JP2016090944A - Spectrum compressor, nonlinear optical microscope, optical analog/digital conversion system, and method for spectrum compression - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spectrum compressor that can realize high spectrum compressibility.SOLUTION: A spectrum compressor 100 includes: a second wavelength dispersion section 102 outputting a second dispersion optical signal 21 by providing a second optical signal 20 having a second center frequency different from a first center frequency of a first dispersion optical signal 11 with second wavelength dispersion with a second dispersion amount twice or half as large as a first dispersion amount of the first dispersion optical signal 11; and a four-wave mixing section 103 outputting an optical signal 30 subjected to spectrum compression by generating four-wave mixing with the first and second dispersion optical signals 11 and 21 synchronizing with each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a spectral compression apparatus that performs spectral compression of an optical signal, a nonlinear optical microscope and an optical analog / digital conversion system including such a spectral compression apparatus, and a spectral compression method.

  In various technical fields using optical signals (for example, Optical Frequency Division Multiplexing (OFDM), optical analog / digital conversion, nonlinear optical microscope, etc.), spectral compression techniques of optical signals are used. For example, in a coherent anti-Stokes Raman scattering (CARS) microscope, spectral compression of pump light is performed in order to increase the spectral resolution of CARS light (see, for example, Non-Patent Document 1). In Non-Patent Document 1, self-phase modulation is used for spectrum compression.

Masahiro Hamada, Naoki Karasawa, “Experiment and Analysis of Single Beam Light Source Using PCF for CARS Spectroscopy”, IEICE Technical Report, OPE, Optoelectronics, vol. 111, no. 185, pp. 7-10, August 2011 T.A. Konishi, et al. "All-optical analog-to-digital converter by use of self-frequency shifting in fiber and a pulse-shaping technique", JOSA B, vol. 19, Issue 11, pp. 2817-2823, 2002

  However, when spectral compression is performed using self-phase modulation as in Non-Patent Document 1, the spectral compression depends on the physical characteristics of the optical device that generates the self-phase modulation. In other words, the spectral compression ratio is limited by the physical limit of the characteristics related to the self-phase modulation of the optical device.

  Therefore, the present invention provides a spectral compression apparatus and the like that can realize a high spectral compression ratio.

  According to an aspect of the present invention, there is provided a spectrum compression device that adds an optical signal having a second center frequency different from the first center frequency of the first dispersed optical signal to twice the first dispersion amount of the first dispersed optical signal. Alternatively, a wavelength dispersion unit that outputs a second dispersion optical signal by synchronizing with the first dispersion optical signal and the second dispersion optical signal by providing wavelength dispersion of the second dispersion amount that is a half. And a four-wave mixing unit that outputs a spectrum-compressed optical signal by generating four-wave mixing.

  According to this configuration, the first dispersed optical signal having the first dispersion amount and the second dispersed optical signal provided with the second chromatic dispersion of the second dispersion amount that is twice or half of the first dispersion amount. Can be used in a synchronized state to cause four-wave mixing. Therefore, it is possible to realize a narrow band of idler light generated by four-wave mixing, and output a spectrum-compressed optical signal. That is, a high spectral compression ratio can be easily realized by four-wave mixing.

  For example, the spectral compression device further provides a first wavelength dispersion unit that outputs the first dispersion optical signal by giving wavelength dispersion of the first dispersion amount to the first optical signal having the first center frequency. May be provided.

  According to this configuration, it is possible to output the first dispersed optical signal by giving the first chromatic dispersion of the first dispersion amount to the first optical signal. Therefore, even if the input optical signal (first optical signal) does not have an appropriate amount of dispersion, spectral compression of the input optical signal can be realized, and versatility can be improved.

  A nonlinear optical microscope according to one aspect of the present invention is a nonlinear optical microscope that irradiates a sample with pump light and Stokes light, and detects output light generated by the nonlinear optical phenomenon from the sample, and includes the spectral compression device described above. The spectral compression device is used for spectral compression of the pump light or the output light.

  According to this configuration, a spectrally compressed optical signal output from the spectral compression device can be used as pump light. Alternatively, spectral compression of output light generated from the sample can be performed. Therefore, the spectral resolution of output light generated from the sample can be improved.

