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WO2023037510A1 - Dispositif de verrouillage de longueur d'onde, photodiode de surveillance, diviseur de faisceau et procédé d'alignement de dispositif de verrouillage de longueur d'onde - Google Patents

Dispositif de verrouillage de longueur d'onde, photodiode de surveillance, diviseur de faisceau et procédé d'alignement de dispositif de verrouillage de longueur d'onde Download PDF

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Publication number
WO2023037510A1
WO2023037510A1 PCT/JP2021/033376 JP2021033376W WO2023037510A1 WO 2023037510 A1 WO2023037510 A1 WO 2023037510A1 JP 2021033376 W JP2021033376 W JP 2021033376W WO 2023037510 A1 WO2023037510 A1 WO 2023037510A1
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WIPO (PCT)
Prior art keywords
light
reflecting surface
wavelength
monitor
beam splitter
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PCT/JP2021/033376
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English (en)
Japanese (ja)
Inventor
進一 金子
Original Assignee
三菱電機株式会社
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Application filed by 三菱電機株式会社 filed Critical 三菱電機株式会社
Priority to PCT/JP2021/033376 priority Critical patent/WO2023037510A1/fr
Publication of WO2023037510A1 publication Critical patent/WO2023037510A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687—Stabilising the frequency of the laser
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors

Definitions

  • the present disclosure relates to wavelength lockers, monitor photodiodes, beam splitters, and wavelength locker alignment methods.
  • Patent Document 1 discloses a light source device having a plurality of laser diodes whose central wavelength of output light changes with temperature.
  • this light source device part of the light output from the laser diode is branched by the first coupler film and the second coupler film respectively provided on the glass block.
  • the light split by the first coupler film passes through the etalon filter and is converted by the first photodetector into an electrical signal corresponding to its intensity.
  • the light branched by the second coupler film is directly converted by the second photodetector into an electric signal corresponding to its intensity.
  • the transmittance of the etalon filter varies periodically according to the wavelength or frequency of light. Therefore, the wavelength can be controlled by changing the temperature of the laser diode so that the ratio of the received light levels of the first and second photodetectors is constant.
  • Optical communication light source modules that require highly accurate wavelength control may have a built-in wavelength locker.
  • Wavelength lockers include, for example, beam splitters, etalons, and photodiodes for optical output monitoring. These components are mounted on the thermoelectric element so that the etalon's transmittance does not change as the ambient temperature changes.
  • the wavelength locker is large, it is assumed that the thermoelectric element mounting the wavelength locker will be large and expensive.
  • the light source module incorporating the wavelength locker becomes large, and there is a possibility that it cannot be mounted on a small optical transceiver.
  • An object of the present disclosure is to obtain a wavelength locker capable of miniaturizing the wavelength locker, a monitor photodiode, a beam splitter, and a wavelength locker alignment method.
  • the wavelength locker according to the first disclosure includes a beam splitter that splits incident light into outgoing light and split light, a first reflecting surface that reflects the split light, and the first reflecting surface facing the first reflecting surface.
  • a first monitor photodiode having a second reflective surface that reflects light reflected by the The first monitor photodiode functions as an etalon whose light absorption rate depends on the wavelength by repeating reflection on the first reflecting surface and the second reflecting surface.
  • a wavelength locker includes a first reflecting surface that branches incident light into outgoing light and branched light, a second reflecting surface that reflects the branched light, and the second reflecting surface facing the second reflecting surface. a beam splitter having a third reflecting surface that reflects light reflected by the reflecting surface; The beam splitter functions as an etalon in which the transmittance of the transmitted light depends on the wavelength by repeating reflections on the second reflecting surface and the third reflecting surface.
  • a monitor photodiode includes a first reflecting surface, a second reflecting surface facing the first reflecting surface and reflecting light reflected by the first reflecting surface, the first reflecting surface and the and a first light absorbing layer provided between the second reflecting surfaces, and functions as an etalon whose light absorption rate depends on the wavelength by repeating reflection between the first reflecting surface and the second reflecting surface. do.
  • a beam splitter includes a first reflecting surface that splits incident light into outgoing light and branched light, a second reflecting surface that reflects the branched light, and the second reflecting surface facing the second reflecting surface. and a third reflecting surface for reflecting light reflected by the reflecting surface, and by repeating reflection by the second reflecting surface and the third reflecting surface, the transmittance of the light from the second reflecting surface varies depending on the wavelength. Acts as a dependent etalon.
