JPS59228133A - Spectroscope device - Google Patents

Abstract

PURPOSE:To make it possible to obtain compact configuration and high integration and to improve resolution and accuracy, by measuring the spectrum distribution of light, which is inputted to an optical modulator by a Fourier spectroscopy method based on the wevelength dependence of the modulation degree of the optical modulator. CONSTITUTION:An operation control part 5 sweeps the output voltage of a power source 35 in a certain range. An optical modulator 3 outputs light corresponding to a voltage, which is applied across electrodes. A light receiving element 4 converts the output light into an electric signal. The signal is inputted into the operation control part 5. The operation control cirpart 5 has a CPU52 and a memory 53. The spectrum distribution of the light, which is inputted to the optical modulator 3 by a Fourier spectroscopy method, is obtained based on the wavelength dependence of the optical modulator 3. The result is displayed on a display device 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a spectroscopic device using an electro-optic material having an electro-optic effect, such as PLZT.

[Description of prior art]

FIGS. 1 and 2 are explanatory diagrams showing an example of a conventionally known spectroscopic device.

In the apparatus shown in FIG. 1, light incident through an entrance slit 11 is made into a parallel beam bundle by a concave mirror 12, and is made incident on a diffraction grating 13, and the transmitted light or diffracted light is imaged by a concave mirror 14. In this device, in order to increase resolution, it is necessary to make the slit on the light receiving side thinner, and it is difficult to improve resolution and precision at the same time.

The device shown in FIG. 2 is a spectroscopic device based on the principle of Fourier spectroscopy using a two-beam East interferometer. The light incident through the entrance slit 21 is converted into parallel light by a lens 22, and this parallel light is converted into a half mirror. 23 into two beams, each beam is reflected by a reflecting mirror 24, 25, and each of these reflected beams is made to enter a slit 27 via a lens 26. In this device, when one of the reflecting mirrors 24 and 25 is moved in the direction shown by the arrow, and the optical path difference between the two beams is completely changed, the signal obtained from the light receiving element 28 that receives the light sound that has passed through the slit 27 is intersected. A ferogram is a Fourier transform of incident light, and this inverse transform is performed to determine the original spectral distribution.

Compared to the device shown in Figure 1, this device does not require an entrance slit, can simultaneously measure the entire spectrum of light entering the photodetector, has a large amount of light so 87N is good, and has high wavelength accuracy. Although there are advantages, there are disadvantages such as the need to move the reflecting mirror to change the optical path difference, which requires mechanical precision, and difficulty in miniaturization and integration.

[Object of the present invention]

Here, the present invention aims to realize a spectroscopic device that does not have mechanical components, is small in size, can be integrated, and has good resolution and accuracy.

[Summary of the invention]

The device according to the present invention includes an optical modulator made of an electro-optic material having an electro-optic effect, a light-receiving element that receives light that has passed through the optical modulator, and a light-receiving element that receives a signal from the light-receiving element and modulates the light. The device is characterized in that the spectral distribution of light incident on the optical modulator can be determined by Fourier spectroscopy from the wavelength dependence of the degree of modulation of the optical modulator.

[Explanation of principle]

FIG. 3 is a diagram for explaining the principle of the device according to the present invention, and shows an example of an optical modulator used in the present invention.

In the figure, 3 is an electro-optic material having an electro-optic effect (
For example, PLZT or LsNbO5), 31.32 is an electrode provided on two parallel surfaces of this electro-optic material 3, 33.3
Reference numeral 4 denotes a polarizer and an analyzer placed between the electro-optic material 3i on the light incident side and the light output side, respectively, and the direction of the polarization plane is 45 degrees with respect to the electric field E generated by the electrodes 31 and 32.
It is tilted and parallel.

In an optical modulator having such a configuration, when a voltage vf: is applied between the electrodes 31 and 32, the incident light Pln and the output light P
Ratio with OTII'l' T = POUT/P t n
can be expressed as (11).

