _{DUT of the laser 10. As a result, the laser frequency ν DUT} can be measured with an accuracy higher than that of the optical frequency comb 20 even in the averaging time region where the stability of the optical frequency comb 20 is low. On the other hand, when the averaging time T _Gate is other than the predetermined time domain T _Range , the second beat frequency f _DL and the first beat frequency f _LC are measured at the same time, and the sum or difference between the measured values is taken. As a result, the frequency fluctuation of the frequency stabilization laser 30 is canceled out, and the frequency ν _DUT of the measurement target laser 10 with respect to the optical frequency comb 20 can be measured.

Here, an example of how to determine the predetermined time domain T _{Range is shown in FIG. The stability σ Comb} of the optical frequency comb 20 and the stability σ _Laser of the frequency stabilization laser 30 are measured in advance, and the _{region where the stability σ Laser} of the frequency stabilization laser 30 is high (small value) is defined as T _Range. ..

As _{a method for measuring σ Comb} and σ _Laser , respectively, relative stability measurement using two same devices is generally used, and the method will be briefly described with reference to FIG. _{Let the frequencies ν 1} and ν ₂ and their fluctuations of the two evaluation objects prepared for relative comparison be _{δf 1} and δf ₂ . The frequency signals of the two evaluation objects are input to the comparison device 60 and the deviation is measured. A common method in the comparison device 60 is to measure the beat frequency generated by interfering two lasers in an optical frequency region such as a laser. On the other hand, in the case of a microwave frequency domain such as a reference frequency oscillator, it is often a mechanism for electrically comparing the phase difference of each electric signal of two reference frequencies. The relationship between the frequency difference Δf of the two evaluation objects and the frequencies ν ₁ and ν ₂ is shown as follows.
Δf = ν ₁ − ν ₂ … (3)

Considering that there is no correlation between the fluctuations of the two evaluation objects because they are independent devices, the squared average of the fluctuations δf of Δf is the sum of the _{squared averages of δf 1} and δf _2.

Assuming that the two evaluation objects are similarly manufactured devices of the same quality, it is safe to assume that the following equation is obtained.

Therefore, since the equation (4) can be transformed into the equation (5), the frequency fluctuation (stability) of the object can be evaluated from the measurement result obtained by the comparison device 60.

Next, another method for determining the predetermined time domain T _{Range is shown.} Measurement uncertainty is determined by stability (variation) and bias (offset to true value). FIG. 5 shows the situation in the form of a probability density distribution in which the horizontal axis represents frequency and the vertical axis represents frequency. The stability is a numerical value of the range of variation from the representative values such as the center value and the average value. On the other hand, the bias indicates how much the representative value deviates from the true value. Uncertainty indicates how far the measured value may deviate from the true value, so it is estimated by combining factors such as stability (variation) and bias. Here, the relationship between the _{reference frequency and the uncertainty with respect to the averaging time T Gate} of the frequency stabilization laser 30 will be described by taking the case where the uncertainty is expressed by the simple addition of stability and bias as an example.

When the averaging time T _Gate is short, the stability of the reference frequency is low (large variation) as illustrated in FIG. 6A, so that the stability is high (variation is large) even if the oscillation frequency is biased. The uncertainty of the frequency-stabilized laser 30 (smaller) The uncertainty of the U _Laser is smaller than the uncertainty of the reference frequency, that is, the uncertainty of the optical frequency com 20 U _Comb. On the other hand, as the averaging time T _{Gate becomes longer, the uncertainty U Comb} becomes smaller than the biased uncertainty U _Laser because the stability of the reference frequency becomes higher as illustrated in FIG. 6 (b). Become.

Therefore, the uncertainty is calculated in consideration of not only the frequency stability of the frequency stabilization laser 30 but also the bias. Then, as shown in FIG. 7, the frequency-stabilized laser 30 is used with the averaging time region in which the uncertainty of the frequency-stabilized laser 30 becomes smaller than the uncertainty of the reference frequency oscillator, that is, the optical frequency comb 20, _{as the T Range.} The frequency of the laser 10 to be measured is measured.

The optical frequency comb 20 may be used as a method for measuring the deviation of the oscillation frequency in order to calculate the uncertainty of the frequency stabilization laser 30. _{By substituting the measurement result of the beat frequency f LC} with the optical frequency comb 20 obtained by the measurement system shown in FIG. 8 into _{f B} of the equation (2), _{the absolute frequency ν Laser} of the frequency stabilization laser 30 is set as _{ν DUT.} Can be measured. As a result, the deviation of the representative value of the frequency can be reduced to the uncertainty of the optical frequency comb 20. Since the uncertainty of measurement by the optical frequency comb 20 depends on the averaging time, _{when calibrating the absolute frequency ν Laser} of the frequency stabilization laser 30 (measuring the bias), it takes a sufficiently long time to calibrate. .. By doing so, it becomes more effective because it can be used as a laser with less uncertainty with less frequency bias. At that time, as shown in FIG. 8, the optical frequency comb 20 is measured even if the one in the laser frequency measuring device proposed in the present invention is used, or even if a separate optical frequency comb is prepared for calibration. It is clear that there is no difference in the effect even though there is a difference in the effort.

