JPH1114307A - Optical processing device and optical measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten signal light intensity after wave front correction to which a photorefractive effect is applied to enable high accuracy and high sensitivity measurement without having effect of an object for measurement and measuring environment by receiving outgoing light from a photorefractive element and light amplifying the same while the phase information is still held. SOLUTION: A collimator lens 9 shapes the beam diameter of output light 20 from a laser light source 3 uniform, and a beam splitter 10 separates the output light 20 which has passed through the collimator lens 9 into output light 21 and reference light 23. A beam splitter 6 further separates the output light 21 into output light 22 and reference light 24. A photorefractive element 1 applies the output light 22 to a measured object 4, and receives signal light 25 where scattered light is condensed by a condensing lens 11 and the reference light 24, and wave front corrected signal light is received by a light amplifier 2 through a condensing lens 12. Thus, the spectrum analysis, shape measurement, position measurement or the measurement of displacement for the measured object 4 can be performed with good accuracy even if the surface is rough and the wave front is harassed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the application of photorefractive effect to optical measurement, and more particularly, to an optical processing device using a photorefractive element and an optical measuring device using the optical processing device. .

[0002]

2. Description of the Related Art By irradiating a measuring object with laser light and measuring the reflected light or the scattered light, for example, by interference measurement,
In the spectral analysis of the object, the shape measurement, the position measurement, or the optical measurement for measuring the amount of displacement thereof, if the object surface is a rough surface, the incident laser light becomes weak by scattering, and Since the wavefront is disturbed, optical measurement using the coherence of laser light, such as interference measurement, may not be performed on the scattered light in some cases. Therefore, by applying the generation of phase conjugate light by four-wave mixing or the two-wave mixing, which is an interference phenomenon of light waves caused by the photorefractive effect, light scattered on the surface of the object to be measured is converted into, for example, BSO (paraelectric material). Light is received by a photorefractive element such as Bi ₁₂ SiO ₂₀ ) or ferroelectric LiNbO ₃ , and the wavefront once disturbed is corrected. Also, even if the object surface is not rough, even if the refractive index distribution in the space between the measurement object and the photorefractive element fluctuates randomly due to uneven temperature distribution or the influence of wind, etc. Although the above-described wavefront disturbance occurs, the wavefront is similarly corrected by the photorefractive element.

[0003]

However, in the photorefractive element, although the wavefront is corrected, the problem that the intensity of the output light is weak is caused. Especially,
High-frequency noise that cannot be followed with the minimum response time of the photorefractive element, for example, due to fluctuations in the refractive index distribution in the space between the measurement target and the photorefractive element and vibrations of the measurement target, is generated from the measurement target. In the case where accurate wavefront correction becomes impossible when superimposed on the scattered light of, for example, the response time of the above-mentioned BSO is as slow as milliseconds, and the response time of ferroelectrics is as slow as seconds or more. Therefore, the need to use a more responsive compound semiconductor photorefractive element arises, but the compound semiconductor is excellent in responsiveness, but the electro-optic coefficient is small, and the intensity of the output light is further weakened.
This has been a problem when it is necessary to ensure high-speed response and high output simultaneously. The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical processing device capable of increasing the signal light intensity after performing a wavefront correction applying a photorefractive effect, and to provide a wavefront correction. Another object of the present invention is to provide a high-precision and high-sensitivity optical measurement device which is not affected by the measurement object and the measurement environment, using the optical processing device.

[0004]

A first feature of the present invention to achieve this object is that, as described in claim 1 of the claims, the optical processing apparatus according to the present invention comprises: It is characterized by comprising a photorefractive element and an optical amplifier that receives light emitted from the photorefractive element and directly amplifies the received light while retaining phase information.

According to a second feature of the present invention, in addition to the first feature of the present invention, the photorefractive element is a compound semiconductor having a quantum well structure, as described in claim 2 of the claims. At one point.

A third characteristic configuration is that, as described in claim 3 of the claims, the optical measuring device according to the present invention measures the laser light source and the output light from the laser light source. An optical processing device having the above-described first or second characteristic configuration capable of receiving signal light composed of reflected light or scattered light obtained by irradiating an object;
It comprises a reference light generating means for generating a reference light for light wave mixing, and a light detecting device for detecting an output signal light from the light processing device.

