Wavelength-locking laser generation device and method

Abstract

Disclosed are: a laser generation device having a wavelength locking function by integrating a laser light source and a wavelength locking chip; and an operation method thereof. The laser generation device having a wavelength locking function, according to one embodiment, may comprise: a metal stem; a thermoelectric cooler (TEC) provided on the upper surface of the metal stem; a light source provided on the TEC; a wavelength locker comprising a first grating coupler for guiding an optical signal outputted from one surface of the light source to a waveguide; a first photodiode (PD) for detecting the strength of the optical signal guided to the waveguide; a second PD for detecting the wavelength of the optical signal guided to the waveguide; and a control unit for controlling the temperature of the TEC on the basis of an output signal of the first PD and the second PD.

Description

Wavelength-locked laser generating device and method

[0001] In particular, as a laser generation technology, the invention relates to a laser generating device equipped with a wavelength locking function by integrating a laser light source and a wavelength locking chip, and a method of operation thereof.

[0002] Conventionally, wavelength locking was achieved through complex external devices or lens systems to fix the wavelength of a laser. In particular, there were difficulties in locking the laser to a specific wavelength selected in WDM systems. Furthermore, complex configurations based mainly on etalons were used for the wavelength locking function, and multiple lenses and photodiodes were required to increase the input and output efficiency of optical signals. This presented limitations in device miniaturization and cost reduction, resulting in the problem that the existing methods were unsuitable for use in low-cost, miniaturized communication systems.

[0003] The purpose is to provide a laser generating device equipped with a wavelength locking function by integrating a laser light source and a wavelength locking chip, and a method of operation thereof.

[0004] According to one aspect, a laser generating device having a wavelength locking function may include: a metal stem; a thermoelectric cooler (TEC) provided on the upper surface of the metal stem; a light source provided above the thermoelectric cooler; a wavelength locker comprising a first grating coupler that guides a light signal output from one side of the light source into a waveguide; a first photodiode (PD) that detects the intensity of the light signal guided into the waveguide; a second photodiode that detects the wavelength of the light signal guided into the waveguide; and a control unit that controls the temperature of the thermoelectric cooler based on the output signals of the first photodiode and the second photodiode.

[0005] The light source may be configured to output a light signal in a direction parallel to the upper surface of the metal stem.

[0006] The wavelength fixing part is provided so as to be inclined at a predetermined angle in the vertical direction of the upper surface of the metal stem, so that the first grating coupler can guide the optical signal output from the light source at a predetermined angle into the waveguide.

[0007] The wavelength fixing unit may further include a power divider that separates the optical signal induced through the first grating coupler into two optical signals.

[0008] The wavelength fixing unit may include a second grating coupler and a third grating coupler that output the optical signal separated through a power splitter to a first photodiode and a second photodiode.

[0009] The wavelength fixing unit may further include a ring resonator filter that selectively filters the wavelength of the optical signal.

[0010] The second photodiode can receive an optical signal filtered through a ring resonator filter and detect the wavelength of the optical signal.

[0011] The first photodiode and the second photodiode may be provided on one side of the wavelength fixing part into which the optical signal is input.

[0012] The first photodiode and the second photodiode may be provided on the upper surface of the thermoelectric cooler.

[0013] The first photodiode and the second photodiode may be provided on the lower surface of the light source facing one surface of the wavelength fixing part into which the optical signal is input.

[0014] The laser generating device further includes a reflective mirror, and an optical signal output from the other side facing one side of the light source that outputs an optical signal to the wavelength fixing part can be reflected by the reflective mirror and output in a direction perpendicular to the upper surface of the metal stem.

[0015] The control unit can control the temperature of the thermoelectric cooler based on the ratio of the output signals of the first photodiode and the second photodiode.

[0016] It is possible to provide a miniaturized light source module incorporating wavelength locking functionality by using silicon photonics-based ultra-small integrated circuits. This enables direct coupling of laser light to a wavelength locking chip without the need for a separate lens system, and by integrating it into a TO-CAN package, simultaneous miniaturization and cost reduction can be achieved.

