WO2022018850A1

WO2022018850A1 - Laser device

Info

Publication number: WO2022018850A1
Application number: PCT/JP2020/028413
Authority: WO
Inventors: 彰裕藤江; 貴敬鈴木; 裕太竹本; 智浩秋山; 俊行安藤
Original assignee: 三菱電機株式会社
Priority date: 2020-07-22
Filing date: 2020-07-22
Publication date: 2022-01-27
Also published as: JPWO2022018850A1; JP7143553B2

Abstract

This laser device is provided with a sub-array creation unit which turns multiple signal lights obtained from a single laser into a sub-array, a spatial distribution unit (7) which converts locally emitted light obtained from the laser beam into a form in which the light is arranged in positions other than the optical axis center, and a wave combining unit which generates an interference signal light by combining signal light that has been turned into sub-arrays by the sub-array creation unit and locally emitted light after conversion by the spatial distribution unit (7), and which emits said interference signal light into space.

Description

Laser device

The present disclosure relates to a laser device that emits signal light into space.

Conventionally, there is known a laser device that emits a signal light, which is a high-output laser beam, into space by using a coherent beam combining (CBC) technique (see, for example, Patent Document 1). The CBC technique is a technique in which a single laser beam is divided into a plurality of laser beams, the laser beams are amplified, and then coherently coupled.

Japanese Unexamined Patent Publication No. 2000-323774

On the other hand, in a conventional laser device, when transmitting signal light to a distant communication station or target, a telescope optical system for condensing the signal light to a distant place is required.

Examples of this telescope optical system include a casegren reflection optical system that is resistant to changes in the surrounding environment such as vibration. The casegren catadioptric system has a secondary mirror that expands the beam diameter of the incident laser light and a primary mirror that emits the laser light after enlargement by the secondary mirror into space.

However, when the conventional laser device is used in combination with the Kasegren catadioptric system, the central part of the laser beam is removed by using an annular mirror in order to avoid heat generation due to the high output return light from the secondary mirror. It is necessary to make it incident on the secondary mirror. Therefore, when the conventional laser device is used in combination with the casegren reflection optical system, the utilization efficiency of the laser light is lowered by the amount that the central portion of the laser light is removed.

The present disclosure has been made to solve the above-mentioned problems, and provides a laser apparatus capable of improving the utilization efficiency of laser light with respect to the conventional configuration even when used in combination with a Cassegrain reflective optical system. The purpose is to do.

In the laser apparatus according to the present disclosure, a sub-array unit that sub-arrays a plurality of signal lights obtained from a single laser beam and local emission obtained from the laser beam are arranged at positions other than the center of the optical axis. Interference signal light is generated by combining the space distribution unit that converts the shape into the shape, the signal light after sub-array formation by the sub-arraying unit, and the station emission after conversion by the space distribution unit, and the interference signal light is used in space. It is characterized by having a combined wave portion that emits light to the light.

According to the present disclosure, since the configuration is as described above, it is possible to improve the utilization efficiency of the laser beam as compared with the conventional configuration even when used in combination with the Cassegrain reflection optical system.

It is a figure which shows the structural example of the laser apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the structural example of the element circuit in Embodiment 1. FIG. It is a figure which shows the structural example of the collimator array in Embodiment 1. FIG. It is an image diagram which shows the beam arrangement example of the signal light used in the laser apparatus which concerns on Embodiment 1 and the interference signal light by a local emission. It is a figure which shows the structural example of the laser apparatus which concerns on Embodiment 2. It is an image diagram which shows the beam arrangement example of the signal light used in the laser apparatus which concerns on Embodiment 2 and the interference signal light by a local emission. It is a figure which shows the structural example of the laser apparatus which concerns on Embodiment 3. FIG. It is a figure which shows the driving example of the conical prism in Embodiment 3. FIG.

