JP2000074742A - Spectroscope and light spectrum analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a spectroscope easy to realize a good resolution, downsizing and cost reduction by placing a phosphor in the front of an array element, and detecting a fluorescent light excited by long-wavelength light, using the array element. SOLUTION: A wavelength converter 110 composed of a phosphor is disposed in front of a photo detecting array element 15 and irradiated with a light dispersed through a wavelength dispersion element 13. The wavelength converter 110 has a part excited to emit a fluorescent light when this part is irradiated with a light to be measured. The array element 15 behind it detects the fluorescent light to measure the intensity of the light to be measured. If the phosphor of the wavelength converter 110 is formed only at a part corresponding to a photo element, the fluorescent light will not so spread as to be detected by adjacent elements on the array elements 15, thus easily improving the resolution. If a phosphor film is formed on the surface of the array element 15 by the deposition, etc., the phosphor well adheres to the array element 15 to reduce a stray light due to sneaking of the fluorescent light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polychromator type spectrometer using a wavelength dispersion element and an array of photodetectors, and more particularly to wavelength conversion of a photodetector.

[0002]

2. Description of the Related Art FIG. 13 shows an example of a conventional optical spectrum analyzer having a built-in polychromator type spectroscope. The optical spectrum analyzer includes a spectroscope 10 having a wavelength dispersion element and an array element, a driving device 20 for driving an array element of the spectrometer 10 and reading signals,
It comprises an arithmetic unit 30 and a display unit 40.

The spectroscope 10 comprises a slit 11, a collimating mirror 12, a wavelength dispersing element 13 composed of a diffraction grating, a focusing mirror 14, and an array element 15 for receiving light.

The light to be measured incident through the entrance of the slit 11 becomes parallel light by the collimating mirror 12 and enters the wavelength dispersion element 13. Light emitted from the wavelength dispersion element 13 is converged on the array element 15 by the focusing mirror 14. In this case, the wavelength dispersion element 13 is fixed, and the position of the light spot hitting the array element 15 is shifted according to the wavelength of the light to be measured.

[0005] The array element is formed by arranging strip-shaped or dot-shaped light receiving portions (hereinafter referred to as elements or light receiving elements). The position of each element corresponds to the wavelength, and the optical spectrum is measured by reading out the light intensity of each element by the driving device 20 for driving the array element and reading out the signal and performing appropriate processing by the arithmetic unit 30. You.
The light spectrum can be displayed on the display device 40.

The arithmetic unit 30 can also accurately interpolate the center wavelength of the laser beam from the output of each element, for example, assuming a Gaussian distribution.

As an array element for light detection, an element covering the wavelength region of the light to be measured is used. For example, at a short wavelength of 1 μm or less, Si is used and 1.3 μm is used.
In a long wavelength band such as m or 1.55 μm, InGaAs or Ge is used.

In the long-range and medium-range communication areas except LAN, a wavelength multiplexing system in which a plurality of lasers in a long wavelength band of 1.3 μm or 1.55 μm are used and a signal is carried on laser light of each wavelength has been put into practical use. Is being done.

In a polychromator used for spectroscopy in this field, an InGaAs photodiode array is used as a photodetector. Generally, in this detector, it is difficult to form a photodetector and a multiplexer for sequentially transmitting a detected signal on the same material, such as short-wavelength Si.
The detection module is made by hybrid-connecting the As photodetector and a signal processing unit such as a multiplexer formed on Si using wire bonding or flip chip bonding.

[0010]

However, III-
InGaAs, which is a group V material, is brittle and expensive, so it is practically difficult to realize a device having a large area. In addition, since it is necessary to adopt a hybrid configuration with Si, it is difficult to mount it on a small element integrated with the signal processing unit, such as a short-wavelength band Si detector (for example, a CCD). Tends to.

Although it is possible to improve the spectral resolution by increasing the element density and increasing the number of elements as in the case of Si, the wiring area with the signal processing system becomes larger than the element area. There was a problem that the entire configuration became large. At present, 2048 or 4096 for Si one-dimensional CCD array
Although devices have been realized, it is not easy for InGaAs to realize 256 devices without defects.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to dispose a phosphor on the front surface of an array element to detect light whose wavelength has been converted by an array element for short wavelength, which is easy to increase the number of elements. Accordingly, the present invention provides a spectroscope that can easily realize high resolution, small size, and low cost. Another object of the present invention is to realize an optical spectrum analyzer using a spectroscope which has solved the problems as described above.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a wavelength dispersion element for dispersing the wavelength of light to be measured and an array element for receiving light of the dispersed wavelength. In a spectroscope having a basic configuration, a phosphor is arranged on the front surface of the array element, and fluorescence excited by long-wavelength light is detected by the array element.