  • a wavelength locker alignment method includes a first reflecting surface that splits incident light into outgoing light and branched light, a second reflecting surface that reflects the branched light, and a second reflecting surface that faces the second reflecting surface. and a beam splitter having a third reflecting surface for reflecting light reflected by the second reflecting surface; and a monitor photodiode on which transmitted light of the branched light that has passed through the second reflecting surface is incident. , the beam splitter repeats reflections on the second reflecting surface and the third reflecting surface, so as to align a wavelength locker functioning as an etalon in which the transmittance of the transmitted light depends on the wavelength. Spontaneous emission light from a laser or optical amplifier is used.
  • the wavelength locker according to the first disclosure miniaturization is possible because the monitor photodiode also functions as an etalon.
  • miniaturization is possible because the beam splitter also functions as an etalon. Since the monitor photodiode according to the third disclosure also functions as an etalon, the wavelength locker can be miniaturized. Since the beam splitter according to the fourth disclosure also functions as an etalon, the wavelength locker can be miniaturized.
  • the wavelength locker alignment method according to the fifth disclosure the beam splitter also functions as an etalon, so the wavelength locker can be miniaturized.
  • spontaneous emission light from a laser or an optical amplifier is used as incident light, interference effects do not appear, and the beam splitter or monitor photodiode can be easily aligned.
  • FIG. 1 is a plan view of a wavelength locker according to Embodiment 1;
  • FIG. 2 is a cross-sectional view of a monitor photodiode according to Embodiment 1;
  • FIG. 5 is a diagram showing wavelength characteristics of absorptivity of the monitor photodiode according to the first embodiment;
  • FIG. FIG. 4 is a plan view of a light source module for optical communication incorporating a wavelength locker according to a comparative example;
  • FIG. 8 is a plan view of a wavelength locker according to Embodiment 2;
  • FIG. 8 is a front view of a monitor photodiode according to Embodiment 2;
  • 8 is a cross-sectional view of a monitor photodiode according to Embodiment 2;
  • FIG. 10 is a diagram showing wavelength characteristics of absorptance of a monitor photodiode according to Embodiment 2;
  • FIG. 11 is a plan view of a wavelength locker according to Embodiment 3;
  • FIG. 10 is a diagram showing wavelength characteristics of a photocurrent of a monitor photodiode according to Embodiment 3;
  • FIG. 11 is a diagram showing current sums and current differences of a monitor photodiode according to Embodiment 3;
  • FIG. 12 is a diagram showing current sums when the current ratio of the monitor photodiode according to the third embodiment is changed;
  • FIG. 11 is a plan view of a wavelength locker according to Embodiment 4;
  • FIG. 11 is a cross-sectional view of a beam splitter according to Embodiment 4;
  • FIG. 11 is a plan view of a wavelength locker according to Embodiment 5;
  • FIG. 10 is a diagram showing wavelength characteristics of photocurrent of a monitor photodiode according to Embodiment 5;
  • FIG. 11 is a diagram showing current sums and current differences of a monitor photodiode according to Embodiment 5;
  • FIG. 11 is a diagram for explaining a method of aligning a wavelength locker according to Embodiment 6;
  • FIG. 12 is a diagram showing a light output distribution on a light receiving surface of a monitor photodiode according to Embodiment 6;
  • a wavelength locker, a monitor photodiode, a beam splitter, and a wavelength locker alignment method according to each embodiment will be described with reference to the drawings.
  • the same reference numerals are given to the same or corresponding components, and repetition of description may be omitted.
  • FIG. 1 is a plan view of a wavelength locker 100 according to Embodiment 1.
  • the monitor photodiode is hereinafter also referred to as monitor PD.
  • beam splitter 40 splits a portion of incident light 80 from the light source as split light 81 .
  • the monitor PD 20 receives the branched light 81 .
  • the beam splitter 30 splits incident light into outgoing light 83 and split light 82 .
  • the monitor PD 10 receives the branched light 82 .
  • the monitor PD 10 has an etalon function as described later.
  • a monitor PD 10 , a monitor PD 20 , a beam splitter 30 and a beam splitter 40 are mounted on the thermoelectric element 50 .
  • the thermoelectric element 50 keeps the temperature of the mounted component constant.
  • a control circuit 70 is also connected to the monitor PDs 10 and 20 .
  • the control circuit 70 controls the wavelength and optical output of the emitted light 83 according to the photocurrents of the monitor PDs 10 and 20 .
  • the control circuit 70 has, for example, an arithmetic circuit 71 that performs arithmetic operations for various controls, and a memory 72 that stores information used for the arithmetic operations performed by the arithmetic circuit 71 .
  • the arithmetic circuit 71 is a CPU, a processor, or the like, and the memory is a non-volatile memory or the like.