Hereinafter, embodiments will be described in detail with reference to the drawings.
Embodiment 1.
FIG. 1 is a diagram showing a configuration example of the laser device according to the first embodiment.
As shown in FIG. 1, the laser apparatus includes a reference light source 1, an optical distributor 2, a collimator lens 3, K circuit arrays 4 _k , a signal processing unit 5, a control signal generation unit 6, a space distribution unit 7, and an introduction coupling. The unit 8 and the casegren reflection optical system 9 are provided. Here, k = 1 to K, and in the first embodiment, K = 2.

The reference light source 1 outputs a single frequency laser beam. As the reference light source 1, for example, a narrow line width laser light source that oscillates in a single mode can be used.

The light distributor 2 distributes the laser light output by the reference light source 1 into a single station emission and K × N signal lights. N is a natural number of 2 or more.

The reference light source 1 and the optical distributor 2 are connected via an optical path such as an optical fiber.

The collimator lens 3 is an optical lens that collimates the local light emitted by the light distributor 2.

The circuit array _4k is an optical phased array in which N signal lights of the signal lights obtained by the optical distributor 2 are subjected to variable phase modulation (variable phase control). As shown in FIG. 1, the circuit array 4 _k _{is composed of N element circuits 41 kn} arranged in parallel. Here, n = 1 to N.

As shown in FIG. 2, the element circuit 41 _kn includes an optical phase modulator (optical phase controller) 411 _kn , an optical amplifier 412 _kn , an optical circulator 413 _kn , a photoelectric converter (photodetector) 414 _kn, and a phase-locked loop. It has _{415 kn.} Further, as shown in FIG. 2, the phase-locked loop 415 _kn _{includes a reference signal source 416 kn} , a variable phase shifter 417 _kn , a phase comparator 418 _kn , a loop filter 419 _kn, and a signal generator 420 _kn . ..

The optical phase modulator 411 _kn is a variable phase controller that modulates the phase of the signal light obtained by the optical distributor 2. The modulation amount in the optical phase modulator 411 _kn is a modulation amount according to the optical phase control signal generated by the signal generator 420 _kn of the phase-locked loop 415 _kn. As the optical phase modulator 411 _kn , for example, an LN (LiNbO ₃ ) phase modulator or a semiconductor optical modulator can be used.

The optical amplifier 412 _kn amplifies the signal light after phase modulation by the optical phase modulator 411 _kn.

The optical circulator 413 _kn outputs the signal light after amplification by the optical amplifier 412 _{kn to the introduction coupling unit 8.} Further, the optical circulator 413 _kn outputs the light reflected by the introduction coupling portion 8 to the photoelectric converter 414 _kn.

The photoelectric converter 414 _kn converts the light output by the optical circulator 413 _kn into an electric signal. As the photoelectric converter 414 _kn , for example, a photodiode can be used.

The reference signal source 416 _kn outputs an electric signal (reference signal) having a reference frequency in the high frequency band.

The variable phase shifter 417 _kn shifts the phase of the electric signal output by the reference signal source 416 _kn. The phase shift amount in the variable phase shifter 417 _kn is a phase shift amount according to the external control signal A41 _kn generated by the control signal generation unit 6.

The phase comparator 418 _kn is a phase error signal having a current or voltage according to the phase error between the electric signal obtained by the photoelectric converter 414 _kn and the electric signal after the phase shift by the variable phase shifter 417 _kn. Generate.

The loop filter 419 _kn filters the phase error signal generated by the phase comparator 418 _{kn to generate a control voltage.}

The signal generator 420 _kn generates an optical phase control signal having an oscillation frequency corresponding to the control voltage generated by the loop filter 419 _kn.

The configuration of the phase-locked loop 415 _kn shown in FIG. 2 is an example, and is not limited thereto.

In FIG. 1, the number of element circuits 41 _{1n included in} _{the circuit array 4 1} and the number of element circuits _{4 12} _{2n included in} the circuit array 4 2 are the same. However, the number of element circuits 41 _kn in each circuit array 4 _k may be different.

The optical distributor 2 and the circuit array _4k are connected via an optical path such as an optical fiber.

