Optical comb light source and measuring device

Abstract

The optical frequency of one mode of an optical comb can be changed by more than half the repetition frequency of the optical comb. [Solution] The optical comb light source 1 outputs an optical comb having multiple modes. The optical comb light source 1 includes an optical comb generation unit 11 that generates an optical comb, an optical frequency change unit 14 that receives a reference wavelength light having a predetermined optical frequency νcw and changes the optical frequency νcw of the reference wavelength light to output, a mode optical frequency νm which is the optical frequency of one of the multiple modes, and a target optical frequency νcw+f which is the optical frequency of the output of the optical frequency change unit 14. AO The difference between this and the predetermined value (beat frequency) f beat The optical comb generation unit 11 includes a mode optical frequency control unit 18 that controls the mode optical frequency to achieve the desired result. The optical comb generation unit 11 changes the optical frequencies of multiple modes according to the controlled mode optical frequency νm to produce the output of the optical comb light source 1.

Description

[Technical Field]

[0001] This invention relates to the control of the optical frequency of an optical comb. [Background technology]

[0002] In a conventionally known optical comb light source, the frequency of the optical comb is stabilized by adjusting the frequency of the carrier envelope offset signal to a predetermined value and adjusting the frequency of the beat signal between the output of a reference wavelength light source and one mode of the optical comb to a predetermined value. However, the optical frequency of the output of the reference wavelength light source is controlled with high precision to match the frequency of the absorption lines of the gas, etc. Furthermore, by phase-synchronizing the carrier envelope offset signal with one RF reference signal and phase-synchronizing the beat signal with another RF reference signal, the frequency of the beat signal can be matched to the frequency of the other RF reference signal. In addition, the frequency of the beat signal f beat This is the difference between the optical frequency νcw of the output of the reference wavelength light source and the optical frequency νm of one mode in the optical comb.

[0003] In addition, in other conventional optical comb light sources, the frequency of the optical comb is stabilized by matching the repetition frequency of the optical comb to the output frequency of the RF synthesizer (see, for example, Patent Document 1 and Non-Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-77979 [Non-patent literature]

[0005] [Non-Patent Document 1] Sho Okubo, et al., "Near-infrared broadband dual-frequency-comb spectroscopy with a resolution beyond the Fourier limit determined by the observation time window", Optics Express, December 2015, Vol.23, No.26, p.33184-33193

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, in a certain optical frequency comb light source in the above prior art, there may be a case where it is desired to change the optical frequency νm of one mode of the optical frequency comb. In this case, if the frequency f beat of the beat signal is changed, the optical frequency νm can be changed.

[0007] However, f beat must be less than f rep / 2 (where f rep is the repetition frequency of the optical frequency comb). When f beat becomes f rep / 2 or more, f rep -f beat becomes f beat or less, so the component of f rep -f beat cannot be ignored. Therefore, there is a limitation in the range in which the optical frequency νm can be changed.

[0008] Therefore, an object of the present invention is to enable the optical frequency of a certain mode of the optical frequency comb to be changed beyond half of the repetition frequency of the optical frequency comb.

Means for Solving the Problems

[0009] The optical comb light source according to the present invention is an optical comb light source that outputs an optical comb having multiple modes, comprising: an optical comb generation unit that generates the optical comb; an optical frequency change unit that receives a reference wavelength light having a predetermined optical frequency and changes the optical frequency of the reference wavelength light to output it; and a mode optical frequency control unit that controls the mode optical frequency so that the difference between a mode optical frequency, which is the optical frequency of one of the multiple modes, and a target optical frequency, which is the optical frequency of the output of the optical frequency change unit, is a predetermined value, wherein the optical comb generation unit is configured to change the optical frequencies of the multiple modes according to the controlled mode optical frequency to obtain the output of the optical comb light source.