  The optical analog / digital conversion system which concerns on 1 aspect of this invention is an optical analog / digital conversion system which converts an analog optical signal into a digital signal, Comprising: The said analog optical signal respond | corresponds to the signal strength of the said analog optical signal By measuring the wavelength of the spectrum-compressed optical signal output from the spectrum compression device, the conversion unit that converts the wavelength into the first optical signal, the spectrum compression device that performs spectrum compression of the first optical signal, A measurement unit that obtains a digital signal corresponding to the signal intensity of the analog optical signal, and the spectral compression device gives a first chromatic dispersion of a first dispersion amount to the first optical signal, thereby providing a first dispersion. A first wavelength dispersion unit that outputs an optical signal, and a second optical signal having a second center frequency different from the first center frequency of the first optical signal, A second chromatic dispersion unit that outputs a second dispersed optical signal by providing a second chromatic dispersion of a second dispersion amount that is twice or a half of the first dispersion amount; and the first dispersed optical signal, And a four-wave mixing unit that outputs a spectrum-compressed optical signal by generating four-wave mixing using the second dispersed optical signal in a synchronized state.

  According to this configuration, it is possible to improve the compression ratio of the spectrum of the first optical signal having a wavelength corresponding to the signal intensity of the analog optical signal using the spectrum compression device. Therefore, the resolution in the optical analog / digital conversion can be improved.

  The present invention can be realized not only as a spectrum compression apparatus, a nonlinear optical microscope, and an optical analog / digital conversion system including such characteristic components, but also, for example, a characteristic configuration included in the spectrum compression apparatus. It can be realized as a spectrum compression method in which processing executed by an element is a step.

  The spectrum compression device and the like according to one embodiment of the present invention can improve the spectrum compression rate of an optical signal.

FIG. 1 is a configuration diagram of a spectrum compression apparatus according to the first embodiment. FIG. 2 is a flowchart showing the spectrum compression method according to the first embodiment. FIG. 3 is a graph for explaining four-wave mixing according to the first embodiment. FIG. 4 is a graph showing a simulation result according to the first embodiment. FIG. 5 is a graph showing a simulation result according to the first embodiment. FIG. 6 is a configuration diagram of the optical analog / digital conversion system according to the second embodiment. FIG. 7 is a configuration diagram of a nonlinear optical microscope according to the third embodiment.

  Hereinafter, embodiments will be specifically described with reference to the drawings.

  It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the scope of the claims. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

  Hereinafter, a case where the optical signal is pulsed light will be described.

(Embodiment 1)
[Configuration of spectrum compression device]
FIG. 1 is a configuration diagram of a spectrum compression apparatus 100 according to the first embodiment. The spectrum compression apparatus 100 performs spectrum compression of an optical signal. As shown in FIG. 1, the spectral compression apparatus 100 includes a first wavelength dispersion unit 101, a second wavelength dispersion unit 102, and a four-wave mixing unit 103.

  The first chromatic dispersion unit 101 outputs the first dispersed optical signal 11 by giving the first chromatic dispersion of the first dispersion amount to the first optical signal 10. The first dispersed optical signal 11 is a chirped optical signal.

  In the present embodiment, the first wavelength dispersion unit 101 is a first optical transmission medium (for example, a first optical fiber). The first optical signal 10 propagates in the first optical transmission medium. By propagating through the first optical transmission medium, the first chromatic dispersion is given to the first optical signal 10, and as a result, the first dispersed optical signal 11 is output.

  The second wavelength dispersion unit 102 applies a second dispersion amount to the second optical signal 20 having a second center frequency different from the first center frequency of the first optical signal 10 (that is, the center frequency of the first dispersed optical signal 11). By giving the second chromatic dispersion, the second dispersed optical signal 21 is outputted. The second dispersed optical signal 21 is a chirped optical signal.

  In the present embodiment, the second wavelength dispersion unit 102 is a second optical transmission medium (for example, a second optical fiber). The second optical signal 20 propagates in the second optical transmission medium. By propagating in the second optical transmission medium, the second optical signal 20 is given second chromatic dispersion, and as a result, the second dispersed optical signal 21 is output.

  Here, the second dispersion amount is twice or half of the first dispersion amount. In the present description, “double” and “half” include substantially double and half in addition to exact double and half. That is, “double” and “half” mean “approximately twice” and “approximately half”.

  The four-wave mixing unit 103 outputs the spectrum-compressed optical signal 30 by generating four-wave mixing by using the first dispersed optical signal 11 and the second dispersed optical signal 21 in a synchronized state. That is, the four-wave mixing unit 103 has the first dispersed signal 11 and the second dispersed optical signal in a state where the center of the pulse width of the first dispersed signal 11 and the center of the pulse width of the second dispersed optical signal 21 are substantially matched. 21 is used to produce four-wave mixing. As a result, the spectrally compressed optical signal 30 is output.

  Four-wave mixing is a nonlinear optical phenomenon. In four-wave mixing, when two or more lights having different frequencies or wavelengths are input to an optical transmission medium having a nonlinear optical effect, light having another frequency or wavelength (referred to as idler light) is generated.

In the present embodiment, two idler lights having center frequencies different from the center frequencies of the first dispersed optical signal 11 and the second dispersed optical signal 21 are generated by four-wave mixing. The third center frequency ω ₃ and the fourth center frequency ω ₄ of the two idler lights are the first center frequency ω _{1 of} the first dispersed optical signal 11 (same as the center frequency of the first optical signal 10) and the second dispersed light. Using the second center frequency ω ₂ of the signal 21 (same as the center frequency of the second optical signal 20), it is expressed by the following equation (1).

Here, idler light having the third center frequency ω ₃ is referred to as first idler light, and idler light having the fourth center frequency ω ₄ is referred to as second idler light. At this time, one of the first idler light and the second idler light corresponds to the optical signal 30 subjected to spectral compression.

  Spectral compression means narrowing the bandwidth (spectral width) of an optical signal. That is, spectrum compression means narrowing of the band. The bandwidth (spectrum width) is, for example, a frequency or wavelength range in which the spectrum intensity is equal to or greater than a threshold intensity (for example, half the peak intensity) smaller than the peak intensity.

  The four-wave mixing unit 103 converts one of two idler lights generated by the four-wave mixing using the first dispersed optical signal 11 and the second dispersed optical signal 21 into the first optical signal 10 and the second optical signal 20. It outputs as idler light (spectrum-compressed optical signal 30) having a narrower bandwidth. The details of the principle of spectrum compression in idler light will be described later.

  Here, a specific configuration example of the four-wave mixing unit 103 will be described. In the present embodiment, the four-wave mixing unit 103 includes a nonlinear optical transmission medium 104 and an optical bandpass filter 105.

  The nonlinear optical transmission medium 104 is an optical transmission medium having a nonlinear optical effect. Specifically, the nonlinear optical transmission medium 104 is, for example, a highly nonlinear optical fiber (HNLF).

  The first dispersed optical signal 11 and the second dispersed optical signal 21 output from the first chromatic dispersion unit 101 and the second chromatic dispersion unit 102, respectively, are combined in synchronization and input to the nonlinear optical transmission medium 104, which is nonlinear. It propagates in the optical transmission medium 104. In the nonlinear optical transmission medium 104, four-wave mixing is generated by the first dispersed optical signal 11 and the second dispersed optical signal 21, and as a result, an optical signal including two idler lights is output from the nonlinear optical transmission medium 104.

  The optical bandpass filter 105 extracts the spectrally compressed optical signal 30 (one of the first idler light and the second idler light) from the optical signal output from the nonlinear optical transmission medium 104. In other words, the optical bandpass filter 105 generates the first dispersed optical signal 11, the second dispersed optical signal 21, and unnecessary idler light (first idler light and second idler light) from the optical signal output from the nonlinear optical transmission medium 104. Remove the other of the light).

[Processing in spectrum compression method]
Next, processing in the spectrum compression apparatus 100 configured as described above will be described. FIG. 2 is a flowchart showing the spectrum compression method according to the first embodiment.

  First, the first dispersed optical signal 11 is output by giving the first chromatic dispersion of the first dispersion amount to the first optical signal 10 (S101). Subsequently, the second optical signal 20 having the second center frequency different from the first center frequency of the first optical signal 10 is added to the second dispersion amount that is twice or half the first dispersion amount. By giving chromatic dispersion, the second dispersed optical signal 21 is output (S102). Finally, four-wave mixing is generated using the first dispersed optical signal 11 and the second dispersed optical signal 21 in a synchronized state, thereby outputting the spectrally compressed optical signal 30 (S103).

[Principle of spectrum compression]
Next, the principle of spectrum compression in the present embodiment will be described. Here, a case where the first optical signal 10 and the second optical signal 20 are Gaussian optical pulses will be described.

  First, wavelength dispersion of a Gaussian light pulse will be described.

The Gaussian light pulse is expressed by the following equation (2).

Here, E represents the electric field component of light, T represents time, T ₀ represents the pulse width, and ω _c represents the center frequency.

When chromatic dispersion is given to the Gaussian optical pulse, the dispersed optical signal is expressed by the following equation (3).

Here, z represents a propagation distance, and β ₂ represents a group velocity dispersion (GVD) parameter.

At this time, the instantaneous frequency of the dispersed optical signal is expressed by the following equation (4).

Therefore, the instantaneous frequency of each of the first dispersed optical signal 11 and the second dispersed optical signal 21 can be expressed by the following equation (5).

Here, β ₂₁ and β ₂₂ are GVD parameters in the first wavelength dispersion unit 101 and the second wavelength dispersion unit 102, respectively. Further, ω ₁ and ω ₂ are the first center frequency of the first dispersed optical signal 11 and the second center frequency of the second dispersed optical signal 21, respectively. C (β ₂₁ ) and C (β ₂₂ ) represent the first dispersion amount and the second dispersion amount.

  Next, four-wave mixing will be described.

The instantaneous frequency of the first idler light and the second idler light generated by the four-wave mixing used in a state where the first dispersed optical signal 11 and the second dispersed optical signal 21 are synchronized is expressed by the following equation (6). Is done.

Here, since the second dispersion amount is twice or half of the first dispersion amount, the following expression (7) or expression (8) is established.

Therefore, the instantaneous frequency of the first idler light or the second idler light is expressed by the following formula (9) or formula (10).

  As described above, when the second dispersion amount is twice the first dispersion amount, that is, when the equation (7) is satisfied, the instantaneous frequency of the first idler light is expressed by the equation (9). Is constant. In addition, when the second dispersion amount is half of the first dispersion amount, that is, when Expression (8) is satisfied, the instantaneous frequency of the second idler light is represented by Expression (10). Is constant. In other words, spectrum-compressed idler light (first idler light or second idler light) is generated by four-wave mixing used in a state where the first dispersed optical signal 11 and the second dispersed optical signal 21 are synchronized.

  FIG. 3 is a graph for explaining four-wave mixing according to the first embodiment. In FIG. 3, the vertical axis represents frequency, and the horizontal axis represents time. (A) represents four-wave mixing using the first optical signal and the second optical signal, and (b) represents four-wave mixing using the first dispersed optical signal and the second dispersed optical signal. FIG. 3 shows a case where the second dispersion amount is twice the first dispersion amount.

  As shown in (a), the wavelength time distribution 31a of the first optical signal 10 and the wavelength time distribution 32a of the second optical signal 20 have a vertically long oval shape. That is, each of the first optical signal 10 and the second optical signal 20 includes a relatively wide bandwidth component in a relatively narrow time width. In this case, the wavelength time distribution 33a of the first idler light and the wavelength time distribution 34a of the second idler light also have the same shape as the wavelength time distribution 31a of the first optical signal 10 and the wavelength time distribution 32a of the second optical signal 20. Become.

  On the other hand, as shown in (b), the wavelength time distribution 31b of the first dispersed optical signal 11 and the wavelength time distribution 32b of the second dispersed optical signal 21 have an inclined ellipse shape. Since the second dispersion amount is twice the first dispersion amount, the wavelength time distribution 32b of the second dispersion optical signal 21 is inclined twice as much as the wavelength time distribution 31b of the first dispersion optical signal 11.

  In this case, the wavelength time distribution 33b of the first idler light has a horizontally long oval shape as is apparent from the equation (9). That is, the first idler light includes a component having a relatively narrow bandwidth in a relatively wide time width. That is, the bandwidth of the first idler light is narrower than the bandwidth of each of the first dispersed optical signal 11 and the second dispersed optical signal 21. The wavelength time distribution 34b of the second idler light has the same shape as the wavelength time distribution 32b of the second dispersed optical signal 21.

[simulation result]
Next, the simulation result of the spectrum compression as described above will be described. The conditions for this simulation are as follows.

  The center wavelength of the first optical signal 10 is 1560 nm, and the center wavelength of the second optical signal 20 is 1550 nm. The pulse widths of the first optical signal 10 and the second optical signal 20 are both 2.1 ps.

Further, a first dispersion compensating optical fiber (DCF) having a length of 30 m is used as the first chromatic dispersion unit 101 for giving the first chromatic dispersion to the first optical signal 10. The optical characteristics of the first DCF are as follows.
Nonlinearity: 3.7 / W / km
Dispersion: −106 ps / nm / km
Dispersion slope: 0.06 ps / nm ² / km

Further, a second DCF having a length of 30 m is used as the second wavelength dispersion unit 102 for giving the second wavelength dispersion to the second optical signal 20. The optical characteristics of the second DCF are as follows.
Nonlinearity: 3.7 / W / km
Dispersion: -212 ps / nm / km
Dispersion slope: 0.06 ps / nm ² / km

  As described above, the second dispersion amount in the second wavelength dispersion unit 102 is twice the first dispersion amount in the first wavelength dispersion unit 101.

As the four-wave mixing unit 103, HNLF is used. The optical characteristics of this HNLF are as follows.
Nonlinearity: 6.2 / W / km
Dispersion: 0.325 ps / nm / km
Dispersion slope: 0.031 ps / nm ² / km

  4 and 5 are graphs showing simulation results according to the first embodiment. Specifically, FIG. 4 shows a spectrum of an optical signal output from the HNLF. FIG. 5 shows a spectrum 51 of the first optical signal 10 and a spectrum 52 of the optical signal 30 subjected to spectral compression.

  As shown in FIG. 4, in addition to the first dispersed optical signal 11 (1560 nm) and the second dispersed optical signal 21 (1550 nm), the first idler generated by four-wave mixing is included in the optical signal output from the HNLF. Light (1570 nm) and second idler light (1540 nm) are included. The first idler light is extracted from the optical signal output from the HNLF as an optical signal 30 whose spectrum is compressed.

  At this time, as is apparent from FIG. 5, the half width (0.4 nm) of the spectrum 52 of the optical signal 30 (first idler light) subjected to spectral compression is equal to the half width (2 of the spectrum 51 of the first optical signal 10). .4 nm). Here, the spectrum width is compressed to 1/6, and high spectral compression is realized by four-wave mixing.

[effect]
As described above, the spectrum compression apparatus according to the present embodiment has the first dispersion optical signal having the first dispersion amount and the second dispersion amount that is twice or half the first dispersion amount. Four-wave mixing can be generated using the second dispersed optical signal in a synchronized state. Therefore, it is possible to realize a narrow band of idler light generated by four-wave mixing, and output a spectrum-compressed optical signal. That is, a high spectral compression ratio can be easily realized by four-wave mixing.

  In particular, an apparatus that has conventionally performed spectrum compression using a nonlinear optical effect (for example, a CARS microscope) does not require a complicated configuration to realize the spectrum compression apparatus according to the present embodiment. . Therefore, a high spectral compression ratio can be realized while suppressing an increase in manufacturing cost.

(Embodiment 2)
In the second embodiment, an optical analog / digital conversion system will be described as an application example of the spectrum compression apparatus according to the first embodiment.

[Configuration of optical analog / digital conversion system]
FIG. 6 is a configuration diagram of an optical analog / digital conversion system 1000 according to the second embodiment. In FIG. 6, components that are substantially the same as the components described in FIG. 1 are assigned the same reference numerals, and descriptions thereof are omitted as appropriate.

  The optical analog / digital conversion system 1000 converts an analog optical signal into a digital signal. The optical analog / digital conversion system 1000 includes the spectrum compression apparatus 200 according to Embodiment 1, a conversion unit 300, and a measurement unit 400.

  The converter 300 converts the analog optical signal into a first optical signal having a wavelength corresponding to the signal intensity of the analog optical signal. Specifically, the conversion unit 300 is, for example, a non-linear optical fiber that generates a self-frequency shift.

  The first optical signal resulting from the conversion is input to the spectrum compression apparatus 100.