The fourth characteristic configuration is that, as described in claim 4 of the claims, the optical measuring apparatus according to the present invention measures a laser light source and an output light from the laser light source. An optical processing device having the above-mentioned first or second characteristic configuration capable of receiving signal light composed of reflected light or scattered light obtained by irradiating an object;
Pump light generating means for generating a pair of opposed pump lights for light wave mixing, and a light detecting device for detecting an output signal light from the light processing device, wherein the light processing device comprises the photorefractive element The phase conjugate light of the signal light, which is the light emitted from the optical amplifier, is incident on the object to be measured, is reflected or scattered, and then enters the optical amplifier.

The fifth characteristic configuration is that, as described in claim 5 of the claims, the optical measuring device according to the present invention measures the laser light source and the output light from the laser light source. An optical processing device having the above-described first or second characteristic configuration capable of receiving signal light composed of reflected light or scattered light obtained by irradiating an object, and light for detecting output signal light from the optical processing device Comprising a detection device, the light processing device has a self-excitation type phase conjugate mirror consisting of the photorefractive element, the phase conjugate light of the signal light is light emitted from the photorefractive element, the The point is that it is configured to be incident on the optical amplifier after being incident on the measured object and reflected or scattered.

The operation will be described below. According to the first or second characteristic configuration, even if the wavefront is disturbed due to the fact that the surface of the measurement object described above is a rough surface or the fluctuation of space in the incident signal light, phase distortion occurs, the photorefractive The element can perform wavefront correction on the incident signal light, and further, the optical amplifier directly amplifies the weak light emitted from the photorefractive element, the phase distortion of which is compensated, while retaining the phase information. By doing so, the signal information that the incident signal light originally had can be recovered with an appropriate signal intensity. As a result, by using the optical processing device having this characteristic configuration, since the signal light intensity after the wavefront correction was conventionally weak, the interference measurement and the optical measurement were performed even though the wavefront correction was performed by the photorefractive element. What could not be applied to actual optical measurement such as heterodyne detection can be put to practical use.

Here, in order to apply a weak signal light to the above-mentioned optical measurement, it is necessary to directly amplify the signal light as it is. However, without using a photorefractive element, a semiconductor optical amplifier or a fiber optical amplifier is required. Even if it is attempted to directly amplify the weak signal light using these optical amplifiers, since these optical amplifiers assume laser light as input light, the signal light scattered due to the rough surface of the measurement target is Note that this cannot be used as input light.

In the case where the photorefractive element performs wavefront correction on incident signal light, first, mutually coherent signal light and reference light simultaneously form interference fringes in the photorefractive element. Second, four-wave mixing in which pump light and signal light that are coherently opposed to each other simultaneously enter the photorefractive element and emit phase conjugate light of signal light, and third, There is a self-excitation type in which a photorefractive element employs a resonance mechanism and generates phase conjugate light only with signal light without external pump light.

In the case of two-wave mixing, diffracted light is generated by the phase grating formed by the interference fringes, and the diffracted light including the phase information of the signal light has no wavefront disturbance, that is, no phase distortion has occurred. The reference light is superimposed on the output light, and the wavefront of the signal light is substantially corrected. In the case of the four-wave mixing or self-excitation type, the wavefront correction is performed when the phase conjugate light emitted from the photorefractive element travels to a point before the wavefront of the original signal light is disturbed.

According to the second characteristic configuration, since the response time of the photorefractive element can be reduced to the order of microseconds, the wavefront can be corrected even if high-frequency noise of about 100 kHz is superimposed on the signal light. here,
As described above, in the case of the compound semiconductor, although the response is excellent, the electro-optic coefficient is small and the intensity of the output light is weak. Therefore, in an environment where such high-frequency noise is assumed, the first characteristic configuration is used. It should be noted that practical use can be achieved only by adopting.

[0014] According to the third, fourth or fifth characteristic configuration, the optical processing device is provided for the signal light obtained by irradiating the object to be measured with the output light from the laser light source, Wavefront correction can be performed by generation of phase conjugate light by two-wave mixing and four-wave mixing, or generation of phase conjugate light by self-excitation, respectively. The measurement information of the object to be measured included in the signal light can be efficiently extracted. As a result, in applying the photorefractive effect to various optical measurements, it is possible to greatly reduce the constraints on the use environment and greatly expand the practical range.