[0017] In addition, by integrating a grating coupler, optical splitter, and circular resonator filter inside the wavelength locking chip, it is possible to provide a function that continuously monitors the wavelength using the laser's backlight and automatically locks the wavelength according to external temperature changes.

[0018] This allows for simple assembly in a single bonding step, increasing the efficiency of the assembly process and reducing production costs.

[0019] FIG. 1 is a configuration diagram of a laser generating device according to one embodiment.

[0020] FIG. 2 is an illustrative diagram for explaining a wavelength fixing part according to one embodiment.

[0021] FIGS. 3 to 5 are configuration diagrams of a laser generating device according to one example.

[0022] Figure 6 is an example diagram illustrating a grid coupler according to one example.

[0023] Figure 7 is an example diagram illustrating edge coupling according to one example.

[0024] Figure 8 is an example diagram illustrating wire bonding of a photodiode.

[0025] Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings. In describing the present invention, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions may unnecessarily obscure the essence of the present invention. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0026] Hereinafter, embodiments of a laser generating device and method will be described in detail with reference to the drawings.

[0027] FIG. 1 is a configuration diagram of a laser generating device according to one embodiment.

[0028] Referring to FIG. 1, a laser generating device (100) having a wavelength locking function may include a metal stem (110) and a thermoelectric cooler (TEC) (120) provided on the upper surface of the metal stem (110).

[0029] According to one example, the metal stem (110) serves to support and secure various components related to laser generation. The metal stem (110) is generally composed of a metal material such as Cu, which has high thermal conductivity, and may be plated with Au on its surface. A plurality of lead pins may be provided inside the metal stem (110), and the lead pins may be sealed and secured using glass. For example, the metal stem (110) may be in the form of a circular plate. The metal stem (110) serves as an AC ground, thereby enhancing high-frequency characteristics and improving signal quality. The metal stem (110) can dissipate heat generated from the module.

[0030] According to one example, a thermoelectric cooler (120) is a device that transfers heat using the thermoelectric effect, and a Peltier element may be used. The thermoelectric cooler (120) has the characteristic of absorbing heat on one side and releasing heat on the opposite side when current flows, and thus can cool an object.

[0031] For example, a thermoelectric cooler (120) is composed of a structure in which two semiconductor materials (N-type and P-type) are electrically connected. This structure is called a Peltier element, and these elements are arranged in an array form connected by a conductive material. Each semiconductor constituting the thermoelectric cooler (120) serves to transfer heat, and heat sinks may be attached to the top and bottom.

[0032] According to one embodiment, the laser generating device (100) may include a light source (130) provided on a thermoelectric cooler (120). As an example, the light source may be a laser diode. A laser diode is a device that generates light of a specific wavelength using a semiconductor material and can emit light by injecting electrons and holes into an active region through an electric current. The laser diode is composed of p-type and n-type semiconductor layers surrounding the active region, and light can be emitted when electrons and holes combine at the junction between them. The emitted light causes resonance by a reflective mirror within the active region, and amplified laser light is emitted when specific conditions are met. Through this, the laser diode can emit light with a strong output in a narrow wavelength range.

[0033] For example, a thermoelectric cooler (120) can control the temperature of a light source (130) to maintain a specific wavelength stably. Since the laser diode used as the light source (130) has a wavelength that changes depending on the temperature, the temperature of the laser diode can be precisely controlled through the thermoelectric cooler (120) to ensure that the output at a specific wavelength is maintained stably.

[0034] For example, when current is applied to the thermoelectric cooler (120), one side can be cooled and the opposite side heated by the Peltier effect. This allows the temperature of the light source (130) to be adjusted to a desired level. If the temperature of the light source (130) is higher than the target and the wavelength changes, the wavelength can be adjusted by lowering the temperature of the diode through the thermoelectric cooler (120), and conversely, if the temperature is lowered, the temperature of the light source (130) can be raised to maintain a constant wavelength. The control unit can fix the wavelength of the light signal to a specific wavelength by controlling the temperature of the light source by adjusting the current to the thermoelectric cooler.