In the first embodiment, the frequencies of the optical frequency comb 20 and the frequency stabilization laser 30 are measured in advance, and the one having higher stability or less uncertainty is selected and measured according to the averaging time. It was that.

On the other hand, as in the modified example described below, which one may be used may be selected by using the beat frequency measurement results obtained from the first and second frequency counters 41 and 42. _{The formulas for calculating the frequency ν DUT} of the laser 10 to be measured when the frequency-stabilized laser 30 is used and when the optical frequency comb 20 is used are shown in equations (7) and (8), respectively.
ν _DUT = ν _Laser + f _DL … (7)
ν _DUT = ν _Comb + f _LC + f _DL … (8)

In the calculation formula of the formula (7), the frequency of the measurement target laser 10 is measured with the frequency stabilization laser 30 as a reference by using only _{the second beat frequency f DL obtained from the second frequency counter 42.} On the other hand, in the calculation formula of the formula (8), the sum of _{the second beat frequency f DL obtained by the second frequency counter 42 and the first beat frequency f LC} obtained by the first frequency counter 41 ( Calculate the difference) depending on the sign. Since the frequency of the frequency-stabilized laser 30 is computationally canceled by taking the sum (or difference) of both the measured values of _{f LC} and f _{DL, the difference frequency of the laser 10 to be measured with respect to the optical frequency comb 20 is measured.} Will be there. Therefore, by adding the absolute frequencies of the optical frequency combs 20, frequency measurement based on the optical frequency combs 20 is performed.

The following is an example in which the frequency fluctuations of the laser 10 to be measured, the optical frequency comb 20, and the frequency stabilization laser 30 are set, and f _LC + f _DL and f _DL are estimated by simulation from the measured values obtained at that time. ..

FIG. 9 shows the state of frequency fluctuation with respect to the horizontal axis time, and (a), (b), and (c) represent the measurement target laser 10, the optical frequency comb 20, and the frequency stabilization laser 30 in this order. The vertical axis represents the ratio of the relative fluctuation width with the same width in all of (a), (b), and (c). FIG. 10 shows the result of simulating the beat frequency obtained when such frequency fluctuation is assumed. Since the fluctuation of the frequency of the optical frequency comb 20 is small, the f _LC + f _DL shown in (a) of the figure is data that well reflects the variation of the laser 10 to be measured. On the other hand, in the f _DL of FIG. 10B, the large frequency fluctuation of the frequency-stabilized laser 30 has an effect, and the result is that the data varies more than the fluctuation amount of the measurement target laser 10.

On the other hand, as shown in FIG. 11, when the frequency fluctuation of the optical frequency comb 20 is large, the value of f _LC + f _DL varies more than that _{of f DL.} Therefore, in this case, as shown in FIG. 12, the stability of the measurement target laser 10 can be measured more accurately when _{f DL is selected.}

That is, _{by comparing f LC} + f _DL and f _DL , selecting the one with the smaller variation, and substituting it into the equation (7) or the equation (8), the accuracy is closer to the stability of the laser 10 to be measured. You will be able to measure.

In choosing either the f _DL and f _LC + f _DL is the uncertainty of the frequency stabilized laser 30 and the optical frequency comb 20 in consideration of the deviation amount of the oscillation frequency estimate, in view of the magnitude of uncertainty, The frequency of the laser 10 to be measured can be measured with higher accuracy by determining using either the formula (7) or the formula (8). For example, in FIG. 13, an example of frequency fluctuation of the measurement target laser 10, the optical frequency comb 20, and the frequency stabilization laser 30 is represented by an arbitrary value within the same range on the vertical axis. Further, in the figure, zero, which is the center of the vertical axis, is set as an ideal value for each laser, and in the case of the frequency-stabilized laser 30, the center of frequency fluctuation is offset in the positive direction. ). For frequency-stabilized laser 30, since the frequency variation is offset to the center frequency be small, Figure 14 the value of f _DL, as shown in (b) the frequency offset of the frequency stabilized laser 30 than the true value The result is a deviation. In this case, as can be seen by comparing (a) and (b) of FIG. 14, the uncertainty of the measured value of _{f LC} + f _DL is smaller than that of the measured value of _{f DL.} Alone beat frequency measurement, since only know the width of variation in the frequency, to keep tabs bias frequency as shown in FIG. 13, using either f _DL and f _LC + f _DL upon adding the amount Determine if you want to. As a result, it is possible to obtain a frequency measurement result with low uncertainty.

In this method, it is not necessary to measure the stability of each of the optical frequency comb 20 and the frequency stabilization laser 30 in advance, which is convenient.

The laser frequency measuring device according to the present invention can also be realized in the second embodiment shown in FIG.