[0010] According to the optical comb light source configured as described above, an optical comb having multiple modes is output. An optical comb generation unit generates the optical comb. An optical frequency change unit receives a reference wavelength light having a predetermined optical frequency and changes the optical frequency of the reference wavelength light to output it. A mode optical frequency control unit controls the mode optical frequency, which is the optical frequency of one of the multiple modes, and the target optical frequency, which is the optical frequency of the output of the optical frequency change unit, so that the difference between the mode optical frequency and the target optical frequency is a predetermined value. The optical comb generation unit changes the optical frequencies of the multiple modes according to the controlled mode optical frequency to produce the output of the optical comb light source.

[0011] Furthermore, in the optical comb light source according to the present invention, the optical frequency changing unit may be an acousto-optic modulator.

[0012] Furthermore, in the optical comb light source according to the present invention, the predetermined value may be set to be less than half of the repetition frequency of the optical comb.

[0013] Furthermore, the optical comb light source according to the present invention may be configured so that the amount of change in the optical frequency of the reference wavelength light by the optical frequency changing unit can be changed.

[0014] Furthermore, the optical comb light source according to the present invention may be configured such that the difference between the maximum and minimum values ​​of the change amount is 1 / 2 or more of the repetition frequency of the optical comb.

[0015] Furthermore, the optical comb light source according to the present invention may be configured such that the difference between the maximum and minimum values ​​of the change amount is equal to or greater than the repetition frequency of the optical comb.

[0016] Furthermore, in the optical comb light source according to the present invention, the optical frequency of the reference wavelength light may be determined based on the optical frequency of the absorption line of a predetermined gas.

[0017] Furthermore, in the optical comb light source according to the present invention, the optical comb generation unit may change the optical frequency of a mode adjacent to one of the modes by the amount by which the amount of change is changed.

[0018] Furthermore, in the optical comb light source according to the present invention, if one of the modes is the m-th mode (where m is an integer of 1 or more), and the carrier envelope offset frequency is the remainder when the mode optical frequency is divided by the repetition frequency of the optical comb, the optical comb generation unit may change the repetition frequency to a value obtained by dividing the result of subtracting the carrier envelope offset frequency from the controlled mode optical frequency by m.

[0019] The measuring device according to the present invention comprises two optical comb light sources according to the present invention, an interference signal acquisition unit that acquires an interference signal between a post-irradiated optical comb obtained by irradiating an object to be measured with the output of one of the optical comb light sources and the output of the other optical comb light source, and a frequency spectrum measurement unit that measures the frequency spectrum of the result acquired by the interference signal acquisition unit.

[0020] The measuring device configured as described above includes two optical comb light sources configured as described above. The interference signal acquisition unit acquires the interference signal between the post-irradiation optical comb obtained by irradiating the object to be measured with the output of one of the optical comb light sources and the output of the other optical comb light source. The frequency spectrum measurement unit measures the frequency spectrum of the result acquired by the interference signal acquisition unit. [Brief explanation of the drawing]

[0021] [Figure 1] This is a functional block diagram showing the configuration of the optical comb light source 1 according to the first embodiment of the present invention. [Figure 2] This is the frequency spectrum of an optical comb. [Figure 3] Figure 3(d) shows the frequency spectra of the output of the optical frequency changing unit 14 and the output of the optical comb generation unit 11, with fAO being fAO1 (=60MHz) (Figure 3(a)), fAO being fAO2 (=90MHz) (Figure 3(b)), fAO being fAO3 (=100MHz) (Figure 3(c)), and fAO being fAO4 (=110MHz). [Figure 4] This is a functional block diagram showing the configuration of the measuring device 100 according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0022] Embodiments of the present invention will be described below with reference to the drawings.

[0023] First Embodiment Figure 1 is a functional block diagram showing the configuration of an optical comb light source 1 according to a first embodiment of the present invention. The optical comb light source 1 according to the first embodiment comprises an optical comb generation unit 11, a reference wavelength light source 12, an optical frequency changing unit 14, a controlled mode acquisition unit 16, and a mode optical frequency control unit 18.