According to such a configuration, the optical power of the laser light of a plurality of wavelengths in the long wavelength band dispersed by the dispersive element can be received by the element array for the short wavelength having a large number of elements at low cost, and can be easily obtained. In addition, a compact, high-resolution, low-cost spectrometer can be realized.

In the above invention, if the fluorescent material is formed so that a portion having no fluorescent light and a certain portion are formed in a lattice pattern in accordance with the pitch of the array element, the fluorescent light is spread and the array element is formed. Detection is not performed by the adjacent element, and the spectrum resolution can be improved.

Further, if the fluorescent material is formed in a layered form in close contact with the array element as described in claim 3 or 4, stray light due to the spillage of the fluorescent light to a portion not irradiated with the measured light can be reduced. .

Further, the phosphor may be formed only on the element having the light receiving sensitivity of the array element. Also in this case, similarly to the above, the influence of stray light can be reduced.

Further, according to the invention of claim 6, the array element has two elements.
The elements are arranged in a dimension, and the elements in each row are shifted in the wavelength dispersion direction. According to such a configuration, a power spectrum can be obtained for each column of the element, and the resolution and accuracy in the wavelength direction can be improved.

In this case, a photodetector based on Si can be used as the array element.

The invention according to claim 8 is provided with a shielding mechanism for chopping the measured light, and eliminates saturation of the fluorescent material by refreshing the fluorescent material by shielding the measured light at an appropriate timing. be able to.

According to a ninth aspect of the present invention, the wavelength converter using the phosphor is replaced with a material having a nonlinear optical effect.
In this case, scattering of the beam at the wavelength conversion unit is reduced, and the influence of stray light is reduced.

The light to be measured can be introduced by either a spatial light input or an optical fiber input.

According to an eleventh aspect of the present invention, the depolarizing element is disposed, whereby the influence of the polarization dependence of the diffraction grating is suppressed, and even if the polarization state of the light to be measured fluctuates, the light intensity on the array element is changed. Can be corrected to be constant.

Similar effects can be obtained by using a phosphor instead of a phosphor.

According to a thirteenth aspect, in the spectroscope according to the first aspect,
An optical spectrum analyzer is provided with means for performing an appropriate process on an output signal read from the array element to obtain an optical spectrum of the measured light and displaying the optical spectrum on a display device. According to such a configuration, an optical spectrum analyzer using a small, high-resolution, low-cost spectroscope can be easily realized.

In this case, the spectroscope can be configured as described in claims 14 to 21. Since the respective functions and effects are the same as those described for the spectroscope, description thereof will be omitted.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the spectroscope according to the present invention. The same parts as those in the conventional example of FIG. In the present invention, a wavelength converter 110 made of a phosphor is disposed in front of the light detection array element 15.

The light split by the wavelength dispersion element 13 is applied to the wavelength converter 110. The wavelength conversion section 110 emits fluorescence when a portion to which the light to be measured is irradiated is excited.
Here, the wavelength converter is also called a phosphor. The intensity of the light to be measured can be measured by receiving the fluorescence with the array element 15 located behind it.

FIG. 2 (side view) shows another embodiment of the present invention. The phosphor of the wavelength conversion unit 110 in FIG. 1 is formed only in a portion corresponding to an optical element. According to such a configuration, the amount of spread of fluorescence and detection by adjacent elements on the array element 15 is extremely reduced, and the spectral resolution can be easily improved.

FIG. 3 (a is a front view, b is a side view) is a view showing still another embodiment of the present invention. In this embodiment, the phosphor film 113a is formed on the surface of the array element 15 by vapor deposition, sputtering, printing, or the like. In this case, the fluorescent substance 113a is in close contact with the array element 15, and there is a feature that stray light due to the sneak of the fluorescent light to a part not irradiated with the light to be measured is reduced.

FIG. 4 (a is a front view, b is a side view) is a view showing still another embodiment. In the configuration of FIG. 4, the phosphor film 113 b is formed on the surface of the array element 15 similarly to the configuration of FIG. 3, but by forming the phosphor only on the array element 15, stray light to adjacent elements of the array element 15 is Can be further reduced.