[0015]

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

FIG. 1 is a schematic configuration diagram of an interference measuring device which is an embodiment of an optical measuring device using the optical processing device according to the present invention. As shown in FIG. 1, an interference measuring apparatus according to the present embodiment includes a laser light source 3, a first collimating lens 9 for shaping a beam diameter of output light 20 from the laser light source 3 to a constant value, and the first collimating lens. 9, a first beam splitter 10 for splitting the output light 20 into two systems of an output light 21 and a first reference light 23, and further dividing the output light 21 into two systems of an output light 22 and a second reference light 24. A second beam splitter 6 that divides the light into an object to be measured 4 and scatters the light scattered on the surface of the object to be measured 4 with a condenser lens 1
The photorefractive element 1 receiving the signal light 25 and the second reference light 24 condensed at 1 and the signal light having been subjected to wavefront correction, which is the light 26 emitted from the photorefractive element 1, is transmitted through the second condensate 12. Optical amplifier 2 for receiving light at the same time, second collimating lens 13, first fixed mirror 14, second fixed mirror 15, third beam splitter 16, light receiving element 1
Photodetector 7 comprising Michelson interferometer
It is comprised including. The optical processing device 5 according to the present invention includes the photorefractive element 1 and the optical amplifier 2.

The photorefractive element 1 is composed of Ga
An As compound semiconductor or an AlGaAs / GaAs quantum well structure compound semiconductor is used. Further, the second beam splitter 6 functions as reference light generating means for generating reference light for two-wave mixing. In the compound semiconductor crystal of the photorefractive element 1,
A strong electric field of about 10 kV / cm is formed by application of an external voltage, and the signal light 25 and the second reference light 24 form a phase grating in real time with a predetermined response time delay in the compound semiconductor crystal. Is expressed. With the appearance of this photorefractive effect,
As described above, the wavefront correction is performed on the incident signal light.

As the optical amplifier 2, for example, an optical fiber amplifier such as an erbium-doped optical fiber amplifier (EDFA) or a semiconductor optical amplifier is used. The oscillation wavelength of the laser light source 3 is firstly determined in a range of 0.8 μm to 1.5 μm in accordance with the sensitivity range of the photorefractive element 1. Is determined in consideration of For example, ED
In FA, the energy difference between specific levels of erbium ion energy levels is equal to 0.5 μm, 0.6 μm,
When optical signals of 0.8 μm, 0.98 μm and 1.48 μm enter, the optical signals are amplified by stimulated emission.
Therefore, in the present embodiment, the laser light source 3 has an oscillation wavelength of 0.8 μm, 0.98 μm, and 1.48 μm.

The photodetector 7 outputs the output signal light 27 optically amplified by the optical amplifier 2 to the third beam splitter 16 via the second collimating lens 13 and the first fixed mirror 14, Further, the first reference light 23 is configured to directly enter the third beam splitter 16.

As described above, the interference measurement apparatus having the configuration of the present embodiment performs spectrum analysis, shape measurement, position measurement, or measurement of the amount of variation of the object 4 to be measured, for example. Even if the surface is rough and the incident output light 22 is weakened by scattering and the wavefront is disturbed, or the refractive index distribution of the space between the measured object 4 and the photorefractive element 1 is not good. Even if a phase distortion of the signal light occurs due to a random fluctuation due to a uniform temperature distribution, the influence of wind, or the like, the signal light can be accurately detected. Also, 100 kHz caused by fluctuation of the refractive index distribution in the space between the measured object 4 and the photorefractive element 1 and vibration of the measured object 4.
Even if high-frequency noise of a degree or less is superimposed on the signal light, the wavefront can be corrected with high accuracy, and the light intensity of the wavefront-corrected signal light is ensured by the optical amplifier 2. It can be sufficiently detected and can perform its intended function.

Hereinafter, another embodiment will be described. <1> In the above embodiment, the photorefractive element 1 performs wavefront correction of signal light using two-wave mixing, but may perform wavefront correction using generation of phase conjugate light by four-wave mixing. I do not care. In this case, as shown in FIG. 2, a pair of opposed pump lights 28 for four-wave mixing is used instead of the reference light generating means for generating the two-wave mixing reference light.
Is provided. In the present embodiment, the second beam splitter 6 is used as it is as the pump light generating means 8 for generating one of the pump lights 28. Further, after one of the pump lights 28 generated by splitting by the second beam splitter 6 passes through the photorefractive element 1, the fixed mirror 18
And the other of the pump light 28 is generated. The fixed mirror 18 functions as a part of the pump light generation unit 8. The optical amplifier 2 is arranged as shown in FIG. That is, the photorefractive element 1
After the phase conjugate light 29 emitted in the opposite direction to the incident direction of the signal light 25 from the object 4 is re-irradiated and reflected or scattered on the object 4 to be measured, the wavefront of the signal light 25 is reversed in the time course of the time. The phase conjugate light 30 that has been corrected and wavefront corrected is arranged to be able to receive light.