[0024] Figure 2 shows the frequency spectrum of the optical comb. The optical comb generation unit 11 generates the optical comb. The vertical axis in Figure 2 represents the optical power. Referring to Figure 2, the optical comb has multiple modes, for example, m-2, m-1, m, m+1, m+2 (th) modes. The frequency νm = f of the frequency spectrum of the mth optical comb. ceo +m·f rep (repetition frequency f) rep ) However, f ceo This is the carrier envelope offset frequency, which is the remainder frequency when the optical comb frequency is extrapolated to the 0th element. The optical comb light source 1 outputs an optical comb having multiple modes, which is generated by the optical comb generation unit 11.

[0025] Furthermore, the carrier envelope offset frequency is stabilized. For example, the carrier envelope offset frequency is stabilized by phase-locking the carrier envelope offset frequency signal with a predetermined RF reference signal.

[0026] The controlled mode acquisition unit 16 acquires one mode (for example, the m-th mode, with an optical frequency of νm) from among the multiple modes of the optical comb generated by the optical comb generation unit 11 (where m is an integer of 1 or greater). The optical frequency of this one mode is called the mode optical frequency νm. Note that the carrier envelope offset frequency f ceo This is where the mode optical frequency νm is the repetition frequency f of the optical comb. rep It can also be said that it is the frequency of the remainder when divided by .

[0027] The reference wavelength light source 12 is a light source that outputs reference wavelength light (optical frequency νcw). The optical frequency νcw of the reference wavelength light is determined based on the optical frequency of the absorption line of a predetermined gas and is controlled with high precision.

[0028] The optical frequency changing unit 14 receives reference wavelength light having a predetermined optical frequency νcw from the reference wavelength light source 12, and converts the optical frequency νcw of the reference wavelength light into an optical frequency change amount f AO Only this value is changed and output. The optical frequency of this output (called the target optical frequency) is νcw+f AO That is the case.

[0029] The optical frequency conversion unit 14 is, for example, an acousto-optical modulator (AOM). In this case, the output of the optical frequency conversion unit 14 contains almost no component of the reference wavelength light (optical frequency νcw). Moreover, the reference wavelength light is hardly attenuated and becomes the output of the optical frequency conversion unit 14. Therefore, it is preferable that the optical frequency conversion unit 14 is an acousto-optical modulator.

[0030] However, the optical frequency changing unit 14 does not have to be an acousto-optic modulator; it may be a device that performs phase modulation. However, in this case, the output of the optical frequency changing unit 14 will contain a considerable amount of the reference wavelength light (optical frequency νcw) and sideband components. Therefore, it is conceivable to suppress these components using a filter or the like.

[0031] The mode optical frequency control unit 18 controls the mode optical frequency νm and the target optical frequency νcw+f AO The difference between this and the predetermined value (beat frequency) f beat The mode light frequency νm is controlled to achieve this.

[0032] The optical comb generation unit 11 changes the optical frequencies of multiple modes according to the controlled mode optical frequency νm to produce the output of the optical comb light source 1.

[0033] Figure 3 shows the frequency spectra of the output of the optical frequency changing unit 14 and the output of the optical comb generation unit 11, f AO ga f AO1 (=60MHz) (Figure 3(a)), f AO ga f AO2 (=90MHz) (Figure 3(b)), f AO ga f AO3 (=100MHz) (Figure 3(c)), f AO ga f AO4 The case where the frequency is (=110MHz) is shown (Figure 3(d)). In Figure 3, the frequency spectrum of the output of the optical frequency changing unit 14 is shown by vertical arrows, and the frequency spectrum of the output of the optical comb generation unit 11 is shown by equally spaced straight lines.

[0034] predetermined value f beat The repetition frequency f of the optical comb rep It is less than half of a given value f. beat = 10MHz, and the repetition frequency of the optical comb f rep1 ,f rep2 ,f rep3 and f rep4 Since it is approximately 40MHz, the predetermined value f beat This is less than half the repetition frequency of the optical comb.