[0035] According to one embodiment, the light source (130) may be configured to output a light signal in a direction parallel to the upper surface of the metal stem (110). Referring to FIG. 1, the light source (130) is configured in a direction parallel to the upper surface of the metal stem (110). Accordingly, a light signal emitted from one side of the light source (130) is incident on the wavelength fixing part (140), and a light signal output from the other side may be output in a direction perpendicular to the upper surface of the metal stem (110) through a mirror (160).

[0036] According to one embodiment, the laser generating device (100) may include a wavelength locker (140) comprising a first grating coupler that guides a light signal output from one side of a light source (130) into a waveguide.

[0037] A grating coupler can perform light coupling between silicon photonics-based circuits. The grating coupler can incident or emit light in a vertical direction on an integrated circuit, guide light from an optical fiber to a circuit, or conversely, couple light from a circuit to an optical fiber. Referring to FIG. 6, the grating coupler may include a Si substrate, a lower SiO2 layer (B), a SiN layer, a grating structure (Si), and an upper SiO2 layer (T).

[0038] For example, the Si substrate serves as the base layer of the lattice coupler and can support the entire structure. The lower SiO2 layer (B) is an oxide layer placed on the substrate and acts as a block to prevent light from being lost to the substrate. This layer is essential for defining the light propagation path and is used to reduce losses. The SiN layer acts as a waveguide that forms the path for light propagation. This layer is formed at a specific height (h1) so that it can effectively propagate light of the desired wavelength.

[0039] The lattice structure (Si) is a Si pattern periodically arranged in a square shape on an oxide film (SiO2) formed on top of a SiN layer. In FIG. 5, an example is shown in which the Si pattern has regularity in spacing and height but is in a square shape with different sizes; however, the differences in square shapes or sizes of the square Si patterns in FIG. 5 are merely examples and do not limit the embodiments of the present invention.

[0040] This structure is arranged at regular intervals (s), and the height of each pattern can be defined as h2. This periodic grating changes the phase of light to induce diffraction in the desired direction. The upper SiO2 layer (T) is an upper oxide layer located on the grating and can serve to protect and stabilize the optical path from the external environment.

[0041] For example, the angle of incidence (θ) of the grating coupler is the angle of light incident on the grating coupler, and the coupling efficiency can vary significantly depending on this angle. The distance from the grating (z) is the distance between the incident optical signal and the grating structure, and this distance plays an important role for optimal coupling.

[0042] According to one embodiment, the wavelength fixing part (140) is provided to be inclined at a predetermined angle in the vertical direction of the upper surface of the metal stem (110) so that the first grating coupler can guide the optical signal output from the light source into the waveguide at a predetermined angle. Referring to FIG. 2, the wavelength fixing part (140) can be configured so that the optical signal output from the light source (130) can reach at a predetermined angle. Through this, the optical signal can be input into the waveguide through the first grating coupler (141).

[0043] According to one embodiment, the wavelength fixing unit (140) may further include a power divider (not shown) that separates the optical signal induced through the first grating coupler (141) into two optical signals.

[0044] A power divider is a component that divides the power of an optical signal into multiple paths for transmission. By splitting a single optical signal into multiple signals and transmitting them through each path, a power divider can transmit signals to multiple devices from a single light source or be utilized in various optical circuits.

[0045] For example, a fiber optic splitter can physically split incident light into specific ratios. Photonic Integrated Circuit (PIC)-based power dividers can split light through optical circuits within the chip. PICs enable smaller size and more precise control, and can perform various functions, such as separating or recombining light of specific wavelengths through wavelength splitting and phase control.

[0046] According to one embodiment, a laser generating device (100) may include a first photodiode (PD) (150) that detects the intensity of an optical signal induced in a waveguide and a second photodiode (155) that detects the wavelength of an optical signal induced in a waveguide. For example, the two photodiodes may each perform power monitoring and wavelength monitoring. For example, the power photodiode detects the intensity of the optical signal and outputs an output current (I p It can generate ) and monitor changes in laser output power. The wavelength photodiode detects changes in the wavelength of the optical signal and output current (I λ It generates ) and can monitor the oscillation wavelength in real time. The ratio of the output currents of these two photodiodes (I λ / I p ) can be used as a key signal for wavelength stabilization feedback.