2′ T = pO, T/pin=kCO8(i Δα(V
)) ......-ill where k, lc'
is a constant (k≦1), λ is the wavelength of the incident light, Δα(V)/λ
is the amount of birefringence (rad) due to the electro-optic effect.

number), and if we rewrite hI as ′, we get (2
) is as follows.

T = POUT/PIN = k C082 (k'fΔ
α(v)) = (x+cos(2 to 'r Jα(V)
) ) -... (21 In equation (2), if the spectral distribution of the incident light flux is set as B (f), the output light P OUT
is as shown in equation (3) (Pin is replaced by B (f)) in the same way as equation (2).

The second term on the right side of equation (3) is the Fourier cosine transform of B (f). Therefore, the spectral distribution of the incident light B (f)
can be obtained by inverse Fourier transform.

Here, Vo is Δα(Vo)=0 (usually V.=o
) is easy to choose, so by substituting this into equation (3), equation (4) is obtained.

By substituting equation (4) into equation (3), iBi' of equation (5)
).

As is clear from equation (5), from PoUT(■), −
PO[TT (VD), and if the remaining terms are inverse Fourier cosine transformed, the spectral distribution B(f) of the incident light P1n is obtained.
'! r I can know.

[Explanation of Examples]

FIG. 4 is a block diagram showing an example of a device according to the present invention. In this figure, 3 is an optical modulator having the configuration shown in FIG. 3, which satisfies equation (1). 35 is a power source that applies a voltage between the electrodes of this optical modulator; 4 is a light receiving element that receives the light emitted from the optical modulator 3; 5 is a power source that inputs and stores a signal from this light receiving element;
For example, the signal from the light receiving element 4 is sent to a human/
It is composed of an A/D converter 51 that performs D conversion, a microprocessor 52 that inputs digital signals from the A/D converter 51, and a memory 53 coupled thereto. Reference numeral 6 denotes a display device for displaying the calculation results of the calculation control section 5.

The operation of the device configured as described above is as follows. First, the arithmetic control unit 5 sweeps the output voltage of the power supply 35 from ■ to v2 within a certain range. The optical modulator 3 is
Depending on the voltage applied between the electrodes, light P OUT as expressed by equation (5) is emitted.

The light receiving element 4 converts the output light P OUT into an electrical signal,
Arithmetic control H (55K is input. The memory means 53 in this arithmetic control unit 5 stores the voltage applied to the optical modulator 3 and the signal from the light receiving element 4 at that time between ■ and v2.
Remember. Here, if necessary, the S/H may be improved by sweeping from ■ to v2 several times, taking several pieces of data, and averaging the results.

The data stored in the memory means 53 can be calculated from equation (5) by B
Inverse Fourier transform calculation for determining (f), light receiving element 4
A correction calculation is performed on the zero wavelength-sensitivity characteristic, the wavelength-transmittance characteristic of the optical modulator 3 itself, etc., to obtain the spectra of the incident lights P and n, and the result of this calculation is displayed on the display 6.

FIGS. 5 to 8 are explanatory diagrams showing other configuration examples of optical modulators that can be used in the apparatus of the present invention.

In both Figures 5 and 6, (A) is a plan view, (
B) is a sectional view taken along line XX in FIG.

The optical modulator shown in FIG. 5 has branched phase modulation/interference type optical waveguides 35 and 36' formed on a dielectric substrate 3o, and electrodes 31 and 32 placed between the optical waveguides 35 and 35. Here, the substrate 3o and the optical waveguides 35 and 36 may be formed, for example, as follows.

(i) Ti 'i! on LINbO3 board. ``Heat spreads.

(ii) Ion diffusion of Ag+ into the LINbos substrate. In this case, so-called optical damage can be reduced.

(iii) Cu is diffused into the LITa05 substrate.

(1y) PLZT Metal ion exchange is performed on a transparent ceramic substrate.

(V) GaAS, In-P substrate is irradiated with protons.