[0035] however, Repetition frequency f of the optical comb rep1 is, f AO ga f AO1 This is the repetition frequency of the optical comb when it is (=60MHz) (see Figure 3(a)), Repetition frequency f of the optical comb rep2 is, f AO ga f AO2 This is the repetition frequency of the optical comb when it is (=90MHz) (see Figure 3(b)), Repetition frequency f of the optical comb rep3 is, f AO ga f AO3 This is the repetition frequency of the optical comb when it is (=100MHz) (see Figure 3(c)), Repetition frequency f of the optical comb rep4 is, f AO ga f AO4 This is the repetition frequency of the optical comb when it is (=110MHz) (see Figure 3(d)).

[0036] Note that the change in the optical frequency νcw of the reference wavelength light by the optical frequency changing unit 14 is f AO This can be changed.

[0037] Change f AO The difference between the maximum and minimum values ​​is the repetition frequency f of the optical comb. rep It may be more than half of the value. For example, change amount f AO The minimum value of f AO1 (=60MHz) (see Figure 3(a)), and the change in amount f AO The maximum value is f AO2 In cases like (=90MHz) (see Figure 3(b)), 90-60=30MHz is f rep It is more than half of that (approximately 20 MHz).

[0038] Change f AO The difference between the maximum and minimum values ​​is the repetition frequency f of the optical comb. rep That's fine too.

[0039] For example, the change in quantity fAO The minimum value of f AO1 (=60MHz) (see Figure 3(a)), and the change in amount f AO The maximum value is f AO3 In the case where (=100MHz) (see Figure 3(c)), 100-60=40MHz is f rep It is above (approximately 40MHz).

[0040] For example, the change in quantity f AO The minimum value of f AO1 (=60MHz) (see Figure 3(a)), and the change in amount f AO The maximum value is f AO4 In cases like (=110MHz) (see Figure 3(d)), 110-60=50MHz is f rep It is above (approximately 40MHz).

[0041] The optical comb generation unit 11 generates a carrier envelope offset frequency f from the mode optical frequency νm controlled by the mode optical frequency control unit 18. ceo The result obtained by subtracting from the repetition frequency f is divided by m. rep Change it.

[0042] For example, νcw = 194.36985 THz, predetermined value f beat =10MHz, carrier envelope offset frequency f ceo Let's assume =30MHz and m=4,859,247.

[0043] f AO ga f AO1 If (=60MHz) (see Figure 3(a)), the repetition frequency f of the optical comb rep1 The frequency is 39,999,997.94 Hz (approximately 40 MHz), and the mode optical frequency νm is 194.36990 THz.

[0044] Here, the optical frequency changing unit 14 controls the amount of change f of the optical frequency νcw of the reference wavelength light. AO f AO1 (=60MHz) to f AO2 Let's assume it's changed to (=90MHz) (see Figure 3(b)).

[0045] The mode optical frequency control unit 18 controls the mode optical frequency νm such that the difference between the mode optical frequency νm and the target optical frequency νcw + f AO becomes a predetermined value f beat . In the above case, since the change amount f AO has increased by 90 - 60 = 30 MHz, the mode optical frequency control unit 18 controls the mode optical frequency νm to also increase by 30 MHz. Then, the mode optical frequency νm becomes 194.36993 THz.

[0046] Here, the optical comb generation unit 11 changes the repetition frequency f ceo to the value obtained by dividing the result of subtracting the carrier - envelope offset frequency f rep from the mode optical frequency νm controlled by the mode optical frequency control unit 18 by m. That is, the repetition frequency f rep is changed to f rep2 = 40,000,004.12 Hz (approximately 40 MHz). The repetition frequency f rep2 is 6.18 Hz higher than the repetition frequency f rep1 .