In this second embodiment, the beam splitter 32 of the first embodiment is omitted, and the output light of the laser 10 to be measured is input to the beam splitter 31, while the branching device 80 is provided on the output side of the first photodetector 24. The output is _divided by the f LC filter 81 and the f _DC filter 82, and the beat frequency measuring unit 40 is provided with a third frequency counter 43 for counting the output _{of the f DC filter 82.} This second embodiment can be used when the laser 10 to be measured has sufficient power to obtain an interference beat signal with sufficient S / N.

In this second embodiment, the output light of the laser 10 to be measured is branched into two, and the beat frequency f _{DC with the output light of the optical frequency comb 20 and the beat frequency f DL} with the output light of the frequency stabilization laser 30. To measure.

In this second embodiment, the beat signal obtained from the first photodetector 24 includes the beat frequency f _{LC by the optical frequency comb 20 and the frequency stabilization laser 30, and the beat frequency f DC} by the optical frequency comb 20 and the measurement target laser 10. Both are included. Therefore, the signal is divided into two by the branch device 80, and the filters 81 and 82 are inserted in the respective signal lines _{to take out f LC} and f _DC , and the respective frequencies are measured by the frequency counters 41 and 43.

In this second embodiment, since the beat frequency of the laser 10 to be measured is directly measured by each of the optical frequency comb 20 and the frequency stabilization laser 30, the difference in frequency fluctuation can be easily determined. Can be used to more easily determine whether to measure the frequency of the laser 10 to be measured.

In the second embodiment, the signal obtained from the first photodetector 24 is branched into two by the branching device 80, and the filters 81 and 82 and the frequency counters 41 and 43 are arranged and measured in each of the two. As shown, the same effect can be obtained by using the method of switching the filters 81 and 82 and measuring the beat frequency with one frequency counter (41 or 43) without using the branching device 80.

10 ... Laser to be measured 20 ... Optical frequency com 24, 34 ... Photodetector 30 ... Frequency stabilization laser 40 ... Beat frequency measurement unit 41, 42, 43 ... Frequency counter 50 ... Calculation unit 51 ... Computer (PC)
60 ... Comparison device 80 ... Branch device 81, 82 ... Filter f _LC , f _DL , f _DC ... Beat frequency

Claims (7)

Optical frequency comb and
Frequency-stabilized laser and
A first frequency counter that measures the first beat frequency generated when the optical frequency comb and the frequency stabilizing laser interfere with each other.
A second frequency counter that measures the second beat frequency generated between the frequency-stabilized laser and the laser to be measured, and
It is provided with a calculation unit that calculates the frequency of the laser to be measured based on the first and second beat frequencies.
An optical frequency comb characterized in that the frequency of the laser to be measured is measured by using the second beat frequency or the first and second beat frequencies according to the averaging time at the time of frequency measurement. Laser frequency measuring device used. Regarding the averaging time during frequency measurement
The laser frequency measurement using the optical frequency comb according to claim 1, wherein in the region of a predetermined averaging time, the frequency of the measurement target laser is measured using only the second beat frequency. apparatus. The area of the predetermined averaging time is
The laser frequency measuring apparatus using an optical frequency comb according to claim 2, wherein the stability of the frequency-stabilized laser is in an averaging time region higher than the stability of the optical frequency comb. The area of the predetermined averaging time is
The laser frequency measuring apparatus using an optical frequency comb according to claim 2, wherein the uncertainty of measurement by the frequency-stabilized laser is an averaging time region smaller than the uncertainty of the optical frequency comb. The area of the predetermined averaging time is
The optical frequency according to claim 2, wherein the variation of the second beat frequency is a region smaller than the variation of the value obtained by adding or subtracting the first beat frequency and the second beat frequency. Laser frequency measuring device using a comb. The area of the predetermined averaging time is
The uncertainty in consideration of the variation of the second beat frequency and the bias of the oscillation frequency of the frequency stabilization laser is the variation of the value obtained by adding or subtracting the first beat frequency and the second beat frequency and the light. The laser frequency measuring device using an optical frequency comb according to claim 2, wherein the region is smaller than the uncertainty in consideration of the bias of the oscillation frequency of the frequency comb. Optical frequency comb and
Frequency-stabilized laser and
A first frequency counter that measures the first beat frequency generated when the optical frequency comb and the frequency stabilizing laser interfere with each other.
A second frequency counter that measures the second beat frequency generated between the frequency-stabilized laser and the laser to be measured, and
It is provided with a third frequency counter that measures a third beat frequency generated when the optical frequency comb and the laser to be measured interfere with each other.
In addition to the first beat frequency generated when the optical frequency comb interferes with the frequency stabilizing laser and the second beat frequency generated between the frequency stabilizing laser and the measurement target laser. , by measuring the third beat frequency generated when causing interference and the optical frequency comb and the measurement target laser, light you characterized in that it is to be determined the difference in frequency variation Laser frequency measuring device using frequency comb.

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