The signal processing unit 5, FFP in the laser device (Far Field Pattern), or based on the wavefront shape of the output light at desired Cassegrain reflective optical system 9, to calculate the phase shift amount in the circuit array _{4 k.}

The control signal generation unit 6 generates an external control signal A41 _kn for the variable phase shifter 417 _kn _{of the circuit array 4 k} based on the calculation result by the signal processing unit 5.

The space distribution unit 7 converts the locally emitted light (colimated light) that has been collimated by the collimator lens 3 into a shape in which the light is arranged at a position other than the center of the optical axis. The space distribution unit 7 shown in FIG. 1 is composed of a conical prism 71 and a conical prism 72.

The conical prism 71 is a prism in which one surface in the axial direction is formed in a conical shape and the other surface is formed in a planar shape. In the conical prism 71, the other surface faces the exit surface of the collimator lens 3, and the local emission that has been collimated by the collimator lens 3 is refracted and spatially distributed.

The conical prism 72 is a prism in which one surface in the axial direction is formed in a conical shape and the other surface is formed in a planar shape. The conical prism 72 has one surface facing the one surface of the conical prism 71, and converts the local emission after space distribution by the conical prism 71 into an annular local emission. The conical prism 72 may be a lens such as a conical lens, a spherical lens, or an achromat lens.

In the above, the case where the space distribution unit 7 composed of the conical prism 71 and the conical prism 72 converts the local emission into an annular shape is shown. However, not limited to this, the space distribution unit 7 may use a prism or a lens to convert the local emission into an annular shape other than the annular shape, for example, an angular ring shape.

The introduction coupling unit 8 _{sub-arrays N signal lights after variable phase modulation by the circuit array 4 k} into K sets, and combines the signal light after the sub-array and the station emission obtained by the space distribution unit 7. And exit into space. As shown in FIG. 1, the introduction coupling portion 8 is composed of a reflector 81 _k , a collimator array 82 _k , and a beam combiner 83 _k .

The reflector 81 _k reflects the local emission after conversion by the space distribution unit 7. The reflector 81 _k may be a right-angle prism.

As shown in FIG. 3, the collimator array 82 _k _{has N partial reflectors 821 kn} and N optical collimators 822 _kn .

The partial reflector 821 _kn reflects a part of the signal light after the variable phase modulation by the circuit array 4 _{k and passes the rest.} The above reflection may be realized by utilizing the Fresnel reflection generated at the partial reflection optical system or the fiber end instead of the partial reflector 821 _kn. Further, the partial reflector 821 _kn passes the local emission that has passed through the beam combiner 83 _k.
Further, in the above, the case where a part of the signal light after the variable phase modulation is reflected is shown, but the present invention is not limited to this, and a part of the signal light may be refracted.

The optical collimator 822 _kn collimates the signal light that has passed through the partial reflector 821 _kn.

The beam combiner 83 _k combines the signal light collimated by the collimator array 82 _k _{and the local emission reflected by the reflector 81 k} and emits them to the casegren reflection optical system 9 side. Further, the beam combiner 83 _k passes a part of the local light emitted by the reflector 81 _{k and} _{emits light to the partial reflector 821 kn} .

As shown in FIG. 4, these reflectors 81 _k , collimator array 82 _k, and beam combiner 83 _k are arranged in an annular shape in accordance with the shape of the axicon optical system 91, avoiding the central portion of the axicon optical system 91. Will be done. In FIG. 4, reference numeral 401 indicates an interference signal light generated by the combined wave of the signal light and the local emission.

The introduction coupling unit 8 is a "sub-arraying unit that sub-arrays a plurality of signal lights obtained from a single laser beam" and a "signal light after sub-arraying by the sub-arraying unit and after conversion by the space distribution unit". It corresponds to a "combined part" that generates interference signal light by combining local light emission and emits the interference signal light into space.

The Cassegrain reflective optical system 9 expands or contracts the beam diameter of the light after the combined wave by the introduction coupling portion 8. As shown in FIG. 1, the casegren reflection optical system 9 is composed of an axicon optical system 91 as a secondary mirror and an axicon optical system 92 as a primary mirror.