[0047] According to one embodiment, the wavelength fixing unit (140) may include a second grating coupler (142) and a third grating coupler (143) that output an optical signal separated through a power splitter to a first photodiode (150) and a second photodiode (155). Referring to FIG. 2, an optical signal output from a light source (130) is input through a first grating coupler (141), and the input optical signal can be separated through a power splitter and guided to a second grating coupler (142) and a third grating coupler (143), respectively. The optical signal thus guided can be output through the second grating coupler (142) and the third grating coupler (143) and transmitted to a first photodiode (150) and a second photodiode (155).

[0048] According to one example, the wavelength fixing unit (140) can directly output the optical signal separated through the power splitter to the first photodiode (150) and the second photodiode (155) through edge coupling.

[0049] According to one embodiment, the wavelength fixing unit (140) may further include a ring resonator filter (145) that selectively filters the wavelength of an optical signal. The ring resonator filter (145) resonates in a specific wavelength band and can perform filtering necessary for wavelength monitoring. The ring resonator filter (145) provides information about the laser oscillation wavelength, and since the output characteristics of the ring resonator filter change whenever the oscillation wavelength changes, it can be used to monitor and lock the wavelength.

[0050] According to one embodiment, the second photodiode can receive an optical signal filtered through a ring resonator filter and detect the wavelength of the optical signal. For example, the output of the ring resonator filter is a wavelength monitoring current I at the second photodiode (155). λ It is converted into, and this current can be used for wavelength locking feedback. The spectrum of the ring resonator filter shifts with temperature changes and can be adjusted to match changes in the laser's oscillation wavelength.

[0051] According to one embodiment, the laser generating device (100) may include a control unit (not shown) that controls the temperature of a thermoelectric cooler based on the output signals of a first photodiode (150) and a second photodiode (155). For example, wavelength fixing may include a thermistor control method and a wavelength fixing control method.

[0052] According to one embodiment, the control unit can control the temperature of the thermoelectric cooler based on the ratio of the output signals of the first photodiode and the second photodiode. For example, the control unit can control the wavelength of the optical signal through a wavelength locking method. For example, the control unit [controls] the first photodiode output current (I p ) and the second photodiode output current (I λ Detecting ) and the ratio of the two signals (I λ / I pThe wavelength can be fixed by maintaining the temperature constant. At this time, the control unit can maintain the temperature of the laser diode constant by controlling the current of the thermoelectric cooler (120) based on the output signals of the first photodiode (150) and the second photodiode (155). Through this, the control unit can correct for the change in wavelength according to the temperature change.

[0053] According to one embodiment, the first photodiode (150) and the second photodiode (155) may be provided on one side of the wavelength fixing part (140) into which the optical signal is input. This arrangement is designed so that the optical signal can reach the photodiode directly, enabling real-time monitoring of the optical signal and precise wavelength control.

[0054] For example, as shown in FIG. 3, the first photodiode (150) and the second photodiode (155) may be arranged side by side on one side of the wavelength fixing unit (140). In this case, the wavelength fixing unit (140) may output an optical signal to the first photodiode (150) and the second photodiode (155) through the second grating coupler (142) and the third grating coupler (143).

[0055] For example, the first photodiode measures the power of the output light, and the second photodiode monitors the response to a specific wavelength in real time, thereby enabling accurate monitoring of the wavelength of the optical signal. Additionally, this structure simplifies the assembly process by integrating the photodiode and the optical signal input, and allows the wavelength fixing function to be integrated into a small space. This makes it easy to apply to small packages such as TO-CAN packages, and assembly efficiency can be increased as it can be completed in a single bonding step. Furthermore, the photodiodes located in the wavelength fixing section can respond sensitively to wavelength changes caused by temperature fluctuations of the laser, thereby supporting fine adjustment of the wavelength.

[0056] According to one embodiment, the first photodiode (150) and the second photodiode (155) may be provided on the upper surface of the thermoelectric cooler (120). Referring to FIG. 4, the first photodiode (150) and the second photodiode (155) are provided on the upper surface of the thermoelectric cooler (120) and may be located on the left or right side or the side surface of the lower surface of the wavelength fixing part (140). That is, the photodiodes may be mounted separately on the side surface of the wavelength fixing part (140) and the submount (131) of the light source.