The optical modulator shown in FIG. 6 is based on the same principle as the one shown in FIG. be. The semiconductor substrate 30 is made by epitaxially growing 1-GaA830P to a thickness of several pm on an n-GaAs substrate 30n, on which ohmic electrodes 31a and 31b are formed, and an ohmic electrode 32t on the entire surface of the n-GaAs substrate 30n side. - It is not formed. In this configuration, the electrode 31a (
When a voltage is applied between 31b) and 32, the depletion layer near the Pn junction expands9, and at the same time, the carrier concentration decreases, causing the refractive index to rise, and depending on the applied voltage! Optical waveguides 35 and 36 are selectively formed under the electrode on the P-GaAS substrate 30P side.

Note that the depletion layer is wide on the n -GaAs side and on the P -GaAs side.
Narrow on the As side. Here, when the voltage applied between the electrodes 3i and 32 is adjusted, the guided light passing through the optical waveguides 35 and 36t undergoes a phase change due to the electro-optic effect of GaAS, so a phase difference occurs between each guided light. , can be optically modulated.

In this example, GaAS f is used as an example, but n
-1np substrate and P-Inp epitaxial layer.

The optical modulators shown in FIGS. 7(A) and 7(=) each have a light receiving element 4 integrated on a substrate 30.

What is shown in (a) is an optical waveguide 3 formed on a substrate 30.
A transparent electrode 41 is provided on the light emitting portion of the 5 (36), and amorphous silicon (a
-S+), CdS or znS is provided,
An electrode layer 43 made of At or the like is formed thereon.

Here, as the transparent electrode 41, In2O3.5n02
It can be formed by a vacuum deposition method, a plasma deposition method, or the like. Further, the a-8t photoelectric layer 42 has a film thickness of about 0.5 to 1.07'm, and has a monosilane (S
iH4), JF4 plasma decomposition, reactive sputtering, CVD method, etc.

In the one shown in (b), the light receiving element 4 is of a PIN type, and an n-as1 layer 42n is formed on the transparent electrode 41 in order.

1-asi layer 42i, P-asi layer 42P'f
: It is formed. Note that the PIN layer is multi-layered (PI
N PIN...) may be used. Also, a-8IC may be used instead of a-8i.

The optical modulators shown in FIGS. 8(a) and 9(b) each have a light receiving element 4 integrated on a semiconductor waveguide.

The one shown in (a) is a substrate 30n such as H-Ga AS.
Form a layer 30P'r of P-GaAs on top,
A semiconductor waveguide is made, an electrode 43 is provided on it, and P
It has a photodiode PDI configuration using an N junction.

In the example shown in (b), a metal material capable of Schottky junction is used as the electrode 43, and a Schottky barrier diode SD that fully utilizes the Schottky junction is constructed.

Note that in the above embodiment, the light is guided to the optical modulator 3 and
The means were not specifically explained, but known methods,
For example, a prism coupler, a grating coupler, etc. are used. Further, the optical modulator 3 may have a structure other than those shown in FIGS. 5 to 8, for example, a structure in which memory means, a microprocessor, etc. are integrated on a substrate constituting the modulator. But that's fine.

[Effects of the present invention]

As described above, according to the present invention, since it does not have mechanical components, it is possible to realize a spectroscopic device that is small in size, can be integrated, and has high reliability. Furthermore, since slits and the like are not required, an apparatus with high S/N and good accuracy can be realized.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing an example of a conventionally known spectroscopic device, FIG. 3 is a diagram for explaining the principle of the device of the present invention, and FIG. 4 is a diagram showing an example of the device according to the present invention. The configuration block diagrams of FIGS. 5 to 8 are configuration diagrams showing other examples of optical modulators that can be used in the apparatus of the present invention. 3... Light modulator 4... Light receiving element 5... Arithmetic control unit 6... Display device (Figure 6) (B) Figure 7 (B) %8 Figure (A) (B) 3z A4

Claims (1)

[Claims] (1) An optical modulator made of an electro-optic material having an electro-optic effect, a light-receiving element that receives the light that has passed through the optical modulator, and a signal from the light-receiving element that is stored and performs predetermined calculations. and an arithmetic control unit that controls a signal applied to the optical modulator, and the spectrometer is configured to determine the spectral distribution of light incident on the optical modulator by Fourier spectroscopy from the wavelength dependence of the degree of modulation of the optical modulator. Device.