  • a circuit for detecting photocurrent, a circuit for controlling the temperature of the light source, and the like are omitted.
  • FIG. 2 is a cross-sectional view of the monitor photodiode 10 according to Embodiment 1.
  • the monitor PD 10 includes a reflective surface 12 that reflects the branched light 82, a reflective surface 11 that faces the reflective surface 12 and reflects the light reflected by the reflective surface 12, and a light beam provided between the reflective surface 11 and the reflective surface 12. and an absorbent layer 13 .
  • the light absorption layer 13 absorbs incident light and converts it into photocurrent.
  • a part of the branched light 82 incident on the monitor PD 10 is absorbed by the light absorption layer 13, and the light transmitted through the light absorption layer 13 is reflected by the reflection surface 12 and absorbed by the light absorption layer 13 again.
  • the light transmitted through the light absorption layer 13 is reflected by the reflecting surface 11 and absorbed by the light absorption layer 13 again.
  • the monitor PD 10 functions as an etalon whose light absorption rate depends on the wavelength by repeating reflection on the reflecting surface 11 and the reflecting surface 12 . Note that the light output gradually decreases due to absorption in the light absorption layer 13 .
  • absorptivity has been used in the description here, the transmittance also depends on the wavelength.
  • the transmittance T PD and reflectance R PD of the monitor PD 10 having the function of an etalon will be described. Transmittance and reflectance are generally calculated assuming no light loss in the etalon. However, the monitor PD 10 has a light absorbing layer 13 between the reflecting surfaces 11 and 12 . Therefore, the transmittance T_PD and the reflectance R_PD of the monitor PD 10 are expressed by the following equations 1 and 2, where T ab is the transmittance per pass through the light absorption layer 13 .
  • R 1 is the reflectance of the reflecting surface 11 and R 2 is the reflectance of the reflecting surface 12 .
  • ⁇ is the phase difference due to multiple reflections and is wavelength dependent.
  • FIG. 3 is a diagram showing wavelength characteristics of absorptance of the monitor photodiode 10 according to the first embodiment.
  • the absorptivity shown in FIG. 3 was calculated from equations 1,2,3. In the calculation, R1 was 30%, R2 was 95% and Tab was 70%. As shown in FIG. 3, photocurrent changes of 10% to 95% with wavelength change were obtained. Therefore, by controlling the wavelength of the light source so that the photocurrent is constant, the wavelength of the light source can be controlled to be constant.
  • R1 of 30% is equivalent to the Fresnel reflectance of InP, which is commonly used as a material for monitor PDs. Therefore, it can be easily realized without applying a coating to the incident surface of the monitor PD10. Also, R2 of 95% can be easily realized by the reflectance of the metal formed on the back surface as the electrode.
  • the light output of the emitted beam can be kept constant by keeping the light receiving current of the normal monitor PD 20, which does not have an etalon function, constant.
  • monitor PDs 10 and 20 can be used to keep the optical power and wavelength of the output beam constant. That is, the control circuit 70 controls the wavelength of the emitted light 83 according to the photocurrent of the monitor PD10, and controls the output of the emitted light 83 according to the photocurrent of the monitor PD20.
  • FIG. 4 is a plan view of an optical communication light source module incorporating a wavelength locker 800 according to a comparative example.
  • the light source module for optical communication light emitted from a semiconductor laser 51 as a light source is converted into parallel light by a lens 52 . This parallel light enters wavelength locker 800 as incident light 80 .
  • the beam splitter 30 splits part of the incident light 80 as split light 82 .
  • the branched light 82 passes through the etalon 55 whose transmittance depends on the wavelength and is received by the monitor PD 20a.
  • the beam splitter 40 splits part of the incident light as split light 81 .
  • the branched light 81 is received by the monitor PD 20b. Note that the monitor PDs 20a and 20b are normal monitor PDs that do not have an etalon function.
  • a wavelength locker 800 including the beam splitters 30, 40, the etalon 55, and the monitor PDs 20a, 20b is mounted on the thermoelectric element 50 and kept constant in temperature.
  • Package 60 accommodates semiconductor laser 51 and wavelength locker 800 .
  • the structure of the light source module for optical communication according to the present embodiment is also the same as the structure shown in FIG. 4 if the wavelength locker 800 is replaced with the wavelength locker 100 .
  • the output of the emitted beam can be kept constant by keeping the photocurrent of the monitor PD 20b constant.
  • the transmittance of the etalon 55 exhibits wavelength dependence similar to the characteristic shown in FIG. Therefore, the wavelength of the output beam can be kept constant by keeping the photocurrent of the monitor PD 20a constant.