  The spectrum compression apparatus 200 performs spectrum compression of the first optical signal. Specifically, the spectrum compression apparatus 200 includes a first wavelength dispersion unit 201, a second wavelength dispersion unit 202, and a four-wave mixing unit 203.

  The first wavelength dispersion unit 201 outputs the first dispersed optical signal by giving the first optical signal the first wavelength dispersion of the first dispersion amount. The first wavelength dispersion unit 201 corresponds to the first wavelength dispersion unit 101 in the first embodiment.

  The second wavelength dispersion unit 202 has a second dispersion amount that is twice or half of the first dispersion amount in a second optical signal having a second center frequency different from the first center frequency of the first optical signal. By giving the second chromatic dispersion, a second dispersed optical signal is output. The second wavelength dispersion unit 202 corresponds to the second wavelength dispersion unit 102 in the first embodiment.

  The four-wave mixing unit 203 outputs a spectrum-compressed optical signal by generating four-wave mixing by using the first dispersed optical signal and the second dispersed optical signal in a synchronized state. The four-wave mixing unit 203 includes a nonlinear optical transmission medium 104 and an optical bandpass filter 205.

  The optical bandpass filter 205 extracts a spectrally compressed optical signal (one of the first idler light and the second idler light) from the optical signal output from the nonlinear optical transmission medium 104. In other words, the optical bandpass filter 205 generates a first dispersed optical signal, a second dispersed optical signal, and unnecessary idler light (of the first idler light and the second idler light) from the optical signal output from the nonlinear optical transmission medium 104. The other of the above is removed.

  The measurement unit 400 acquires the digital signal corresponding to the signal intensity of the analog optical signal by measuring the wavelength of the spectrally compressed optical signal output from the spectral compression apparatus 200. Specifically, the measurement unit 400 is, for example, an arrayed waveguide grating (AWG).

  Note that the conversion unit 300 and the measurement unit 400 are the same as in Non-Patent Document 2, and thus detailed description thereof is omitted.

[effect]
As described above, according to the optical analog / digital conversion system 1000 according to the present embodiment, the compression ratio of the spectrum of an optical signal having a wavelength corresponding to the signal intensity of the analog optical signal using the spectrum compression device 200. Can be improved. Therefore, the resolution in the optical analog / digital conversion can be improved.

(Embodiment 3)
In the third embodiment, a nonlinear optical microscope will be described as an application example of the spectrum compression apparatus according to the first embodiment.

[Configuration of nonlinear optical microscope]
FIG. 7 is a configuration diagram of the nonlinear optical microscope 2000 according to the third embodiment. In FIG. 7, components that are substantially the same as the components described in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted as appropriate.

  The nonlinear optical microscope 2000 irradiates the sample 70 with pump light and Stokes light having a wavelength different from that of the pump light, and detects output light generated by the nonlinear optical phenomenon from the sample 70. Specifically, the nonlinear optical microscope 2000 is, for example, a CARS microscope.

  The nonlinear optical microscope 2000 includes a light source 500 and a spectroscope 600.

  The light source 500 irradiates the sample 70 with pump light and Stokes light. Specifically, the light source 500 includes, for example, an ultrashort optical pulse laser (not shown). Furthermore, the light source 500 includes a spectral compression device 100. The light source 500 irradiates the sample 70 with the spectrally compressed optical signal output from the spectral compression apparatus 100 as pump light.

  The spectroscope 600 detects output light generated by a nonlinear optical phenomenon generated from the sample 70. Specifically, the spectrometer 600 detects CARS light generated from the sample 70.

  Note that components other than the spectral compression device 100 of the nonlinear optical microscope 2000 may be the same as those in Non-Patent Document 2, and thus detailed description thereof is omitted.

[effect]
As described above, according to the nonlinear optical microscope 2000 according to this embodiment, the spectrally compressed optical signal output from the spectral compression apparatus 100 can be used as pump light, and the output light generated from the sample 70 can be used. Spectral resolution can be improved.

(Other embodiments)
The spectral compression apparatus, the optical analog / digital conversion system, and the nonlinear optical microscope according to the embodiment of the present invention have been described above, but the present invention is not limited to this embodiment. Unless it deviates from the gist of the present invention, various modifications conceived by those skilled in the art have been made in this embodiment, and forms constructed by combining components in different embodiments are also included in the scope of the present invention. May be.