The axicon optical system 91 is configured in a convex substantially disk shape and has a reflecting surface 911. The reflective surface 911 enlarges the beam diameter (inner diameter and outer diameter) of the incident light. The reflective surface 911 is configured to project in a curved surface so that the apex of the curved surface is located at the center of the axicon optical system 91. The axicon optical system 91 is arranged so that the reflecting surface 911 faces the introduction coupling portion 8.

The axicon optical system 92 is configured in a concave substantially disk shape, and has a reflecting surface 921 and holes 922. The reflecting surface 921 emits the light expanded by the Axicon optical system 91 into space. The reflective surface 921 is configured to be recessed in a curved surface shape so that the apex of the curved surface is located at the center of the axicon optical system 92. The diameter of the reflective surface 921 is larger than the diameter of the reflective surface 911. The hole 922 is a through hole formed with the apex of the reflecting surface 921 as the axis. In the axicon optical system 92, the axis of the hole 922 is arranged so as to be along the optical axis of the light from the introduction coupling portion 8. Further, in the Axicon optical system 92, the reflecting surface 921 faces the reflecting surface 911, and the axis of the reflecting surface 921 coincides with the axis of the reflecting surface 911.

Note that FIG. 1 shows a case where the laser device is provided with the Cassegrain reflective optical system 9. However, the present invention is not limited to this, and the Cassegrain reflection optical system 9 may be provided outside the laser apparatus.
Further, FIG. 1 shows a case where the laser apparatus includes a reference light source 1, an optical distributor 2, a collimator lens 3, K circuit arrays 4 _k , a signal processing unit 5, and a control signal generation unit 6. However, the present invention is not limited to this, and the reference light source 1, the optical distributor 2, the collimator lens 3, the K circuit array 4 _k , the signal processing unit 5, and the control signal generation unit 6 may be provided outside the laser device. good.

The laser apparatus according to the first embodiment has a space distribution unit 7, an introduction coupling unit 8, and a Cassegrain reflection optical system 9 added to the conventional configuration.
Then, the laser apparatus according to the first embodiment converts a single local emission into a shape in which the light is arranged at a position other than the center of the optical axis in the space distribution unit 7, and the Cassegrain in the introduction coupling unit 8. A plurality of sub-arrayed signal lights are introduced from the side surface of the reflected optical system 9 and coherently synthesized.
As a result, the laser apparatus according to the first embodiment can arrange the beam without being kicked by the Axicon optical system 92, which is the primary mirror of the Cassegrain reflective optical system 9.

The laser device according to the first embodiment has the following effects as compared with the conventional configuration.

First, in the conventional configuration, in order to avoid the reflected return light from the secondary mirror constituting the Axicon optical system, it is necessary to remove the central part of the laser beam by the annular mirror, and the utilization efficiency of the laser beam is lowered. On the other hand, in the laser apparatus according to the first embodiment, the Cassegrain reflection optical system combines the local emission converted into a shape in which the light is arranged at a position other than the center of the optical axis and the signal light after a plurality of sub-arrays. It is incident on 9. As a result, this laser device can generate a beam without removing the central portion of the laser beam, and can improve the utilization efficiency of the laser beam.

Further, in the conventional configuration, when a plurality of sub-arrays of signal light are coherently coupled, the beam diameter of the local emission is expanded to maintain uniform amplitude and phase in order to cover the entire beam range of each signal light. It was necessary to generate local emission or to increase the size of the beam splitter. In this case, in the conventional configuration, as the number of subarrays increases, phase noise occurs due to wavefront distortion or optical alignment error. On the other hand, the laser device according to the first embodiment converts the local light emission into a shape in which the light is arranged at a position other than the center of the optical axis. As a result, this laser device can reduce the beam diameter of the local emission coupled with the signal light, so that phase noise can be suppressed and the number of subarrays can be increased.