[0057] For example, the first photodiode (150) and the second photodiode (155) may partially overlap when viewed from above the wavelength fixing part (140). This is so that an optical signal output from the waveguide of the wavelength fixing part (140) can be input to the first photodiode (150) and the second photodiode (155). For example, as shown in FIG. 4, when the first photodiode (150) and the second photodiode (155) are provided on the upper surface of the thermoelectric cooler (120), the waveguide included in the wavelength fixing part (140) may be configured in a direction in which the first photodiode (150) and the second photodiode (155) are provided, and an optical signal may be directly output to the first photodiode (150) and the second photodiode (155) through edge coupling without a separate grating coupler. At this time, the optical signal output from the waveguide may spread out to a predetermined range, but the spreading range may be covered by the area of ​​the first photodiode (150) and the second photodiode (155).

[0058] FIG. 7 shows how an optical signal is transmitted to a photodiode (750) through edge coupling. The optical signal originates from a light source and can be coupled to a cross-section of a SiN (silicon nitride) waveguide. The edge coupling method efficiently transmits the optical signal by utilizing the difference in refractive index between the waveguide and the optical fiber, and allows light to propagate along the SiN waveguide.

[0059] The SiN waveguide has a high refractive index and effectively traps and transmits light through upper and lower SiO2 (silicon oxide) cladding layers. The optical signal propagated along the waveguide reaches the photodiode (750) at the end of the structure. The edge coupling-based design has significant advantages in that it minimizes optical loss and is compatible with silicon-based CMOS processes, making large-scale integration and production easy.

[0060] As shown in FIG. 4, when the first photodiode (150) and the second photodiode (155) are provided on the upper surface of the thermoelectric cooler (120), the anode and cathode pads of the photodiode can be directly wire-bonded with lead pins penetrating the metal stem, making electrical connection simple and assembly easy.

[0061] Referring to FIG. 8, the multilayer substrate is depicted as having a layered shape and serves as a base for connecting a device with a photodiode attached to it and a circuit board. In FIG. 8(b), a pad area electrically connected to a photodiode pin (PIN-PD) through a via within the multilayer substrate is shown.

[0062] For example, this structure can improve light efficiency through a design that allows light input and output from the side of the waveguide. This structure can increase efficiency by ensuring that 100% of the output is incident on the photodiode without being affected by wavelength. In addition, by mounting the photodiode on top of the thermoelectric cooler, the thermoelectric cooler and the photodiode can operate at the same temperature, thereby improving temperature uniformity. Through this, wavelength shift caused by thermal fluctuations of the laser can be minimized.

[0063] According to one embodiment, the first photodiode (150) and the second photodiode (155) may be provided on the lower surface of a light source facing one surface of a wavelength fixing part into which a light signal is input.

[0064] Referring to FIG. 5, the first photodiode (150) and the second photodiode (155) may be provided on a submount (131) of a light source facing one side of the wavelength fixing part (140). At this time, the first photodiode (150) and the second photodiode (155) may be in close contact with a thermoelectric cooler (121). Through this, the anode and cathode pads of the photodiode can be directly wire-bonded with lead pins penetrating the metal stem. In addition, by providing the photodiode on the upper part of the thermoelectric cooler, the thermoelectric cooler and the photodiode can operate at the same temperature, thereby improving temperature uniformity. Through this, wavelength shift due to thermal fluctuations of the laser can be minimized.

[0065] Referring to FIG. 5, the first photodiode (150) and the second photodiode (155) face the wavelength fixing part (140) so that they can receive an optical signal output through the second grating coupler (142) and the third grating coupler (143) provided in the wavelength fixing part (140). For example, as shown in FIG. 6, the optical signal can be received through the grating coupler of the photodiode (650). The grating coupler is located at the top of the silicon nitride (SiN) waveguide, and the periodically arranged grating structure serves to emit the optical signal to the outside. The optical signal propagated along the waveguide can interact with the grating structure and be diffracted at a specific angle (θ). Through this, the optical signal can pass through the upper SiO2 layer inside the waveguide and be output to the outside.

[0066] At this time, the first photodiode (150) and the second photodiode (155), and the second grating coupler (142) and the third grating coupler (143) may be positioned apart by a predetermined distance. Accordingly, the optical signal output from the second grating coupler (142) and the third grating coupler (143) may be diffused and spread out. However, since the spreading area may be covered by the area of ​​the first photodiode (150) and the second photodiode (155), the optical signal may be incident normally on the first photodiode (150) and the second photodiode (155).

[0067] According to one embodiment, the laser generating device (100) further includes a reflective mirror (160), and an optical signal output from the other side facing one side of the light source that outputs an optical signal to the wavelength fixing part (140) can be reflected by the reflective mirror and output in a direction perpendicular to the upper surface of the metal stem.

[0068] The laser generating device (100) additionally includes a reflective mirror (160) and has a structure in which a light source outputs an optical signal toward a wavelength fixing part (140). At this time, the optical signal output from one side opposite the light source is reflected by the reflective mirror inside the device and can be output in a direction perpendicular to the upper surface of the metal stem (110) inside the TO-CAN package. That is, the light emitted from the front is reflected at a 45-degree angle and directed toward the lens of the TO-CAN package to be combined with the optical fiber located at the top, and the light emitted from the rear is input to the wavelength fixing part to promote wavelength stabilization.

[0069] The present invention has been described above focusing on its preferred embodiments. Those skilled in the art will understand that the present invention may be implemented in modified forms without departing from the essential characteristics of the invention. Accordingly, the scope of the present invention should not be limited to the aforementioned embodiments but should be interpreted to include various embodiments within the scope equivalent to those described in the claims.

Claims

1. In a laser generating device having a wavelength locking function, Metal stem; A thermoelectric cooler (TEC) provided on the upper surface of the metal stem; A light source provided on the above-mentioned thermoelectric cooler; A wavelength locker comprising a first grating coupler that guides an optical signal output from one side of the light source into a waveguide; A first photodiode (PD) for detecting the intensity of an optical signal induced in the above waveguide; A second photodiode for detecting the wavelength of an optical signal induced in the above waveguide; A laser generating device comprising a control unit that controls the temperature of the thermoelectric cooler based on the output signals of the first photodiode and the second photodiode.

2. In Paragraph 1, A laser generating device configured such that the light source outputs a light signal in a direction parallel to the upper surface of the metal stem.

3. In Paragraph 2, The above wavelength fixing part A laser generating device configured to be inclined at a predetermined angle in the vertical direction of the upper surface of the metal stem, wherein the first grating coupler guides a light signal output from the light source into a waveguide at a predetermined angle.

4. In Paragraph 3, The above wavelength fixing part A laser generating device further comprising a power divider that separates an optical signal induced through the first grating coupler into two optical signals.

5. In Paragraph 4, The above wavelength fixing part A laser generating device comprising a second grating coupler and a third grating coupler that output an optical signal separated through the power splitter to the first photodiode and the second photodiode.

6. In Paragraph 5, The above wavelength fixing part A laser generating device further comprising a ring resonator filter that selectively filters optical signal wavelengths.

7. In Paragraph 6, The above second photodiode is A laser generating device that receives an optical signal filtered through the above-mentioned ring resonator filter and detects the wavelength of the optical signal.

8. In Paragraph 7, A laser generating device wherein the first photodiode and the second photodiode are provided on one surface of a wavelength fixing part into which the optical signal is input.

9. In Paragraph 7, The laser generating device, wherein the first photodiode and the second photodiode are provided on the upper surface of the thermoelectric cooler.

10. In Paragraph 7, A laser generating device in which the first photodiode and the second photodiode are provided on the lower surface of the light source facing one surface of the wavelength fixing part into which an optical signal is input.

11. In Paragraph 1, It further includes a reflective mirror, A laser generating device in which a light signal output from the other side facing the one side of the light source that outputs the light signal to the wavelength fixing part is reflected by the reflecting mirror and output in a direction perpendicular to the upper surface of the metal stem.

12. In Paragraph 1, The above control unit A laser generating device that controls the temperature of the thermoelectric cooler based on the ratio of the output signals of the first photodiode and the second photodiode.

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