  • the wavelength locker 800 according to the comparative example incorporates the etalon 55, it may become large. Along with this, the thermoelectric element 50 for adjusting the temperature of the wavelength locker 800 also becomes large, which may increase the member cost.
  • the monitor PD 10 has an etalon function, so there is no need to implement an etalon. Therefore, the wavelength locker 100 can be miniaturized. In particular, as can be seen by comparing FIGS. 1 and 4, the width of the wavelength locker 100 in the lateral direction with respect to the emitted light 83 can be reduced. Furthermore, the downsizing of the wavelength locker 100 also allows the thermoelectric element 50 to be downsized, thereby reducing member costs.
  • each part shown in FIG. 1 is an example.
  • the monitor PD10 may be arranged on the light source side with respect to the monitor PD20.
  • wavelength locker can be appropriately applied to the wavelength locker, monitor photodiode, beam splitter, and wavelength locker alignment method according to the following embodiments. Since the wavelength locker, the monitor photodiode, the beam splitter, and the method of aligning the wavelength locker according to the following embodiments have many points in common with the first embodiment, the points of difference from the first embodiment will be mainly described. explain.
  • FIG. 5 is a plan view of wavelength locker 200 according to the second embodiment.
  • two monitor PDs 210a and 210b are formed as one monitor PD210.
  • the monitor PD 210 is a dual monitor PD.
  • the monitor PD 210a has an etalon function, and the monitor PD 210b does not have an etalon function.
  • Incident light 80 from the light source is split into outgoing light 83 and split light 82 by the beam splitter 30 .
  • the branched light 82 is received by both monitor PDs 210a and 210b formed adjacent to each other.
  • FIG. 6 is a front view of the monitor photodiode 210 according to Embodiment 2.
  • FIG. FIG. 7 is a cross-sectional view of monitor photodiode 210 according to the second embodiment. Similar to the monitor PD 10, the monitor PD 210 has a reflecting surface 212 that reflects the branched light 82 incident on the monitor PD 210a, and a reflecting surface 211 that faces the reflecting surface 212 and reflects the light reflected by the reflecting surface 212.
  • a light absorbing layer 213 a is provided between the reflecting surface 211 and the reflecting surface 212 .
  • the monitor photodiode 210 further has a non-reflective surface 214 facing the reflective surface 212 and provided with an anti-reflective coating, and a light absorption layer 213 b provided between the reflective surface 212 and the non-reflective surface 214 .
  • the non-reflective surface 214 can be formed by applying an anti-reflective coating to the incident surface of the monitor PD 210b.
  • the non-reflective surface 214 and the reflective surface 211 are provided adjacent to each other on the side of the monitor PD 210 on which the branched light 82 is incident. Part of the branched light 82 is incident on each of the non-reflecting surface 214 and the reflecting surface 211 .
  • the incident light 80 and the branched light 82 from the light source have beam diameters of, for example, several hundred microns. If the light receiving portions of the monitor PDs 210 a and 210 b are arranged so as to be within the beam diameter of the branched light 82 , both the monitor PDs 210 a and 210 b can receive part of the branched light 82 .
  • FIG. 8 is a diagram showing wavelength characteristics of absorptance of the monitor photodiode 210 according to the second embodiment.
  • the dashed line 101 indicates the calculation result of the absorption characteristic of the monitor PD 210b
  • the solid line 102 indicates the calculation result of the absorption characteristic of the monitor PD 210a.
  • the reflectance R1 of the reflective surface 211 was 30%
  • the reflectance R2 of the reflective surface 212 was 95%
  • the transmittance Tab per passage through the light absorption layer 213a was 70%.
  • the monitor PD 210b calculated the reflectance R1 of the non-reflecting surface 214 to be 0.5%, the reflectance R2 of the reflecting surface 212 to be 95%, and the transmittance T ab per passage through the light absorption layer 213b. 5%.
  • the control circuit 70 controls the wavelength of the emitted light 83 according to the photocurrent of the monitor PD 210a, and controls the wavelength of the emitted light 83 according to the photocurrent of the monitor PD 210b. output should be controlled.
  • the wavelength of the light source By controlling the wavelength of the light source so that the current value of the monitor PD 210a is constant, the wavelength of the light source can be controlled to be constant. Also, by keeping the current value of the monitor PD 210b constant, the output of the light source can be controlled to be constant.
  • one beam splitter 30 can split light to the monitor PDs 210a and 210b. Therefore, the size of the wavelength locker 200 can be further reduced.
  • FIG. 9 is a plan view of a wavelength locker 300 according to Embodiment 3.
  • the wavelength locker 300 of this embodiment includes a monitor PD10 having an etalon function and a monitor PD20 provided on the opposite side of the beam splitter 30 from the monitor PD10.