<2> In the embodiment shown in FIG. 2, instead of providing the pump light generating means 8, the photorefractive element 1 may be used by itself or in combination with a fixed mirror to determine the incident direction of the signal light 25 In a preferred embodiment, the device is configured to function as a self-excitation type phase conjugate mirror that emits the phase conjugate light 29 in the opposite direction.

<3> Photorefractive element 1
Is not necessarily a GaAs compound semiconductor or AlG
It does not have to be an aAs / GaAs quantum well structure compound semiconductor. For example, in the case of a quantum well structure compound semiconductor, an AlGaInP / GaInP system, InGaAsP /
An InGaAs-based or InGaAsP / InP-based compound semiconductor may be used. In this case, the oscillation wavelength of the laser light source 3 is 0.5 μm to 0.8 μm and 1.4 μm to 1.9, respectively, in accordance with the sensitivity range of each compound semiconductor.
μm, 1.4 μm to 1.7 μm. Furthermore,
If the use environment related to high-frequency noise is favorable, for example,
It may be configured using BSO. in this case,
The oscillation wavelength of the laser light source 3 needs to be determined according to the sensitivity range of BSO, and is in the range of 0.4 μm to 0.7 μm.

<4> In each of the above embodiments, a Michelson interferometer was used as the photodetector 7, but another photodetector may be used.

[0025]

As described above, according to the present invention,
It becomes possible to increase the signal light intensity after performing the wavefront correction applying the photorefractive effect by the optical processing device according to the present invention, and achieve both high-speed response and high output of the wavefront correction, and furthermore, It has become possible to provide a highly accurate and highly sensitive optical measurement device that uses an optical processing device and is not affected by a measurement object or a measurement environment.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the accompanying drawings.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an optical measurement device using an optical processing device according to the present invention.

FIG. 2 is a schematic configuration diagram of another embodiment of an optical measurement device using the optical processing device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photorefractive element 2 optical amplifier 3 laser light source 4 object to be measured 5 light processing device 6 reference light generating means 7 photodetector 8 pump light generating means 20, 21, 22 output light 23 first reference light 24 second reference light 25 Signal light 26 Outgoing light 27 Output signal light 28 Pump light 29, 30 Phase conjugate light

Claims (5)

[Claims] 1. A photorefractive element (1) and light (2) emitted from the photorefractive element (1).
An optical processing device comprising: an optical amplifier (2) for receiving the light of (6) and directly amplifying the received light while retaining the phase information. 2. The optical processing apparatus according to claim 1, wherein the photorefractive element is a compound semiconductor having a quantum well structure. 3. A laser light source (3) and a signal light (2) comprising reflected light or scattered light obtained by irradiating an output light (22) from the laser light source (3) onto an object to be measured (4).
3. An optical processing device (5) according to claim 1 or 2, which is capable of receiving said light processing device, and a reference light generating means (6) for generating a reference light for two-wave mixing that can be incident on said optical processing device (5). And an optical detection device (7) for detecting an output signal light (27) from the optical processing device (5). 4. A laser light source (3) and a signal light (2) comprising reflected light or scattered light obtained by irradiating an output light (22) from the laser light source (3) onto an object to be measured (4).
3. An optical processing device (5) according to claim 1 or 2, which is capable of receiving light from the light source, and a pump light generating means for generating a pair of opposed pump lights for four-wave mixing that can be incident on the optical processing device (5). (8), and a photodetector (7) for detecting an output signal light (27) from the optical processing device (5), wherein the optical processing device (5) includes the photorefractive element (1). )) Is the signal light (2)
An optical measurement device configured to cause the phase conjugate light (29) of (5) to enter the optical amplifier (2) after being incident on the measured object (4) and reflected or scattered. 5. A laser light source (3) and a signal light (2) composed of reflected light or scattered light obtained by irradiating an output light (22) from the laser light source (3) onto an object to be measured (4).
The optical processing device (5) according to claim 1 or 2, which is capable of receiving light from the optical processing device (5), and an output signal light (2) from the optical processing device (5).
And a photodetector (7) for detecting the photorefractive element (7), wherein the optical processing device (5) has a self-excited phase conjugate mirror comprising the photorefractive element (1), and The phase conjugate light (29) of the signal light (25), which is the outgoing light (26) from 1), is incident on the object to be measured (4) and is reflected or scattered before being incident on the optical amplifier (2). Optical measuring device configured to: