Phase-locked laser device

Abstract

The phase synchronization laser device of the present application has: an optical circulator (2) that receives laser light and supplies it to a transmission optical path and outputs return light received from a return optical path; a light splitter (3) that branches laser light received from the optical circulator via the transmission optical path into reference light and signal light; an element circuit (4) that each has a phase compensator that outputs signal light that has been phase controlled with respect to the branched signal light; an optical partial reflector (5) that is incident with reference light or phase-controlled signal light as incident light, reflects a portion of the incident light as reflected light, and transmits the remaining portion of the incident light; and an optical-electricity converter (6) that receives return light and performs optical-electricity conversion, the return light being laser light that has been combined by the light splitter with respect to the reflected light, each of the element circuits frequency-converts the output of the optical-electricity converter (6) to detect a phase error of an electrical signal having a frequency component corresponding to each of the element circuits, and each of the phase compensators compensates for the detected phase error.

Description

Technical Field

[0001] This disclosure relates to phase-synchronized laser devices. Background Technology

[0002] As a method for realizing high-output laser systems, a technique known as coherent beam combining (CBC) is widely known. Coherent beam combining is a technique that uses a single laser as a seed light for optical amplification, branches the laser into multiple lasers (signal lights), amplifies each of the branched lasers, and then combines the amplified lasers (for example, see Patent Document 1). Figure 1 The high-output laser device using CBC outputs a single beam with high output and high brightness by synchronizing the phase of each optical path and combining multiple beams.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2000-323774

[0004] According to the high-output laser system described in Patent Document 1, there is a problem that as the number of signal beams increases, a larger optical component is needed to combine the local oscillator beam and multiple signal beams. Summary of the Invention

[0005] This disclosure was made to solve such a problem, and its purpose is to provide a phase-synchronized laser device that can be miniaturized even with an increase in the number of signals.

[0006] The phase-synchronized laser device according to the embodiments of this disclosure includes: an optical circulator that receives laser light emitted from a reference light source at a first port and supplies it to a transport optical path, and outputs return light received from a return optical path at a second port; a beam splitter that branches the laser light received from the optical circulator via the transport optical path into a reference light and a plurality of signal lights; a plurality of element circuits, each element circuit having a phase compensator that performs phase control on the plurality of signal lights branched from the beam splitter and outputs a plurality of phase-controlled signal lights; a plurality of optical partial reflectors that reflect a portion of the incident light as reflected light when the reference light or the plurality of phase-controlled signal lights are incident light, and allow the remaining portion of the incident light to pass through; and a photoelectric converter that receives the return light and performs photoelectric conversion, outputting a photoelectric converted electrical signal, wherein the return light is laser light obtained by combining the plurality of reflected lights using the beam splitter, each element circuit performs frequency conversion on the electrical signal output by the photoelectric converter to detect the phase error of the electrical signal having a frequency component corresponding to each element circuit, and each phase compensator compensates for the detected phase error.

[0007] The phase-synchronized laser device according to the embodiments of this disclosure can be miniaturized compared to conventional devices, even with an increase in the number of signals. Attached Figure Description

[0008] Figure 1 This is a diagram illustrating an example of the configuration of the phase-synchronized laser device according to Embodiment 1.

[0009] Figure 2 This is a diagram illustrating an example of the configuration of the element circuitry of the phase-synchronized laser device according to Embodiment 1.

[0010] Figure 3A This is a schematic diagram of the spectrum of the received signal received by the photodiode. Figure 3B This is a schematic diagram of the spectrum of the received signal after being divided by a 1 / 2 frequency divider. Figure 3C This is a schematic diagram of the spectrum of the received signal after band limiting by a band limiting filter.

[0011] Figure 4 This is a diagram illustrating an example of the configuration of the element circuitry of the phase-synchronized laser device according to Embodiment 2.

[0012] Figure 5 This is a diagram illustrating an example configuration of the phase-synchronized laser device according to Embodiment 3.

[0013] Figure 6 This is a diagram illustrating an example of the configuration of the element circuitry of the phase-synchronized laser device according to Embodiment 3.

[0014] Figure 7 This is a diagram showing an example of the output beam pattern when the number of subarrays is 3.

[0015] Figure 8 This is a diagram illustrating an example configuration of the phase-synchronized laser device according to Embodiment 4.

[0016] Figure 9 This is a diagram illustrating an example of the configuration of the element circuitry for the local oscillator light of the phase-synchronized laser device according to Embodiment 4.

[0017] Figure 10 This is a diagram illustrating an example of the configuration of the element circuitry for the signal light of the phase-synchronized laser device according to Embodiment 4.

[0018] Figure 11A This is a schematic diagram of the spectrum of the received signal from the local oscillator. Figure 11B This is a schematic diagram of the spectrum of the received signal after being divided by a 1 / 2 frequency divider. Figure 11C This is a schematic diagram of the optical signal spectrum of subarray ♯1. Figure 11D This is a schematic diagram of the spectrum of the received signal of subarray ♯1. Figure 11E This is a schematic diagram of the spectrum of the received signal after band limiting by a band limiting filter in subarray ♯1.

[0019] Figure 12 This is a diagram illustrating an example configuration of the phase-synchronized laser device according to Embodiment 5. Detailed Implementation

[0020] Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Components labeled with the same or similar reference numerals in the drawings have the same or similar structure or function, and repeated descriptions of such components are omitted. Furthermore, in this disclosure, unless otherwise stated, the term "or" implies a logical OR.

[0021] Implementation method 1.

[0022] <Composition>

[0023] Reference Figure 1 The phase-synchronized laser device CL1 according to Embodiment 1 of this disclosure will be described. For example... Figure 1 As shown, as an example, the phase-synchronous laser device CL1 includes a reference light source 1, an optical circulator 2, a beam splitter 3, element circuits 4 (4-1 to 4-N), collimators 5 (5-1 to 5-N; optical partial reflectors), photodiodes 6, and a distributor 7.

[0024] More specifically, the phase-synchronized laser device CL1 includes: an optical circulator 2, which receives laser light emitted from a reference light source 1 at a first port and supplies it to a transport optical path, and outputs return light received from a return optical path at a second port; a beam splitter 3, which branches the laser light received from the optical circulator via the transport optical path into a reference light and multiple signal lights; multiple element circuits 4, each element circuit having a phase compensator that performs phase control on the multiple signal lights branched from the beam splitter and outputs multiple phase-controlled signal lights; and multiple collimators 5, which are incident on the reference light or the laser light received from the reference light and the laser light received from the return optical path. Multiple phase-controlled signal beams are used as incident beams. A portion of the incident beams is reflected as reflected beams, allowing the remaining portion of the incident beams to pass through. A photodiode 6 receives the returned beams, performs photoelectric conversion, and outputs a photoelectric converted electrical signal. The returned beams are laser beams obtained by combining the multiple reflected beams using a beam splitter. Each component circuit performs frequency conversion on the electrical signal output from the photoelectric converter to detect the phase error of the electrical signal having a frequency component corresponding to each component circuit. Each phase compensator compensates for the detected phase error. The components of the phase-synchronized laser device CL1 will be described in more detail below.

[0025] (Reference light source)

[0026] The reference light source 1 is, for example, a narrow-linewidth laser light source that oscillates in a single mode. The reference light source 1 is connected to the optical circulator 2 via optical fiber. The reference light source 1 supplies the oscillating laser light to the optical circulator 2 via the optical fiber.

[0027] (Optical Circulator)

[0028] The optical circulator 2 has three ports and is an optical circulator that separates the transmission light and the return light. For example, the optical circulator 2 receives the laser light from the reference light source 1 via port A (port 1) as the transmission light, outputs the received transmission light from port B, and outputs the return light received from port B from port C (port 2).

[0029] Optical circulator 2 and optical splitter 3 are connected by optical fiber. Optical circulator 2 supplies the transmission light received from reference light source 1 to optical splitter 3 via optical fiber.

[0030] In addition, the optical circulator 2 and the photodiode 6 are connected via optical fiber. The optical circulator 2 supplies the return light received from the beam splitter 3 to the photodiode 6 via the optical fiber.

[0031] (Optical splitter; optical coupler)

[0032] Optical splitter 3 branches the transport light supplied from optical circulator 2 into N signal beams and one reference beam. N is any positive integer. Optical splitter 3 is connected to N element circuits 4 (4-1 to 4-N) via optical fibers. The optical path between optical splitter 3 and the N element circuits 4 is... Figure 1 The optical paths are indicated by optical paths 1, ..., and N. The beam splitter 3 supplies each signal light to an element circuit 4 via an optical path. For example, the beam splitter 3 supplies a certain signal light to element circuit 4-1 via optical path 1, and supplies other signal lights to element circuit 4-N via optical path N.

[0033] Additionally, beam splitter 3 and collimator 5-N+1 (collimator R) are connected via optical fiber. The optical path between beam splitter 3 and collimator 5-N+1 (collimator R) is... Figure 1 The beam splitter 3 supplies the reference light (local oscillator light) to the collimator 5-N+1 (collimator R) via the optical path R.

[0034] In this disclosure, a beam splitter may sometimes be referred to as an optical coupler. Beam splitters and optical couplers are the same device. Depending on whether it is used as a splitter for separating a single beam into multiple beams or as a coupler for coupling multiple beams into a single beam, the terms beam splitter and optical coupler may sometimes be distinguished.

[0035] (Element circuit)

[0036] Element circuit 4 is a circuit that controls the optical phase of the signal light. Element circuits 4-1 to 4-N have the same configuration and perform phase modulation (phase control) on the signal light input from optical paths 1 to N to generate N phase-modulated optical signals (phase-controlled optical signals). Element circuits 4-1 to 4-N supply the generated phase-modulated optical signals to collimators 5-1 to 5-N (collimators 1 to 5-N). A more detailed description of the configuration of element circuit 4 will be given later.

[0037] (Collimator)

[0038] Collimator 5 spatially outputs the received signal light. During spatial output of the signal light, Fresnel reflection produces reflected light. In this disclosure, the collimator is an example of a partial reflector.

[0039] (Photodiode)

[0040] The photodiode 6 performs photoelectric conversion on the received return light and supplies the converted electrical signal to the distributor 7. In this disclosure, the photodiode is an example of a photoelectric converter.

[0041] (Distributor)

[0042] Distributor 7 distributes the received signal, which is the electrical signal received from the photodiode, to each element circuit 4 (4-1 to 4-N).

[0043] (Element circuit; details)

[0044] Next, refer to Figure 2 The detailed structure of element circuit 4 is explained below. For example... Figure 2 As shown, the element circuit 4 includes a modulation signal source 10, an optical phase modulator 8, an optical frequency shifter 9, a 1 / 2 frequency divider 11, a mixer 12, a bandwidth limiting filter 17, a reference signal source 13, a phase comparator 14, a loop filter 15, and a VCO 16.

[0045] (Modulation signal source)

[0046] The modulation signal source 10 is a signal source that outputs a modulation signal (jitter signal) at a different frequency for each element to identify each signal light.

[0047] (Optical phase modulator)

[0048] The optical phase modulator 8 is driven by the modulation signal output from the modulation signal source 10 to modulate the phase of the signal light. Different modulation signals are supplied to N element circuits 4 (4-1 to 4-N), and the different modulation signals are superimposed on the phases of the N signal lights.

[0049] (Optical frequency shifter; phase compensator)

[0050] Optical frequency shifter 9 compensates for the phase of the optical signal output from optical phase modulator 8. Optical frequency shifter 9 compensates for the phase of the optical signal output from optical phase modulator 8 by shifting the frequency of the frequency modulation signal output from VCO 16. Since phase is represented by the time integral of frequency, in other words, frequency is represented by the time derivative of phase, phase control (phase compensation) can be performed through frequency control. Optical frequency shifter 9 outputs a phase-compensated optical signal. Optical frequency shifter 9 is an example of a phase compensator in this disclosure.

[0051] (1 / 2 frequency divider)

[0052] The 1 / 2 frequency divider 11 divides the frequency of the received signal, which is received by the photodiode 6 and distributed by the distributor 7, by half and outputs the divided signal. Through frequency division, the phase of the return path quantity of the return light is removed.

[0053] (Mixer)

[0054] Mixer 12 mixes the signal output from divider 11 and the modulation signal (jitter signal), and outputs the mixed signal.

[0055] (Bandwidth limiting filter)

[0056] The band-limiting filter 17 extracts the desired frequency band signal from the signal output from the mixer 12.

[0057] (Reference signal source)

[0058] The reference signal source 13 generates a reference signal that serves as a phase reference and outputs the generated reference signal.

[0059] (Phase comparator)

[0060] Phase comparator 14 compares the phase of the reference signal received from reference signal source 13 with the phase of the received signal received via band-limiting filter 17, and outputs a phase error signal as the result of the comparison.

[0061] (Loop filter)

[0062] The loop filter 15 calculates the control signal based on the phase error signal received from the phase comparator 14 and outputs the calculated control signal.

[0063] (VCO; Voltage-Controlled Oscillator)

[0064] VCO16 oscillates a frequency-modulated signal in accordance with the frequency of the control signal output from the loop filter 15, and outputs the oscillated frequency-modulated signal.

[0065] <Action>

[0066] Next, the overall operation of the phase-synchronized laser device CL1 will be explained. The laser light output from the reference light source 1 is propagated into the transport optical path via the optical circulator 2. The laser light from the reference light source 1 propagates in the transport optical path and is split by the beam splitter 3 into a reference light (local oscillator light) for the optical path R and a signal light for the optical paths (signal optical paths) 1 to N. After splitting, the signal light is spatially output from collimators 5-1 to 5-N via element circuits 4 (4-1 to 4-N), and the local oscillator light is spatially output from collimator 5-N+1.

[0067] During spatial output, Fresnel reflection generates reflected light. The reflected light of the signal light is output to the beam splitter 3 via element circuit 4, while the reflected light of the local oscillator light is output directly to the beam splitter 3 without passing through element circuit 4. The beam splitter 3 combines (couples) the multiple reflected lights of the signal light and the reflected light of the local oscillator light to generate a combined light. The combined light output from the beam splitter 3 is propagated to the return optical path through the optical circulator 2. The combined light is then received by photodiode 6 and undergoes photoelectric conversion. The received signal, which is the electrical signal output from photodiode 6, is distributed by the distributor 7 to a quantity corresponding to the number of signal lights and input to each element circuit 4.

[0068] The laser input to element circuit 4 is phase-modulated by an optical phase modulator 8 driven by a weak modulation signal from modulation signal source 10. The laser output from optical phase modulator 8 is frequency-shifted by an optical frequency shifter 9 with a feedback phase control signal, and the frequency-shifted laser is output.

[0069] Here, a schematic diagram of the spectrum of the received signal received by photodiode 6 is shown. Figure 3A Since the laser light passes through twice in element circuit 4, serving as both the transmission and return light, if the frequency shift of optical frequency shifter 9 is set to f... AOM Set the modulation frequency of the modulation signal source 10 in the i-th element circuit 4-i to f. i Then the carrier signal has 2f AOM The frequency of the sidecar generated by phase modulation has 2(f) AOM ±f i The frequency of ) is determined by using a 1 / 2 frequency divider 11 to divide the frequency so that each frequency is as follows. Figure 3B As shown, it becomes half. Then, frequency conversion is performed using the output signal from the modulation signal source 10, so that the frequency of the signal output from the mixer 12 (mixer output signal) becomes f. AOM At frequency f AOMAfter the central band-limiting filter 17 suppresses unwanted signals from the mixer output signal, the signal output from the band-limiting filter 17 and the signal from the frequency (f) are compared. AOM The reference signal of the reference signal source 13 driven by the reference signal source 13 is phase compared to extract the error signal relative to the reference signal. Figure 3C This is a schematic diagram of the spectrum of the received signal after band limiting by the band limiting filter 17 when i=1.

[0070] (Establishment of phase synchronization)

[0071] Let φ be the phase change of the local oscillator light in the optical path R during a single pass. R Let φ be the phase change of the signal light in optical path i (where i is an integer from 1 to N) during a single pass. i Set the phase control quantity under the optical frequency shifter 9 in element circuit 4 to φ. AOM The beat signal of the optical path i and the optical path R of the signal received by photodiode 6 is approximately represented by the following formula.

[0072]

[0073] If we focus on the phase term of the Cos function, then the phase of the signal after frequency division by 1 / 2 becomes φ. R -φ i -φ AOM .

[0074] If the phase of the reference signal source 13 is set to φ r Then, when phase synchronization is established, the relationship of equation (2) holds.

[0075]

[0076] If equation (2) is transformed, equation (3) can be obtained.

[0077]

[0078] In addition, the phase of the signal light i output by space is represented by the following equation (4).

[0079]

[0080] Therefore, according to the phase-synchronized laser device CL1 involved in Embodiment 1, it can be known that the signal light i output in space does not depend on the phase variation (φ) generated by the optical path i. i ).

[0081] As described above, in the configuration where the signal light passes through the signal optical path twice, phase synchronization is established after frequency division of the received signal by using Fresnel reflection light in the collimator of the signal light. This allows for the coherent synthesis of multiple beams without being affected by phase variations in the signal optical path. Since this configuration can be constructed using only an optical fiber system, no alignment or optical system for phase error detection is required, and miniaturization can be achieved even with an increase in the number of signals. Furthermore, since the configuration of the mixer stage in the component circuit is identical for all components, adjustments are easy.

[0082] The above description shows an example of using an optical frequency shifter 9 for phase synchronization, but it is also possible to use an optical fiber stretcher instead of an optical frequency shifter 9, or to use bias control of an optical phase modulator.

[0083] Implementation method 2.

[0084] The following is for reference Figure 4 The phase-synchronized laser device CL2 according to Embodiment 2 will be described. Since the overall structure of the phase-synchronized laser device CL2 according to Embodiment 2 is the same as that of the phase-synchronized laser device CL1 according to Embodiment 1, it will not be described again. Figure 4 This is a diagram showing the configuration of the essential circuit elements of the phase-synchronized laser device CL2 according to Embodiment 2. Figure 4 Elements that are the same or similar to those in Implementation 1 are marked with the same reference numerals and will not be described again.

[0085] The difference between Embodiment 2 and Embodiment 1 is that in Embodiment 2, a semiconductor optical amplifier 18 without isolators at the input and output ends is added to the output of the optical frequency shifter 9. Since the addition of the semiconductor optical amplifier 18 can enhance not only the output optical power but also the return optical level, it can improve the received signal-to-noise ratio (SNR) and achieve high-precision optical phase synchronization.

[0086] The gain of semiconductor optical amplifier 18 is assumed to be G. SOA At this time, compared with embodiment 1, the output optical level can be enhanced by G. SOA The amount. Similarly, the reflected light based on Fresnel reflection also enhances G. SOA If the loss from Fresnel reflection is set as I... F Then, set the output optical level of the optical frequency shifter to P. AOM In the case of implementation method 1, the returned optical level becomes P. AOM -I F When using Figure 4 In the case of the configuration, the received level becomes P. AOM +G SOA -IF +G SOA It can enhance 2G SOA The received level of the quantity.

[0087] As described above, by using this embodiment, not only the output light level but also the return light level is enhanced, thereby enabling high-precision optical phase synchronization. In phase error detection systems using Fresnel reflection, due to the weak received light level, there are issues such as deteriorated phase synchronization accuracy compared to existing configurations. By using this embodiment, high-precision phase synchronization can be achieved by improving the received SNR.

[0088] Implementation method 3.

[0089] The following is for reference Figures 5-7 The phase-synchronized laser device CL3 involved in Embodiment 3 will be described. Figure 5 This is a diagram showing an example of the overall configuration of the phase-synchronized laser device CL3. Figure 6 This is a diagram illustrating an example of the configuration of the essential circuitry of the phase-synchronized laser device CL3. Figure 7 This is a diagram illustrating an example of the output beam pattern when the number of subarrays is 3 (N=3). Figure 5 as well as Figure 6 In this document, elements that are the same or similar to those in Implementation 1 are marked with the same reference numerals and will not be described again.

[0090] The phase-synchronized laser device CL3 according to Embodiment 3 has a configuration suitable for using a high-output optical amplifier 30 with irreversible input, such as an optical fiber amplifier or a waveguide-type optical amplifier, for the signal optical path. More specifically, the phase-synchronized laser device CL3 has a local oscillator control unit 28 that subarrays the configuration of Embodiment 1 or Embodiment 2 to supply multiple local oscillators. By having such a local oscillator control unit 28, the signal light can be subarrayed.

[0091] In a high-output optical amplifier 30, such as an fiber optic amplifier, which can achieve high output optical power, reverse input from the output side as described in Embodiment 2 is not possible. Therefore, in the phase-synchronized laser device CL3 equipped with the high-output optical amplifier 30, a method such as... Figure 7The signal light is sub-arrayed as shown to increase the number of elements. However, during sub-arraying, due to the configuration of synchronizing the signal light with a single local oscillator, it is difficult to increase the signal light as the beam diameter increases with the number of elements. Therefore, it is advisable to prepare multiple local oscillators for phase synchronization. In view of this, in this embodiment, multiple local oscillators for phase synchronization are prepared by performing phase synchronization using Fresnel reflection as shown in Embodiment 1 in the local oscillator control unit 28 which does not have a high-output optical amplifier. As a result, since multiple local oscillators with phase synchronization can be supplied, the phase-synchronized laser device CL3 equipped with the high-output optical amplifier 30 can cope with the increase in the number of elements (the increase in the number of signal lights). That is, according to the configuration of the phase-synchronized laser device CL3, the number of sub-arrays can be increased scalably.

[0092] like Figure 5 As shown, the phase-synchronized laser device CL3 according to Embodiment 3 includes: a reference light source 1; a beam splitter 19 that branches the laser emitted from the reference light source 1 into laser beams directed to a local oscillator optical path 20 and laser beams directed to a signal optical path 21; a local oscillator control unit 28 that receives the laser beams from the local oscillator optical path 20 and generates multiple local oscillator beams that are phase-synchronized; a beam splitter 22 that branches the laser beams from the signal optical path 21 into multiple signal beams; and a signal beam control unit 29 that controls the signal beams based on the multiple signal beams branched by the beam splitter 22. The signal beam control unit 29 includes multiple signal photon arrays that subarray the multiple signal beams obtained from the laser beams emitted from the reference light source 1. The local oscillator control unit 28 supplies the multiple local oscillator beams that have been phase-synchronized to the multiple signal photon arrays.

[0093] The local oscillator control unit 28 has the configuration described in Embodiment 1. Figure 5 In the example shown, the local oscillator control unit 28 generates N local oscillators that are phase-synchronized. N represents the number of subarrays.

[0094] More specifically, the local oscillator control unit 28 includes: an optical circulator 2, which receives the laser light from a first port and supplies it to the transmission optical path, and outputs the return light received from the return optical path from a second port; a beam splitter 3, which branches the laser light received from the optical circulator 2 via the transmission optical path into a reference beam and multiple local oscillator beams; multiple element circuits 4, each element circuit 4 having an optical frequency shifter 9 (phase compensator) that performs phase control on the multiple local oscillator beams branched from the beam splitter and outputs multiple phase-controlled local oscillator beams; and multiple collimators 5, which are used to collimate the incident reference light or the multiple phase-controlled local oscillator beams. As incident light, a portion of the incident light is reflected as reflected light, allowing the remaining portion of the incident light to pass through; and photodiode 6 (first photoelectric converter) receives the returned light and performs photoelectric conversion, outputting a photoelectric converted electrical signal. The returned light is laser light obtained by combining the multiple reflected lights using beam splitter 3. Each element circuit 4 (first element circuit) performs frequency conversion on the electrical signal output by photodiode 6, detects the phase error of the electrical signal having the frequency component corresponding to each element circuit 4, and each optical frequency shifter 9 (phase compensator) compensates for the detected phase error. Among them, collimators 5-1 to 5-N are in Figure 5 The signal light control unit 29 is shown as a component of the signal light control unit 29, but as explained above, the local oscillator light control unit 28 may include collimators 5-1 to 5-N.

[0095] like Figure 5 As shown, the signal light control unit 29 includes N signal photonic arrays 23 (23-1 to 23-N). Each signal photonic array 23 has: N signal lights within the subarray S Quantity element circuit 24 (24-N-1~24-NN) S ; second element circuit); and element circuit 24 (24-N-1~24-NN) S The corresponding N is used to collimate the signal light output from the element circuit. S 50 collimators (50-N-1~50-NN) S ); Acceptance from N S 50 collimators (50-N-1~50-NN) S A beam splitter 25-N (SN) generates a combined beam using the signal light output from the collimator 5 (5-N) and the local oscillator light output from the collimator 5 (5-N), outputting a portion of the generated combined beam as the signal light for output and a portion of the generated combined beam as the signal light for phase error detection; a photodiode 26-N (second photoelectric converter) performs photoelectric conversion on the signal light for phase error detection output from the beam splitter 25-N; and a distributor 27-N distributes the electrical signal output from the photodiode 26-N to multiple element circuits 24.

[0096] Next, the overall operation of the phase-synchronized laser device CL3 will be explained. The laser output from the reference light source 1 is split by the beam splitter 19 into a laser beam directed to the local oscillator optical path 20 and a laser beam directed to the signal optical path 21.

[0097] In the local oscillator optical path 20, phase synchronization is achieved by the local oscillator optical control unit 28 using the output of the collimator as a reference.

[0098] In signal optical path 21, the laser light from beam splitter 19 is split into multiple (NxNs) signal beams by beam splitter 22. As mentioned above, Ns represents the number of signal beams in the subarray, and N represents the number of subarrays. For example, when Ns is set to 7 and N is set to 3, the total number of components is 21. Since the local oscillator requires a subarray, it is 3. An output diagram in this case is shown below. Figure 7 .

[0099] The signal light split by beam splitter 22 is collected into a signal photon array 23 with each Ns beam splitter. Within each signal photon array, the signal light split by beam splitter 22 is amplified by element circuit 24 (24-N-1~24-N-Ns) and then collimated by collimator 50 (50-N-1~50-NN). S The signal light (emitted light) output from space is split by beam splitter 25-N (SN) into a signal light for phase error detection and a signal light for output. The signal light for phase error detection is combined (optical mixing) with the local oscillator light input from the opposite port of beam splitter 25-N (SN), and the mixed light generated by the combination (mixing) is received by photodiode 26-N. The received signal is distributed to each component circuit by distributor 27-N.

[0100] In element circuit 24 (24-1-1~24-N-Ns), the signal light after being phase-controlled by the optical frequency shifter 9 for phase control is amplified by the high-output optical amplifier 30, and the amplified signal light is output.

[0101] The phase-synchronized laser device CL3 described above enables online optical phase synchronization among multiple local oscillators, thus achieving scalability with reduced alignment requirements.

[0102] Implementation method 4.

[0103] The following is for reference Figures 8-1 1. The phase-synchronized laser device CL4 involved in Embodiment 4 will be described. Figure 8 This is a diagram showing an example of the overall configuration of the phase-synchronized laser device CL4. Figure 9 This is a diagram illustrating an example of the circuit configuration for the local oscillator light of the phase-synchronous laser device CL4. Figure 10This diagram illustrates an example of the circuitry configuration for the signal light components of the phase-synchronized laser device CL4. Figure 8 , Figure 9 as well as Figure 10 In this document, elements that are the same or similar to those in Embodiment 1, Embodiment 2, or Embodiment 3 are marked with the same reference numerals and will not be described again.

[0104] The difference between implementation method 4 and implementation method 3 is that all the optical frequency shifters of the local oscillator are set to different frequencies (f). AOM_i In Embodiment 3, phase-modulated light of different frequencies was used to identify multiple local oscillator beams, but in Embodiment 4, the identification of multiple local oscillator beams is performed by individually setting the frequency shift amount. In other words, in Embodiment 3, a modulation signal source 10, an optical phase modulator 8, and a mixer 12 were used for the identification of local oscillator beams, but these components are not used in Embodiment 4. On the other hand, in the signal optical path, in order to coherently synthesize the combined output, the frequency shift amount superimposed by the optical frequency shifter 9 is made to be the same frequency shift amount (f). AOM ).

[0105] Next, the overall operation will be explained. Multiple local oscillator beams are obtained by branching the laser from reference light source 1 into multiple branches. These multiple local oscillator beams are then subjected to different frequency shifts via element circuits 31-i (i = 1~N). For example... Figure 9 As shown, the reference signal source 33-i outputs a certain frequency f. AOM_i The reference signal, frequency f AOM_i They differ for i = 1 to N. The optical frequency shifter 35-i is tuned to the corresponding center frequency.

[0106] In the signal light element circuit 24 (24-1-1~24-N-Ns), the sidecarrier beat signal generated by heterodyne detection of the local oscillator light and the phase-modulated signal light is converted into f. AOM_s -f AOM_i At the center frequency f AOM_s -f AOM_i After the band-limiting filter 17 suppresses unwanted signals, the phase of the signal output from the band-limiting filter 17 is compared with the reference signal (f) by the phase comparator 14. AOM_s -f AOM_i Phase synchronization is established by comparing the phases of the two phases.

[0107] Figure 11 shows the spectrum of the signal in each segment. Figure 11A This is a schematic diagram of the spectrum of the received signal from the local oscillator. Figure 11B This is a schematic diagram of the spectrum of the received signal after being divided by the 1 / 2 frequency divider 11.

[0108] Figure 11CThis is a schematic diagram of the optical signal spectrum of subarray ♯1. Figure 11D This is a schematic diagram of the spectrum of the received signal of subarray ♯1. Figure 11E This is a schematic diagram of the spectrum of the received signal after the frequency band is limited by the frequency band limiting filter 17 in subarray ♯1.

[0109] By individually setting the frequencies of multiple local oscillators as in Embodiment 4, unwanted frequency components of the local oscillators can be eliminated. This reduces sidecarrier signals generated by phase modulation during heterodyne detection of the signal light and local oscillators, enabling phase synchronization with a simple configuration.

[0110] Implementation method 5.

[0111] The following is for reference Figure 12 The phase-synchronized laser device CL5 according to Embodiment 5 of this disclosure will be described. Figure 12 This is a diagram showing an example of the overall configuration of the phase-synchronized laser device CL5. Figure 12 Elements that are the same or similar to those in Embodiment 1, Embodiment 2, Embodiment 3 or Embodiment 4 are marked with the same reference numerals and are not described again.

[0112] The difference between Embodiment 5 and Embodiment 4 is that Embodiment 5 includes a light source modulator 36 for modulating the reference light source 1. Embodiment 4 describes a reference light source 1 that emits a narrow-linewidth laser, but in this case, the output of the high-output optical amplifier 30 is limited by nonlinear optical effects. Since frequency modulation or phase modulation is superimposed on the reference light source 1 as in this embodiment, the linewidth of the reference light source 1 can be virtually widened, thus achieving further high output.

[0113] Furthermore, implementation methods can be combined, or appropriately modified or omitted.

[0114] Industrial availability

[0115] The phase-synchronized laser device disclosed herein can be used, for example, as a laser device for laser processing.

[0116] Explanation of reference numerals in the attached figures

[0117] 1...reference light source; 2...optical circulator; 3...beam splitter; 4 (4-1~4-N)...element circuit; 5 (5-1~5-N+1)...collimator; 6...photodiode; 7...distributor; 8...optical phase modulator; 9...optical frequency shifter; 10...modulation signal source; 11...1 / 2 frequency divider; 12...mixer; 13...reference signal source; 14...phase comparator; 15...loop filter; 17...bandwidth limiting filter; 18...semiconductor optical amplifier; 19...beam splitter; 20...local oscillator optical path; 21...signal optical path; 22...beam splitter; 23...signal photonic array; 24 (24-1-1~24-NN) S 25...Element Circuit (Element 1); 26...Beam Splitter; 27...Photodiode; 28...Distributor; 29...Local Oscillator Control Unit; 30...Signal Optical Control Unit; 31 (31-1~31-N)...Element Circuit (Element 1); 33-i...Reference Signal Source; 35-i...Optical Frequency Shifter; 36...Light Source Modulator; CL (CL1~CL5)...Phase Synchronized Laser Device; 50 (50-1-1~50-NN) S ...collimator.

Claims

1. A phase-synchronized laser device, characterized in that, have: The optical circulator receives laser light emitted from the reference light source at port 1 and supplies it to the delivery optical path, and outputs return light received from the return optical path at port 2. The beam splitter splits the laser beam received from the optical circulator via the transmission optical path into a reference beam and multiple signal beams; Multiple element circuits, each element circuit having a phase compensator that performs phase control on multiple signal lights branched from the beam splitter and outputs multiple phase-controlled signal lights; Multiple optical partial reflectors are used to reflect a portion of the incident light, either the reference light or the multiple phase-controlled signal lights, as incident light, while allowing the remaining portion of the incident light to pass through. as well as The photoelectric converter receives the returned light and performs photoelectric conversion, outputting a photoelectric converted electrical signal. The returned light is a laser beam resulting from the multiple reflected beams being combined using the beam splitter. Each component circuit performs frequency conversion on the electrical signal output by the photoelectric converter to detect the phase error of the electrical signal having a frequency component corresponding to that of each component circuit. Each phase compensator compensates for the detected phase error.

2. The phase-synchronized laser device according to claim 1, characterized in that, Each component circuit has a semiconductor optical amplifier that does not have isolators at the input and output terminals after each phase compensator.

3. A phase-synchronized laser device, characterized in that, have: The signal light control unit includes multiple signal photonic arrays formed by sub-arraying multiple signal lights obtained from laser light emitted from a reference light source; and The local oscillator control unit supplies multiple local oscillator beams, which have been phase-synchronized, to the multiple signal photonic arrays. The local oscillator control unit includes: The optical circulator receives the laser light from port 1 and supplies it to the delivery optical path, and outputs the return light received from the return optical path from port 2. The beam splitter splits the laser beam received from the optical circulator via the transmission optical path into a reference beam and multiple local oscillator beams; Multiple first element circuits, each first element circuit having a phase compensator that performs phase control on multiple local oscillator beams branched from the beam splitter and outputs multiple phase-controlled local oscillator beams; Multiple optical partial reflectors are used to reflect a portion of the incident light, either the reference light or the multiple phase-controlled local oscillators, as incident light, and allow the remaining portion of the incident light to pass through. as well as The first photoelectric converter receives the returned light and performs photoelectric conversion, outputting a photoelectric converted electrical signal. The returned light is a laser beam resulting from the multiple reflected beams being combined using the beam splitter. Each first element circuit performs frequency conversion on the electrical signal output by the first photoelectric converter to detect the phase error of the electrical signal having a frequency component corresponding to each first element circuit. Each phase compensator compensates for the detected phase error.

4. The phase-synchronized laser device according to claim 3, characterized in that, Each signal photon array has: A beam splitter performs optical mixing between a portion of the emitted light and the local oscillator light to generate mixed light. The second photoelectric converter performs photoelectric conversion on the mixed light and outputs the converted electrical signal. as well as The second element circuit uses an electrical signal output from the second photoelectric converter to compensate for the phase error of one of the plurality of signal lights.

5. The phase-synchronized laser device according to claim 4, characterized in that, The multiple local oscillators are mutually recognized through phase modulation.

6. The phase-synchronized laser device according to claim 4, characterized in that, The local oscillator control unit includes an optical frequency shifter that superimposes different frequency shift amounts on each of the plurality of local oscillators to identify them. The signal light control unit has optical frequency shifters with superimposed frequency shift amounts.

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