  • Incident light 80 from the light source is split into output light 83 and split light 82 by the beam splitter 30 .
  • Light 84 of the branched light 82 reflected by the monitor PD 10 enters the monitor PD 20 .
  • FIG. 10 is a diagram showing wavelength characteristics of photocurrents of the monitor photodiodes 10 and 20 according to the third embodiment.
  • a solid line 103 indicates the photocurrent of the monitor PD10
  • a solid line 104 indicates the photocurrent of the monitor PD20.
  • the wavelength dependence of these photocurrents was calculated using Eqs. Since the monitor PD20 receives the light reflected by the monitor PD10, the photocurrent of the monitor PD20 is calculated as the reflectance of the monitor PD10. In the calculation, R1 was 30%, R2 was 95% and Tab was 70%.
  • the wavelength dependence of the photocurrent of the monitor PD 10 having the etalon function and the wavelength dependence of the photocurrent of the monitor PD 20 not having the etalon function exhibit opposite characteristics.
  • FIG. 11 is a diagram showing current sum 105 and current difference 106 of monitor photodiodes 10 and 20 according to the third embodiment.
  • the calculated photocurrent shown in FIG. 10 was used for the sum and difference calculations.
  • a current difference 106 between the monitor PDs 10 and 20 varies greatly with a change in wavelength. Therefore, by using the difference between the photocurrents of the monitor PDs 10 and 20, wavelength control can be performed with higher accuracy. Further, the current sum 105 of the monitor PDs 10 and 20 changes little with respect to the change in wavelength, and becomes a substantially constant value. Therefore, by controlling the sum of the photocurrents of the monitor PDs 10 and 20 to be constant, the light output from the light source can be controlled to be constant.
  • the reflectance on the back side of the monitor PD 10 is not 100%. Also, the ratio of the branched light 82 received by the monitor PD 10 and the ratio of the reflected light 84 received by the monitor PD 20 are not equal. Therefore, the simple sum of the photocurrents of the monitor PDs 10 and 20 is not necessarily constant with respect to wavelength.
  • FIG. 12 is a diagram showing current sums when the current ratio of the monitor photodiodes 10 and 20 according to the third embodiment is changed.
  • a ⁇ IPD10 +b ⁇ IPD20 (equation 4) is calculated, where I PD10 is the photocurrent of the monitor PD10, I PD20 is the photocurrent of the monitor PD20, and a and b are real numbers.
  • the current ratio can be determined, for example, according to the maximum and minimum values of wavelength change of the photocurrents of the monitor PDs 10 and 20 .
  • the wavelength can be controlled with higher accuracy by multiplying the current difference by an appropriate current ratio and calculating the difference. That is, a ⁇ I PD10 ⁇ b ⁇ I PD20 (Equation 5) is calculated.
  • the control circuit 70 of the present embodiment performs linear computation of the photocurrents of the monitor PDs 10 and 20, and controls the wavelength and optical output of the emitted light 83 according to the computation results.
  • a linear operation is an operation represented by Equations 4 and 5.
  • the control circuit 70 can control the output of the light source to be constant by keeping the sum of the photocurrents obtained by Equation 4 constant. Further, the control circuit 70 can control the wavelength of the light source to be constant by keeping the difference between the photocurrents obtained by Equation 5 constant.
  • one beam splitter 30 can split light to the monitor PDs 10 and 20 . Therefore, the wavelength locker 300 can be miniaturized. In particular, compared with the first embodiment, the size in the traveling direction of the emitted beam can be reduced.
  • FIG. 13 is a plan view of wavelength locker 400 according to the fourth embodiment.
  • the incident light 80 from the light source is partly branched as branched light 81 by the beam splitter 40 and received by the monitor PD 20b.
  • the light transmitted through the beam splitter 40 enters the beam splitter 430 .
  • the beam splitter 430 has an etalon function as described later.
  • the beam splitter 430 splits incident light into outgoing light 83 and transmitted light 85 .
  • the transmitted light 85 is incident on the monitor PD 20a.
  • the monitor PDs 20a and 20b, the beam splitter 40 and the beam splitter 430 are mounted on the thermoelectric element 50 and kept constant in temperature.
  • a control circuit 70 is connected to the monitor PDs 20a and 20b.
  • the control circuit 70 controls the wavelength and optical output of the emitted light 83 according to the photocurrents of the monitor PDs 20a and 20b. Note that the monitor PDs 20a and 20b are normal monitor PDs that do not have an etalon function.
  • FIG. 14 is a cross-sectional view of beam splitter 430 according to Embodiment 4.