[0047] Note that it can also be considered that the repetition frequency f rep2 and the repetition frequency f rep1 are also approximately equal (approximately 40 MHz). Therefore, it can also be considered that while keeping the repetition frequency constant, the optical frequency of the modes in the vicinity of one mode (the m - th mode) is changed by the amount of movement of the optical frequency of one mode (90 - 60 = 30 MHz).

[0048] Note that the amount of movement of the optical frequency of one mode (the m - th mode) can be said to be the changed amount f AO - f AO2 = 30 MHz. Therefore, it can also be considered that the optical comb generation unit 11 changes the optical frequency of the modes in the vicinity of one mode (the m - th mode) by the amount of change f AO1 - f AO = 30 MHz. AO2 - f AO1 = 30 MHz.

[0049] The optical frequency changing unit 14 controls the amount of change f of the optical frequency νcw of the reference wavelength light. AO f AO1 (=60MHz) to f AO3 (=100MHz) (See Figure 3(c)) (or f AO4 The same applies when the frequency is changed to (=110MHz) (see Figure 3(d)).

[0050] That is, similarly to the above, the repetition frequency f rep3 ,f rep4 The optical comb generation unit 11 changes the amount of change f. AO The amount f that was changed AO3 -f AO1 =40MHz (or f AO4 -f AO1 It can also be considered that only 50MHz is changing the optical frequency of the neighboring modes of one mode (the mth mode). In this case, referring to Figure 3(c), one mode (the mth mode) can be changed to the same optical frequency as the (m+1)th mode in Figure 3(a). Furthermore, referring to Figure 3(d), one mode (the mth mode) can be changed to an optical frequency 10MHz higher than the (m+1)th mode in Figure 3(a).

[0051] Next, the operation of the first embodiment will be described.

[0052] From the optical comb generated by the optical comb generation unit 11 (see Figure 2), one mode (the mth mode) is acquired by the controlled mode acquisition unit 16, and a signal with mode optical frequency νm is supplied to the mode optical frequency control unit 18.

[0053] The reference wavelength light (optical frequency νcw) output from the reference wavelength light source 12 is converted by the optical frequency change unit 14 by an optical frequency change amount f AO Only the target optical frequency νcw+f is changed. AO The signal is supplied to the mode optical frequency control unit 18. Optical frequency change amount f AO The frequency can be changed from 60MHz to 90MHz (100MHz or 110MHz).

[0054] The mode optical frequency control unit 18 controls the mode optical frequency νm and the target optical frequency νcw+f AO The difference between this and the predetermined value f beat The mode optical frequency νm is controlled so that it becomes =10MHz. That is, the optical frequency change amount f AO The mode optical frequency νm should be changed by the amount that has been altered.

[0055] For example, the change in the optical frequency νcw of a reference wavelength light f AO f AO1 (=60MHz) (See Figure 3(a)) from f AO2 If you change it to (=90MHz) (see Figure 3(b)), you should increase the mode optical frequency νm by 30MHz.

[0056] The optical comb generation unit 11 changes the optical frequencies of multiple modes according to the controlled mode optical frequency νm to produce the output of the optical comb light source 1. For example, the optical comb generation unit 11 changes the carrier envelope offset frequency f from the mode optical frequency νm controlled by the mode optical frequency control unit 18. ceo The result obtained by subtracting from the repetition frequency f is divided by m. rep Change it.

[0057] For example, as mentioned above, the repetition frequency f rep2 (See Figure 3(b)) with a repetition frequency f rep1 Increase the frequency by 6.18 Hz compared to (see Figure 3(a)).

[0058] Or, if the change in optical frequency f AO Regardless of the change, if we assume that the repetition frequency near the m-th mode is constant at approximately 40 MHz, then the optical frequency of the mode near the m-th mode can be expressed as the optical frequency change f AO You only need to change the amount of change (i.e., the amount of shift in the mode optical frequency νm).