As described above, according to the first embodiment, the laser apparatus has a sub-array unit that sub-arrays a plurality of signal lights obtained from a single laser light, and a local emission obtained from the laser light. Interference by combining the space distribution unit 7 that converts the light into a shape in which the light is arranged at a position other than the center of the optical axis, the signal light after the sub-array formation by the sub-arraying unit, and the station emission after the conversion by the space distribution unit 7. It is provided with a wave junction that generates signal light and emits the interference signal light into space. As a result, even when the laser device according to the first embodiment is used in combination with the Cassegrain reflective optical system 9, the output scalability can be ensured and the utilization efficiency of the output light can be improved as compared with the conventional configuration.

Embodiment 2.
In the laser apparatus according to the first embodiment, the case where the number of sub-arrays of the signal light is 2 (K = 2) is shown, but the present invention is not limited to this. In the laser apparatus according to the second embodiment, the configuration in which the number of sub-arrays (K) of the signal light is expanded to a natural number of 2 or more to improve the emission intensity of the output light is shown.

FIG. 5 is a diagram showing a configuration example of the laser device according to the second embodiment. The configuration example of the laser apparatus according to the second embodiment shown in FIG. 5 is the same as the configuration example of the laser apparatus according to the first embodiment shown in FIG. 1 except that the number of subarrays of the signal light is different.

In the laser apparatus according to the second embodiment, the circuit array 4 _k , the reflector 81 _k , the collimator array 82 _k, and the beam combiner 83 _k are arranged for the number of sub-arrays of signal light. Further, as shown in FIG. 6, the reflector 81 _k , the collimator array 82 _k, and the beam combiner 83 _k are arranged in an annular shape in accordance with the shape of the axicon optical system 91, avoiding the central portion of the axicon optical system 91. Ru. In FIG. 6, reference numeral 601 indicates the interference signal light generated by the combined wave of the signal light and the local emission.

The laser apparatus according to the second embodiment has the following effects as compared with the laser apparatus according to the conventional configuration and the first embodiment.

First, in the conventional configuration, since the signal light and the local emission are combined using a beam splitter, the number of signal light subarrays that can be added is limited to 2. On the other hand, in the laser apparatus according to the second embodiment, the number of sub-arrays of the signal light is 2 or more, and the laser light can be arranged and synthesized without a gap, so that the laser light can be increased in output. Further, since this laser device can generate a beam without removing the central portion of the laser beam, it is possible to realize an optical phased array with high synthesis efficiency.

Further, in the laser apparatus according to the second embodiment, the signal light and the combined light of the station emission can be arbitrarily arranged with two or more sub-arrays. Further, this laser device can apply an arbitrary external control signal A41 _kn to the variable phase shifter 417 _{kn of} _{each element circuit 41 kn.} Therefore, this laser device is conventionally configured or implemented by appropriately designing the _{number of arrangements of the reflector 81 k} , the collimator array 82 _k and the beam combiner 83 _k , or the external control signal A41 _kn for the variable phase shifter 417 _kn. Compared with the laser apparatus according to the first embodiment, it is possible to generate output light having various phase distributions.

Embodiment 3.
In the third embodiment, a drive mechanism by external control is added to the conical prism 72 included in the space distribution unit 7, and a variable function of the beam diameter of the light emitted from the Cassegrain reflection optical system 9 is added.
FIG. 7 is a diagram showing a configuration example of the laser device according to the third embodiment. In the laser apparatus according to the third embodiment shown in FIG. 7, a signal processing unit 10 and a drive control unit 11 are added to the laser apparatus according to the second embodiment shown in FIG. Other configurations are the same as those of the laser apparatus according to the second embodiment, and the same reference numerals are given and only different parts will be described.

The signal processing unit 10 calculates the driving amount of the conical prism 72 according to the desired beam diameter.

The drive control unit 11 drives the conical prism 72 in the optical axis direction with the drive amount calculated by the signal processing unit 10.

FIG. 8 is a diagram showing an arrangement example of the conical prism 71 and the conical prism 72.
When the distance between the conical prism 71 and the conical prism 72 changes, the beam diameter of the local emission changes. Therefore, the laser device according to the second embodiment can change the beam diameter of the light emitted from the Cassegrain reflection optical system 9 by driving the conical prism 72 in the optical axis direction. In FIG. 8, reference numeral 801 indicates the driving direction of the conical prism 72, and reference numeral 802 indicates the beam diameter of the local emission after conversion by the space distribution unit 7.