  For example, in each of the above embodiments, the spectrum compression apparatus includes the first wavelength dispersion unit, but may not include the first wavelength dispersion unit. In this case, the first dispersion optical signal having the first dispersion amount may be input to the spectrum compression device.

  In the third embodiment, the spectrum compression apparatus is used for the spectrum compression of the pump light. However, the use of the spectrum compression apparatus in the nonlinear optical microscope is not limited to this. For example, the spectral compression device may be used for spectral compression of output light (for example, CARS light) generated from a sample. Thereby, the spectral resolution of the output light generated from the sample 70 can be improved.

  In the second and third embodiments, the application example in which the spectrum compression device is used in the optical analog / digital conversion system and the nonlinear optical microscope has been described. However, the spectrum compression device may be applied to other devices. For example, the spectrum compression device may be used for a signal separation device or a wavelength meter for optical OFDM.

  The present invention can be used as a spectral compression device that performs spectral compression of an optical signal, and can be applied to an optical analog / digital conversion system, a nonlinear optical microscope, a wavelength meter, or the like.

DESCRIPTION OF SYMBOLS 10 1st optical signal 11 1st dispersion | distribution optical signal 20 2nd optical signal 21 2nd dispersion | distribution optical signal 30 Optical signal 31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b Wavelength time distribution 51, 52 Spectrum 70 Sample 100, 200 Spectrum compression apparatus 101, 201 First wavelength dispersion unit 102, 202 Second wavelength dispersion unit 103, 203 Four-wave mixing unit 104 Non-linear optical transmission medium 105, 205 Optical bandpass filter 300 Conversion unit 400 Measurement unit 500 Light source 600 Spectrometer 1000 Optical analog / digital conversion system 2000 Nonlinear optical microscope

Claims (5)

An optical signal having a second center frequency that is different from the first center frequency of the first dispersed optical signal has a second dispersion amount that is twice or a half of the first dispersion amount of the first dispersed optical signal. A wavelength dispersion unit that outputs the second dispersion optical signal by providing wavelength dispersion;
A four-wave mixing unit that outputs a spectrum-compressed optical signal by generating four-wave mixing using the first dispersed optical signal and the second dispersed optical signal in a synchronized state. . The spectral compression device further includes:
The spectrum compression according to claim 1, further comprising: a first wavelength dispersion unit that outputs the first dispersion optical signal by giving wavelength dispersion of the first dispersion amount to the first optical signal having the first center frequency. apparatus. A nonlinear optical microscope that irradiates a sample with pump light and Stokes light, and detects output light generated by the nonlinear optical phenomenon from the sample,
A spectral compression apparatus according to claim 1,
The spectral compression device is a nonlinear optical microscope used for spectral compression of the pump light or the output light. An optical analog / digital conversion system for converting an analog optical signal into a digital signal,
A converter that converts the analog optical signal into a first optical signal having a wavelength corresponding to the signal intensity of the analog optical signal;
A spectral compression device for performing spectral compression of the first optical signal;
A measurement unit that obtains a digital signal corresponding to the signal intensity of the analog optical signal by measuring the wavelength of the spectrally compressed optical signal output from the spectral compression device;
The spectral compression device comprises:
A first chromatic dispersion unit that outputs a first dispersed optical signal by giving a first chromatic dispersion of a first dispersion amount to the first optical signal;
The second optical dispersion having a second dispersion amount that is twice or half the first dispersion amount is applied to a second optical signal having a second center frequency different from the first center frequency of the first optical signal. A second wavelength dispersion unit that outputs a second dispersion optical signal by providing,
A four-wave mixing unit that outputs a spectrum-compressed optical signal by generating four-wave mixing using the first dispersed optical signal and the second dispersed optical signal in a synchronized state; Digital conversion system. An optical signal having a second center frequency that is different from the first center frequency of the first dispersed optical signal has a second dispersion amount that is twice or a half of the first dispersion amount of the first dispersed optical signal. A chromatic dispersion step of outputting a second dispersed optical signal by providing chromatic dispersion;
A four-wave mixing step of outputting a spectrum-compressed optical signal by generating four-wave mixing by using the first dispersed optical signal and the second dispersed optical signal in a synchronized state. .

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