  • FIG. Beam splitter 430 has reflective surfaces 431 , 432 , 433 , entrance surface 434 and exit surface 435 .
  • An incident surface 434 is provided with an anti-reflection coating.
  • Reflective surface 431 reflects a portion of incident light 80 .
  • the incident light 80 from the incident surface 434 is split into the outgoing light 83 and the split light.
  • the light that has passed through the reflecting surface 431 is emitted as emitted light 83 from an emitting surface 435 to which anti-reflection coating is applied.
  • the reflective surfaces 432 and 433 are perpendicular to the entrance surface 434 and the exit surface 435 . Reflective surfaces 432 and 433 are provided along the traveling direction of emitted light 83 .
  • the reflective surface 432 reflects the branched light from the reflective surface 431 . Part of the light reflected by the reflecting surface 432 is reflected again by the reflecting surface 431 . Of the light reflected by the reflective surface 432 , the light transmitted through the reflective surface 431 is reflected by the reflective surface 433 facing the reflective surface 432 . Part of the light reflected by the reflecting surface 433 is reflected by the reflecting surface 431 again.
  • the transmitted light 85 that has passed through the reflecting surface 432 is incident on the monitor PD 20a.
  • the beam splitter 430 functions as an etalon in which the transmittance of the transmitted light 85 depends on the wavelength by repeating reflection on the reflecting surfaces 432 and 433 .
  • the transmittance and reflectance of the beam splitter 430 can also be obtained by Equations 1 and 2.
  • the transmittance of the beam splitter 430 corresponds to the output ratio of the transmitted light 85 from the reflecting surface 432 .
  • the reflectance of the beam splitter 430 corresponds to the output ratio of light from the reflecting surface 433 .
  • the reflecting surface 432 of the beam splitter 430 corresponds to the reflecting surface 11 of the monitor PD10 in Embodiment 1
  • the reflecting surface 433 of the beam splitter 430 corresponds to the reflecting surface 12 of the monitor PD10.
  • the branching loss due to the reflecting surface 431 of the beam splitter 430 corresponds to the absorption loss due to the light absorption layer 13 of the monitor PD 10 .
  • the wavelength dependence of the optical output of the transmitted light 85 is similar to the characteristics shown in FIG. Therefore, by controlling the photocurrent of the monitor PD 20a that receives the transmitted light 85 to be constant, the wavelength of the light source can be controlled to be constant. Further, by keeping the photocurrent of the monitor PD 20b constant, the optical output of the emitted light 83 can be kept constant. That is, the control circuit 70 controls the wavelength of the emitted light 83 according to the photocurrent of the monitor PD 20a, and controls the output of the emitted light 83 according to the photocurrent of the monitor PD 20b.
  • the wavelength locker 400 of this embodiment since the beam splitter 430 has the function of an etalon, it is not necessary to mount an etalon. Therefore, the wavelength locker 400 can be miniaturized. In particular, the lateral width of the wavelength locker 400 with respect to the emitted light 83 can be reduced.
  • FIG. 15 is a plan view of a wavelength locker 500 according to Embodiment 5.
  • the wavelength locker 500 includes a beam splitter 430 having an etalon function, a monitor PD 20a on which the transmitted light 85 from the beam splitter 430 is incident, and a monitor PD 20b provided on the opposite side of the beam splitter 430 from the monitor PD 20a.
  • the transmitted light 86 transmitted through the reflecting surface 433 enters the monitor PD 20b.
  • FIG. 16 is a diagram showing wavelength characteristics of photocurrents of the monitor photodiodes 20a and 20b according to the fifth embodiment.
  • FIG. 16 shows the wavelength dependence of the photocurrents of the monitor PD 20a and the monitor PD 20b calculated using Equations 1 and 2.
  • FIG. 16 the photocurrent of the monitor PD 20a is indicated as transmittance 110, and the photocurrent of the monitor PD 20b is indicated as reflectance 111.
  • the wavelength dependencies of the photocurrents of the monitor PDs 20a and 20b exhibit opposite characteristics.
  • FIG. 17 is a diagram showing current sum 112 and current difference 113 of monitor photodiodes 20a and 20b according to the fifth embodiment.
  • a current difference 113 between the monitor PDs 20a and 20b changes greatly with a change in wavelength. Therefore, wavelength control can be performed with higher accuracy by control according to the difference in photocurrent between the monitor PDs 20a and 20b. Further, the sum of the currents of the monitor PDs 20a and 20b changes little with respect to the change in wavelength and becomes a substantially constant value. Therefore, the light output from the light source can be controlled to be constant by control according to the sum of the photocurrents of the monitors 20a and 20b.
  • the ratio of the transmitted light 85 received by the monitor PD 20a and the ratio of the transmitted light 86 received by the monitor PD 20b are not necessarily equal. For this reason, as in the third embodiment, rather than simply summing the photocurrents of the monitor PDs 20a and 20b, the sum may be calculated after multiplying each of the monitor PDs 20a and 20b by the current ratio as shown in Equation 4. . This makes it possible to make the current sum even more constant with respect to the wavelength.
  • the current ratio can be determined, for example, according to the maximum and minimum values of wavelength change of the photocurrents of the monitor PDs 20a and 20b.
  • the control circuit 70 of the present embodiment performs linear computation of the photocurrents of the monitor PDs 20a and 20b, and controls the wavelength and optical output of the emitted light 83 according to the computation results.
  • a linear operation is an operation represented by Equations 4 and 5.
  • the control circuit 70 can control the output of the light source to be constant by keeping the sum of the photocurrents obtained by Equation 4 constant. Further, the control circuit 70 can control the wavelength of the light source to be constant by keeping the difference between the photocurrents obtained by Equation 5 constant.
  • one beam splitter 430 can split light to the monitor PDs 20a and 20b. Therefore, the wavelength locker 300 can be miniaturized. In particular, compared with the fourth embodiment, the size in the traveling direction of the emitted beam can be reduced.
  • Embodiment 6. 18A and 18B are diagrams for explaining a method of aligning the wavelength locker 400 according to the sixth embodiment.
  • the wavelength locker 400 according to the fourth embodiment will be described as an example.
  • FIG. 18 shows a beam splitter 430 having an etalon function and a monitor PD 20 that receives light from the beam splitter 430 .
  • the incident light 80 to the beam splitter 430 is split by the reflecting surface 431 into the outgoing light 83 and the split light 87a.
  • a portion of the branched light 87a passes through the reflecting surface 432 and is received by the monitor PD20.
  • a part of the branched light 87a is reflected by the reflecting surfaces 432 and 433 to become a branched light 87b.
  • Part of the branched light 87b passes through the reflecting surface 432 and is received by the monitor PD20.
  • An arrow d1 indicates the alignment direction of the monitor PD20.
  • Arrow d2 indicates the alignment direction of beam splitter 430 .
  • FIG. 19 is a diagram showing the light output distribution on the light receiving surface of the monitor photodiode 20 according to Embodiment 6.
  • FIG. A solid line 90a indicates the optical output distribution of the branched light 87a
  • a solid line 90b indicates the optical output distribution of the branched light 87b.
  • a solid line 91 shows the optical output distribution when the branched lights 87a and 87b interfere to maximize the optical output
  • a dashed line 92 shows the optical output distribution when the branched lights 87a and 87b interfere to minimize the optical output. 4 shows the light output distribution.
  • the monitor PD20 is adjusted in the direction indicated by the arrow d1. As a result, the position of the monitor PD 20 is adjusted on the extension of the vertical line of the emitted light 83 so that the position of the beam splitter 430 is the foot of the vertical line.
  • the angle of beam splitter 430 is adjusted in the direction indicated by arrow d2.
  • the photocurrent of the monitor PD 20 is not necessarily high depending on the value of the phase difference .delta. Therefore, the light output distribution may change, for example, as indicated by solid line 91 and dashed line 92 .
  • phase difference ⁇ by changing the wavelength or the like while changing the angle of the beam splitter 430 to perform alignment at the point where the maximum interference can be obtained.
  • the angle is adjusted so that the difference between the light output distributions indicated by the solid line 91 and the broken line 92 is maximized. For this reason, there was a possibility that it would take time and effort to align the core.
  • the alignment of the beam splitter 430 is performed using the spontaneous emission light of the laser as the incident light 80 .
  • the injection current to the semiconductor laser which is the light source, is set below the threshold so that only the spontaneous emission light is output. Spontaneous emission does not interfere. Therefore, the light output distribution on the light receiving surface of the monitor PD 20 becomes the light output distribution indicated by the solid line 91 obtained by adding the light output distributions of the branched lights 87a and 87b.
  • the angle of the beam splitter 430 can be easily and optimally aligned by performing alignment so that the photocurrent in the monitor PD 20 is maximized.
  • amplified spontaneous emission light from the optical amplifier may be used for alignment.