FIG. 5 (a is a front view, b is a side view)
FIG. 7 is a configuration diagram showing still another embodiment of the present invention. The array elements 116 are arranged two-dimensionally, and the elements in each row are arranged with a shift in the wavelength dispersion direction, and a phosphor 117a is formed on the array elements 116.

In the measurement, the output signal level of each element is obtained by scanning each column, and this is stored in a storage device (not shown) in the arithmetic unit 30. Then, the center wavelength and the level are calculated for each column, and the center wavelength of the light is determined based on the calculation result of the column in which the measured power level of the element is close to the calculated power level.

With this method, the resolution and accuracy in the wavelength direction can be improved. In addition, FIG. 6 (a is a front view,
(b is a side view) is one in which a phosphor 117a is formed on each element similarly to FIG.

FIG. 7 is a block diagram showing still another embodiment. Phosphors are saturated when exposed to strong light. In order to solve this, in the present embodiment, for example, a shutter mechanism 17 that blocks light to be measured is provided. The phosphor is refreshed while the light to be measured is blocked by the shutter 17, so that a predetermined sensitivity can always be obtained. Further, the dark current level of the array element 15 at that time can also be measured by the shutter. By subtracting this value from the measured value, the influence of the drift of the dark current can be removed, and highly accurate measurement can be realized.

FIG. 8 is a block diagram showing still another embodiment, in which a display device 40 is added to the configuration of FIG. 6 to form an optical spectrum analyzer.

FIG. 9 (a is a front view, b is a side view) is a configuration diagram showing still another embodiment, in which the wavelength conversion section using the phosphor of the above embodiment is made of a material 118a having a nonlinear optical effect. Then, the second harmonic of the light applied to the material is received by the array element 15. in this case,
Although the efficiency is reduced, the scattering of the beam in the wavelength converter is reduced, and the influence of the stray light is reduced.

FIG. 10 (a is a front view, b is a side view)
Is formed by forming a material 118b having a non-linear optical effect on each element as in FIG.

FIG. 11 is a block diagram showing still another embodiment. In the above embodiment, the spatial light input is assumed, but in this embodiment, the spatial light input section is connected to the optical fiber 1.
8 (optical fiber input). Therefore, alignment becomes easy, and stable measurement with good reproducibility can be realized.

FIG. 12 is a block diagram showing still another embodiment. A wavelength dispersion element, particularly a diffraction grating, has a large polarization dependence.
In order to remove this polarization dependence, a depolarizing element 16 is arranged so that the array element 1 can be operated even when the polarization state of the measured light changes.
On 5, the light intensity is corrected so as to be constant.

It should be noted that the present invention is not limited to the above-described embodiments, and that the present invention can include modifications or alterations of the configuration of each embodiment. For example, in the above embodiment, a reflection optical system is used, but a transmission optical system using a lens or the like may be used. In addition, a configuration in which the components of each of the above-described embodiments are appropriately rearranged may be adopted.

Further, a phosphor may be used instead of the phosphor. Further, the wavelength dispersion element is not limited to a diffraction grating, and a prism may be used. Furthermore, a combination with an inclined optical film may be used.

[0043]

As described above, according to the present invention, the following effects can be obtained. According to the first aspect of the present invention, the fluorescent material is arranged on the front surface of the array element, and the fluorescent light (optical power) excited by the laser light of a plurality of wavelengths in the long wavelength band dispersed by the wavelength dispersive element can be produced at low cost. Since the light is received by the short wavelength optical element array having a large number of elements, a small-sized, high-resolution, low-cost spectroscope can be easily realized.

Further, by providing such a spectroscope with means for subjecting an output signal read from the array element to appropriate processing to obtain an optical spectrum of the light to be measured and displaying the spectrum on a display device, a small and high resolution device can be provided. -An optical spectrum analyzer using a low-cost spectroscope can be easily realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a spectroscope according to the present invention.

FIG. 2 is a diagram showing another embodiment of the array element section of the present invention.

FIG. 3 is a diagram showing still another embodiment of the array element section of the present invention.

FIG. 4 is a diagram showing still another embodiment of the array element section of the present invention.

FIG. 5 is a diagram showing still another embodiment of the array element section of the present invention.