Note that FIGS. 7 and 8 show a case where the drive control unit 11 drives the conical prism 72. However, the present invention is not limited to this, and the drive control unit 11 may drive the conical prism 71 instead of the conical prism 72, or may drive both the conical prism 71 and the conical prism 72.

Further, FIGS. 7 and 8 show a case where the space distribution unit 7 is composed of a conical prism 71 and a conical prism 72. However, even when the space distribution unit 7 is composed of other prisms or lenses, control by the signal processing unit 10 and the drive control unit 11 can be added as described above.

Further, the signal processing unit 10 and the drive control unit 11 correspond to "an adjustment unit that changes the beam diameter of the station emission after conversion by the space distribution unit by driving at least one of the optical elements in the axial direction". do.

The laser apparatus according to the third embodiment has a large axicon optical system 91 and an axicon optical system 92 constituting the casegren reflection optical system 9 as compared with the conventional configuration, the laser apparatus according to the first embodiment and the second embodiment. The beam diameter of the light emitted from the casegren reflection optical system 9 can be changed without driving.

It should be noted that it is possible to freely combine each embodiment, modify any component of each embodiment, or omit any component in each embodiment.

Even when the laser device according to the present disclosure is used in combination with the casegren reflection optical system, it is possible to improve the utilization efficiency of the laser light as compared with the conventional configuration, and the laser device is used for a laser device or the like that emits signal light into space. Suitable for.

1 reference light source, 2 optical distributor, 3 collimeter lens, 4 _k circuit array, 5 signal processing unit, 6 control signal generation unit, 7 spatial distribution unit, 8 introduction coupling unit, 9 casegren reflection optics, 10 signal processing unit, 11 drive control unit, 41 _kn element circuit, 71 conical prism, 72 conical prism, 81 _k reflector, 82 _k collimeter array, 83 _k beam combiner, 91 axicon optics, 92 axicon optics, 411 _kn optical phase modulator, 412 _kn optical amplifier, 413 _kn optical circulator, 414 _kn photoelectric converter, 415 _kn phase synchronization circuit, 416 _kn reference signal source, 417 _kn variable phase shifter, 418 _kn phase comparator, 419 _kn loop filter, 420 _kn signal generation. Instrument, 821 _kn partial reflector, 822 _kn optical collimeter.

Claims

A sub-array unit that sub-arrays multiple signal lights obtained from a single laser beam,
A spatial distribution unit that converts the local light emitted from the laser beam into a shape in which the light is arranged at a position other than the center of the optical axis.
It is provided with a wave-setting unit that generates interference signal light by combining the signal light after sub-arraying by the sub-arraying unit and the station emission after conversion by the space distribution unit, and emits the interference signal light to space. Laser device.
An optical phase controller that performs variable phase control on a plurality of signal lights obtained from the laser beam according to the optical phase control signal.
The signal light after variable phase control by the optical phase controller is partially reflected or refracted, and is generated by the combined wave of the signal light partially reflected or refracted and the local emission obtained from the laser light. Interference signal An optical detector that converts light into an electrical signal,
A phase-locked loop that generates the optical phase control signal based on the phase error between the electrical signal and the reference signal obtained by the photodetector is provided.
The laser device according to claim 1, wherein the sub-array unit collimates the signal light after variable phase control by the optical phase controller and sub-arrays the signal light after the collimation.
The laser device according to claim 1, wherein the space distribution unit is configured by using a plurality of optical elements including a prism or a lens.
The laser device according to claim 1, wherein the space distribution unit uses a plurality of optical elements including a conical prism or a conical lens to convert local emission obtained from the laser light into an annular shape.
The laser apparatus according to claim 4, further comprising an adjusting unit for changing the beam diameter of the station emission after conversion by the space distribution unit by driving at least one of the optical elements in the axial direction. ..
The laser apparatus according to any one of claims 1 to 5, further comprising a Cassegrain reflective optical system for expanding or reducing the beam diameter of the interference signal light emitted by the combiner.