  • the alignment of the beam splitter 430 has been described here, spontaneous emission light or amplified spontaneous emission light can also be used for alignment of the monitor PD 20 . Further, the alignment method of this embodiment can also be applied to the wavelength locker 500 of the fifth embodiment.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Semiconductor Lasers (AREA)

Abstract

Un dispositif de verrouillage de longueur d'onde selon la présente divulgation comprend : un diviseur de faisceau pour faire bifurquer la lumière d'entrée en une lumière de sortie et en une lumière bifurquée ; et une première photodiode de surveillance comprenant une première surface réfléchissante réfléchissant la lumière bifurquée, une seconde surface réfléchissante opposée à la première surface réfléchissante et réfléchissant la lumière réfléchie par la première surface réfléchissante, et une première couche d'absorption optique disposée entre la première surface réfléchissante et la seconde surface réfléchissante. La première photodiode de surveillance répète les réflexions entre la première surface réfléchissante et la seconde surface réfléchissante, fonctionnant ainsi en tant qu'étalon dont l'absorbance optique dépend de la longueur d'onde.
PCT/JP2021/033376 2021-09-10 2021-09-10 Dispositif de verrouillage de longueur d'onde, photodiode de surveillance, diviseur de faisceau et procédé d'alignement de dispositif de verrouillage de longueur d'onde WO2023037510A1 (fr)

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Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0257927A (ja) * 1988-08-24 1990-02-27 Fujitsu Ltd 半導体受光素子
JPH05267639A (ja) * 1992-03-17 1993-10-15 Sony Corp 受光素子
JPH06323900A (ja) * 1993-04-30 1994-11-25 American Teleph & Telegr Co <Att> 共鳴キャビティを有する光ディテクタ
JPH06334209A (ja) * 1993-04-30 1994-12-02 American Teleph & Telegr Co <Att> 光電子検出器
JPH10206228A (ja) * 1996-11-19 1998-08-07 Commiss Energ Atom 多スペクトル共振空洞検出器
JP2002111124A (ja) * 2000-09-29 2002-04-12 Sumitomo Electric Ind Ltd 発光モジュール
WO2002090881A1 (fr) * 2001-05-08 2002-11-14 Precision Photonics Corporation Verrouilleur en longueur d'onde a un seul etalon
US20030152127A1 (en) * 2002-02-12 2003-08-14 Fibera, Inc. Integrated etalon-beam splitter
JP2004502141A (ja) * 2000-06-26 2004-01-22 ジェイディーエス　ユニフェイズ　コーポレーション 光パワーおよび波長モニター
WO2006059086A1 (fr) * 2004-11-30 2006-06-08 Bookham Technology Plc Dispositif de surveillance de lumière
JP2008053555A (ja) * 2006-08-25 2008-03-06 Fujitsu Ltd 波長ロッカー
JP2016520218A (ja) * 2013-05-27 2016-07-11 華為技術有限公司Ｈｕａｗｅｉ Ｔｅｃｈｎｏｌｏｇｉｅｓ Ｃｏ．，Ｌｔｄ． フィルタ、フィルタを製作する方法、およびレーザ波長監視装置

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0257927A (ja) * 1988-08-24 1990-02-27 Fujitsu Ltd 半導体受光素子
JPH05267639A (ja) * 1992-03-17 1993-10-15 Sony Corp 受光素子
JPH06323900A (ja) * 1993-04-30 1994-11-25 American Teleph & Telegr Co <Att> 共鳴キャビティを有する光ディテクタ
JPH06334209A (ja) * 1993-04-30 1994-12-02 American Teleph & Telegr Co <Att> 光電子検出器
JPH10206228A (ja) * 1996-11-19 1998-08-07 Commiss Energ Atom 多スペクトル共振空洞検出器
JP2004502141A (ja) * 2000-06-26 2004-01-22 ジェイディーエス　ユニフェイズ　コーポレーション 光パワーおよび波長モニター
JP2002111124A (ja) * 2000-09-29 2002-04-12 Sumitomo Electric Ind Ltd 発光モジュール
WO2002090881A1 (fr) * 2001-05-08 2002-11-14 Precision Photonics Corporation Verrouilleur en longueur d'onde a un seul etalon
US20030152127A1 (en) * 2002-02-12 2003-08-14 Fibera, Inc. Integrated etalon-beam splitter
WO2006059086A1 (fr) * 2004-11-30 2006-06-08 Bookham Technology Plc Dispositif de surveillance de lumière
JP2008053555A (ja) * 2006-08-25 2008-03-06 Fujitsu Ltd 波長ロッカー
JP2016520218A (ja) * 2013-05-27 2016-07-11 華為技術有限公司Ｈｕａｗｅｉ Ｔｅｃｈｎｏｌｏｇｉｅｓ Ｃｏ．，Ｌｔｄ． フィルタ、フィルタを製作する方法、およびレーザ波長監視装置

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