FIG. 6 is a diagram showing still another embodiment of the array element section of the present invention.

FIG. 7 is a diagram showing another embodiment of the spectroscope according to the present invention.

FIG. 8 is a view showing still another embodiment of the spectroscope according to the present invention.

FIG. 9 is a view showing still another embodiment of the array element section of the present invention.

FIG. 10 is a diagram showing still another embodiment of the array element section of the present invention.

FIG. 11 is a view showing still another embodiment of the spectroscope according to the present invention.

FIG. 12 is a view showing still another embodiment of the spectroscope according to the present invention.

FIG. 13 is a configuration diagram illustrating an example of a conventional spectroscope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Spectroscope 11 Slit 12 Collimating mirror 13 Wavelength dispersion element 14 Focusing mirror 15, 116 Array element 16 Depolarization element 17 Shutter mechanism 18 Optical fiber 20 Driving device 30 Computing device 40 Display device 110, 111 Wavelength converter 113a, 113b Wavelength converters 118a, 118b Wavelength converters

Claims (21)

[Claims] 1. A spectroscope having a wavelength dispersion element for dispersing a wavelength of light to be measured and an array element for receiving light of the dispersed wavelength, wherein a phosphor is disposed in front of the array element. A spectroscope characterized in that fluorescence excited by long-wavelength light is detected by an array element. 2. The spectroscope according to claim 1, wherein the phosphor has a portion where there is no fluorescence and a portion where there is no fluorescence in a lattice shape in accordance with the pitch of the array element. 3. The spectroscope according to claim 1, wherein said phosphor is formed in a layered form in close contact with said array element. 4. The spectroscope according to claim 3, wherein said phosphor layer is formed on the array element by vapor deposition or coating. 5. The spectroscope according to claim 3, wherein said phosphor is formed only on an element having a light receiving sensitivity of the array element. 6. The device according to claim 3, wherein the array elements are arranged two-dimensionally, and the elements in each row are displaced with respect to the wavelength dispersion direction. Spectrograph. 7. The spectroscope according to claim 1, wherein said array element is a photodetector based on Si. 8. The spectroscope according to claim 1, further comprising a shielding mechanism for chopping the light to be measured in order to eliminate saturation of the phosphor. 9. A wavelength converter using said phosphor, wherein a material having a non-linear optical effect is used, and a second harmonic of light applied to said material is received by said array element. 9. The spectroscope according to claim 1, wherein the spectroscope is used. 10. The spectroscope according to claim 1, wherein the light to be measured is introduced through a spatial light input or an optical fiber input. 11. The spectroscope according to claim 1, wherein a depolarizing element is arranged so that a change in the polarization state of the measured light does not affect the light intensity of the array element. 12. A spectroscope according to claim 1, wherein said phosphor is a phosphor. 13. A wavelength dispersive element for dispersing the wavelength of a light to be measured and an array element for receiving light of the disperse wavelength. A phosphor is disposed in front of the array element, and a long wavelength light is provided. A spectroscope configured to detect the excited fluorescence with an array element, and a means for performing appropriate processing on an output signal read from the array element to obtain an optical spectrum of the measured light and displaying the same on a display device. An optical spectrum analyzer. 14. An optical spectrum analyzer according to claim 13, wherein said phosphor has a portion having no fluorescence and a portion having a lattice shape in accordance with a pitch of an array element. 15. An optical spectrum analyzer according to claim 13, wherein said phosphor is formed in a layered form by vapor deposition or coating on said array element. 16. The apparatus according to claim 13, wherein said phosphor is formed only on an element having a light receiving sensitivity of said array element.
Optical spectrum analyzer as described. 17. The optical spectrum analyzer according to claim 13, further comprising a shielding mechanism for chopping the measured light in order to eliminate the saturation of the phosphor. 18. A wavelength conversion unit using the phosphor, wherein a material having a nonlinear optical effect is used, and a second harmonic of light applied to the material is received by the array element. The optical spectrum analyzer according to claim 13, wherein: 19. The optical spectrum analyzer according to claim 13, wherein the light to be measured is introduced through a spatial light input or an optical fiber input. 20. The optical spectrum analyzer according to claim 13, wherein a depolarizing element is arranged so that a change in the polarization state of the measured light does not affect the light intensity of the array element. 21. An optical spectrum analyzer according to claim 13, wherein a phosphor is used as said phosphor.