[0059] For example, the change in the optical frequency νcw of a reference wavelength light f AO f AO1(=60MHz) (See Figure 3(a)) from f AO2 When changed to (=90MHz) (see Figure 3(b)), the mode optical frequency νm and the optical frequencies of modes near the m-th mode are increased by 30MHz.

[0060] For example, the change in the optical frequency νcw of a reference wavelength light f AO f AO1 (=60MHz) (See Figure 3(a)) from f AO3 When changed to (=100MHz) (see Figure 3(c)), the mode optical frequency νm and the optical frequencies of modes near the m-th mode are increased by 40MHz.

[0061] For example, the change in the optical frequency νcw of a reference wavelength light f AO f AO1 (=60MHz) (See Figure 3(a)) from f AO4 When changed to (=110MHz) (see Figure 3(d)), the mode optical frequency νm and the optical frequencies of modes near the m-th mode are increased by 50MHz.

[0062] According to the first embodiment, the optical frequency νm of one mode of the optical comb is the repetition frequency f of the optical comb. rep It can be changed by more than half. This allows the frequency of the optical comb to be shifted.

[0063] That is, a predetermined value f beat However, unless it is more than half the repetition frequency of the optical comb, the mode optical frequency νm is the repetition frequency f rep Even if you change it by more than half, the predetermined value f beat However, this remains true because it is less than half the repetition frequency of the optical comb.

[0064] Second Embodiment The measuring device 100 according to the second embodiment includes an optical comb light source 1 according to the first embodiment and an optical comb light source 2 similar thereto, and measures the object to be measured (DUT: Device Under This measures Test 4.

[0065] Figure 4 is a functional block diagram showing the configuration of a measuring device 100 according to a second embodiment of the present invention. The measuring device 100 according to the second embodiment comprises (one) optical comb light source 1, (the other) optical comb light source 2, a band pass filter (BPF) 5, an interference signal acquisition unit 6, and a frequency spectrum measurement unit 8.

[0066] (On the other hand) the optical comb light source 1 has a carrier envelope offset frequency of f ceo1 The mode light frequency is νm1, and the beat frequency is f beat1 Aside from that, it is the same as the first embodiment, and therefore the explanation will be omitted.

[0067] The (other) optical comb light source 2 comprises an optical comb generation unit 21, a reference wavelength light source 12, an optical frequency changing unit 14, a controlled mode acquisition unit 26, and a mode optical frequency control unit 28. The reference wavelength light source 12 and the optical frequency changing unit 14 are also provided in the (one) optical comb light source 1.

[0068] The optical comb generation unit 21, the controlled mode acquisition unit 26, and the mode optical frequency control unit 28 are the same as the optical comb generation unit 11, the controlled mode acquisition unit 16, and the mode optical frequency control unit 18 provided in (one of) the optical comb light sources 1, respectively, and their description is omitted.

[0069] However, in the (other) optical comb light source 2, the carrier envelope offset frequency is f ceo2 The mode light frequency is νm² and the beat frequency is f beat2 Furthermore, the repetition frequency of the optical comb generated by the optical comb generation unit 11 and the repetition frequency of the optical comb generated by the optical comb generation unit 21 are slightly different.

[0070] Furthermore, the optical comb output from the (other) optical comb light source 2 is supplied to the bandpass filter (BPF) 5 without passing through the (first) optical comb light source 1.

[0071] The object under test (DUT) 4 is, for example, a gas in a gas cell. The object under test 4 is irradiated with an optical comb output from (one) optical comb light source 1. The optical comb obtained by irradiating the object under test 4 with the optical comb output from (one) optical comb light source 1 is called the post-irradiation optical comb.

[0072] The bandpass filter (BPF) 5 is illuminated by the optical comb output from the (other) optical comb light source 2. The interference signal acquisition unit 6 acquires the interference signal between the post-irradiation optical comb and the output of the (other) optical comb light source 2 that has passed through the bandpass filter 5. The frequency spectrum measurement unit 8 measures the frequency spectrum of the result acquired by the interference signal acquisition unit 6.

[0073] According to the second embodiment, the optical frequency νm of one mode of the optical comb can be changed by more than half of the repetition frequency of the optical comb. Moreover, in conjunction with the change in the mode optical frequency νm, the frequencies of the optical combs output by the optical comb light sources 1 and 2 in the measuring device 100 can be shifted. [Explanation of Symbols]

[0074] 1 (One) Optical Comb Light Source 2. (The other) optical comb light source 4 Device Under Test (DUT) 5. Bandpass Filter (BPF) 6. Interference signal acquisition unit 8. Frequency spectrum measurement unit 100 measuring devices 11, 21 Optical comb generation section 12 Reference wavelength light source 14 Optical frequency changing section 16, 26 Control target mode acquisition unit 18, 28 Mode Optical Frequency Control Unit f ceo ,f ceo1 ,f ceo2 Carrier envelope offset frequency νcw: Optical frequency of reference wavelength light f AO,f AO1 ,f AO2 ,f AO3 ,f AO4 Change in optical frequency νm, νm1, νm2 mode optical frequencies f rep ,f rep1 ,f rep2 ,f rep3 ,f rep4 Repetition frequency f beat Beat frequency

Claims

1. An optical comb light source that outputs an optical comb having multiple modes, An optical comb generation unit that generates the aforementioned optical comb, An optical frequency changing unit receives a reference wavelength light having a predetermined optical frequency and outputs a change in the optical frequency of the reference wavelength light, A mode optical frequency control unit controls the mode optical frequency so that the difference between the mode optical frequency, which is the optical frequency of one of the plurality of modes, and the target optical frequency, which is the optical frequency of the output of the optical frequency changing unit, is a predetermined value. Equipped with, The optical comb generation unit changes the optical frequencies of the plurality of modes according to the controlled optical frequencies of the modes to obtain the output of the optical comb light source. Optical comb light source.

2. The optical comb light source according to claim 1, An optical comb light source in which the optical frequency changing unit is an acoustic-optic modulator.

3. The optical comb light source according to claim 1, An optical comb light source in which the predetermined value is less than half the repetition frequency of the optical comb.

4. The optical comb light source according to claim 1, An optical comb light source in which the amount of change in the optical frequency of the reference wavelength light by the optical frequency changing unit can be changed.

5. The optical comb light source according to claim 4, An optical comb light source in which the difference between the maximum and minimum values ​​of the amount of change is 1 / 2 or more of the repetition frequency of the optical comb.

6. The optical comb light source according to claim 4, An optical comb light source in which the difference between the maximum and minimum values ​​of the aforementioned change amount is greater than or equal to the repetition frequency of the optical comb.

7. The optical comb light source according to claim 1, An optical comb light source in which the optical frequency of the aforementioned reference wavelength light is determined based on the optical frequency of the absorption line of a predetermined gas.

8. The optical comb light source according to claim 4, The optical comb light source is an optical comb generation unit that changes the optical frequency of a mode adjacent to one of the modes by the amount by which the amount of change has been changed.

9. The optical comb light source according to claim 1, The aforementioned mode is the m-th mode (where m is an integer greater than or equal to 1), When the carrier envelope offset frequency is defined as the remainder obtained by dividing the mode optical frequency by the repetition frequency of the optical comb, The optical comb generation unit changes the repetition frequency to a value obtained by dividing the result of subtracting the carrier envelope offset frequency from the controlled mode optical frequency by m. Optical comb light source.

10. The device comprises two optical comb light sources as described in any one of claims 1 to 9, An interference signal acquisition unit acquires an interference signal between a post-irradiated optical comb obtained by irradiating an object to be measured with the output of one of the optical comb light sources and the output of the other of the optical comb light sources. A frequency spectrum measuring unit that measures the frequency spectrum of the result obtained by the interference signal acquisition unit, A measuring device equipped with this device.

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